U.S. patent application number 13/929396 was filed with the patent office on 2014-06-05 for methods and systems for respiratory monitoring with photoplethysmography.
This patent application is currently assigned to UNIVERSITY OF FLORIDA RESEARCH FOUNDATION, INC.. The applicant listed for this patent is Brian S. Fuehrlein, Richard J. Melker. Invention is credited to Brian S. Fuehrlein, Richard J. Melker.
Application Number | 20140155704 13/929396 |
Document ID | / |
Family ID | 29734122 |
Filed Date | 2014-06-05 |
United States Patent
Application |
20140155704 |
Kind Code |
A1 |
Melker; Richard J. ; et
al. |
June 5, 2014 |
Methods And Systems For Respiratory Monitoring With
Photoplethysmography
Abstract
The present invention relates to optimized gas supply utilizing
photoplethysmography. Flow rate, pressure or amount of gas is
adjusted as a function of blood oxygen saturation data,
photoplethysmography signals, or both, obtained from the pulse
oximeter probe.
Inventors: |
Melker; Richard J.;
(Gainesville, FL) ; Fuehrlein; Brian S.;
(Gainesville, FL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Melker; Richard J.
Fuehrlein; Brian S. |
Gainesville
Gainesville |
FL
FL |
US
US |
|
|
Assignee: |
UNIVERSITY OF FLORIDA RESEARCH
FOUNDATION, INC.
Gainesville
FL
|
Family ID: |
29734122 |
Appl. No.: |
13/929396 |
Filed: |
June 27, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11535295 |
Sep 26, 2006 |
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13929396 |
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10751308 |
Jan 2, 2004 |
7127278 |
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11535295 |
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10749471 |
Dec 30, 2003 |
7024235 |
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10751308 |
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10176310 |
Jun 20, 2002 |
6909912 |
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10749471 |
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Current U.S.
Class: |
600/301 ;
128/204.23; 600/324 |
Current CPC
Class: |
A61M 16/0057 20130101;
A61M 2202/0208 20130101; A61B 5/682 20130101; A61M 2210/0662
20130101; A61M 16/021 20170801; A61M 16/0051 20130101; A61B 5/6826
20130101; A61M 2230/30 20130101; A61M 2202/03 20130101; A61B 5/0205
20130101; A61B 5/0816 20130101; A61M 2230/06 20130101; A61M 16/0003
20140204; A61M 16/20 20130101; A61M 2210/0625 20130101; A61B
5/02416 20130101; A61B 5/0261 20130101; A61B 5/4818 20130101; A61M
16/0666 20130101; A61M 2205/3561 20130101; A61B 5/02427 20130101;
A61B 5/14552 20130101; A61M 2230/205 20130101; A61B 5/0295
20130101; A61B 5/14551 20130101; A61B 5/036 20130101; A61M 2230/42
20130101; A61M 16/085 20140204; A61M 2205/3569 20130101; A61B
5/0836 20130101; A61B 5/6829 20130101; A61M 2230/432 20130101; A61B
5/7282 20130101; A61M 16/08 20130101; A61B 5/087 20130101; A61B
5/0873 20130101; A61B 5/7278 20130101; A61M 16/0672 20140204; A61B
5/6819 20130101; A61B 2560/0276 20130101; A61B 2562/247 20130101;
A61M 2210/0618 20130101; A61B 5/4836 20130101; A61M 2230/205
20130101; A61M 2230/005 20130101; A61M 2230/42 20130101; A61M
2230/005 20130101; A61M 2230/432 20130101; A61M 2230/005 20130101;
A61M 2202/0208 20130101; A61M 2202/0007 20130101 |
Class at
Publication: |
600/301 ;
600/324; 128/204.23 |
International
Class: |
A61B 5/00 20060101
A61B005/00; A61M 16/00 20060101 A61M016/00; A61B 5/0205 20060101
A61B005/0205; A61B 5/1455 20060101 A61B005/1455 |
Claims
1. A method of monitoring respiration in an individual, comprising
isolating a DC component of a plethysmograph; and monitoring with a
computer changes in an envelope of the isolated DC component of the
plethysmograph to monitor respiration.
2. The method of claim 1, further comprising quantifying the
changes in the envelope of the isolated DC component to determine
respiratory rate.
3. The method of claim 1, wherein the plethysmograph is obtained
from a plethysmography probe secured at a central source site.
4. The method of claim 3, wherein the central source site is the
nasal alar.
5. The method of claim 1, wherein the plethysmograph is obtained
from a spontaneously breathing individual.
6. The method of claim 1, wherein changes in the envelope of the
isolated DC component are used to determine the optimal level of
positive end expiratory pressure (PEEP).
7. The method of claim 6, wherein in the method further comprises
adjusting the level of PEEP in response to the changes in the
envelope of the plethysmograph.
8. The method of claim 1, further comprising monitoring respiration
with a separate monitoring sensor.
9. The method of claim 8, wherein the separate monitoring sensor
detects nasal air pressure, nasal air flow, or both.
10. The method of claim 8, wherein the separate monitoring sensor
comprises a capnography sensor.
11. A system for monitoring respiration in an individual
comprising: a computer configured to isolate a DC component from a
plethysmograph, and to evaluate changes in an envelope of the
isolated DC component to determine a breathing cycle of the
individual.
12. The system of claim 11, wherein the computer is further
configured to determine respiration rate from the changes in the
envelope of the isolated DC component.
13. The system of claim 11, further comprising a pulse oximetry
probe configured to secure to the nose of the individual.
14. The system of claim 13, wherein the pulse oximetry probe is
configured to secure to the nasal alar of the individual.
15. The system of claim 11, wherein the system is further
configured to increase or decrease a supply of oxygen to the
individual in response to the changes in the envelope of the
isolated DC component.
Description
CLAIM OF PRIORITY
[0001] This application is a continuation of Ser. No. 11/535,295,
which is a continuation of U.S. patent application Ser. No.
10/751,308, Filed Jan. 2, 2004, which is a continuation in part of
application Ser. No. 10/749,471 filed Dec. 30, 2003, now U.S. Pat.
No. 7,024,235, which is a continuation in part of application Ser.
No. 10/176,310, filed Jun. 20, 2002, now U.S. Pat. No. 6,909,912
and International Application No. PCT/US03/19294, filed Jun. 19,
2003, and claims benefits under 35 U.S.C. .sctn.120 for all
above-noted applications. These patent applications are hereby
incorporated by reference into this application in their
entireties.
FIELD OF THE INVENTION
[0002] The present invention relates to the field of non-invasive
measurement of signals indicating arterial blood oxygen saturation
by means of pulse oximetry, and of photoplethysmographic signals
indicating pressure and flow characteristics, and in particular,
configurations of a pulse oximeter probe that sample across the
cheek or the lip of a living subject. Such probes optionally
include provision of a supply of oxygen or oxygen-enriched gas to a
patient whose blood oxygen saturation is being measured, and/or a
sampler of exhaled breath for capnography.
BACKGROUND OF THE INVENTION
[0003] Diseases, acute injuries, and other conditions can adversely
affect blood flow to and in the limbs. In a general sense, agents
and factors that may affect and lower circulation to the limbs,
also known as peripheral circulation, include certain drugs,
especially vasoconstrictors, poor perfusion per se due to shock,
such as results from low blood volume, or septic or cardiogenic
shock, certain traumas, external pressure (as from burns),
hypothermia, and other mechanical abnormalities or injuries. In
particular, decreased peripheral circulation may be caused by a
number of disorders within the body including, but not limited to,
atherosclerosis, Raynaud's disease, Buerger's disease, chronic
obstructive pulmonary diseases (COPD), and embolic occlusive
disease.
[0004] Poor blood flow reduces the amount of oxygen that is carried
in the blood stream to cells. Emergency rooms, intensive care
units, burn units, operating rooms, and ambulances treat a variety
of critically ill patients in need of continuous monitoring of real
time hemoglobin saturation and/or blood pressure readings. If
oxygen levels in the blood become very low at peripheral sites, a
variety of problems may occur which include inadequate
resuscitation, cell death or necrosis that can lead to non-healing
lesions, gangrene and amputation of limbs. Also, in progressive
diabetes and other conditions that may result in atherosclerosis
that affect peripheral circulation and perfusion, non-invasive
measurement of circulation and/or resistance status is useful to
monitor the progression of the disease and the effectiveness of
treatments.
[0005] Also, many patients, especially among the elderly, are on
chronic oxygen therapy; they are in need of supplemental oxygen on
a routine basis. Such patients may have impaired and/or diminished
cardiopulmonary capacity. When such patients are ambulatory, their
supply of oxygen (usually a tank of compressed oxygen or liquid
oxygen) must be transported with them wherever they travel. Oxygen
from such supply passes through a regulator and thence, typically,
via a tube to the nose where it is inhaled (e.g., via a nasal
cannula or the like). Alternatively, the oxygen may be delivered by
a cannula directly into the trachea (transtracheal supplemental
oxygen). Embodiments of the present invention combine the supply of
oxygen or oxygen-rich air with a pulse oximeter that adjusts the
release of the supply to better match the actual bodily requirement
based on the measured blood oxygen saturation. A pulse oximeter
that receives the signal from the pulse oximeter probe is located a
distance from the probe itself, and provides a blood oxygen
saturation measurement to the user (and/or to a remote monitor),
and/or, in certain embodiments acts to adjust the inflow rate or
quality of the oxygen or oxygen-rich gas being supplied. This,
depending on each particular user and his/her baseline settings,
can either extend the life of a given supply of compressed oxygen
or oxygen-rich gas, or provide oxygen or oxygen-rich gas on a more
accurate, as-needed basis, in the latter case improving the health
and/or performance of the user.
[0006] As to the latter benefit of this aspect of the present
invention, provision of an accurate, as-needed supply of oxygen
reduces the risk of and/or alleviates problems of hypoxia that are
associated with improper adjustment of supplemental oxygen to
patients in need thereof. Hypoxia, low oxygen delivery, or
hypoxemia, low oxygen tension in the blood, cause a number of
maladies including polycythemia (increased hematocrit) which leads
to abnormal clotting. Polycythemia is a compensatory mechanism to
chronic hypoxemia that typically builds up over weeks to months. It
is typical in persons with chronic lung disease (and also persons
living at high altitudes).
[0007] A more immediate, primary physiologic compensatory response
to oxygen deficit is increased cardiac output. This is normal, such
as during increased physical exertion. However, in persons who have
impaired cardiocirculatory reserve, increased cardiac output in
response to low arterial oxygen level can, under certain
circumstances, eventually lead to death. The second immediate
physiologic compensatory response to oxygen deficit is the
extraction of more oxygen from hemoglobin within the capillaries of
the body's organs. This normally happens either during an increase
in oxygen demand (i.e., exercise, fever, shivering, etc.), or
during normal demand but decreased oxygen delivery (i.e., due to
inadequate blood flow, anemia, hypoxia). In such instances,
metabolically active cells draw additional oxygen from the red
blood cells which ultimately resulting in a decrease in the mixed
venous blood's oxygen saturation falling from a typical 65% to 80%
level to levels as low as 32% (see Hemodynamic Monitoring--Invasive
and Noninvasive Clinical Application, by Gloria Oblouk Darovic,
3.sup.rd Ed., 2002, Chapter 12). Chronic hypoxemia can lead to a
switch by metabolically active cells to anaerobic metabolism,
which, especially in patients with limited cardiopulmonary reserve,
can lead to lactic acidosis and eventually death.
[0008] Hypoxemia also causes cognitive dysfunction either acutely
or chronically which can lead to early dementia and death.
Generally, based on the compensatory mechanisms and effects on body
tissues, chronic hypoxemia may affect all organs in the body
leading to failure of any or all organs.
[0009] In general, blood oxygen levels are currently measured by
pulse oximetry, which can be divided into transmittance and
reflectance types. Transmittance, or transillumination oximetry,
involves the process whereby a sensor measures light extinction as
light passes through a portion of blood-perfused tissue. Light is
transmitted from one side of a portion of blood-perfused tissue,
and is recorded by a sensor situated across the portion of tissue.
Reflectance oximetry, on the other hand, has both the light source
and the sensor on one side of the tissue, and measures reflectance
back from the tissue. For both types of oximetry, multiple signals
from the light sensor, or detector, are used to estimate the oxygen
saturation and pulse rate from changes in absorption of the light
detected throughout blood pulse cycles. The technology is based on
the differential absorbence of different wavelengths of light by
different species of hemoglobin.
[0010] Conventional pulse oximetry measurement in certain classes
of patients, for instance severely burned patients, can be a
significant challenge, yet this monitoring data is vital in
operating room and intensive care settings. Most current pulse
oximetric approaches depend upon available peripheral sites
permitting transillumination oximetry which is sufficient for most
surgical conditions and procedures. However, in one example,
patients with severe burns often have only a few sites suitable for
the effective placement of the transmitting pulse oximeter sensor.
These patients often have severe circulatory compromise rendering
the current peripheral pulse oximeters less effective.
[0011] The technology of pulse oximeters is well known (See "Pulse
Oximetry: Principles and Limitations," J. E. Sinex, Am. J. Emerg.
Med., 1999, 17:59-66). Pulse oximetry includes a sensor, or probe,
with light source(s) generating at least two different wavelengths
of light, and a detector placed across a section of vascularized
tissue such as on a finger, toe, or ear lobe. Pulse oximetry relies
on the differential absorbance of the electromagnetic spectrum by
different species of hemoglobin. In a typical system, two distinct
wavelength bands, for instance 650-670 nm and 880-940 nm, are used
to detect the relative concentrations of oxygenated hemoglobin
(oxyhemoglobin) and non-oxygenated reduced hemoglobin,
respectively. The background absorbance of tissues and venous blood
absorbs, scatters and otherwise interferes with the absorbance
directly attributable to the arterial blood. However, due to the
enlargement of the cross-sectional area of the arterial vessels
during the surge of blood from ventricular contraction, a
relatively larger signal can be attributed to the absorbance of
arterial hemoglobin during the systole.
[0012] By averaging multiple readings and determining the ratio
peaks of specific wavelengths, a software program can estimate the
relative absorbance due to the arterial blood flow. First, by
calculating the differences in absorption signals over short
periods of time during which the systole and diastole are detected,
the peak net absorbance by oxygenated hemoglobin is established.
The signals typically are in the hundreds per second. The software
subtracts the major "noise" components (from non-arterial sources)
from the peak signals to arrive at the relative contribution from
the arterial pulse. As appropriate, an algorithm system may average
readings, remove outliers, and/or increase or decrease the light
intensity to obtain a result. The results from one site provide a
measurement of arterial oxygen saturation at that site, and also
allows calculation of the shape of the pulse at the placement site
of the probe, which can be developed into a plethysymograph. Among
the various sources of signal interference and modification, it is
noted that the shape of red blood cells changes during passage
through arterial and venous vessels. This change in shape affects
scattering of the light used in pulse oximetry. Algorithms are
designed to correct for such scattering.
[0013] More sophisticated pulse oximetry systems detect at more
than merely two bands, such as the 650-670 nm and 880-940 nm
wavelength bands. For instance, the pulse oximetry article from a
uni-erlangen web site stated that four LEDs, at 630, 680, 730 and
780 nm, each with 10 nm bandwidths, can determine the four common
species of hemoglobin. The article further calculated that the
detection of nine wavelengths in the range of 600 to 850 nm would
provide greater accuracy in assessing these four forms of
hemoglobin, oxyhemoglobin (O.sub.2Hb), reduced hemoglobin (HHb),
methemoglobin (MetHb), and carboxyhemoglobin (COHb). As used in the
present invention, the term "pulse oximeter" or "oximeter" is meant
to include all designs and types of pulse oximeters, including
current and later developed models that transmit and detect at more
than two wavelengths associated with absorption differences of
these hemoglobin species.
[0014] At present, peripheral vascular resistance can only be
measured invasively, or non-invasively by skilled technicians using
Doppler flow devices. The use of Doppler and Doppler waveform
analysis is now a standard investigation technique for obtaining
measurements in blood flow resistance patients with possible
circulatory disorders. For example, Dougherty and Lowry (J. Med.
Eng. Technol., 1992: 16:123-128) combined a reflectance oximeter
and a laser Doppler flowmeter to continuously measure both blood
oxygen saturation and perfusion.
[0015] A number of patents have been issued directed to monitors,
sensors and probes for use in pulse oximetry procedures. For
instance, U.S. Pat. No. 6,334,065, issued on Dec. 25, 2001 to
Al-Ali, et al., discloses a stereo pulse oximeter that provides for
simultaneous, non-invasive oxygen status and photoplethysmograph
measurements at both single and multiple sites. The invention is
directed to the detection of neonatal heart abnormalities,
particularly related to defects of heart-associated vessels, and
specifically directed to Persistent Pulmonary Hypertension in
Neonates (PHHN), Patent Ductus Arteriosis (PDA), and Aortic
Coarctation. All of these conditions result in a flow of
differentially oxygenated blood to different peripheral
extremities. For instance, in PHHN and PDA, the blood that flows to
the right hand is unaffected by the abnormal shunt that results in
less oxygenated blood flowing to other areas. Thus, comparison of
oxygen saturation values between a pulse oximeter sensor at the
right hand and at, for instance, a foot site, is stated to detect
or confirm the diagnosis of such neonatal heart abnormalities.
Continuous monitoring with such pulse oximetry also is proposed, to
provide feedback on the effectiveness of treatments or surgery to
deal with these neonatal cardio/cardiopulmonary conditions. U.S.
Pat. No. 6,334,065 does not address the use of two probes for
detection, confirmation, or monitoring of perfusion- and
resistance-related conditions in the patient. Such conditions would
not be expected in a neonatal patient, and are instead more likely
found in aging patients and in patients with certain accident
conditions unrelated to neonatal heart and heart-associated vessel
anomalies.
[0016] U.S. Pat. No. 6,263,223 was issued on Jul. 17, 2001 to
Shepard et al., and teaches a method for taking reflectance
oximeter readings within the nasal cavity and oral cavity and down
through the posterior pharynx. Whereas the conventional
transillumination pulse oximeter probe detects the light not
absorbed or scattered as it crosses a vascularized tissue covered
by skin (i.e., the LEDs and photodetector are separated by the
tissue), a reflectance oximeter probe detects light by
backscattering of light that traverses vascularized tissue not
bounded by skin and is reflected back to a detector positioned on
the same side of the tissue as the LEDs (e.g., on tissue in the
mouth). The method includes inserting a reflectance pulse oximeter
sensor into a cavity within a subject's skull and contacting a
capillary bed disposed in the cavity with the reflectance pulse
oximeter sensor. The method uses standard pulse oximeter sensor
probes placed over capillary beds close to a buccal surface,
posterior soft palate, hard palate or proximal posterior pharynx,
including the tongue, nares or cheek. Reflectance pulse oximetry at
these sites determines arterial oxygen saturation. One major
problem with this device is that it does not permit cross-site
comparisons of oxygen saturation values between several tissue
sites. In addition, the pulse oximeter device used in this
invention is an elongated tube that is inserted far into the nasal
or oral cavity down into the pharynx, which is a highly invasive
procedure.
[0017] U.S. Pat. No. 4,928,691, issued on May 29, 1990 to Nicolson
et al., and currently withdrawn, discloses a non-invasive,
electro-optical sensor probe and a method for its use. The sensor
is enabled to measure light extinction during transillumination of
a portion of blood-perfused tissue and to calculate the oxygen
saturation and pulse rate from changes in absorption of the light
detected. The sensor probe is placed at a central site such as the
tongue, cheek, gum or lip of the patient and provides continuous
assessment of arterial oxygen saturation and pulse rate. The sensor
is malleable and extremely flexible, and is stated to conform to
the structure of the skin and underlying tissue. U.S. Pat. No.
4,928,691 states that measurement at the preferred central sites
provide accurate oxygen saturation and pulse readings for "patients
with lowered or inconsistent peripheral perfusion." Critically, the
probes according to U.S. Pat. No. 4,928,691 are highly flexible,
leading to a high likelihood that upon typical movement of the
patient there would be mal-alignment between the light source(s)
and sensor, resulting in skewed, non-usable, or unreliable signals
and results. Also, there is no teaching or suggestion to compare
oxygen saturation values between several tissue sites to identify,
characterize, or monitor peripheral perfusion conditions in such
patients.
[0018] U.S. Pat. No. 5,218,962 was issued on Jun. 15, 1993 to
Mannheimer et al., teaches a pulse oximetry system which monitors
oxygen saturation and pulse rates by sensing the blood
characteristics at two or more peripheral sites. The device
includes one or more pulse oximetry probes which passes light
through unique regions of tissue and a sensor which detects the
amount of light passing through the tissue, and an instrument that
independently calculates oxygen saturation level within each
region. The difference in values represents how much the oxygen
saturation of the first region of tissue differs from the oxygen
saturation of the second region of tissue. When the difference
between the two values is below a set threshold, the '962 patent
attributes this to a sufficiently high probability that the value
is true, and displays an oxygen saturation value that is a function
of the two independent values. Where there is a difference greater
than a set threshold, no oxygen saturation value is displayed.
Thus, the '962 patent attributes substantial differences between
two sites to be due to error, rather than to an indication of a
problem with peripheral perfusion and/or resistance.
[0019] U.S. Pat. No. 5,335,659, issued on Aug. 9, 1994 to Pologe,
teaches a nasal septum probe for photoplethysmographic measurements
that clips onto a patient's nasal septum. Pulse oximetry is one of
the stated applications for the apparatus. Structurally, the
apparatus disclosed and claimed in the '659 patent has a body, or
housing, from which two probe arms extend, these arms being sized
to enter the nostrils of a nose. One arm bears at least two light
sources, and the other arm bears at least one light detector. The
probe apparatus securely grasps the nasal septum in such a way that
there is contact on both sides of the nasal septum at the same time
with both the light sources and the light detector. In all
embodiments, the light sources and the light detector actually
protrude from the main body of the respective probe arm, and are
positioned to exert pressure upon and indent the tissue of the
nasal septum. In some embodiments and all claims, a supply of gas
is also provided from a source through a support means and to the
nasal septum. However, the '659 patent does not disclose a nasal
pulse oximeter probe that does not need to press into the tissue of
the nasal septum in order to obtain reliable pulse oximetry data,
nor a probe that includes an angle, or bend, to reach a desired
highly vascular plexus on the septum.
[0020] U.S. Pat. No. 6,144,867, issued on Nov. 7, 2000 to Walker,
teaches a flexible pulse oximeter sensor assembly capable of
doubling over to surround a body part, such as an ear lobe, and
comprised of a flexible base having a hole passing through it, a
post preferably having a sharp tip, and a grommet. In use the
sensor assembly wraps around a body part, and the post, or pin,
passes through the body part to secure the probe to the body part.
The grommet frames the hole and engages and holds the post. The
patent discloses that body parts other than the ear lobe that may
be pierced by the post (and, presumably, therefore suitable as a
site for use of the sensor) include the webbing between the fingers
and toes, the tongue, the nose, eyebrows, cheek/lip, breast
nipples, and the foreskin.
[0021] WIPO Application No. WO0021435A1, to Barnett et al., was
published Apr. 20, 2000. This publication teaches a non-invasive
spectrophotometric examination and monitoring of blood metabolites
in multiple tissue regions on an ongoing and instantaneous basis.
The method includes attaching multiple sensors to a patient and
coupling each sensor to a control and processing station enabled to
analyze signals conveyed thereto. The control and processing
station visually displays the data from multiple sites for direct
mutual comparison of oxygen saturation values from multiple sites.
A key aspect of the invention is the use of a "near" and a "far"
(or "deep") detector at each detection site. Based on the
positioning of the light-generating devices and the near and far
sensors, the far sensor receives absorption signals from deeper
inside the brain tissue. In a basic configuration, the "near"
sensor, or detector, principally receives light from the source
whose mean path length is primarily confined to the layers of skin,
tissue, and skull, while the "far" detector which receives light
sprectra that have followed a longer mean path length and traversed
a substantial amount of brain tissue in addition to the bone and
tissue traversed by the "near" detector. Other configurations
indicate receptors receive signals from sources across the entire
brain cross-section. This is stated to provide information about,
by calculation differences, the condition of the deeper tissue, in
particular the brain. The method is directed to compare oxygen
saturation values for cerebral tissue, such as comparing the two
hemispheres during surgery. The WO0021435A1 invention distinguishes
itself from standard pulse oximetry of arteries close to the
surface of the body, and focuses primarily on analysis of deeper
tissues and organs. The application does not teach a method to
measure "surface" peripheral or central tissue sites for
development of information regarding perfusion status.
[0022] WIPO Application No. WO0154575A1, to Chen et al., was
published on Aug. 2, 2001. This publication teaches a non-invasive
apparatus and method for monitoring the blood pressure of a
subject. A monitor is used for continuous, non-invasive blood
pressure monitoring. The method includes using sensors to detect a
first blood pressure pulse signal at a first location on patient
and detecting a second blood pressure pulse signal at a second
location on the patient; measuring a time difference between
corresponding points on the first and second blood pressure pulse
signals; and, computing an estimated blood pressure from the time
difference. The first and second sensors are placed at locations
such as a finger, toe, wrist, earlobe, ankle, nose, lip, or any
other part of the body where blood vessels are close to the surface
of the skin of a patient where a blood pressure pulse wave can be
readily detected by the sensors, and/or where a pressure pulse wave
from the patient's heart takes a different amount of time to
propagate to the first location than to the second location.
[0023] In one regard, a superior monitor system would be able to
provide real-time continuous measurements of signals that would be
analyzed to provide arterial oxygen saturation, blood pressure, and
pulse rate. A superior monitor system would utilize at least two
pulse oximeter probes, one of which is placed at a highly perfused
central tissue, such as the lip, tongue, nares, cheek, and a second
probe placed at a typically less perfused areas such as a finger or
toe. Also, in some situations, a peripheral probe may be placed at
sites in or distal from areas that may be or are affected by
disease- or accident-related diminished blood perfusion to
tissues.
[0024] An additional aspect of a superior oximeter system provides
both an inflow means of oxygen or oxygen-rich gas to a patient in
need thereof, and an integral or adjoining pulse oximeter probe.
This aspect is in conjunction with the above-described two pulse
oximeter probe system, or in a system that only has one oximeter
probe. In either case, one pulse oximeter probe, positioned at the
nose or mouth, detects the levels of oxygenation saturation of
blood in the patient, and detection of low or lowering oxygenation
saturation levels results in one or more of: setting off a local or
remote alarm or message; increasing the flow of oxygen or
oxygen-rich gas to said patient. Likewise, detection of higher or
increasing oxygenation levels results in one or more of: setting
off a local or remote alarm or message; decreasing the flow of
oxygen or oxygen-rich gas to said patient. Preferably, the pulse
oximeter probe at the nose or mouth is integral with the delivery
means of the oxygen or oxygen-rich gas. Preferably, the control of
oxygenation levels is by signaling to (manually or automatically)
adjust a valving mechanism that controls output flow from a source
of auxiliary of oxygen or oxygen-rich gas. By such feedback
mechanism the quantity of oxygen or oxygen-rich gas is conserved,
and the needs of such patient are more closely attuned to the
fluctuations in oxygen demand during activities at varying levels
of exertion during a period of time.
[0025] As to references that pertain to the combining of a pulse
oximeter with a system to control the inflow of oxygen or other
oxygen-rich gas to a patient in need thereof, the following U.S.
patents, and references contained therein, are considered to
reflect the state of the current art: U.S. Pat. Nos. 4,889,116;
5,315,990; 5,365,922; 5,388,575; 6,371,114; and 6,512,938. None of
these references are specifically directed to a combined,
preferably integral combined pulse oximeter sensor/nasal cannula,
which, when combined with an oximeter, or with an oximeter that
controls the inflow of such oxygen or other oxygen-rich gas to the
patient, provide the advantages disclosed and claimed herein.
[0026] All patents, patent applications and publications
(scientific, lay or otherwise) discussed or cited herein are
incorporated by reference to the same extent as if each individual
patent, patent application or publication was specifically and
individually set forth in its entirety.
SUMMARY OF THE INVENTION
[0027] One aspect of the present invention relates to a novel
non-invasive vascular perfusion/resistance monitor system having at
least two pulse oximeter probes positioned at locations on the body
of a patient, the signals from which may be capable of indicating a
problem with peripheral perfusion and/or resistance. In practice
each probe emits at least two different light frequencies, such as
by light-generating diodes (LEDs), and such emitted light is
detected by at least one light detector, such as a photodiode
detector. A general-purpose computer or a special purpose computer
is employed to perform complex mathematical computations based,
typically, on the signal intensity and timing from the at least two
pulse oximeter probes, and on signals from the light detectors of
each of the probes. Proper analysis by software programming in such
general-purpose computer or special purpose computer outputs
results to a display, printer, etc. that suggests or indicates
(depending on relative differences in the signals at different
locations, and upon other conditions) whether a condition of
diminished or abnormal vascular perfusion/resistance may exist in a
selected body area. The system also monitors changes in such
conditions during treatment interventions.
[0028] In a preferred embodiment, software programming provides for
a signal to a user of the device to alert the user when signals
from a central or a non-central probe are of such low pulse
amplitude that either the probe needs repositioning or that the
patient is experiencing extremely low pulse at the probe site (and
is therefore in need of acute intervention). The software program
also converts the signals from the light detectors to calculate
various oxygen saturation values and various blood pressure values
(either simultaneously or separately). These values are used for
evaluating the vascular perfusion/resistance and/or blood pressure
of a patient based on the locations of the two or more probes.
[0029] Each probe is designed for monitoring blood oxygen
saturation and/or blood pressure at different vascular bed sites on
a patient. Critically, one of the at least two sites on a patient
is at what is designated a "central source" site ("CSS"). The
inventors have discovered that flow directed through the carotid
artery and detected at CSS sites, such as the lip, tongue, nasal
nares, and facial cheek, are typically strong and unaffected by
perfusion-lowering conditions. In patients who do not have
perfusion-lowering conditions, a second or third probe site at
"non-central" site (NCS), such as an extremity (i.e., fingers,
toes, etc.), provides oxygen saturation and pulse values fairly
comparable to values from the CSS. However, when a patient has a
perfusion-lowering condition, the probe site at an affected
extremity provides noticeably different oxygen saturation and pulse
values compared to the CSS values. The difference in saturation
values between the CSS and one or more sites is then used to assess
peripheral vascular resistance, perfusion and/or peripheral
vascular disease.
[0030] As used in this disclosure, when a particular wavelength or
band of wavelength is stated at which an LED or other
light-generating source emits light, it is understood that such
light-generating source may and probably does emit light across a
broader range. However, what is meant by such statement is that
such light-generating source is designed to emit at a frequency
curve which has a peak at or near such stated wavelength or band.
It is further understood that any known means of limiting
non-desired light energy, such as by selective filtration, may be
used in conjunction with such light-generating sources to improve
the accuracy and/or precision of the emissions of such
light-generating sources.
[0031] As used in this disclosure, a "pad" is meant to indicate a
housing, or an enclosure, over a light-generating or a
light-sensing device on the probe, which provides a barrier to
fluids, and permits transmission of light of the relevant
wavelengths to the present invention. A typical pad has a
composition of clear plastic.
[0032] As used in this disclosure, a "conductor" is meant to
indicate any physical pathway or any system that communicates a
signal or electricity from a first to a second location. Signals
and electricity can be conducted by conventional means, such as by
sending electrical impulses along a continuous copper wire, by more
sophisticated means, such as by converting the signals into radio
waves and transmitting these waves such that a receiver receives
the signals and thereafter sends them to the controller, or by any
other way now known or later developed.
[0033] As used in this disclosure, whether or not so stated in a
particular sentence, the term "oxygen" may be taken to mean "oxygen
or any oxygen-rich air or other gas mixture that contains oxygen"
which is used for provision of oxygen to a patient or to a person
in need thereof. The context of a particular usage in this
disclosure indicates whether this broader definition is to be used,
or whether a particular example is referring instead to the use of
pure oxygen exclusively.
[0034] While some researchers have attempted to gauge accuracy by
comparing the results from two different pulse oximeter probe sites
(see U.S. Pat. No. 5,218,962), and other researchers generally
recognized that "central" sites are generally more reliable and
responsive than "peripheral" sites (see U.S. Pat. Nos. 6,263,223,
and 4,928,691), the present invention recognizes the reasons for
the inconsistently different results between CSS and non-CSS sites.
Specifically, patients having compromised peripheral circulation
and/or resistance will tend to have lower peripheral values than
patients without such compromised conditions. By such recognition,
detection and monitoring impaired peripheral circulation is
possible through the present disclosure. The monitoring system of
the present invention, in certain embodiments, additionally
provides an indication of vascular resistance through continuous
monitoring of the transit time difference of the blood oxygen
saturation values and the blood pressure values between the two
sites.
[0035] It is an object of the present invention to provide a
monitoring system which includes two pulse oximeter sensors, or
probes, connected to a monitor system as a non-invasive means for
continuously measuring blood oxygen saturation values and/or blood
pressure and/or pulse values, wherein the system detects and
monitors changes in vascular perfusion and resistance in a patient.
The overall system particularly assesses differences in peripheral
blood flow which may be impaired in certain illnesses and accident
conditions.
[0036] Another object of the present invention is to provide probes
functionally constructed to provide more reliable signal reception
and transmission for patients, such as those in ICU, surgery,
post-operative care, and patients with respiratory, circulatory
problems, or under anesthetics. In particular, pulse oximeter
probes are configured to be placed, respectively, across the lip or
cheek, in the nostrils of the nose, and on the tongue.
[0037] Thus, one object of the invention is to provide a novel
configuration of an oximeter probe that is well-suited for
placement across the lip of the mouth of a patient, or the cheek of
a patient, in which one side of the probe is situated outside the
oral cavity and a second side is positioned inside the mouth
cavity, and the tissue between the two sides is assessed by
transillumination pulse oximetry. Another object of the invention
is to combine the probe for placement across the lip or cheek of
the present invention with sampling devices for capnography
sampling, either with or without a structure or assembly for the
supply of oxygen, as from a cannula. Another object of the
invention is to combine with the probe for placement across the lip
or cheek a disposable cover to slip over the probe.
[0038] Still another object of the present invention is to utilize
the photoplethysmographic data obtained from the probes of the
present invention for diagnosis and monitoring of clinical
conditions.
[0039] Another object of the invention is to provide a novel
configuration of an oximeter probe that is well-suited for
placement at the nasal cavity of a patient, in which one side of
the probe is situated to the left side of the nasal septum, and a
second side is positioned to the right side of the nasal septum,
and the tissue between the two sides is assessed by
transillumination pulse oximetry. This design, in a preferred
embodiment, also functions to provide oxygen to the patient through
channels provided in the structure of the probe. The embodiments of
the nasal probe of the present invention advance the art by
obtaining reliable and repeatable pulse oximetry and
plethysmography data from the interior nasal septum with the
extensions going into the nose being designed and spaced so as to
not press into the tissue of the septum. Further, the extensions of
the probe, where the light-generating and the light-detecting
components are positioned, do not simultaneously contact the
respective areas of mucosal tissue of the nasal septum. This
provides a more comfortable probe than the prior art that,
advantageously, does not impair blood flow in the vascular tissue
being evaluated, and does not harm that tissue as may occur from a
probe that exerts simultaneous pressure from both sides.
[0040] Another object of the invention is to combine the nasal
probe of the present invention with sampling devices for
capnography sampling, either with or without a structure or
assembly for the supply of oxygen, as from a cannula. Another
object of the invention is to provide a novel configuration of an
oximeter probe that is well-suited for placement on both sides of
either the right or the left nasal alar (i.e., the alar nari). One
side of the probe is situated to the outside of the nasal nari, and
a second side is positioned to the inside of the nasal nari, and
the tissue between the two sides is assessed by transillumination
pulse oximetry.
[0041] Another object of the invention is to provide a novel
configuration of an oximeter probe that is well-suited for
placement on the tongue of a patient, in which one part of the
probe is situated along one surface of the tongue, and an opposing
part is positioned in such a manner as to capture a section of the
tongue such that a transilluminable cross-section of tongue tissue
is held between the two probe parts, and the tongue tissue between
the two probe parts is assessed by transillumination pulse
oximetry.
[0042] It is another object of the present invention to provide
pulse oximeter probes dimensioned and configured to be expandable,
spring-loaded, and flat surfaced for utilizing measurements on
extremities and earlobes; buccal mucosal-buccal surface or dorsal
ventral portion of the tongue; and properly sized configurations
for the nasal alars (i.e., alar nares) and cheek and/or tongue for
critically ill, burned, or traumatized patients. A related object
is to provide a configuration for an oximeter probe that utilizes
two opposed, substantially flat probe surfaces that tend toward
each other, such as by spring tensioning.
[0043] It is a further object of the present invention to provide a
monitoring system that measures vascular resistance and/or
perfusion continuously to improve volume resuscitation and/or drug
therapy.
[0044] It is still a further object of the present invention to
provide a monitoring system that can be used as a multi-probe pulse
oximeter to monitor blood oxygen saturation differences, pulse
transit time differences, or blood pressure, or any combination
thereof.
[0045] It is still another further object of the present invention
to provide specifically constructed probes used to transmit and
receive the light to vascular bed sites that are not normally
available for use due to burns, trauma, and surgery on the
extremity.
[0046] It is still another further object of the present invention
to provide a monitoring system that is easily fabricated from low
cost material and is adaptable for use in an operating room,
intensive care unit, emergency room or other areas to treat
patients in need of hemodynamic monitoring.
[0047] Still another object of the present invention is to provide
a pulse oximeter probe and a supply of oxygen or oxygen-rich air,
in combination, and functioning in concert with each other and with
oximetry circuitry, such that the level and trend in blood oxygen
saturation are determined by the pulse oximeter and changes in
blood oxygen saturation direct a change (i.e., an increase or a
decrease) in the release of oxygen or oxygen-rich air to the
patient whose blood oxygen saturation is being measured. In one
type of control of the flow of oxygen or oxygen-rich air, an
electronic regulator is controlled by signals from a processor that
receives data from the pulse oximeter.
[0048] Thus, one particular object of the present invention is to
integrate a novel nasal pulse oximeter probe of the present
invention with a nasal cannula. Another particular object of the
present invention is to integrate a pulse oximeter probe with
either a self-container breath apparatus (SCBA) or with the
regulator of a self-contained underwater breathing apparatus
(SCUBA). Blood oxygen measurements obtained by the so integrated
pulse oximeter probe then are used to regulate the percentage
oxygen in the supply of gas to the user, and/or to regulate the
flow rate to the user upon inhalation. In the case of a SCBA
apparatus that is combined with a pulse oximeter probe and
oximeter, where that mask is worn in environments with toxic or
noxious atmospheres, a critical role of the sensor is to indicate
to the user when they are becoming hypoxemic, i.e. when there are
potentially dangerous gases leaking into the mask. In the case of a
SCUBA apparatus that is combined with a pulse oximeter probe and
oximeter, for any dive the oximeter can provide information related
to the formation of an air embolus. For deep dives, where specialty
mixed gases are used and oxygen concentration in such mixtures are
actually reduced from its concentration in air, the oximeter data
on blood oxygen saturation provides a warning of current or pending
hypoxemia. When further combined with a control to adjust the
relative concentration of oxygen to other gases, this device serves
to increase the relative oxygen concentration delivered to the
diver when the oximeter data trend so indicates the need.
[0049] Still another object of the present invention is to provide
a pulse oximeter probe and a supply of oxygen or oxygen-rich air,
in combination, and functioning in concert with each other and with
oximetry circuitry, such that the level and trend in blood oxygen
saturation are determined by the pulse oximeter and changes in
blood oxygen saturation that indicate a sufficient downtrend in the
blood oxygenation status results in a local or remote alarm to
alert the patient and/or others to the problem.
[0050] Still another object of the present invention is to utilize
the photoplethysmographic data obtained from the probes of the
present invention for diagnosis and monitoring of clinical
conditions.
[0051] The foregoing has outlined some of the more pertinent
objectives of the present invention. These objectives should be
construed to be merely illustrative of some of the more prominent
features and applications of the invention. Many other beneficial
results can be attained by applying the disclosed invention in a
different manner of modifying the invention as will be
described.
[0052] It is to be understood that the foregoing general
description and the following detailed description are exemplary
and explanatory only and are not to be viewed as being restrictive
of the present, as claimed. These and other objects, features and
advantages of the present invention will become apparent after a
review of the following detailed description of the disclosed
embodiments and the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0053] FIG. 1 illustrates a side view of a hook-shaped pulse
oximeter probe showing a preferred positioning of a LED pad having
two LED's and at least one photodiode detector according to the
present invention. This probe is configured for positioning across
the lip or cheek of a patient.
[0054] FIGS. 2A-C provide top, front, and cross-sectional views,
respectively, of a pulse oximeter probe for positioning in the
nares of a nose of a patient. Connecting wires are shown in
schematic format, not to scale. FIG. 2D provides an enlarged view
of one area of FIG. 2A. FIG. 2E provides a perspective view of a
protective sheath used to cover the pulse oximeter probe of this
figure. FIG. 2F provides a front view of an alternative embodiment
of a nasal probe with a widened area to accommodate the size of the
nasal columella. FIG. 2G provides a cross-sectional view of the
alternative embodiment of FIG. 2F.
[0055] FIG. 3A-B depicts a side view and a top view of a pulse
oximeter probe for positioning on the tongue of a patient.
[0056] FIG. 4 illustrates a perspective angled side view and an
exploded frontal cross-sectional side view of a flat surfaced,
elongated spring-loaded pulse oximeter probe showing the
configuration of the LED's and the photodiode detector according to
the present invention.
[0057] FIG. 5 illustrates an internal view of the pulse oximeter
sheath according to the present invention.
[0058] FIG. 6 illustrates a perspective angled side view of a flat
surfaced, elongated spring-loaded pulse oximeter probe showing the
features of the pulse oximeter sheath according to the present
invention.
[0059] FIG. 7 is a flow chart showing one method utilized by the
non-invasive vascular perfusion/resistance monitoring system to
measure oxygen saturation values according to the present
invention.
[0060] FIGS. 8A and 8B provide front and side views, respectively
of a novel combined nasal pulse oximeter probe/oxygen cannula.
[0061] FIG. 9A provides a side view of a typical self-contained
underwater breathing ("SCUBA") apparatus typical of the prior art
apparatuses. FIG. 9B provides a side view of a SCUBA apparatus of
the same configuration, with a cross-lip pulse oximeter sensor
added to this apparatus.
[0062] FIG. 10 provides a schematic flow diagram for control signal
transmission from a pulse oximeter sensor to a control circuit to
an oxygen control valve being controlled by data output from the
sensor, where the control valve regulates oxygen to a patient
wearing the sensor.
[0063] FIG. 11 provides a diagrammatic profile of a human subject
indicating the angle of the upper lip, and how this affects the
positioning of a nasal probe of the present invention.
[0064] FIGS. 12A-15B display data from a comparison of positions on
the nasal interior septum of one volunteer subject, indicating the
difference in signal strength and quality when the nasal probe is
positioned to obtain data through a vascularized plexus identified
as Kiesselbach's plexus.
[0065] FIGS. 16A-C display data from a volunteer subject in which
three pulse oximeter probes were evaluated and compared--one at the
nasal interior septum, one at the cheek/lip, and one at the
finger.
[0066] FIGS. 17A-C display data from three different volunteer
subjects, all of whom, during a surgical procedure, experienced
arrhythmias that were detected differentially by the three probes
being evaluated and compared (one at the nasal interior septum, one
at the cheek/lip, and one at the finger). FIG. 17D provides a
comparison of the three probes in their ability to detect a
dicrotic notch.
[0067] FIG. 18A-C displays data from a nasal probe on one volunteer
subject, where the position of the probe was adjusted to three
different positions. FIG. 18D depicts a side view sketch of a
profile of a subject with an alternative nasal probe design that
reaches to a desired location for obtaining data.
[0068] FIG. 19A is a plan/cut-away view of a nasal probe of the
present invention in combination with a known design of a
capnography sampling/oxygen supply device. FIG. 19B is a
perspective diagrammatic view of an embodiment, in place on a
subject, of the combination device depicted in FIG. 19A.
[0069] FIG. 20 is a side view of a lip/cheek in combination with a
design of a capnography sampling/oxygen supply device.
DETAILED DESCRIPTIONS OF EMBODIMENTS
[0070] The present invention discloses pulse oximeter probes for
use with pulse oximeter systems in general. The present invention
also discloses a novel non-invasive vascular perfusion and/or
resistance status monitor apparatus and methods of using the
same.
[0071] FIG. 1 illustrates a pulse oximeter probe, 10, of the
invention, that is configured for placement with a section of the
probe placed inside the mouth for measurement across the
vascularized tissue of the lip or cheek. The probe, 10, as depicted
in FIG. 1, is comprised of a frame that is generally hook-shaped,
having a longer proximal arm, 1, a curved bridging section, 2, and
a shorter distal arm, 3, the latter arm having a free end, 4, that
enters the mouth when in use. At least one portion of the proximal
arm, 1, is positioned at a specified distance, 5, from an opposing
portion of the distal arm, 2, to provide a distance between the
closest points of the two opposing arms, 6, that accommodates the
thicknesses of the lips and/or cheeks of a desired range of
patients. As shown in FIG. 1, the opposing portions of the proximal
arm, 1, and the distal arm, 2, that are the specified distance, 5,
represents most of the lengths of these arms. In other embodiments
of this probe, a smaller percentage of the total span of opposing
arm sections may be set to such specified distance.
[0072] The probe may be used once and disposed, or may be
repeatedly used on different patients. Preferably, the probe frame
is constructed of metals, plastics, and other materials subjectable
to repeated cleaning with standard antiseptic solutions, or
sterilizable by other means. A cable, 7, houses conductors (not
shown), such as but not limited to insulated electrical wires, that
connect operative components further in the probe, 10, with an
oximeter monitor (not shown). A boot, 8, connects the cable, 7, to
the proximal arm, 1, of the hook-shaped frame of the probe 10.
Preferably the cable, 7, is flexible. The boot, 8, primarily serves
to connect the cable, 7, with the frame, and secondarily to provide
a handle with which the patient or attendant grip the probe. In
other designs of the lip/cheek probe, a boot is not required where
a direct connection is made between the cable and the frame of the
probe.
[0073] In the embodiment depicted in FIG. 1, the probe 10 comprises
two LEDs 17 within an LED pad, 12, and one photodiode detector 15
within a photodetector pad, 14. These are the operative components
of the probe, 10, and are connected to a monitor system (not shown)
by conductors (not shown) to transmit electrical signals. It is
noted that although the two LEDs, 17, are shown as two physically
separate components in FIG. 1, when present on a circuit board,
typical LEDs are very small (about the size of a pencil point), yet
discrete components. Thus, the two LEDs alternately can be
represented as both being present on a single structure in other
figures.
[0074] Each probe 10 is sized appropriately to be placed with the
open end, 4, inside a patient's mouth, so that the distance, 6,
between the LED pad, 12, and the photodetector pad, 14, conforms to
the thickness of the lip or cheek vascular bed of the patient. It
is noted that FIG. 1 is not accurately drawn to scale, and given
the true small size of the pads 12 and 14, the actual difference
between the distances 5 and 6 is less than about 0.5 inches. In
practice, one probe 10P (not shown) is sized for the average
pediatric patient, age 6-12, and another probe 10A (not shown) is
sized for the average adult patient.
[0075] The embodiment depicted in FIG. 1 has the light-sensing
device, such as the photodiode detector, 15, positioned in the
mouth, on the side with the open end, 4, as shown in FIG. 1. Having
the light-sensing device on the inside side of the cheek or lip
minimizes erroneous readings due to interference from ambient light
sources. Such light sources are much more likely to affect a
light-sensing source that is positioned on the outside side of the
cheek or lip. However, having the light-sensing source positioned
on the outside side of the cheek or lip is within the scope of the
invention.
[0076] Individual conductors provide electrical signals that power
the LEDs 17. Other conductors carry signals from the photodetector,
15. Optionally, other sensors, such as for temperature, may be
added to the probe, 10, and have individual conductors for them
also passing in the cable, 4, to the frame of the probe, 10. The
probe, 10, is used to generate data used to calculate oxygen
saturation, pulse shape, blood pressure measurement (by measurement
of pulse transit time to a second site), and any combination of
these.
[0077] The bridging section, 2, flexes to permit conformance to a
range of tissue thicknesses greater than the nominal unflexed
spans, as depicted by distances 5 and 6. The probe in FIG. 1
preferably is constructed of materials, such as nylon plastic, that
impart a resiliency such that after bending, the probe returns
substantially to its original shape. This resiliency allows the
angular and dimensional relationships between the light-generating
sources and the opposingly placed light detector to remain
substantially consistent. Thus, the material for one embodiment of
the probe has a degree of flexibility, and the material has
sufficient memory to substantially return to its original shape
after a normal flexion. This allows for standard use that may
involve placement across lip and cheek tissue sections having
different thicknesses, and movement across a thicker tissue section
to ultimate placement at a thinner section.
[0078] For instance, in one embodiment of this configuration, the
body of the probe, 10, is made of nylon plastic. The flexibility of
the bridging section, 2, the proximal arm, 1, and the distal arm,
3, is such that less than 5 grams of force deflects the open end,
4, in one direction or the other (toward or away from the opposing
section) by about 1/16 inch. The force required increases
logarithmically, such that to move the open end, 4, outwardly 0.25
inch required between about 1,250 to 1,550 grams of force, and the
force required to move the open end, 4, inwardly (toward the
opposing section) required between about 2,200 to 2,700 grams of
force. After such forces the nylon material demonstrated memory,
returning to within 1/16 inch of the original position, thus
demonstrating a resilient quality to the structure of the
probe.
[0079] In addition, the material of each of the LED pad, 12, and
the photodetector pad, 14, deflects upon application of pressure
from adjacent tissue by up to about 0.050 inch. Thus, the overall
flexibility is sufficient to accommodate a wide range of sizes of
cheek and lip sections, which the axis of light transmission from
the LEDs is reliably aligned to the photodiode or other light
sensor. While not being bound to a particular theory, it is
believed that maintaining appropriately narrow alignment of these
elements improves the reliability, precision and accuracy of the
signals from the probe.
[0080] More flexible probes are alternate embodiments of the
present invention. For instance, the structural material and
thickness is adjustable such that only between about 150 to 1,250
grams of force moves the open end, 4, outwardly 0.25 inch, and
between about 200 to 2,200 grams of force the force moves the open
end, 4, inwardly (toward the opposing section).
[0081] Less flexible probes also are alternate embodiments of the
present invention. For instance, the structural material and
thickness is adjustable such that between about 1,550 to 3,500
grams of force moves the open end, 4, outwardly 0.25 inch, and
between about 2,700 to 5,000 grams of force the force moves the
open end, 4, inwardly (toward the opposing section). Alternately,
in a more rigid probe, the structural material and thickness is
adjustable such that between about 3,500 to 5,500 grams of force
moves the open end, 4, outwardly 0.25 inch, and between about 5,000
to 8,000 grams of force the force moves the open end, 4, inwardly
(toward the opposing section). Such probes are made of metals or
polymer composite materials. The resiliency is expected to vary
inversely, roughly, with the flexibility of probes of such
alternative embodiments.
[0082] Although in FIG. 1 the bridging section, 2, is curved, other
embodiments of this lip/cheek probe may have a bridging section of
any shape and angle, so long as it spans a distance and connects
the opposing sides upon which the operative components of the probe
are placed. Further, as to all lip/cheek probes of the present
invention, it is noted that the dimensions, materials and
structures of such probes provide for maintaining a desired
position on the lip or cheek of a patient, such that the insertion
of a post, or pin, through the lip or cheek, so as to retain such
desired position of the respective probe, is not required.
[0083] FIG. 2A-D illustrates a second pulse oximeter probe, 50, of
the invention, that is configured for placement inside the nostrils
of the nose for measurement across the vascularized tissue of the
nasal septum. The nasal septum generally is defined as the bone and
cartilage partition between the nasal cavities, or the dividing
wall that runs down the middle of the nose so that there are
normally two sides to the nose, each ending in a nostril. As used
herein, the term nasal septum is comprised of at least two parts. A
columella nasi ("exterior septum" or "columella") is defined as the
fleshy lower margin (termination) of the nasal septum at the
opening of the nose (i.e., the nostrils or nares). A more interior
part, broadly termed herein the "interior septum," extends
interiorly from the columella and is comprised of the cartilaginous
and bony part of the septum. Along this interior part of the nasal
septum is found the vascularized tissue of the nasal septum,
including certain highly vascularized areas. In most noses, the
columella, or exterior septum, is the widest part of the nasal
septum.
[0084] FIG. 2A is a top view, FIG. 2B is a side view, and FIG. 2C
shows two cut-away views from a single mid-section line viewing
opposite ends of the probe. From a main section, 52, of a resilient
plastic housing, extend two extensions, 54 and 56, that are sized
to enter the nares of the nose in similar fashion to a nasal
cannula oxygen supply. These extensions, 54 and 56, are flattened
in one dimension, as depicted in FIGS. 2A and 2B, and are shown
angled at about 60 degrees in a second dimension, as viewed in FIG.
2C. This angle of inflection, 70, is properly drawn from a line
drawn from one edge of the main section, 52. As discussed in
greater detail below, the 60 degrees as depicted is not within the
preferred range.
[0085] In specific embodiments depicted herein, two general
approaches are used to protect the components of the pulse oximeter
probe, 50, from moisture and contamination. Other approaches, as
known in the art of medical device construction, also may be used.
First, a clear plastic covering, shown as 61 in FIGS. 2A and 2B,
and better viewed in FIGS. 2C and 2D, is placed over, to cover,
each distal half of the two extensions, 54 and 56. It is noted that
in the embodiment shown, the molded outer shell, 69, that forms and
covers the main section, 52, also covers the approximately proximal
half of the two extensions, 54 and 56, and the outer side of the
upper, or distal halves of these extensions, but does not cover the
front and rear sides, nor the inner sides, 65, of these extensions.
To cover these exposed sides, a clear plastic covering, 61, is
constructed, fitted over, and adhered to the existing components to
form an integral protective exterior surface with the molded outer
shell, 69. This is viewable in FIGS. 2C and 2D. Such plastic
covering, 61, typically is manufactured by heat sealing pre-cut
and/or pre-formed pieces, such as a cylinder or tube of heat-shrink
plastic, to form a fitted covering over the distal halves of
extensions 54 and 56. Then this is shrink-wrapped over the
components of the distal half of the two extensions, 54 and 56. In
the present embodiment, as depicted in FIG. 2A-D, after
heat-shrinking a cylinder of heat-shrink plastic, 61, over each of
the two extensions, 54 and 56, the distal end of this plastic is
glued together to forms an end, 61E, over the distal end of each of
the two extensions, 54 and 56. These ends, 61E, are viewed in FIG.
2C.
[0086] Also, typically these pieces of heat-shrink wrap plastic,
61, are sized and positioned to extend onto the approximate bottom
half of two extensions, 54 and 56, by about 1/16 inch, to form an
integral seal against moisture (this overlap is shown at arrow X in
FIGS. 2C and 2D). (It is noted that neither these nor other figures
are drawn to scale, nor do they provide consistent proportions from
figure to figure). In particular, FIGS. 2C and 2D show that a
plastic cover, 61, is fitted over each of the circuit boards, 63,
that contain the LEDs 62 and 64, located on extension 54, and the
photodetector, 66, located on extension 56 (see FIG. 2C for details
of LEDs 62 and 64, and photodetector 66). The plastic covers, 61,
preferably do not interfere with light transmission in the critical
wavelength ranges of the LEDs 62 and 64. Apart from heat-shrink
sealing, other means of attaching the plastic covers, 61, to the
extensions 54 and 56, include, but are not limited to, sonic
welding, spot gluing, hot gluing, press fitting, and other such
methods of attachment, as are employed in the art, that are used to
attach components of a medical device for entry into an orifice of
a living subject. Also, other means of providing a protective
covering, such as are known to those skilled in the art, may be
used instead of the above-described approach.
[0087] The above-described first protective approach is sufficient
to prevent moisture and contamination of the components within the
distal halves of the two extensions, 54 and 56. A second approach,
which is an optional and not required for the operation of the
pulse oximeter probe, 50, provides additional protection to this
and other parts of the pulse oximeter probe, 50. This is shown in
FIG. 2E. A protective sheath, 75, of clear plastic, is dimensioned
to slip over the entire two extensions, 54 and 56, and then has
flaps, 76, that loosely cover the main section, 52. The protective
sheets are manufactured and priced so as to be disposable, so that
after each use by a patient the protective sheath, 75, is slipped
off the pulse oximeter probe, 50, and disposed of. Then the
exterior surfaces of the pulse oximeter probe, 50, are wiped with
alcohol or other suitable disinfectant. Then, prior to the next
use, a new protective sheath, 75, is slipped over the indicated
parts of the pulse oximeter probe, 50. Alternatively, the
protective sheath, 75, is made of a material that will withstand
repeated rigorous disinfection procedures (such as steam
autoclaving) without deformation or degradation, such as is known
in the art, and such protective sheathes are used on numerous
patients, with a disinfection process conducted between each
use.
[0088] In certain embodiments, the two extensions, 54 and 56, are
spaced apart from one another so that, upon insertion into the
nostrils of a patient, the inner sides, 65 of the extensions, 54
and 56, fit snugly against the tissue of each side of the septum,
to avoid interference from ambient lighting.
[0089] Moreover, in certain embodiments, the relationship between
the inner sides, 65, and the adjacent tissue of the interior septum
is described as A non-contiguous fit as to the interior septum
wall, such that, even considering irregularities of the nasal
interior septum surface and patient movement, the inner sides, 65,
do not make contact with the nasal interior septum mucosal tissue
for most, or for all, depending on the patient, of the length of
the respective extension's insertion into the nasal passage.
[0090] More particularly, a non-contiguously-fitting probe (such as
50, and its extensions, 54 and 56) is sized and constructed so that
when placed into a nose size for which it designed (i.e., adult
size, etc.), there is not a pressing or a continuous contact
against the mucosal tissue of the interior nasal septum by both
extensions where are positioned the light-generating components
(such as LEDs 62 and 64) and the light detecting component(s) (such
as photodetector 66). This contrasts with prior art that is
disclosed to provide a continuous, even if light, pressure upon
both sides of the interior nasal septum mucosal tissue, and/or that
clips the probe against the mucosal tissue of the interior septum.
Also, as to construction compared with the latter prior art
example, the dimensions, materials and assembly of the present
invention are such that there is not imparted to the two
extensions, 54 and 56, an inward-flexing compressive force that
causes attachment (as contrasted with incidental and/or partial
contact) of the two extensions, 54 and 56, to the mucosal tissue of
the nasal interior septum. Even more particularly, in part to avoid
the possibility of irritation of the mucosal tissue of the interior
septum walls, further, in certain embodiments, the entire surface
of the inner sides, 65, from the inner faces, 67 (of the molded
outer shell, 69) to the distal end of each extension, is planar and
without any protruding areas, sections or components.
[0091] As to an example of the relative sizing between the
thickness of the nasal interior septum and the span, 70, between
the inner sides, 65, of opposing extensions, 54 and 56, FIG. 2D
provides a diagrammatic representation. For an adult-sized nasal
probe of this configuration, the span, 70, is 0.360 inches (9.1 mm)
between the inner faces of extensions, 54 and 56. This is uniform
inward, to and including where the LEDs 62 and 64 of extension 54,
lie opposite the photodetector 66, of extension 56. Measurements of
the interior septa of a number of adults with a caliper provides an
average of about 0.250 inches septum thickness. The difference
between 0.360 and 0.250 inches provides a sufficient gap to allow
for the presence of deviated septa. Also, it has been found that
this gap of 0.360 inches is sufficiently narrow so as to not allow
ambient light, under normal circumstances, to impair the overall
functioning of the pulse oximeter probe. Thus, for a typical
adult-sized nasal probe of the present invention, a space of about
0.065 inches on each side, between the surface of the inner face,
67, and the mucosal tissue of the nasal interior septum has been
found to provide a "non-contiguous fit."
[0092] Further, in certain embodiments of the present invention,
the space between inner sides, 65, of opposing extensions 54 and
56, where the light-generating and the light-detecting components
are positioned, for adult-sized probes, is between about 0.300 and
0.420 inches. In other embodiments, for such adult-sized probes,
the space is between about 0.330 and 0.390 inches. In other
embodiments, for such adult-sized probes, the space is between
about 0.350 and 0.370 inches. Corresponding size ranges are within
the skill of the art to determine for pediatric-sized nasal pulse
oximeter probes comprising a non-contiguous fit, based on the
measured thickness of the nasal interior septum for such pediatric
patients, and the range of spacing given factors of comfort and
probable incidence of ambient light interference (recognizing, for
instance, that neonates have greater light transmission through
their tissues).
[0093] In certain embodiments support for the distal ends of the
inner sides, 65, generally is through contact with columella. This
fleshy tissue extends laterally, to various extents in different
individuals, from a plane generally defined by the surface of the
more interior mucosal lining of the interior septum. The columella
is less sensitive and less subject to damage by direct contact than
that more interior mucosal lining of the interior septum. Thus, in
embodiments such as that depicted in FIG. 2A-D, having
substantially parallel inner sides, 65, when opposing parts of the
respective inner sides, 65, fit snugly against the columella (i.e.,
the inner faces, 67, of the molded outer shell, 69), this helps
position the more distal sections of the extensions to minimize or
prevent continuous contact between these more distal sections and
the interior septum mucosal lining. Also, when a particular
patient's columella is being compressed by both inner faces, 67,
this results in less pressure by any incidental contact by a more
distal section of one or the other extension against the interior
nasal septum mucosal lining. Without being bound to a theory, it is
believed this is because the more outward section of that extension
is in contact with and is being partially supported by the
columella. Based on such analysis, contact of the nasal probe
extensions, on one or both of the columellae, is less damaging to
the patient than prior art devices that actually clamp to the more
interior mucosal lining of the nasal interior septum.
[0094] Thus, when the extensions 154 and 156 fit snugly against the
columella, and are not found uncomfortable over time by the user,
this comprises one example of a good fit. Further, such bracing
contact with tissue of the columella is not mutually exclusive with
the fit described as non-contiguous. That is, in many uses, the
same embodiment both contacts the columella with its extensions
and, more interiorly, there is not a pressing or a continuous
contact against the mucosal tissue of the interior nasal septum by
both extensions where are positioned the light-generating
components (such as LEDs 62 and 64) and the light detecting
component(s) (such as photodetector 66). More broadly speaking, the
same embodiment may both 1) provide a beneficial fit against the
columella and 2) provide a non-contiguous fit more interiorly.
[0095] However, it has been observed that certain larger
columellae, in certain patients, deviate outward the extensions of
the nasal probe such that the distal ends of the two extensions,
respectively bearing the light-generating and the light-detecting
components, are positioned an undesirably long distance from each
other. To deal with this, in other certain embodiments, each of the
inner faces of the extensions comprise a deviation in the shape of
the extension to allow for a relatively larger-sized columella.
This is advantageous for persons having large columellae, so that
their columellae do not force the extensions to spread outwardly to
an undesirable distance from the interior nasal septum. In such
embodiments, depending on the sizing of the nasal probe (see below)
and the size of the patient's nose and columella, there might be no
contact with the columella, in which case the support for the
weight of the extensions is on the part(s) of the probe main
section that is in contact with the upper lip. Where, given the
respective sizes of probe and columella, there is contact, with
such accommodation for the columella the spreading of the ends of
the extensions is less than it would be otherwise.
[0096] FIG. 2F provides a side view, comparable with the view of
FIG. 2B, of one embodiment of the nasal probes of the present
invention that comprises a deviation in the shape of the extensions
to allow for a relatively larger-sized columella. For an
adult-sized nasal probe of this configuration, the maximum span,
110, is 0.500 inches (12.7 mm) between the inner faces of
extensions 54 and 56. This is where the nasal probe main section,
52, and the two extensions, 54 and 56, meet, and the wider span is
generally aligned to accommodate the width of the columella upon
insertion of the nasal probe to its operational position. Further
distal on the two extensions, 54 and 56, where the inner sides, 65,
are shown in substantially parallel orientation, are found the LEDs
62 and 64 of extension 54 positioned opposite the photodetector 66,
of extension 56. Along this substantially parallel length the span
between the inner sides, 65, is 0.360 inches. This is shown as gap
70. Although this columella-widened embodiment in FIG. 2F is shown
without a cannula, and without means for sampling exhaled gas for
capnography, embodiments of nasal probes with such capabilities and
features (discussed, infra) also may have a columella-widened
aspect such as depicted in FIG. 2F.
[0097] FIG. 2G provides a cut-away view of FIG. 2F, showing a
conduit, 82, within which are electrically conductive wires (or
other types of signal transmission means, such as fiberoptic cable)
to pass electrical signals to and from the two light-emitting
diodes, 62 and 64, and the opposing photodetector, 166. Also
apparent is the angle, or inward inflection, of the substantially
parallel lengths of the two extensions, 54 and 56. A bend such as
this, as discussed herein, achieves placement of the two
light-emitting diodes, 62 and 64, and the opposing photodetector,
166, adjacent to a vascularized region of the nasal septum that
advantageously provides superior pulse oximetry data.
[0098] Further, it is recognized that the flexibility of the nasal
probe main section, 52, and the two extensions, 54 and 56, are
important in achieving the operational performance of the nasal
probes of the present invention. One nasal probe has been
constructed with TPE plastic and had a measured flexibility of 60
durometer units. Another nasal probe, also made with TPE plastic,
was manufactured and had a measured flexibility of 87 durometer
units. In general, with regard to the plastic used for nasal probe
main section, 52, and the two extensions, 54 and 56, the preferred
range for plastic flexibility is between about 60 and about 90
durometer units.
[0099] Per the above, the distance between the probe extensions in
relation to the average dimensions of the septa of the target
patient group is one factor that provides for a suitable
non-contiguous fit to obtain good pulse oximetry data without
undesirable patient discomfort and/or tissue damage that results
from a direct clipping of the probe extensions (arms) to the
mucosal tissue of the nasal septum. Critical to this approach is
not designing nor operating the nasal probe to applying pressure
to, attach to, or clamp on to, the nasal mucosal tissue where the
pulse oximeter readings are being taken. It has been noted that
practitioners in the field have expressed the need to, and have
practiced, applying pressure to a probe in order to stabilize the
probe. While this may be required in finger or other extremity
probes, this is contraindicated when considering the delicate
mucosal tissue that lines the septum. Thus, in the present
invention, the nasal probes, in their sizing, material selection,
and overall design, are such that they perform to obtain pulse
oximetry data by passing light through the nasal septum, and the
probes do this without applying pressure to the nasal septum from
both sides at the same time. That is, if any incidental contact is
made to the actual nasal mucosal tissue from one extension, where
either the light-generating or the light-detecting component is
positioned, the other such area (where the light-generating or the
light-detecting component is positioned) on the other extension is
not then in contact with the opposing side of the nasal septum
mucosal tissue.
[0100] In summary, the nasal pulse oximeter probes of the present
invention are designed, sized and constructed to direct light
against sensitive and highly vascularized mucosal tissue of the
nasal septum without pressing against such tissue from both sides
simultaneously, and to provide for long-term use with minimal
irritation or tissue necrosis.
[0101] Another aspect of certain embodiments of the present
invention is that the light-generating and the light-detecting
components do not protrude from the respective planes of the inner
faces of their respective extensions. This is consistent with the
teaching of the present invention that there is neither a need nor
a desire to press into the mucosal tissue of the nasal septum at
the site adjacent to these components. In most embodiments, these
components are positioned on respective diode pads. These pads are
placed within the respective extensions, and as a result, in
certain embodiments, are recessed within the respective
extensions.
[0102] Further as to the specific construction of the embodiment
depicted in FIG. 2A-D, using the shrink-wrapping construction
described above to cover the distal halves of the extensions 54 and
56, and dimensioning the spacing between the extensions 54 and 56,
so as to fit snugly against the tissue of each side of the septum,
these are found to fit without irritation, as from a rough or
uneven surface. For example, without being limiting, when using
heat sealing plastic as the covering, 61, the thickness of this
material, and any finish on the adjoining edge, will affect the
extent of a sensible ridge at the junction of the covering, 61, and
the molded outer shell, 69.
[0103] As to the specific area of the nasal septum that is
preferred for use of a nasal pulse oximeter probe such as the one
depicted in FIGS. 2A-D, it has been learned that the area of the
nasal interior septum closest to the face (e.g., the proximal area
of the middle alar), is more consistently vascularized and thereby
provides more consistent and reliable signals than the areas more
distal, i.e., the interior septum closer to the point of the nose.
In particular, and more specifically, a highly vascularized region
of the septum known alternately as Kiesselbach's plexus and
Little's area, is a preferred target area for detection of blood
oxygen saturation levels by a nasal pulse oximeter probe of the
present invention. In the particular device shown in FIGS. 2A-D, an
angle of inflection, 70, is shown between plastic housing, 52, and
the two extensions, 54 and 56. This angle properly is measured as
an interior (proximal) deviation from a straight line extended from
the plastic housing, 52. In preferred embodiments, the angle of
inflection, 70, is between about 0 and about 33 degrees, in more
preferred embodiments, the angle of inflection, 70, is between
about 10 and about 27 degrees, and in even more preferred
embodiments, the angle of inflection, 70, is between about 10 and
about 20 degrees. In FIG. 8B, the angle, 70, is about 15 degrees.
This angle has been found to provide superior results in testing.
Therefore, the angle shown in FIG. 2C, namely 60 degrees, is not a
preferred angle of inflection.
[0104] Thus, in general, the two extensions, 54 and 56, are angled
so that upon insertion and proper placement into position in the
nostrils, the LEDs 62 and 64, located on extension 54, emit light
directed through a region that includes the preferred, proximal
area of the nasal septum. Most preferably, the LEDs 62 and 64,
located on extension 54, directed light exclusively through the
highly vascularized region of the septum known alternately as
Kiesselbach's plexus and Little's area.
[0105] In addition, a stabilizer, 58, embodied in FIG. 1 as a flat
plate flush with and extending downward from the inside edge of the
lower plane of the extensions 54 and 56 (before the extensions
angle inward, see FIG. 2C), is designed to press against the area
between the upper lip and nose to hold the desired position of the
probe, 50, and in particular the LEDs 62 and 64, in relation to
preferred, proximal area of the nasal septum. The stabilizer, 58,
alternately previously considered part of a preferred embodiment
but not a necessary component, and, on later testing, to irritate
many users, is now considered to be valuable when properly oriented
in relation to other components of the probe, 50. Additional means
of stabilizing the probe, 50, such as elastic straps from any part
of the device that span the head of the patient, may be employed
with or separately from the stabilizer, 58. Thus, in preferred
embodiments, no stabilizer, 58, is used, and the design of the
device, as shown in other figures provided herein, with or without
additional stabilizing means, are adequate to stabilize the probe,
50, during normal wear.
[0106] As for the probe described above in FIG. 1, timed electrical
impulses from a pulse oximeter monitor system pass through two
wires (not shown) in cables 61R and/or 61L to produce the light
from LEDs 62 and 64. At least one photodetector, 66, is positioned
on extension 56 to face and oppose LEDs 62 and 64 of extension 54.
The photodetector 66, which typically is a light-sensing
photodiode, detects changes in the light emitted by the LEDs 62 and
64 as that light is differentially absorbed between and during
pulses across the capillaries of the septum tissue between the two
extensions, 54 and 56. In one embodiment, LED 62 emits light around
650-670 nm, and LED 64 emits light around 880-940 nm. The
electrical impulses are timed to be offset from one another. The
photodetector, 66, detects the light passing through the septum of
the nose, which is situated between extensions 54 and 56 when the
probe 50 is in use. As discussed above, loss of signal through
vascularized tissue such as the nasal septum is due both to
background tissue absorption and the absorption by the blood in the
arteries, which expands during a pulse. The signals from
photodetector 66 pass through conductors (not shown) to the
processor of the monitor system (not shown). The "signal" as used
here, is meant to indicate the signal from a photodetector
receiving light from one or more light sources of the pulse
oximeter probe, which provides information about differential
absorption of the light during different parts of the pulse. These
signals are to be distinguished in this disclosure from signals
(electrical impulses) that are sent to the light sources to emit
light, and from control signals that are sent, in certain
embodiments, to control a valve to supply more or less gas to a
system.
[0107] Cables 61R and 61L preferably form a loop that may lie above
the ears of the patient, and join to form a single cable (not
shown). This single cable preferably terminates in an electrical
plug suited for insertion into a matching socket in the pulse
oximeter monitor system (not shown). In another preferred
embodiment, the single cable terminates by connecting to an adapter
cable, which in turn connects to a socket in the pulse oximeter
monitor system (not shown). In a typical application, the signals
from the light-sensing photodetector, 66, are ultimately received
and processed by a general purpose computer or special purpose
computer of the monitor system (not shown). As used herein, the
terms "monitor system" and "monitoring system," may refer to the
component that receives data signals from one or more probes, that
is, the component that comprises the general or specific-purpose
computer that analyzes those data signals (i.e., the processor).
This may be a stand-alone unit (i.e., a console or, simply, pulse
oximeter), or a module that transmits data to a central system,
such as a nurse's station. However, depending on the context, the
terms "monitor system" and "monitoring system" also may encompass
the entire assemblage of components, including such component and
the one or more probes and the conductors (i.e., connecting wiring)
that transmit data and control signals.
[0108] Also, it has been learned that a nasal probe, such as 50 in
FIG. 2A-D, fits better and is found more comfortable by a patient
when the cables are glued to the main section, 52, of the body of
the probe, 50, in the following way. This method takes advantage of
the natural bend in cable (and tubing) that comes from the rolled
storage of such material on a spool. That is, wire, cable, tubing
and the like that are rolled onto spools have a natural bend
imparted thereby. It has been learned that if this bend is
disregarded when assembling the cable sections to the main section,
52, then, for many nasal probes assembled with cables that go over
the ears when in use, the probe, 50, and particularly its
extensions, 54 and 56, will have a tendency to rotate axially (in
relation to the cable crossing the lip laterally) outward or
inward. This leads to discomfort, effort to readjust, and, at
times, poor data acquisition. To solve this problem, a section of
cable long enough for both sides of the probe is cut and placed
unobstructed on a flat surface. The natural bend from the spool
configures this section in a curvilinear shape, typically nearly
forming a circle. The two ends of this section of cable are
inserted into the respective holes for these in the molded flexible
plastic that comprises the main section, 52, of the probe, 50 (an
arrow in FIG. 2E points to a hole filled by a cable). The
contiguous extensions 54 and 56 (typically part of the same molded
piece as the main body, 52), are positioned flatly against the flat
surface, so the desired inward inflection (i.e., of 15 degrees) is
directed toward that flat surface, and preferably so the most
inward points of the extensions 54 and 56 (i.e., those that will be
farthest in the nose when in operational position) contact the flat
surface. In this position, the cables are adhered or otherwise
secured to the main section, 52, of the probe, 50. Typically, this
is done by application of a liquid adhesive to the holes where the
cable ends enter the main section, 52 (i.e., see arrow in FIG. 2E).
The cable then is cut to provide two lengths, each one attached to
one side of the main section, 52.
[0109] When this method is practiced, due to the natural bend of
the rolled cable (or tubing), the resultant cables 61R and 61L,
when placed over the ears, tend to gently orient the probe
extensions, 52 and 54, axially inward, toward a desired
vascularized part of the nasal septum. As such, comfortable nasal
probes are produced, and the probes are more easily adjusted to
desired positions. Also, it has been observed that probes made this
way more generally maintain their desired positions, and this is
believed due to there being no undesirable countervailing force
(i.e., the rotational force of some cables not assembled per this
method) against whatever means are used to keep the probes in
place.
[0110] Further with regard to embodiments of the nasal probe that
provide a non-contiguous fit when inserted into a nose of a
patient, use of such probes thusly to obtain photoplethysmographic
data unexpectedly provides superior results in comparison to prior
art methods that simultaneously press (albeit lightly) both sides
of the interior nasal septum, or, more severely, that grasp the
nasal septum in such a way that there is contact on both sides of
the nasal septum at the same time with both the light sources and
the light detector. That is, an improved method for obtaining pulse
oximetry and other photoplethysmographic data is described as
follows:
[0111] a) Through size estimation of the nasal septum to be used
for data collection, providing a nasal probe for insertion around
the septum such that said probe non-contiguously fits said
septum;
[0112] b) Inserting one extension of the nasal probe into each of
the two nostrils of a patient, wherein one extension comprises at
least two light-generating components that emit light at at least
two different wavelength bands, and the other extension comprises
at least one light-detecting component that detects light
transmitted from said at least two light-generating components;
and
[0113] c) Measuring, selectively, pulse oximetry and/or other
photoplethysmographic properties of the blood flow in vascularized
interior septum tissue positioned between said at least two
light-generating components and said at least one light-detecting
component;
[0114] d) Wherein said blood flow is not dampened by a simultaneous
pressing of said tissue from both sides at the point of measurement
of said data.
[0115] Among other benefits, the data taken from the less dampened
(compared to finger probes) vascularized tissue of the interior
nasal septum provides more distinct signals having clearer
information about cardiovascular parameters.
[0116] Further, it is noted that such method optionally
additionally includes locating a desired highly vascularized
arterial plexus, such as Kiesselbach's plexus, for the point of
measurement, such as by using perfusion index locating means,
detection by lower LED power requirement, or other means known in
the art.
[0117] Further with regard to embodiments of the lip/cheek probes,
use of such probes to obtain photoplethysmographic data provides
superior results. That is, an improved method for obtaining pulse
oximetry and other photoplethysmographic data is described as
follows:
[0118] a) Through size estimation of the thickness of the lip or
cheek to be used for data collection, providing a lip/cheek probe
dimensioned for insertion around the lip or cheek so as to not
squeeze the tissue, to avoid constriction of blood vessels therein
(such constriction measurable by comparative data with probes
having different distances between the pads);
[0119] b) Placing the distal arm of said probe into the mouth to a
desired position; and
[0120] c) Measuring, selectively, pulse oximetry and/or other
photoplethysmographic properties of the blood flow in vascularized
tissue positioned between said at least two light-generating
components and said at least one light-detecting component.
[0121] In particular, it is noted that the probe, after initial
placement to a desired position, is adjusted to a more desired
position providing a good signal. This is done such as by comparing
signals from the different possible positions. Thereafter the cable
leading from the probe (which typically is placed over the top of
one ear) is taped to the outside cheek to stabilize and maintain
this selected position. It has been found that a desired
positioning often is with the bridging section, 2, of the probe
positioned in or near one corner of the mouth, with the cable
leading over one ear. In such positioning the light-generating and
the light-detecting components are positioned around an area of the
cheek a distance from the corner of the mouth. It is noted that the
lip/cheek probe has been found to function consistently, without
interference from movement of the mouth, in patients who are under
anesthesia or on sedating medications. This is not meant to be
limiting, as other uses are considered appropriate, taking into
account, as needed, a possible effect of mouth movement and
resultant interference of signals during periods of such
movement.
[0122] In a variation of the nasal probe, such as is exemplified in
one embodiment in FIG. 2A-D, oxygen is delivered with the same
device that also measures trans-septum arterial oxygen saturation
(see FIG. 8A, B). In another variation, the pulse oximeter sensor
is independent of an oxygen cannula, and is a single-use unit. In
yet another variation, the pulse oximeter sensor is independent of
an oxygen cannula, and is re-usable and readily cleanable with
appropriate antiseptic cleaning agents. Other variations within the
scope of the invention described and pictured can be developed by
those of ordinary skill in the art.
[0123] FIG. 3 illustrates a third pulse oximeter probe, 100, of the
invention, that is configured for placement on the tongue of a
patient for measurement across the vascularized tissue of the
tongue. The probe, 100, has two substantially flat opposing arms,
104 and 106. A housing cover, 105, is joined with a housing base,
107, to form each of the two arms, 104 and 106. At one end of each
of the two arms, 104 and 106, are finger pads, 108 and 110, which
in the embodiment shown in FIG. 3 are on the housing covers, 105,
and possess ridges, 111, to improve the grip.
[0124] The arms, 104 and 106, are tensioned to close against one
another by a spring (not shown) which has a fulcrum at or near an
axle, 109, that hingedly connects the two arms, 104 and 106, near
one end. At or near the other end is an LED pad, 112, on one arm,
104. Within this pad, 112, are two light generating sources, here
shown as LEDs 114 and 115. Opposite this housing, 112, on arm 106,
is a photodetector pad, 116. Within this pad, 116, is at least one
photodetector, 118. Electrical wire conductors (not shown) connect
the LEDs, 114 and 115, and the photodetector, 118, to a pulse
oximeter monitor system (not shown), via a cable, 120, passing from
one end of the arm, 104. The inner surfaces of the arms, 104 and
106, in some variations of this probe are knobby or otherwise
textured, especially around the LED pad, 112, and the photodetector
pad, 116. This texturing is designed to better maintain a stable
position of the probe, 100, on the tongue without use of excessive
pressure of the spring.
[0125] The photodetector 118, which typically is a light-sensing
photodiode, detects changes in the light emitted by the LEDs 114
and 115 as that light is differentially absorbed between and during
pulses across the capillaries of the tongue tissue between the two
arms, 104 and 106. In one embodiment, LED 114 emits light around
650-670 nm, and LED 115 emits light around 880-940 nm. The
electrical impulses are timed to be offset from one another. The
photodetector, 118, detects the light passing through the tongue
which is situated between the first housing, 112, and the second
housing, 116 of arms 104 and 106 when the probe 100 is in use. As
discussed above, loss of signal through vascularized tissue such as
the tongue is due both to background tissue absorption and the
absorption by the blood in the arteries, which expands during a
pulse. The signals from photodetector 118 pass through conductors
(not shown) housed in cable 120 to the processor of the monitor
system (not shown). Cable 120 preferably terminates in an
electrical plug suited for insertion into a matching socket in the
pulse oximeter monitor system (not shown). In another preferred
embodiment, cable 120 terminates by connecting to an adapter cable,
which in turn connects to a socket in the pulse oximeter monitor
system (not shown). In a typical application, the signals from the
light-sensing photodetector, 118, are ultimately received and
processed by a general purpose computer or special purpose computer
of the monitor system (not shown).
[0126] There are numerous means for hingedly joining the first arm
and the second arm other than by an axle passing through the
extensions of each arm (e.g., by axle 109). Other means include
hinges of various materials and designs as known in the art,
co-fabrication of the arms with a thinner section of flexible
plastic between the two arms at one end, and pins, screws, and
other fasteners as are known to those skilled in the art.
[0127] Similarly, means for tensioning the first arm and the second
arm, so as to properly maintain tension on a section of the tongue
of a patient, can be effectuated by means other than the spring
described above. Separate elastic bands may be attached or may
surround the arms, such as by attaching to protrusions spaced
appropriately along the arms. Also, the natural flexibility and
resilience of a co-fabricated structure comprising both arms
connected by a section of resilient plastic can provide both the
means for hinging and the means for tensioning. Such fabrications
may be deemed suitable for disposable units.
[0128] It is noted that for this and other probes disclosed herein,
a single source generating at least two different light frequencies
may be utilized instead of LEDs. Alternately, more than two LEDs
may be used, such as to generate light at more than two frequency
bands, for instance to increase accuracy and/or detect other forms
of hemoglobin. Also, light receiving sensors, or photodetectors,
other than photodiodes may be used, and more than one such sensor
may be used in a single probe.
[0129] The pulse oximeter probes, such as 10, 50, and 100 as
depicted and as used with the monitoring systems in the present
invention, take measurements by transillumination as opposed to
reflectance. This is the preferred configuration. However, for any
of these probes, both the light-generating devices, and the
photodetector devices, can be configured adjacent to one another,
on one arm or extension, to measure reflectance of the tissue on
the interior of the mouth (e.g., the cheek), the lip, the nasal
septum, or the tongue.
[0130] FIG. 4 depicts another general configuration of an oximeter
probe of the present invention. This probe 10 can be dimensioned
and configured to be expandable and tensioned to close by a spring,
18. Near the distal, operative end of one substantially flattened
side, 20, is an LED array, 16, and opposing it near the distal,
operative end of the opposing substantially flattened side, 21, is
a light detecting sensor, preferably a photodiode, 15. A cable, 4,
connects the LED array, 16, and light detecting sensor to a pulse
oximeter monitor system (shown in the magnified end view)). This
pulse oximetry probe can be used to measure pulse-based differences
in light absorbence across vascularized tissue of a patient in a
number of locations, including but not limited to the cheek, the
lip, the nasal alars (alar nari), the nasal septum, fingers, and
toes.
[0131] By "substantially flattened" is meant that the height of the
structure of a side is small relative to the greater of the length
or width of that side. Preferably the ratio of the height to the
greater of the length or width of a "substantially flattened" side
is between about 0.2:1 and 0.001:1, more preferably this ratio is
between about 0.02:1 and 0.005:1, and yet more preferably this
ratio is between about 0.01:1 and 0.005:1. For greater
applicability to typical physical requirements in use, each side
also is substantially longer than wide. By "substantially longer
than wide" is meant that the width of the structure of a side is
small relative to the length of that side. Preferably the ratio of
the width to the length of a side described as "substantially
longer than wide" is between about 0.7:1 and 0.02:1, more
preferably this ratio is between about 0.025:1 and 0.05:1, and yet
more preferably this ratio is between about 0.025:1 and 0.1:1. At a
minimum, with regard to nasal pulse oximeter probes of the present
invention, the key functional attributes of extensions that are
substantially flattened and/or substantially wide, as used herein,
is that the width of such extensions is sufficient to house the
components (i.e., circuit boards bearing LEDs and photodetectors,
or the LEDs and photodetectors themselves), and the length of such
extension is sufficiently long to provide the LEDs and
photodetectors on opposite sides of a desired region of
vascularized tissue. The same functional logic applies to other
sensors disclosed and claimed herein.
[0132] Also, it is noted that in place of the spring, 18, any
hinging means as known in the art can be used. Such hinging means
may include a raised section along or separate from the sides, such
that a fixed space is created at the point of the hinging means.
This would obviate the need for a bend in the sides at the spring,
18, as shown in FIG. 4 (which is required in FIG. 4 to lever open
the operative ends). These substantially flattened probes are
configured such that the inner faces of both sides substantially
oppose each other and, based on the spacing and configuration of
the hinging means, are sufficiently separable to widen to encompass
a desired tissue to be monitored for blood oxygen saturation
between the light emitting structure and the light detecting
structure at the operative end. It is noted that these structure
may each be enclosed in a pad, or may not be so enclosed. As for
other probes disclosed herein, a monitoring system connected to the
probe modulates light signal production and receives signals of
light detected by at least one light-detecting structure positioned
at the operative end of one of the sides, such as 20 or 21 in FIG.
4. Typically a pulse oximeter or photoplethysmography monitoring
system console includes, or can be connected to, a video monitor
that provides graphical and numerical output from the signals
received from the photodetector, which are algorithmically
processed by a special-purpose (or general-purpose) computing
component in the monitoring system console.
[0133] Also, the above substantially flattened sides with hinging
means may be produced without light-emitting and light-detecting
structures, and sleeves, such as described below, bearing such
structures, would then be slipped over the sides to yield an
operable oximeter probe. For instance, as shown in FIGS. 4 and 6, a
probe 10 with a flat surface 20 is suitable for to receive a
flexible sleeve, 22, that bears an LED array, 16, and light
detecting sensor, preferably a photodiode, 15. This slips over the
flat-surfaced structure, as shown about halfway on in FIG. 6. As
for the probe in FIG. 4, a cable, 4, connects the LED array, 16,
and light detecting sensor to a pulse oximeter monitor system (not
shown).
[0134] In operation, the devices depicted in FIGS. 4-6 are placed
around a finger, earlobe, or other extremity in order to obtain
data.
[0135] Thus, another aspect of the present invention is a
disposable sleeve that fits over any of the pulse oximeter probes
disclosed and claimed herein, and over conventional probes. A
sleeve is constructed of a flexible material, and is relatively
thin, in the general range of 0.005 to 0.050 inches thick, more
preferably in the range of 0.010 to 0.025 inches thick, and most
preferably in the range of 0.010 to 0.015 inches thick. The sleeve
is manufactured to slide over the major structural features of the
probe to provide a barrier to reduce the chance of contamination
from one patient to a second patient using the same probe. An
example of such sleeve is shown in FIG. 5, and its implementation
over a probe is shown in FIG. 6. In this case the sleeve is
constructed to include the light generating and the light sensing
features, and associated conductors. However, in other embodiments
of the sleeve, such features are on the major structural features,
whether frames, arms, etc., and the sleeve slides over such
features, and at least in the areas of such light producing and
light sensing features the sleeve is highly transparent to the
critical wavelengths used by the pulse oximeter. The sleeves cover
both arms, or extensions, of probes having two distinct arms.
Preferably a continuously integral section of the sleeve joins the
sleeve sections that cover both arms or extensions of the probe, in
order to, inter alia, protect the intervening parts of the probe.
For a probe such as the probe of FIG. 1, the sleeve is configured
to the shape of the probe and slides over starting at the end, 4,
of the arm, 3, and covers up to, and preferably including, the
boot, 8.
[0136] In some sleeve embodiments, a stretchable aspect of one or
more parts, or of the entire sleeve, stretches over a protuberance
or other prominence at one or more parts of the major structural
features over which the sleeve is sliding, and improves the fit of
the sleeve. This also better assures that the sleeve does not slide
off the probe during normal uses. Alternate means to secure the
sleeve onto the probe such as are known to those of skill in the
art may be used. The sleeves themselves can be disposable; however,
the sleeves also can be made of easily sterilizable materials and
be sterilized between uses.
[0137] The probes and the sleeve covers of the present invention
are supplied as clean or as sterile, depending on the needs of the
end user and the budgetary constraints of the end user. Clean but
not sterile probes and sleeves will be less expensive, and may be
suitable for many applications. Where there is an elevated risk of
major harm from an infection, for instance in immunocompromised
patients undergoing transplants with immunosuppressive drugs or
undergoing chemotherapy, sterile probes would be more appropriate
than merely clean probes. Many configurations of the probes are
cleanable using alcohol and/or detergent/disinfectant solutions,
and other configurations are disposable.
[0138] All of the above disclosed probes operate in a typical
manner of a pulse oximeter, as described herein and in articles and
patents cited and incorporated by reference. Each LED emits its
specific frequency hundreds of times per second, and the absorption
(or transmittance) readings by a sensor, such as a photodiode, are
transmitted to a computer. There a software system performs
averaging (optionally deleting outliers), and by differences in
wavelengths' absorption or transmittance at the pulse peaks,
determines arterial oxygen saturation. In a standard two-LED
system, this is done by an algorithm that calculates the ratio of
the peak absorbence at 650-670 nm divided by the base absorbence at
this wavelength range, and compares this ratio to the peak
absorbence at 880-940 nm to the base absorbence at the 880-940 nm
range. The base absorbence reflects the non-pulse background
absorbence by tissues other than the artery at maximum width during
the pulse. This calculation provides an estimate of arterial oxygen
saturation. A graph of the pulse surge, or shape, over time, also
can be obtained.
[0139] All of the above-disclosed probes are expected to have
significant use in the intensive care units, operating rooms,
post-surgery recovery rooms, and in ambulance related situations
where a patient in need of monitoring has few suitable monitoring
sites. The size and shape of each probe will depend on whether the
patient is an adult or child.
[0140] When two or more probes are used together, data from
multiple probes is processed to provide continuous and simultaneous
cross-site comparisons of the arterial blood oxygen saturation
status at and comparisons between two or more tissue sites (and, as
desired, blood pressure estimates based on transit time differences
and/or other related parameters). The monitoring system receiving
these signals includes at least one program containing computer
software (not shown) comprising instructions which causes the
computer processor to receive and calculate various oxygen
saturation values. Optionally, the monitoring system may receive
signals from separate probes or sensors to assess blood pressure
values, which optionally may be compared (either simultaneously or
separately) with blood pressure estimates based on signals received
from each of the probes determining arterial blood oxygen
saturation and vascular perfusion/resistance of a patient.
Depending upon the software used, and the addition of separate
blood pressure probes or sensors, the monitor may be used as a dual
pulse oximeter, a saturation difference monitor, a transit time
monitor, a periodic blood pressure monitor, or a noninvasive
continuous blood pressure monitor. Specific examples are provided
below that demonstrate a non-exclusive range of applications for
the monitoring system which compares signals from a central source
site (CSS) with signals from at least one advantageously positioned
peripheral site (PS), as those terms are defined herein.
[0141] FIG. 7 depicts the steps of a basic method using the monitor
system that includes one probe positioned in a CSS, and one probe
in a PS. A first pulse oximeter probe is removably affixed to a CSS
in the head of the patient. This is most preferably any of the
specially configured probes, or could be a conventional probe. A
second pulse oximeter probe is removably affixed to a PS such as a
finger or a toe. This can be any of the specially configured
probes, or a conventional probe. The monitoring system is started,
the LEDs or other light generating sources in the probes emit
designated light at designated frequencies and periodicities, and
signals from the CSS and from the PS are measured and transmitted
to the monitoring system computer. Here, adjacent signals of the
same type (wavelength and probe) are averaged to obtain a
statistically reliable average. As appropriate based on the
software program, certain outliers as may be caused by movement of
the patient, light contamination from an outside source, etc., are
eliminated from consideration. The averaging is repeated and the
averaged values are compared based on the time sequencing of the
respective averages. That is, average values from a specific time
from the CSS probe are compared to average values from the same
time span from the PS probe. The software calculates arterial blood
oxygen saturation percentages based on the differential absorption
of the different species of hemoglobin, and percent oxygen
saturation at the CSS and the PS are compared. Based on criteria
input into the monitoring system and reflected in the software's
calculations, the presence or absence of impaired peripheral
perfusion are shown as an output reading of the monitoring system.
Alternatively, if impaired perfusion has already been established,
the tracking of time-based changes in the saturation differences
between the CSS and the PS are read out or charted.
[0142] The method shown in FIG. 7 is conducted with an apparatus
having the stated functional capabilities. Also, an oximeter
monitoring system has the basic physical components that perform
the required centralized functions, and which is attached to at
least two oximeter probes to perform the above-described
method.
[0143] Further, a variation of the method of FIG. 7 is to have an
additional PS probe, and compare not only the first PS probe to the
CSS probe, but to also compare the first and second PS probes'
signals to one another. This can, for instance, demonstrate
impaired peripheral perfusion in one body area, but not in another
body area or extremity.
[0144] The apparatuses, methods and systems of the present
invention can be applied to both humans and animals, i.e., to
living vertebrate organisms. Its application in human medicine
(adult & pediatrics) would significantly improve the estimation
of vascular perfusion or resistance by pulse oximetry; however,
veterinary medicine also would greatly benefit from its use. This
superior monitoring system would utilize at least two pulse
oximeter probes, one of which is designed for use with a highly
perfused central tissue, such as a lip, tongue, nares, cheek; and
the other probe is designed for use to less perfused areas such as
peripheral tissues, or any combination thereof.
[0145] The following specific examples are meant to be
demonstrative, but not limiting, of the possible applications of
the present invention.
Example 1
[0146] Data from a small number of volunteer subjects was obtained.
This data provided preliminary support for the hypothesis that
differences in CSS and PS estimates of arterial blood oxygen
saturation levels can provide diagnostic information about the
status of peripheral blood circulation. These data are summarized
below.
[0147] All sets of data were taken three times, except that data
for subjects 1 and 9 were only taken two times (duplicate data
sets). Subjects 1-3 had no history of chronic obstructive pulmonary
disease or other conditions that would be expected to cause lowered
peripheral circulation. Except for one reading of 93% for subject
1, all estimates of arterial oxygen saturation were 95% or higher,
and the PS (a finger, using a standard commercial probe) readings
were within two percentage points of either CSS sites (lip and
cheek). For the data set in which subject 1's cheek probe reading
was 93%, the lip reading was 98% and the finger reading was 96%.
Overall, the data of subjects 1-3 suggest that in a healthy subject
the CSS and PS readings taken at or near the same time will be
relatively close, within about 5 percentage points or less, and all
of the readings will be high.
[0148] Subject 4 had average readings at the PS finger site of 89%,
and at the CSS cheek site, 88.7%, so these sites has essentially
identical estimates. No signal was recorded at the lip CSS.
Although there was no difference between the CSS cheek and the PS
readings, the oxygen estimate was low and indicated a generalized
problem.
[0149] Subject 5 had a PS average of 85%; the lip CSS average was
88.3%, and the cheek CSS average was 91.3%. The absolute levels are
low, and the difference between CSS and PS values ranges from about
3 for the lip to about 6 for the cheek. This appears to suggest a
peripheral circulation problem, and the low absolute levels
indicate a generalized problem with oxygenation. This subject was
known to have COPD.
[0150] Subjects 6-8 were known to have COPD. The average values for
finger, lip and cheek were 85, 90, and 89, respectively for Subject
6. The 4-5% less percent saturation for the peripheral site
supports the present hypothesis. Subject 7's finger data varied
between 77-80% during the readings, and is considered unreliable.
One of subject 8's data points for the finger was 79%, whereas the
other two were 85%. This suggests that the 79% reading is
erroneous. Disregarding this data point, Subject 8 had 85%, 87.3%,
and 85.6% averages for the finger, lip and cheek sites,
respectively. Here, all readings are fairly close, and the absolute
values are alarmingly low. The data from this subject do not
support the hypothesis; however the circulation for this subject
may not be impaired peripherally. Further investigation can resolve
this and other points.
[0151] Regarding the latter, subject 11's data was anomalous in
that the finger site averaged 93.3%, whereas the lip and cheek
sites averaged 90.7% and 86.7%, respectively. The reason for this
is unknown; the data could be spurious or could indicate unusual
circulation in a small percentage of the population. Individual
differences in circulatory systems (based in part on genetics, and
in part on non-genetically based embryological development, and on
physical conditioning) may form the basis for such anomalies in a
percentage of the population. Highly variable and incomplete data
for Subjects 9 and 10 were considered to render the value of their
data questionable, and those data were not analyzed.
[0152] Thus, this preliminary data provided some indication of
differences between CSS and PS and differences between normal and
circulation-compromised subjects. The data also supported the need
to investigate broader populations with known circulatory
conditions to develop more predictive guidelines for the probe data
differences. Even with the limited data of this example, it is
apparent that the comparison of CSS and PS sites can provide a
useful assessment of the state of the circulatory system even where
there is no major difference, and there is not a disease state
presenting itself. That is, such results of roughly equivalent CSS
and PS data at a high oxygen saturation level would support a
conclusion that the peripheral circulation is not impaired.
Example 2
[0153] An elderly patient with relatively advanced diabetes comes
in for monitoring of the status of perfusion in the right leg,
which is diagnosed with severe atherosclerosis and related impaired
vascular perfusion. A monitor of the present invention is utilized,
with one CSS probe measuring signals across the nasal septum, and a
PS probe on the large toe of the right foot. A new medication is
started, and ongoing weekly data from the monitor tracks the
changes in perfusion in the right leg by comparing oxygen
saturation values of the CSS probe with the values of the PS probe.
Such data indicates the degree of effectiveness of the new
medication.
Example 3
[0154] A critically burned patient is brought into an emergency
room. As vital signs and assessment is taking place, a pulse
oximeter probe as shown in FIG. 1 is placed into the patient's
mouth to read cheek tissue as a central site source, and a pulse
oximeter probe as shown in FIG. 4 is placed at each of the
patient's large toes. Within less than one minute, the monitor of
the present invention indicates below normal blood perfusion in the
right leg, based on the signals from the probe placed on the right
toe, compared to the central source site and the left toe probe. A
probe is placed on a right finger, and this provides comparable
data to the left toe. The attending physician is able to surmise
that an injury or disease condition is adversely affecting
perfusion in the right leg, orders more detailed testing, and
increases the percent oxygen on the respirator to counter the low
oxygen in the affected leg. The monitoring system tracks changes in
the oxygen saturation values of blood in the right toe as this
initial treatment has an effect.
Example 4
[0155] A patient suspected of having Chronic Pulmonary Obstructive
Disease is admitted to an emergency room with breathing
difficulties. The patient also reports pain in both legs after
involved in a minor traffic accident, which is the immediate cause
of admission. Minor bruising is apparent on the front of the left
leg. Along with other tests and monitoring, a pulse oximeter
monitor of the present invention is utilized, with on CSS probe on
the nares of the nose, and a PS probe on the large toe of each of
both feet. Alarmingly, the CSS probe estimates that the arterial
oxygen saturation at the CSS site is below about 85 percent,
indicating hypoxia. The pulse oximeter monitor in both PS sites
estimates even lower oxygen saturation, by about 5 percent,
compared to the CSS site. There is no response to bronchodilator
therapy, and the chest x-ray shows moderate fibrosis, and no
attenuated vessels or hyperinflation. The initial diagnosis, aided
by the pulse oximetry data, is bronchial COPD. Oxygen therapy is
provided, and the pulse oximetry data is utilized to monitor
increases in blood oxygen saturation both at the CSS and PS
sites.
[0156] It is noted that the following paragraphs, through and
including Example 5, describe embodiments of the present invention
which combine, preferably integrally, a pulse oximeter probe with a
nasal cannula through which is delivered a supply of oxygen or
oxygen-rich air. In some of these embodiments, the combined pulse
oximeter sensor/nasal cannula with oximeter is used to monitor and
provide information regarding the oxygen saturation status, using
data obtained from the sensor through the tissue of the nasal
septum, to the user of the device, to caretakers of that user,
and/or to a remote station that utilizes the information. For
instance, the user can view current and/or historical trend data
and manually adjust the flow rate of the oxygen or oxygen-rich air
accordingly. Alternately, a user of said combined pulse oximeter
sensor/nasal cannula with oximeter, in advance of a period of
expected increased exertion, may increase the flow rate of his/her
auxiliary oxygen supply. Then, during such exertion, such user
refers to the oximeter data output and further adjusts the flow
rate as needed to attain or remain within a desired range of blood
oxygen saturation as indicated by the data output from the
oximeter.
[0157] In other embodiments, the combined pulse oximeter
sensor/nasal cannula is used in further combination with a central
processing unit that sends signals to automatically adjust the flow
rate of the oxygen or oxygen-rich air to the use. For instance, and
not to be limiting, during more strenuous exertion, arterial blood
oxygen saturation of a person needing oxygen supplementation
therapy is expected to decline appreciably. In such circumstance,
this drop in oxygen saturation is detected by the pulse oximeter
probe, the trend data is analyzed by a program in the central
processing unit, and a signal is sent to a valving mechanism that
results in a greater oxygen flow directed through the user's
cannula. A feedback loop, the data from the nasal pulse oximeter
going to the central processing unit monitoring system,
subsequently decreases the flow when the data indicates arterial
blood oxygen saturation has exceeded a designated percentage. By
such feedback loop approach, the oxygen delivered via the nasal
cannula is better optimized for actual physical exertion and/or
changing metabolic requirements.
[0158] In other embodiments, which are preferred in certain
applications, the use of data from the nasal pulse oximeter to
regulate oxygen flow to the nasal cannula is combined with other
approaches to conserve oxygen, which include, but are not limited
to:
[0159] 1. detection of the inhalation phase of the respiration
cycle to provide the oxygen (or oxygen-enriched gas) only during
inhalation (or a key segment of the inhalation, i.e., the initial
2/3 of the inhalation);
[0160] 2. providing oxygen every other breath; and
[0161] 3. providing greater volume and/or flow rate at key part(s)
of inhalation cycle (i.e., increased "shot size").
[0162] In yet other embodiments, which are preferred in certain
applications, the data from the nasal pulse oximeter is combined
with data collection of other parameters. For instance, in studying
sleep disorders, a number of parameters are measured, for instance,
pattern or dynamics of respiration (flow rate, inhale/exhale over
time cycles), pulse rate, etc. In embodiments of the present
invention, the use of the combined nasal pulse oximeter probe is
combined with other monitoring sensors at the nose that detect, for
instance, but not to be limiting, air flow and air pressure, such
as during sleep, to analyze an individual's sleep disorder, such as
sleep apnea.
[0163] Thus, when blood saturation information from the so-combined
pulse oximeter probe is processed over time, and when trends are
detected in the oximeter probe data processor that indicate a need
for more or for less oxygen to the patient, based on, respectively,
lower or higher blood oxygen saturation readings than a desired
range, one or more outcomes result. As noted above, one outcome is
to automatically adjust the supply of oxygen or oxygen-rich air to
provide a needed increase (if readings were trending lower) or a
decrease (if readings were trending higher, above a desired range,
and conservation of the supply were desired) of that supply.
Another outcome is to provide an alarm signal (audible, flashing,
etc.) locally, for recognition by the patient or a nearby
attendant. Yet another possible outcome is to provide a remote
alarm, such as by cellular telephone transmission, to a physician's
office, an ambulance service or hospital, etc.
[0164] Further, it is noted that there exist in presently used
devices other approaches to conserving the supply of oxygen or
oxygen-rich air. One commonly used approach, often referred to a
the "pulse-dose" system, delivers oxygen to the patient by
detecting the patient's inspiratory effort and providing gas flow
during the initial portion of inspiration. This method is reported
to reduce the amount of oxygen needed by 50 to 85% (compared to
continuous flow) and significantly reduces the cost, the supplies
needed, and the limitations on mobility caused by a limited oxygen
supply.
[0165] For example, as the patient initiates a breath, the cannula
tip senses the flow, a solenoid valve opens, and a burst of oxygen
is rapidly delivered to the patient. The size of the burst or flow
varies among different manufacturers. Commonly, the pulsed-dose
system takes the place of a flow meter during oxygen therapy and is
attached to a 50 PSIG gas source. In most devices the patient or
operator can choose the gas flow rate and the mode of operation
(either pulse or continuous flow). Typically, a battery-powered
fluidic valve is attached to a gaseous or liquid oxygen supply to
operate the system.
[0166] In addition, other approaches are used to further reduce
oxygen usage when using the pulse-demand system. One such approach
is to reduce the dose of oxygen delivered to the patient during
each pulsation. Another approach, in combination or independently
of the last one, is to deliver a burst only on the second or third
breath instead of every breath. In addition, the size of the oxygen
pulse dose will change with the flow setting with increases in flow
delivering larger doses of oxygen and vice versa.
[0167] It is noted that potential problems encountered when using
the pulse-demand system include: no oxygen flow from the device;
and decreased oxygen saturations in the patient. If no oxygen flow
is detected, then possible causes include a depletion of the gas
supply, an obstruction or disconnection of the connecting tubing,
or, critically for a pulse-demand system, an inability of the
device to detect the patient's effort to breath. If the device
cannot detect the patient's inspiratory effort, the sensitivity
will need to be increased or the nasal cannula will need to be
repositioned in the nares.
[0168] A decrease in the patient's oxygen saturation should always
be a cause for alarm and may indicate a change in the patient's
medical status, tachypnea, or a failure in the device. In any case,
a backup system should be available in order to verify whether the
problem is with the device or with the patient.
[0169] Thus, although in common use, the limitations of many
pulse-dose systems are: relatively high cost of the system;
technical problems may be associated with such a complicated device
(including disconnections, improper placement of the device, and a
possible device failure); lack of accommodation for an increased
need during exercise, stress, illness, etc. and variable operation
of the device if not properly set up.
[0170] Variations on the pulse-dose system include delivering
oxygen to the patient at the leading edge of inspiration. This
allows oxygen to be supplied exactly when needed. Thus, when the
patient inhales, a relatively higher quantity of oxygen is
delivered for travel deep into the lungs, increasing the
probability of greater utilization and uptake in the red blood
cells in the person's bloodstream. Other variations on the
pulse-dose system are known in the art.
[0171] The present invention is used independently of the
pulse-dose system, or, alternatively, in conjunction with such
system, to conserve the supply of oxygen or oxygen-rich gas, and to
better adjust the supply to the actual demands of the patient/user
as that person's physical activities and demands vary over time. In
particularly preferred embodiments, the pulse oximeter probe that
is in combination with an outlet (e.g., the end of a cannula) of
the supply of oxygen or oxygen-rich gas is fashioned to be integral
with, or securely fastened to, that outlet. This provides greater
surety of signals and proper insertion of the outlet. For instance,
when the pulse oximeter probe is integral with the nasal cannula,
if the probe and device are accidentally moved from their proper
location (e.g., entrance of nose, or mouth), then the oximeter
readings (including pulse) will deviate sharply from normal. In
such instance an alarm can be quickly sounded and the problem
rapidly corrected. Thus, this provides a distinct advantage in
comparison to peripheral probes, such as finger or toe probes.
[0172] Another aspect of the present invention is adding as an
additional sensor a capnography sensor (such as an infrared sensor)
to estimate the concentration of carbon dioxide in the exhaled
breath. This may be useful to detect more rapidly than pulse
oximetry the failure of ventilation means (such as the wrong gas
being provided to the patent), or carbon dioxide poisoning.
Regarding the latter, the article entitled "Management of carbon
monoxide poisoning using oxygen therapy" by T W L Mak, C W Kam, J P
S Lai and C M C Tang, in Hong Kong Medicine Journal, Vol. 6, No. 1,
March 2000 is instructive.
[0173] Also, as to the detection of a failure of ventilation means,
when the present invention's combined nasal pulse oximeter
sensor/cannula is attached to a pulse oximeter that is programmed
to distinguish normal from abnormal pulse ranges, and when the
combined nasal pulse oximeter sensor/cannula falls away from the
user's nose (e.g., by accident during sleep or sedation, etc.), an
alarm can be quickly provided based on the lack of pulse in the
proper range. In this way the combined nasal pulse oximeter
sensor/cannula more rapidly detects a loss of supplemental oxygen
more rapidly than typical capnography detectors as to this reason
for loss of ventilation.
[0174] Thus, the following examples are to be understood to be
usable independently or in combination with the above described
other approaches to conserving the supply of oxygen or oxygen-rich
gas, and/or with other approaches known in the art but not
described above, including those referred to in references cited
herein.
Example 5
[0175] FIG. 8 depicts one embodiment of a nasal oximeter probe,
such as depicted in FIGS. 2A-D, in which the oximeter function and
hardware are combined and integral with a cannula to supply oxygen
(or oxygen-rich air or other gas mixture) to via the nostrils of
the patient. The device, 150, shown in FIGS. 8A, B is but one
specific embodiment of a range of designs and combinations that
include a pulse oximeter probe in combination with an outlet for
oxygen or oxygen-rich gas to a person in need thereof. For
instance, while in the present example a cannula (defined as "a
tube for insertion into body cavities and ducts, as for drainage")
is used within the nasal oximeter probe to conduct oxygen-rich air
or other gas mixture into the nostrils of a patient, any of a range
of different conduits can serve this purpose. As one example, not
meant to be limiting, a passage can be formed by molding such
passages within the structure of the nasal oximeter. Such passages
themselves can serve to conduct oxygen-rich air or other gas
mixture into the nostrils of a patient. Alternately, these passages
can be sized and configured to allow cannula tubing to be inserted
through such passages, to provide for relatively easy assembly with
standard cannula tubing which is common with standard regulators
and tanks Thus, the term "passage" is taken to mean any physical
structure, now or later known to those of skill in the art, that
provides for the physical containment of a gas that is being
directed through such structure. Common forms of passages include
cannula tubing, standard plastic tubing, and the continuous voids
in a molded nasal pulse oximeter through which a gas may pass
without loss from seams, etc. in the voids.
[0176] FIG. 8A is a front view, and FIG. 8B is a side view of the
combined, or integral, nasal probe/cannula, 150. From a resilient
plastic housing, here depicted as comprised of a main section, 152,
protrude two extensions, 154 and 156, that are sized to enter the
nares of the nose. Preferably, the lateral cross-sectional surface
area of each of these extensions, 154 and 156, is not greater than
50 percent of the opening cross-section area of a nares at its
widest opening, more preferably the device's inserted
cross-sectional surface area is not greater than 35 percent of such
opening area of a nares, and even more preferably, the device's
inserted cross-sectional surface area is between about 20 and about
35 percent of such opening area of a nares. At the end of these
extensions, 154 and 156, which preferably are of molded plastic and
integral with the major portion, the plastic housing, 152, are
inserted two circuit boards, 163, one containing two light-emitting
diodes, 162 and 164 (shown here on extension 156) and the other
containing a photodetector, 166 (shown here on extension 154).
[0177] As discussed for FIGS. 2A-G, in certain embodiments, the two
extensions, 154 and 156, are spaced apart from one another so as to
fit snugly against the tissue of each side of the septum to avoid
interference from ambient lighting. Moreover, in certain
embodiments as described above, the two extensions, 154 and 156 are
constructed and spaced apart so as to fit non-contiguously with the
mucosal cell lining of the interior septum walls.
[0178] Also, as discussed for FIGS. 2A-G, it is noted that clear
plastic covers, 161, are placed over the molded plastic frame, 169,
that forms the extensions 154 and 156 in FIGS. 8A-B. These plastic
covers typically are heat-sealed over the LEDs 162 and 164 and
photodetector 166. In various embodiments, the sides, 165, of the
clear plastic covers, 161, that are facing or contacting the nasal
septum (not shown) are aligned with the inside faces, 167, of the
extensions 154 and 156, so as to fit, respectively, near or against
the tissue of each side of the septum, without irritation, as from
a rough or uneven surface. As noted in more detail elsewhere, the
covers, 161, preferably have inner faces co-planar with the inner
faces of the two extensions, 154 and 156. This is to ensure a
comfortable fit, good data since ambient light is lessened, and no
necrosis of the tissue being contacted. In all such embodiments, it
is preferred that the two extensions, 154 and 156, deflect from the
septum wall due to flexibility of the structures themselves, 154
and 156. This is particularly helpful when a patient has an
interior septum wall wider than the spacing between the inner
sides, 165 (so that there is substantial contacting), when a
patient has septum wall irregularities (i.e., a deviated septum
wall), or when a patient has a columella substantially wider than
the inner faces, 167. Also, depending on relative sizing of nasal
probe to a septum, embodiments as described herein are designed and
sized to fit providing a space between the inner sides, 165, and
the mucosal lining of the interior septum. Other embodiments are
designed and sized to provide such space, and also to be separated
from, or apply less pressure against, the columella.
[0179] Further as to the plastic covers, 161, one is fitted over
each of the structures, 163, that contain the LEDs 162 and 164,
located on extension 156, and the photodetector 166, located on
extension 154. The plastic covers, 161, preferably do not interfere
with light transmission. Apart from heat-shrink sealing, other
means of attaching the plastic covers, 161, to the extensions 154
and 156, include, but are not limited to, sonic welding, spot
gluing, hot gluing, press fitting, and other such methods of
attachment, as are employed in the art, that are used to attach
components of a medical device for entry into an orifice of a
living subject. In general, the combined nasal pulse oximeter
probe/cannula devices of the present invention are designed to be
disposable, due to problems associated with cleaning between uses.
However, it is within the scope of the invention that appropriate
plastics, components and construction are employed so as to allow
an appropriate level of sterilization of such devices between
uses.
[0180] As for the nasal pulse oximeter probe depicted in FIGS.
2A-D, two extensions, 154 and 156, extend from a main section, 152,
of a resilient housing, typically of plastic, that positions and
spaces the extensions 154 and 156. These two extensions, 154 and
156, are sized to enter the nares of the nose in similar fashion to
a nasal cannula oxygen supply. These extensions, 154 and 156, are
flattened in one dimension, as depicted in FIGS. 8A and 8B, and are
shown angled at about 15 degrees in a second dimension, as viewed
in FIG. 8B. This angle of inflection, 170, is properly drawn from a
line drawn from one edge of the main section, 152. 168 The first
approach described above for the nasal oximeter probe in FIGS. 2A-D
is used to protect the components of the combined nasal pulse
oximeter probe, 150, from moisture and contamination. A clear
plastic covering, shown as 161 in FIG. 8A, is placed over, to
cover, each distal half of the two extensions, 154 and 156. It is
noted that in the embodiment shown, the molded shell, 169, that
forms and covers the main section, 152, also covers the
approximately proximal half of the two extensions, 154 and 156.
Either this, or a separate resilient insert, provides a support for
the upper, or distal halves of these extensions, but does not cover
the front and rear sides, nor the inner sides, 165, of these
extensions. To cover these exposed sides, a clear plastic covering,
161, is constructed, fitted over, and adhered to the existing
components to form an integral protective exterior surface with the
molded outer shell, 169. Such plastic covering, 161, typically is
manufactured by heat sealing pre-cut and/or pre-formed pieces to
form a fitted covering over the distal halves of extensions 154 and
156. Then this is shrink-wrapped over the components of the distal
half of the two extensions, 154 and 156. The plastic covers, 161,
preferably do not interfere with light transmission in the critical
wavelength ranges of the LEDs 162 and 164. Apart from heat-shrink
sealing, other means of attaching the plastic covers, 161, to the
extensions 154 and 156, include, but are not limited to, sonic
welding, spot gluing, hot gluing, press fitting, and other such
methods of attachment, as are employed in the art, that are used to
attach components of a medical device for entry into an orifice of
a living subject. Also, other means of providing a protective
covering, such as are known to those skilled in the art, may be
used instead of the above-described approach.
[0181] Further, using the shrink-wrapping construction described
above to cover the distal halves of the extensions 154 and 156, and
dimensioning the spacing between the extensions 154 and 156 as
indicated above for a non-contiguous fit, the extensions 154 and
156 are found to fit without irritation to the mucosal cells lining
each side of the interior septum, as from a rough or uneven
surface. For example, without being limiting, when using heat
sealing plastic as the covering, 161, the thickness of this
material, and any finish on the adjoining edge, will affect the
extent of a sensible ridge at the junction of the covering, 161,
and the molded outer shell, 169, but nonetheless provide a
comfortable fit.
[0182] The nasal septum extends in the midline from the tip of the
nose anteriorly to the posterior border of the hard palate
posteriorly. It is bordered inferiorly by the roof of the mouth
(the hard palate) and superiorly by the floor of the cranium. As to
a specific area of the nasal septum that is preferred for use of a
nasal pulse oximeter probe such as the one depicted in FIGS. 8A-B,
at least one highly vascularized, and thus more suitable, area of
the nasal septum is located approximately 0.5-1.0 cm. from the
posterior border of the nostril and approximately 2.0-2.5 cm.
superior to the floor of the nasal cavity in the midline. Being
more highly vascularized, such thereby provides more consistent and
reliable signals than less vascularized areas that are, relative to
this, more proximal (the tip of the nose) or more distal (further
posterior towards the back of the nasal cavity). In particular, and
more specifically, the highly vascularized area of the septum,
known alternately as Kiesselbach's plexus and Little's area, is a
preferred target area for detection of blood oxygen saturation
levels by a nasal pulse oximeter probe of the present
invention.
[0183] The pulse oximeter nasal probe of the present invention is
designed so that, when properly positioned, it passes its light
through such highly vascularized areas. In the particular device
shown in FIGS. 8A,B, an angle of inflection, 170, is shown between
plastic housing, 152, and the two extensions, 154 and 156. This
angle properly is measured as an interior deviation from a straight
line extended from the plastic housing, 152. In preferred
embodiments, the angle of inflection, 170, is between about 0 and
about 33 degrees, in more preferred embodiments, the angle of
inflection, 170, is between about 10 and about 27 degrees, and in
even more preferred embodiments, the angle of inflection, 170, is
between about 10 and about 20 degrees. In FIG. 8B, the angle of
inflection, 170, is about 15 degrees. This angle has been found to
provide superior results in testing.
[0184] Further, it is noted that in typical use contact by an inner
face of one extension with nasal mucosal tissue interior to the
columella precludes contact by the inner face of the other
extension with the nasal mucosal tissue interior to the columella.
Further, in many if not most instances, where there is a snug fit
against the columella, there is little or no contact by the more
distal, inward sections of the respective extensions against the
nasal mucosal tissue interior to the columella. Where a patient has
a substantially deviated septum, there may be contact by one
extension on one side, but this is believed, in most cases, to
preclude contact by the other side once interior of any contact
with the columella.
[0185] Thus, for the embodiments depicted in FIGS. 2 and 8, a most
common fit with a nasal septum, when the respective device is in
use, is that certain areas of the inner faces of the extensions
only occasionally or lightly contact a portion of the tissue of the
interior septum wall. Such portion is typically a protruding
portion. It has been learned that this orientation, where the
extensions bearing the light-generating and the light-detecting
structures, does not and need not press against both sides of the
nasal septum. Surprisingly, relative to prior art teachings,
pressing against the tissue of the septum wall is not needed in
order to obtain good pulse oximetry data.
[0186] As noted above, in certain embodiments contact with the
nasal interior septum mucosal tissue is avoided or minimized by one
or more of: sizing of the probe (particularly spacing between
opposing inner faces), flexibility of the material used, other
design features, and lack of design and/or structure to compress or
clip any part of the probe to the tissue of the nasal septum. Thus,
in various more preferred embodiments, the inner sides (i.e., 65 or
165), of the two extensions, (i.e., 54 and 56 or 154 and 156), if
they ever contact the tissue (mucosal nasal lining) of the interior
septum, do so lightly, resting without excessive pressure, so as to
avoid the development of necrosis of the mucosal tissue. This
applies even when the nasal probe is used over extended periods of
time. Also, it is noted that a snugly fitting probe, as described
in certain embodiments and within its broader context, comprises
probes that contact comfortably the columella, whilst remaining
spaced from (i.e., facing, adjacent to), the tissue of the nasal
interior septum.
[0187] Further, referring to FIG. 8A, in general, the two
extensions, 154 and 156, are angled so that upon insertion and
proper placement into position in the nostrils, the LEDs 162 and
164, located on extension 156, emit light directed through a region
that includes a preferred area of the nasal septum. Most
preferably, the LEDs 162 and 164, located on extension 156, direct
light exclusively through the highly vascularized region of the
septum known alternately as Kiesselbach's plexus and Little's area
(or, in The Principles and Practice of Rhinology, Joseph L.
Goldman, Ed., John Wiley & Sons, New York, 1987, Kiesselbach's
plexus is "in" Little's area). Empirically, in certain evaluations,
this highly vascularized region, referred to herein as
Kiesselbach's plexus, is measured to be located approximately 2.0
cm upward and approximately 1.0 cm inward (toward the back of the
head) from the tip of the anterior nasal spine. Kiesselbach's
plexus is the region of the nasal septum where the terminal
branches of at least two arteries meet and supply the tissue. These
major terminal branches in Kiesselbach's plexus are those of the
nasal septal branch of the superior labial branch of the facial
artery and the anterior septal branch of the anterior ethmoidal
artery (see, for example, plate 39 of Atlas of Human Anatomy,
2.sup.nd Ed., Frank H. Netter, M.D., Novartis, 1997). Some terminal
branches of the posterior septal branch of the sphenopalatine
artery may also be found in more posterior regions of Kiesselbach's
plexus.
[0188] Also, because Kiesselbach's plexus actually is comprised of
a region of highly vascularized tissue, rather than a discrete
point, and given anatomical variation among persons, a range of
approximately +/-0.25 cm from the above indicated measured point
also is acceptable as a target area to obtain unexpected superior
results with a nasal pulse oximeter probe. It also is recognized,
based on the approximate size of the Kiesselbach's plexus, that
placing the probe so it measures saturation within a range as large
as approximately +/-0.75 cm from the measured point may also
provide these unexpected superior results (by having the light pass
through this highly vascularized region). However, given the
variations noted above, this is less preferred than the range of
approximately +/-0.25 cm. from the measured point. Under certain
circumstances, a range of approximately +/-0.50 cm. from the
measured point is considered acceptable. Given the basic morphology
and sizing of the nares, design and placement of nasal pulse
oximeter probes such that they pass light through nasal septum
tissue within these larger ranges, but not within the smaller
approximately +/-0.25 cm. range, frequently requires probes of the
present invention that are designed to have smaller (i.e., thinner,
narrower) profiles than the profile depicted in FIGS. 8A and 8B.
This allows these probes to come closer to the outward or inward
structures of the nares and maintain patient comfort.
[0189] Also, for any of these ranges to target Kiesselbach's
plexus, it is appreciated that the angle of a particular
individual's lip in relation to the nose, and the placement of the
nasal probe sensor on the upper lip, affect the exact location of
the probe's light producing and light sensing components on the
plexus. As noted, it has been learned that a nasal pulse oximeter,
such as is depicted by 150 (with or without the oxygen cannula
element), that has an angle of inflection, 170, of about 15
degrees, has been found to provide superior results in testing.
This 15 degree angle to reach Kiesselbach's plexus with the
light-generating and the light-detecting components, in order to
obtain superior sensing data, takes into account that for many
patients, there is an angle of the upper lip, tilting about 15
degrees. This is represented in FIG. 11, a facial profile. FIG. 11
also shows an angle, from a true vertical, starting from the
opening of the nostril at the medial end, 171, of about 30 degrees
that generally leads toward the desired area for obtaining pulse
oximeter data, Kiesselbach's plexus. This 30 degree angle includes
the benefit of the approximately 15 degree angle of the upper lip,
173, upon which the nasal probe of the present invention is placed.
Thus, with this angle of the upper lip, in combination with a 15
degree angle of the nasal probe, the light generating and light
detecting components of the nasal probe are positioned at the
desired vascularized area, generally located along the 30 degree
angle inward and upward from the opening of the nostril at the
medial end, 171. One example of a nasal probe with a 15 degree
angle, or bend, is shown in FIG. 8B. It is noted, however, that a
nasal probe with such angle may be with or without a cannula.
[0190] However, it is appreciated that the shape and angle of
person's upper lip, and orientation to the nasal cavity, do vary.
Thus, in certain embodiments, it is desirable to adjust the exact
angle of the nasal probe in relation to the upper lip (such as by
gently twisting it as it is being secured to the upper lip) to
obtain the most preferred area for data. Also, optionally, the
pulse oximeter is comprised of circuitry and data output that
provides a "perfusion index" to assist in improved placement of the
probe so that the light-generating and light-detecting components
are placed in or near to the desired Kiesselbach's plexus. As known
in the art, the perfusion index is the ratio between the pulsatile
and the non-pulsatile components of the light that reaches the
light-detecting component. This provides a means to find which
position has a greater pulsatile component, and can assist, when
needed, in orienting a nasal probe to obtain a superior or the
preferred site. It is noted, however, that in trials, the probe
having a bend of 15 degrees, as shown in FIG. 8B, has been found to
provide reliable data for 30 patients tested to date without a need
for subtle or time-consuming adjustment of position on the upper
lip.
[0191] Also shown in FIG. 8B is a conduit for oxygen (or
oxygen-rich air or other gas mixture), 180, and a conduit, 182,
within which are electrically conductive wires (or other types of
signal transmission means, such as fiberoptic cable) to pass
electrical signals to and from the two light-emitting diodes, 162
and 164, and the opposing photodetector, 166. 180 Means of
stabilizing the probe, 150, such as elastic straps (not shown) from
any part of the device that span the head of the patient, typically
are employed, and depend on the type of application and the comfort
requirements of the user. More particularly, in order to stabilize
the desired position of the nasal probe of the present invention
(whether it is with or without a cannula), several specific
approaches are useful. One approach to reversible attachment of the
nasal probe to the patient is to apply tape to all or part of the
patient's upper lip, where the side of the tape to the patient's
upper lip has an adhesive suited for the purpose and desired
contact period, and the other, exposed side has one or more
sections of either the hook or the loop of hook-and-loop type
fabric. The side of the nasal probe to rest on the upper lip ("back
side") is comprised of one or more sections of the hook-and-loop
type fabric to complement the sections on the tape's exposed side,
and by virtue of alignment and pressing together of the sections on
the nasal probe and the upper lip, the nasal probe is positioned on
the upper lip. This type of reversible attachment can be modified
as needed, particularly when the strength of the adhesion of the
hook-and-loop type fabric is lessened just to the strength needed
to maintain the probe in position in view of the typical range of
forces acting to dislodge it. A variation is to apply tape to the
back side of the nasal probe, where the tape has adhesive on the
side toward the probe, and hook-and-loop type fabric on the
opposite side, facing and attachable to the hook-and-loop type
fabric on the tape of the upper lip.
[0192] Another approach to reversible attachment of the nasal probe
to the patient is to apply double-sided adhesive tape to all or
part of the patient's upper lip. Then the back side of the nasal
probe is pressed against the adhesive on the upward-facing side of
the double-side adhesive tape. A variation is to apply the
double-sided adhesive tape first to the back side of the nasal
probe, then orient the probe into its position against the upper
lip with the extensions in the nares, and then press against the
upper lip to obtain adhesion thereto. When using such approaches,
it is advantageous to have a stabilizer (such as 58, in FIG. 1,
there shown simply as a flat plate flush with and extending
downward from the inside edge of the lower plane of the extensions
54). This provides additional surface area for contact with the
tape, and improves the stability of the reversible bonding with the
upper lip, and thereby helps maintain a proper orientation to the
desired vascularized areas for detection of the condition of the
arterial blood and its flow.
[0193] Yet another approach to reversible attachment of the nasal
probe to the patient is to apply single-sided adhesive tape over
the top of the nasal probe. This is done before or after the nasal
probe has been positioned with the extensions in the nares and the
back side against the upper lip, and the tape is pressed into the
skin of the face adjoining the nasal probe, to secure the probe in
place.
[0194] As for the probes depicted in FIGS. 1 and 2A-D and described
above, timed electrical impulses from a pulse oximeter monitor
system pass through two wires or other signal transmission means
(not shown) in cables held within conduit passing within 182 to
produce the light from LEDs 162 and 164. At least one
photodetector, 166, is positioned within extension 154 to face and
oppose LEDs 162 and 164 on extension 156. The photodetector 166,
which typically is a light-sensing photodiode, detects changes in
the light emitted by the LEDs 162 and 164 as that light is
differentially absorbed between and during pulses across the
capillaries of the septum tissue between the two extensions, 156
and 154. In one embodiment, LED 162 emits light around 650-670 nm,
and LED 164 emits light around 880-940 nm. The electrical impulses
are timed to be offset from one another, so that the light from
each of the two LEDs, 162 and 164, is emitted at different times.
The photodetector, 166, detects the light passing through the
septum of the nose, which is situated between extensions 156 and
154 when the probe 150 is in use. As discussed above, loss of
signal through vascularized tissue such as the nasal septum is due
both to background tissue absorption and the absorption by the
blood in the arteries, which expands during a pulse. The signals
from photodetector 166 pass through conductors (not shown) to the
processor of the monitor system (not shown). As examples, not meant
to be limiting, a single cable passing from one side of the device,
150, or two cables that may form a loop that may lie above the ears
of the patient, or join to form a single cable (not shown), pass
signals to the two LEDs, 162 and 164, and from the photodetector
166. In one preferred embodiment, a single cable, formed from the
joining of two cables leading from the device, 150, terminates in
an electrical plug suited for insertion into a matching socket in
the pulse oximeter monitor system (not shown). In another preferred
embodiment, the single cable terminates by connecting to an adapter
cable, which in turn connects to a socket in the pulse oximeter
monitor system (not shown). In a typical application, the signals
from the light-sensing photodetector, 166, are ultimately received
and processed by a general purpose computer or special purpose
computer of the monitor system (not shown).
[0195] Per the disclosure preceding this example, this combination
nasal pulse oximeter is used either in combination with the needed
computer processing to interpret and provide a viewable (or audible
in the case of an alarm) data output of arterial blood oxygen
saturation for the user or health care worker, or, in alternative
embodiments, this function is further combined with the means to
regulate and adjust the flow of oxygen or oxygen-rich gas that is
being delivered by adjustment of a valve controlling such flow.
Example 6
[0196] The present invention also is adapted for embodiments which
utilize, in combination, pulse oximeter detection of arterial blood
oxygen saturation, in combination with a supply of oxygen, air, or
a gas mixture providing a variably supply of oxygen, where the flow
rate and/or amount of oxygen provided in the gas mixture is
controlled based at least in part by the changes and levels of
arterial blood oxygen saturation, as detected by the pulse
oximeter. Applications for such combination devices (pulse
oximeter/oxygen supply directed by controller with pulse oximeter
data as an input) include, but are not limited to: self-contained
breathing apparatuses (SCBA); self-contained underwater breathing
apparatuses (SCUBA); high altitude breathing systems, and medical
gas delivery systems. The following figures and related disclosure
provides only one, non-limiting embodiment to present the basic
concepts of the present invention as applied to a SCUBA regulator.
FIG. 10 is used to depict a general control approach for this and
other systems described in this application.
[0197] FIG. 9A presents a diagram of a basic SCUBA regulator, 200,
with key features described. The housing, 220, contains a diaphragm
that senses ambient water pressure which is linked physically to
adjust the delivery pressure to the user via regulation of the
second stage regulator, also within the housing, 220. A supply
hose, 212, carries compressed air, or other gas mixtures, typically
from a supply tank (not shown), to the second stage regulator (not
shown) within the housing, 220. Upon demand from the user, whose
mouth is fitted around the rubber mouthpiece, 201, the air or other
gas from the hose, 212, passes through the second stage regulator,
and through the mouthpiece, 201, to provide the user with a supply
of air or other gas based on the flow pattern of the second stage
regulator. Having the rate of this flow upon demand being variable,
based in part on the type of regulator and its operating conditions
and maintenance, can result in waste of precious air supply. Also,
when the percent of oxygen or other gas in the air supply can be
altered based on data from a pulse oximeter, the body's
physiological requirements can be better met, resulting in a safer
and healthier dive experience.
[0198] FIG. 9B presents a diagram of the basic SCUBA regulator FIG.
9A, however also comprising additional features of the present
invention. In particular, a flexible arm 202 bearing two
light-emitting sources, 204 and 206, (typically LED's) is disposed
in a place exterior to the position of the lip of the diver using
the regulator. The approximate thickness of the lip is represented
in FIG. 9B by the distance, a. Flexibility of the arm 202, is by
the nature of the material such as rubber and/or by spring loading.
By such design, the arm 202 moves easily away during fitting of the
mouthpiece (i.e., the placement of the lip around the flange, 207,
of the mouthpiece, and the teeth over the nubs, 209 (one is shown
as a dashed rectangle to indicate position on the inside surface of
the flange). Then the arm, 202, presses against the lip or against
the skin just below the lower lip, in such an orientation so that
light emitted by the two light-emitting sources, 204 and 206, is
directed toward a photosensor, 208, inset into the outer surface of
the rubber mouthpiece 201. This receives signals through the lower
lip/flesh below the lip, which is sufficiently well-vascularized to
provide a representative reading of the body's oxygen status
expressed as of arterial blood oxygen saturation. Wiring 210 passes
data signals between this pulse oximeter probe and the oximeter
controller (not shown, end of wiring in figure coincides with end
of supply hose, 212). This interprets the data signals from the
pulse oximeter probe and, based on the information received,
directs a separate valve (not shown) to adjust upward or downward
the level and/or pressure of oxygen supplied through the supply
hose 212 to increase or decrease the absolute or relative oxygen
flowing to the regulator at the mouthpiece shown in FIG. 9B.
[0199] For SCUBA systems using HE/Ox mixtures, additional oxygen
can be provided when indicated by the data from the oximeter,
and/or by a manual control (such as the diver pressing a button to
increase, with a second button to decrease oxygen flow
incrementally). The same approaches apply to more complex dive gas
mixtures, such as Triox (oxygen enriched air with helium) and
Trimix (hypoxic oxygen, helium and nitrogen). By appropriate
control mechanisms and algorithms (adjusted to compensate for
physiological differences at different depths), a diver using such
embodiments of the present invention extends the dive time on a
particular quantity of oxygen, and/or has more oxygen when more
oxygen is needed, and less oxygen when less oxygen is sufficient.
This results in a safer, healthier dive experience.
[0200] The above disclosed improvements in the monitoring of blood
oxygen saturation and adjustment of gases supplied to a SCUBA diver
also apply to users of self-contained breathing apparatuses (SCBA)
that are not used for underwater diving. For example, firemen and
other emergency workers use SCBA in environments in which they may
exert considerable energy and have transient very high oxygen
demands. The above-disclosed embodiments, and variations of these
known to those of skill in the relevant arts, provide benefits to
such users.
[0201] FIG. 10 provides a flow diagram of the general information
and control generation of the "pulse flow oxygen sensor" that
controls the level or pressure of oxygen provided to a user wearing
a nasal or mouth pulse oximeter sensor of the present invention in
combination with the gas supply controlled by a controller
receiving data input from that pulse oximeter sensor.
Fundamentally, data signals from the pulse oximeter sensor go to an
arterial blood oxygen saturation/oxygen supply Control Circuit.
Based on analysis of these data signals using an appropriate
algorithm, the arterial blood oxygen saturation/oxygen supply
Control Circuit sends signals to a servodevice that adjusts an
Oxygen Control Valve which receives oxygen under pressure from an
oxygen source. From the O.sub.2 Control Valve, oxygen is directed
to a patient in need of oxygen, where that patient is wearing the
combined nasal or mouth pulse oximeter sensor of the present
invention in combination with the gas supply cannula or
mouthpiece.
Example 7
[0202] As described above, Kiesselbach's Plexus is a vascularized
area in the anteroinferior part of the interior nasal septum, and
is supplied by sphenopalatine, greater palatine, superior labia and
anterior ethmoid arteries. These vessels originate from both the
internal and external carotids and are the most frequent cause of
epistaxis (nose bleed).
[0203] To demonstrate the utility of Kiesselbach's Plexus as a site
for pulse oximetry, data was recorded from a more vascularized
region of the nasal septum (i.e., Kiesselbach's plexus) using a
probe of the present invention in its intended positioning. This
data was compared to data from two adjacent sampling sites, one
inferior and posterior, and one anterior and superior to
Kiesselbach's plexus. Since all three sampling sites are capable of
giving a signal for pulse oximetry with a standard pulse oximeter
monitor, relative LED power provided a marker of utility. A lower
LED power required to obtain a measurement indicates a stronger
source signal. Such lower power requirement is apparent when the
probe is placed so as to transmit light through the vascularized
area identified as Kiesselbach's plexus. Also, as further discussed
herein, a stronger signal source in the nasal or cheek/lip areas
generally provide improved signals for use in plethysmography.
[0204] A nasal probe of the present invention, having a 15 degree
inward angle, or inflection along its extensions, was utilized for
the comparison. This probe has a side view similar to the probe in
FIG. 8B. To obtain what is identified in FIG. 18A as "Approx. 0
Degrees," the probe was angled outward from its normal, desired
position to approximate a position for the light-generating and the
light detecting components over the nasal septum that simulates a
probe having straight extensions (i.e., not having the 15 degree
inward inflection). FIG. 18B, identified as "Approx. 15 Degrees,"
is the probe in its normal, desired position (see FIG. 11 and
related discussion), with the 15 degree inflection positioning the
light-generating and the light detecting components over the nasal
septum at a desired position that, in subjects tested to date,
provides superior results. To obtain what is identified in FIG. 18C
as "Approx. 30 Degrees," the probe was angled inward from its
normal, desired position to approximate a position for the
light-generating and the light detecting components over the nasal
septum that simulates a probe having such components further inward
(anterior and superior) than the position obtained with the 15
degree-inflected probe seated on the upper lip. That is, based on
the upper lip angle of 15 degrees, the probe position for the data
shown in FIG. 18C is approximately 45 degrees inward of vertical
(see FIG. 11 and related discussion).
[0205] The data indicates that the probe in its intended position,
with the back of the probe's main section against the upper lip,
provides superior data. This is indicated by virtue of FIG. 18B's
LED Power reading of 66, compared to the LED Power readings of 108
and 102 for FIGS. 18A and 18C, respectively. Without being bound to
a particular theory, when the probe is in its intended position, it
passes light through the more vascularized section of the nasal
septum (i.e., Kiesselbach's plexus), and the standard algorithm of
the pulse monitor obtains the desired data signals with a lower
power to the LEDs. The data provided in this example is consistent
with earlier testing which demonstrated, unexpectedly and
advantageously, that superior pulse oximetry and plethysmography
data is obtained when the distal end of the pulse oximeter probe
extensions are designed so as to locate the light-generating and
the light detecting components to a desired more vascularized
locus, i.e., Kiesselbach's plexus. Thus, it is further appreciated
that various designs that have the end result of locating the
light-generating and the light detecting components to the desired
more vascularized loci as obtained by the probes of the present
invention, such designs are within the scope of the present
invention. For example, and without being limiting, FIG. 18D
provides an alternative design of an acutely angled nasal probe,
300, that achieves the same positioning as a probe having a profile
of the probe in FIG. 8B.
[0206] Further, it is noted that in some subjects, a nasal probe of
the present invention, when placed in the position as indicated
above for FIG. 18B, provides data that, effectively, goes "off the
scale." Without being bound to a particular theory, this is
believed to be due to peculiarities of the algorithms used in the
processor of a standard pulse oximeter, and/or the fundamental
system logic of a finger pulse oximetry system. For example, the
algorithm and processor of a standard finger pulse oximeter system
are designed to adjust light intensity for a probe positioned on a
finger, where there is a relatively higher percentage of less
vascularized tissue compared to the nose, lip and cheek. In such
circumstances, if a greater than expected amount of light is
received at the photodetector, this may indicate the probe has
slipped from the finger, or from the proper position on the finger.
For such algorithm, a strong signal may be considered
erroneous.
[0207] To address problems of "off scale" readouts for nasal probe
data collected from some subjects, it has been further learned that
various types of "filters" can be implemented to eliminate this
problem. Two general approaches to "filtering" are electrical and
light approaches. An example of the electrical approach is to place
a resistor in series to both of the light producing LEDs. This
proportionally decreases the amount of light emitted at both
wavelengths. As to the light approach, a filter, such as a white
material, a translucent or an opaque cover, can be physically
placed over all or part of the light-producing LEDs, over the
photodetector, or both, to reduce the light input into the
photodetector, such that a readable signal can be generated in such
subjects. This reduces the amount of both wavelengths of light
received at the photodetector without dramatically altering the
ratios of such wavelengths. Without being limited, yet another way
to compensate for the more vascularized, higher light output areas
of the nose, lip and cheek is simply to use smaller light-detecting
photodiodes. If the response curve for the smaller photodiode
remains the same compared to its larger counterpart, just it active
area reduced, this would keep the light level ratios of the
respective wavelengths proportional. For instance, a 0.4 mm size
active area may be used instead of a 0.8 mm size active area. Other
methods as known to those of ordinary skill in the art can likewise
be employed to deal with the higher signal, particularly for probes
that are used in pulse monitor equipment with algorithms designed
for signals from finger probes. By adjusting the amount of light by
any of the above means, and upon consequent adjustment of the
output parameters of the oximeter, as many occur in certain units,
the sensor output achieves a more acceptable range for
monitoring.
[0208] In conclusion, the area of Kiesselbach's plexus across the
nasal septum is the area in the nose of strongest signal for pulse
oximetry as demonstrated by this simple experiment. It is noted
that even using a filtered probe and placing it anteriorly of
Kiesselbach's plexus a power level 2.5 times lower than what is
required by the finger provides a good signal. As discussed above,
one approach to locating this desired site is to use the probes
having the desired bend, or angle of inflection. Another approach,
which may only be needed in a small number of instances, is to use
the perfusion index feature on a pulse oximeter device, and
position where the index is highest.
Example 8
[0209] Several specific profiles of data are provided from patients
who underwent various procedures in a teaching hospital and who
wore the pulse oximeter probes of the present invention. This data
is illustrative of the value of the nasal probes of the present
invention. For all figures below, the data designated as "PULSE OX
1" or "P-OX 1" is from a nasal probe measuring data across the
interior nasal septum, the data designated as "PULSE OX 2" or "P-OX
2" is from a cheek/lip probe measuring data across the cheek (below
the lip), and the data designated as "PULSE OX 3" or "P-OX 3" is
from a conventional finger probe.
[0210] FIG. 16A-C provides photoplethysmographic and arterial blood
oxygenation data from a patient who was undergoing coronary artery
bypass surgery. Pulse oximeter probes of the present invention were
placed in the nose and in the mouth (a cheek/lip probe), and a
conventional probe was placed on a finger. FIG. 16A shows typical
plethysmographic data from all three probes prior to the switching
to bypass. This figure also indicates that the blood oxygenation as
measured by all three probes were similar, as were the
plethysmograph curves.
[0211] FIG. 16B shows data from about one minute after cardiac
activity was reinitiated and the blood flow and pressure returned
following bypass, but during a low flow condition (which was done
to repair a tear in the aorta). This demonstrates that both the
nasal and the cheek/lip probes had sufficient blood flow to obtain
a plethysmograph and pulse and saturation data, whereas the finger
probe did not.
[0212] FIG. 16C shows data near the end of the surgical procedure,
when blood flow had returned to normal. All three sites are
provided readable data. Also, although the plethysmographic data
from the finger site appears stronger (i.e., the peak is higher),
it should be kept in mind that this is the result of algorithms in
the pulse oximeter that automatically adjust power and gain.
[0213] FIGS. 17A-C provide data from three different patients, all
of which experienced cardiac arrhythmias at some time during the
observation period. In all three examples, the nasal probe and the
cheek/lip probe provided clearer imaging of the arrhythmias than
the finger probe. Also, as observable in FIG. 17D, taken from a
fourth patient, the nasal probe most distinctly detected what
appears to be a dicrotic notch (compared with the cheek/lip and
finger probes). Also, it obtained this data with relatively low
energy being supplied to the LED.
[0214] Also, during testing with certain patients, given increased
sensitivity from the nasal probe, it was observed that respiratory
rate can be accurately measured from the nasal photoplethysographs
since the nasal probe is more sensitive to volume changes. That is,
changes in the "envelope" of the plethysmograph DC component
indicates the breathing cycle, and this, upon quantification of
these cycles, can estimate respiratory rate. One example of this is
provided in FIG. 18a, where the space between the two vertical
lines represents one respiration cycle.
[0215] Use of the nasal or cheek probes independently or in
conjunction with the finger probe can also be used to evaluate the
effects on cardiac output, blood pressure and perfusion in
spontaneously breathing and mechanically ventilated patients. For
instance, when a normal subject breathes spontaneously, there is
little or no observable effect on the plethysmograph from a finger
probe. However, both the nasal and cheek probes demonstrate a drop
in the "envelope" of the plethysmograph. This is explained by an
increase in venous return to the right side of the heart and a
decrease in blood flow from the left ventricle due to negative
pressure relative to atmospheric pressure produced in the thoracic
cavity during normal breathing. This fall in the "envelope" of the
plethysmograph is exaggerated during spontaneous breathing against
resistance, such as pulmonary diseases that narrow the airways and
during hypovolemia or low cardiac output. In addition to the fall
in the "envelope" of the plethysmograph, there is often a decrease
in the maximum amplitude of the plethysmograph, which becomes more
pronounced (a greater decrease) with hypovolemia, poor cardiac
output or poor perfusion. Comparing the nasal or cheek
plethysmographs with the finger plethysmograph may be an additional
means to follow these effects over time.
[0216] During mechanical ventilation, changes opposite to those
observed with spontaneous breathing occur in both the "envelope" of
the plethysmograph and the amplitude. Positive pressure ventilation
increases intrathoracic pressure, which in turn increases blood
flow from the left ventricle and results in a rise above baseline
in the "envelope" and an increase in the amplitude of the
plethysmograph. Hypovolemia and/or poor cardiac output diminish
these salutary effects. FIGS. 18A-C demonstrate the effects of
positive pressure ventilation on increasing vasodilatation or
hypovolemia, such as seen during anesthesia. In FIG. 18A each
positive pressure ventilation results in a rise in the
plethysmograph "envelope". In FIGS. 18B and C there are great
excursions in the plethysmograph as the patient becomes vasodilated
and the amplitude of the plethysmograph decreases.
[0217] Further, evaluation of the plethysmograph during both
spontaneous and mechanical ventilation can be used to determine the
optimal level of positive end expiratory pressure (PEEP) for a
patient. PEEP is an important parameter for optimizing the
oxygenation of a patient. Depending on the volume and cardiac
status of a patient, different levels of PEEP can be tolerated.
Since a higher PEEP raises the baseline intrathoracic pressure, it
impedes venous return to the heart and can cause decreased cardiac
output. If a subject is hypovolemic, vasodilated or has poor
cardiac output, excessive PEEP may lead to hypotension, lactic
acidosis and eventually shock. If inadequate PEEP is given, the
patient will be hypoxemic, which can also lead to lactic acidosis
and shock. Thus, there is an optimal PEEP for each subject
depending on his or her pulmonary, volume and cardiac status.
Excessive PEEP narrows the amplitude of the plethysmograph and
causes exaggerated excursions in the "envelope" of the
plethysmograph.
[0218] Evaluation of the "envelope" of the plethysmograph and the
effects of ventilation on the amplitude of the plethysmograph can
be used to provide a level of PEEP that allows adequate oxygenation
without compromising cardiac output. If oxygenation remains poor at
a given level of PEEP, volume expansion with fluids and/or drug
treatment can improve cardiac output and allow the patient to
tolerate the higher level of PEEP. Evaluation of the plethysmograph
provides a non-invasive means of determining the effects of
positive pressure ventilation and PEEP on the cardiac output of the
patient.
[0219] It is noted that an appreciation of data obtainable from
pulse oximetry probes is found in the scientific article, "The
peripheral pulse wave: information overlooked," W. B. Murray and P.
A. Foster, J. Clin. Monitoring 12:365-377, 1996. This reference
discusses in detail the bases for changes in the wave form
obtainable from pulse oximeter peripheral probes, and the
significance of changes in such wave forms during anesthesia. All
material in this reference is hereby particularly incorporated by
reference into this disclosure. Further, it is noted that this
reference focused on the use of the ear, or peripheral locations,
and so did not fully appreciate the types and improved quality of
data obtainable from a desired vascular site of the interior nasal
septum, or from the cheek/lip probe, as described herein. Also, it
is appreciated that the probes of the present invention find
utility not only in patients who are inactive, such as those
undergoing anesthesia during surgery, but also in patients who are
awake and, selectively, ambulatory.
[0220] Thus, as observable from the above figures, the use of a
nasal probe of the present invention, which does not require
pressure against the septum wall to operate, advantageously
provides photophethysmographic data that is able to detect cardiac,
pulmonary, and other abnormalities non-invasively, and better than
more remote sites, such as a finger or a toe. While not being bound
to a particular theory, this is believed due to the combination of:
1) not applying pressure to the vascularized site (thereby not
damping more subtle signals of heartbeat patterns, etc.); 2)
accessing an arterial bed supplied by a major vessel, the internal
carotid artery; and 3) accessing this arterial bed in a position
that is not subject to additional noise and dampening (as is found
in extremity sites, such as the finger or toe).
Example 9
[0221] In many instances when pulse oximetry is being used to
detect, for instance, arterial blood oxygen saturation, and/or,
when plethysmography is being used to detect other cardiovascular
parameters, there also is a desire or need to measure carbon
dioxide during exhalation, particularly the end tidal carbon
dioxide of the patient. It is recognized, for instance, that
monitoring the carbon dioxide during the exhalation cycle more
quickly detects airway obstruction than pulse oximetry, and, where
there is an endotracheal intubation, provides the most reliable
indicator of proper intubation. A graph of the concentration of
carbon dioxide in exhaled gas plotted over time is referred to as a
capnogram. An instrument capable of displaying only end tidal
values is called a capnometer, while an instrument capable of
graphically displaying end tidal carbon dioxide is called a
capnograph. The shape of the capnogram reveals information about
the integrity of a breathing system and the physiology of the
patient's cardiorespiratory system. As such, capnography is the
preferred method of end tidal carbon dioxide monitoring.
[0222] Accordingly, another aspect of the present invention is the
combination of the nasal pulse oximeter of the present invention
with sampling structures that direct exhaled gas for carbon dioxide
measurements to provide data for either a capnometer or a
capnograph.
[0223] For instance, and not to be limiting, FIG. 19A depicts a
combination pulse oximeter/cannula/carbon dioxide sampler, 400.
Here the body of nasal probe, 450, is substantially comprised of
extensions, 454 and 456, each sized to enter the nares, and
integrally molded main section, 452, and is joined with a
cannula/carbon dioxide sampler, 410, that is designed in accordance
with U.S. Pat. No. 6,422,240 B1, issued Jul. 23, 2002. One of the
extensions, 454 comprises the light-generating components (not
specifically shown, but within 470 and including structures such as
LEDs 62 and 64 in FIG. 2A-D). The other extension, 456, comprises a
light detecting component(s) (not specifically shown, but within
472 and including structures such as photodetector 66 in FIG.
2A-D). Connecting wiring, 480, passes between the light-generating
and light-detecting components and the pulse oximeter itself, and
passes through a wire conduit, 482, that selectively travels
contiguously for a length with either the oxygen supply tube, 484,
or the carbon dioxide sampling tube, 486 (shown in FIG. 19A
traveling with the oxygen supply tube, 484). Attaching means, 490,
join the nasal probe, 450, with the structure of the cannula/carbon
dioxide sampler, 410, and may be of any type known in the art,
including, but not limited to: adhesive (i.e., plastic glue,
thermoplastic glue), double-sided tape, and the like.
[0224] In operation, oxygen from a supply source (not shown),
delivered via oxygen supply tube 484, is released at the apertures,
430, in front of the patient's nose and above the patient's mouth
(seen better in FIG. 19B), and upon inhalation, some of this oxygen
is taken up and passes to the lungs of the patient. Upon
exhalation, whether from nose and/or mouth, exhaled gases are
collected in one or more of the three intake ports, 440 (two nasal,
one oral). The exhaled gases are collected and passed through the
tube, 486, to a carbon dioxide detector (not shown). At the same
time that this repeatedly occurs, advantageously, pulse oximeter
data is collected by the nasal probe, 450, by the means described
elsewhere in this disclosure. This data, communicated by connecting
wiring, 480, is analyzed by a pulse oximeter and the output
displayed on an appropriate output monitor (not shown).
[0225] FIG. 19B depicts the combination nasal probe/cannula/carbon
dioxide sampler, 400 positioned on the face of a patient. Arrows
490 depict the flow of oxygen from a dual-gas manifold, 488, which
directs oxygen received from the oxygen supply tube, 484. During
exhalation, the exhaled breath gases, which include carbon dioxide,
are collected from the intake ports, 440, one in the mouth (to
collect when a patient is "mouth breathing"), and one from each
nostril. The nasal pulse oximeter probe, 450, is secured along the
top edge of the manifold, 488, and along the adjacent sides of the
tube wall of the two nasal intake ports, 440. Details of the nasal
pulse oximeter probe, 450, are observable in FIG. 19A.
Example 10
[0226] As for the combinations described above for the nasal probe,
the lip/cheek probe of the present invention also is combined with
1) a carbon dioxide sampling device, 2) a source of oxygen or
oxygen-rich gas; or 3) both of these.
[0227] For example, and not to be limiting, FIG. 20 depicts one
embodiment of a combination of the lip/cheek probe of FIG. 1, 10,
in combination with a carbon dioxide sampler, 90, for use in
capnography. A flexible hollow tube, 92, communicates between a
three-pronged sampling end, 94, and the actual carbon dioxide
detector (not shown). Two upper prongs, 95 and 96, are sized and
spaced for insertion into the nares of the nose of the patient (not
shown), and one lower prong, 97, is sized for insertion into the
mouth of the patient (not shown), or for terminating outside of the
mouth of a patient (not shown), to take up sample outside the
mouth. A section of the tubing, 98, is adjustably engaged to a
corresponding section of the boot, 8. For instance, the distance
between the boot, 8, and the three-pronged sampling end, 94, is
adjusted so as to be without kinking or torsion, thereby providing
for a comfortable fit. The reversible and adjustable engagement of
the tubing between this section and the three-pronged sampling end,
94, is effectuated by any means for attaching known in the art,
which includes, but is not limited to: hook-and-loop adjoining
fabric sections, one or more loops of flexible plastic or other
material encircling both the boot, 8, and the section of the
tubing, 98, a snap fitting with the snap on the tube, 92, slidably
movable along said tube, 92. It is noted that in other embodiments,
not shown, the tubing, 92, engages a part of the probe, 10, other
than the boot, 8 (such as when the probe, 10, is not comprised of a
boot). Such means for attaching the tubing, 92, is present on all
sides of the boot (or other part of the probe, 10), or
alternatively only on one or more of the sides most likely to be
used (i.e., the side situated in an upper position when the probe,
10, is placed so the bridging section, 2, of the probe, 10, is
positioned in or near one corner of the mouth, with the cable
leading over one ear).
[0228] Additionally, the three-pronged sampling end, 94, is taped
or otherwise secured to the upper lip, as may be appropriate for a
particular patient. In use, the carbon dioxide concentration is
measured over time and volume, and one or more capnographs is
obtainable. Such combined apparatus has use with persons undergoing
sleep studies and other research, and in other applications where
oxygen need not be supplied.
[0229] The lip/cheek probe also may be combined with a cannula
device to provide gas, such as oxygen or an oxygen-rich gas
mixture, to a patient in need thereof. For instance, and not to be
limiting, the tubing assembly designated as 90 in FIG. 20
alternatively is used to supply oxygen or an oxygen-rich gas
mixture to both the nose and mouth area (to accommodate mouth
breathing) rather than to sample exhaled breath as described above.
More generally, any number of designs of cannula devices as are
known in the art are so combined, to supply such gas to the nose,
to the mouth, or to both.
[0230] Thus, the lip/cheek probe of the present invention may be
combined to form a single, operational unit with any other style of
oxygen supply/carbon dioxide sampler device, that is, an integral
multi-functional device. This provides the advantage of obtaining
reliable data, such as for arterial oxygen saturation, while only
occupying essentially the same space and path of tubing/wiring, as
does the oxygen supply/carbon dioxide sampler device alone. The
data from the probe can be integrated with the data from the
capnography unit to obtain a better picture of the patient's
respiratory and circulatory function and condition. Additionally,
as for other types of probes described above, an additional feature
is added, namely a control means to adjust the flow rate of the gas
that is provided, where such control is directed by the blood
oxygen saturation data obtained from the probe.
[0231] Although depicted above as separate units combined after
production, the combinations described above alternatively are
integral units designed and sized such that the lip/cheek probe
therein functions as described in this disclosure. Also, protective
sleeves, as described for the lip/cheek probe alone, are envisioned
to be shaped and manufactured in accordance with the teachings
herein, and used for these multi-function devices.
[0232] Preferably, the probes and sleeves are easily fabricated
from low cost materials and are adaptable for use in an operating
room, intensive care unit, emergency department, post-surgery
recovery areas and other areas to treat patients in need of
hemodynamic monitoring. The monitoring system is particularly
applicable for use with patients in whom hypotension or poor
perfusion are problematic. In addition, the monitoring system is
particularly well suited for use with multi-trauma and thermally
injured patients who either have severe peripheral vasoconstriction
or have severely damaged or destroyed peripheral vascular beds.
Through combining at least two pulse oximeters capable of measuring
desired parameters at at least two locations into a single monitor
system, the present invention provides a more accurate assessment
of perfusion and resistance in patients, than any of the presently
available single probe pulse oximeters.
[0233] It should be understood that the examples and embodiments
described herein are for illustrative purposes only and that
various modifications or changes in light thereof will be suggested
to persons skilled in the art and are to be included within the
spirit and purview of this application and the scope of the
appended claims.
* * * * *