U.S. patent application number 13/266747 was filed with the patent office on 2012-05-17 for apparatus and method for monitoring the degree of integration between the functions of the heart and the lungs, and the therapeutic success of resuscitative interventions.
Invention is credited to Awni Ayoubi, Nathan Ayoubi, Ian Brodkin, Fonad Halwani, Arthur Willms.
Application Number | 20120118291 13/266747 |
Document ID | / |
Family ID | 43031624 |
Filed Date | 2012-05-17 |
United States Patent
Application |
20120118291 |
Kind Code |
A1 |
Brodkin; Ian ; et
al. |
May 17, 2012 |
APPARATUS AND METHOD FOR MONITORING THE DEGREE OF INTEGRATION
BETWEEN THE FUNCTIONS OF THE HEART AND THE LUNGS, AND THE
THERAPEUTIC SUCCESS OF RESUSCITATIVE INTERVENTIONS
Abstract
A method, system and apparatus for assessing the coupling
between lung perfusion and ventilation in a patient who is
mechanically ventilated or who is breathing spontaneously through a
conventional artificial airway is provided. Embodiments of the
apparatus comprise an adaptor configured to fit between the
artificial airway and mechanical ventilator (or to attach to the
free end of the artificial airway in cases where the patient is
breathing spontaneously), a measuring chamber in constant fluid
communication with the adaptor via one or more measuring chamber
sampling ports, and a monitoring unit where data obtained from
temperature and relative humidity sensors located in the measuring
is calibrated, sampled, logged and analyzed together with
anthropometric patient data provided by the operator in order to
calculate and/or derive a novel cardio-pulmonary coupling index
termed "Qi" as described, and to enable ongoing diagnostic
cardio-pulmonary monitoring of a patient by comparing changes in
the patient's Qi index during a monitoring interval. The Qi index
is expressed in non-dimensional units, and is displayed relative to
a range of "normal" values defined with reference to values that
are commonly observed at rest in persons in good general health and
who generally match a given patient in gender, age and body size,
and/or as a specific patient's baseline values at rest or under
stress at the outset of a monitoring interval.
Inventors: |
Brodkin; Ian; (Vancouver,
CA) ; Willms; Arthur; (Surrey, CA) ; Halwani;
Fonad; (Kirkland, CA) ; Ayoubi; Awni; (Surrey,
CA) ; Ayoubi; Nathan; (Vancouver, CA) |
Family ID: |
43031624 |
Appl. No.: |
13/266747 |
Filed: |
April 27, 2010 |
PCT Filed: |
April 27, 2010 |
PCT NO: |
PCT/CA10/00684 |
371 Date: |
February 1, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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61173136 |
Apr 27, 2009 |
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Current U.S.
Class: |
128/205.23 ;
128/207.14 |
Current CPC
Class: |
A61M 2205/70 20130101;
A61B 5/097 20130101; A61M 16/021 20170801; A61M 16/0051 20130101;
A61M 16/0816 20130101; A61M 16/161 20140204; A61M 2205/3368
20130101; A61B 5/0816 20130101; A61B 5/01 20130101; A61B 5/087
20130101; A61M 2016/0036 20130101; A61B 5/7285 20130101; A61B
5/0878 20130101; A61M 2205/505 20130101; A61M 16/0858 20140204 |
Class at
Publication: |
128/205.23 ;
128/207.14 |
International
Class: |
A61M 16/00 20060101
A61M016/00; A61B 5/09 20060101 A61B005/09; A61B 5/087 20060101
A61B005/087; A61M 16/04 20060101 A61M016/04; A61B 5/01 20060101
A61B005/01 |
Claims
1. A system for assessing and monitoring the coupling between lung
perfusion and ventilation in a patient who is mechanically
ventilated or who is breathing spontaneously through an artificial
airway, the system comprising: an adaptor configured to fit between
the artificial airway and a mechanical ventilator; a measuring
chamber in constant fluid communication with the adaptor but out of
the main path of gases inhaled and/or exhaled by the patient
through the adaptor, said measuring chamber comprising temperature
and relative humidity sensors for measuring the temperature and
humidity of gases inhaled and/or exhaled by the patient; and, a
monitoring unit in fluid and electrical communication with the
measuring chamber, the monitoring unit comprising: one of a
thermocouple and a flow meter; a suction pump for drawing said
inhaled and/or exhaled gases from said adaptor and through said
thermocouple or flow meter via said measuring chamber; display and
data entry means; and a monitoring unit computer system processor
and memory for the acquisition, conversion, and storage of data
acquired from the temperature and relative humidity sensors, from
the thermocouple or flow meter, and from an operator of the system,
wherein the monitoring unit is configured to: a. detect the
breathing phases of the patient by timing the interval between the
low and/or high temperature and/or humidity plateaus between
individual inhalations and/or exhalations as measured by the
temperature and/or relative humidity sensors; b. obtain base heat
exchange values from the measured temperature and relative humidity
of the inhaled and/or exhaled gases and then repeatedly sample the
temperature and relative humidity of the inhaled and/or exhaled
gases at the prompt of the operator or according to a
pre-determined interval; c. automatically calculate coupling index
Qi of the form
Qi=k.sub.1.DELTA.H.times.k.sub.nb.times.k.sub.v.times.k.sub.pr.times.k.su-
b.pa from sampled temperature and relative humidity readings and
from patient data entered via data entry means by the operator; and
d. display index Qi to the operator via display means over the
course of a monitoring interval.
2. The system of claim 1, further comprising an auxiliary adaptor
configured to fit between the artificial airway and the adaptor and
including a flexible membrane to create pressure differentials by
resisting airflow therethrough, and a spirometer in fluid
communication therewith to measure tidal or minute volume for use
in the calculation of k.sub.1 of coupling index Qi.
3. The system of claim 1, wherein the monitoring unit further
comprises reference temperature and relative humidity sensors, and
wherein the monitoring unit is configured, prior to step (a), to
initially calibrate the measuring chamber temperature and relative
humidity sensors readings relative to the reference temperature and
relative humidity sensor readings, and to apply suitable
compensatory correction factors during the performance of steps (b)
through (d).
4. The system of claim 1, wherein said measuring chamber further
comprises heating resistors for the compensation of heat losses of
said inhaled and/or exhaled gases in said measuring chamber, and
wherein said monitoring unit is configured to calculate and apply
suitable compensatory correction factors by activation of said
heating resistors.
5. The system of claim 2, wherein the breathing phases of the
patient are detected in step (a) from the moments of pressure
reading reversals across the flexible membrane of the auxiliary
adaptor as measured by the spirometer in fluid communication
therewith.
6. Apparatus for the assessment and monitoring the coupling between
lung perfusion and ventilation in a patient who is mechanically
ventilated or who is breathing spontaneously through an artificial
airway comprising: an adaptor configured to fit between the
artificial airway and a mechanical ventilator; a measuring chamber
in constant fluid communication with the adaptor but out of the
main path of gases inhaled and/or exhaled by the patient through
the adaptor, said measuring chamber comprising temperature and
relative humidity sensors for measuring the temperature and
humidity of gases inhaled and/or exhaled by the patient; and, a
monitoring unit in fluid and electrical communication with the
measuring chamber, the monitoring unit comprising: one of a
thermocouple and a flow meter; a suction pump for drawing said
inhaled and/or exhaled gases from said adaptor and through said
thermocouple or flow meter via said measuring chamber; display and
data entry means; and a monitoring unit computer system processor
and memory for the acquisition, conversion, and storage of data
acquired from the temperature and relative humidity sensors, from
the thermocouple or flow meter, and from an operator of the system,
wherein the monitoring unit is configured, in use, to: a. detect
the breathing phases of the patient by timing the interval between
the low and/or high temperature and/or humidity plateaus between
individual inhalations and/or exhalations as measured by the
temperature and/or relative humidity sensors; b. obtain base heat
exchange values from the measured temperature and relative humidity
of the inhaled and/or exhaled gases and then repeatedly sample the
temperature and relative humidity of the inhaled and/or exhaled
gases at the prompt of the operator or according to a
pre-determined interval; c. automatically calculate coupling index
Qi of the form
Qi=k.sub.1.DELTA.H.times.k.sub.nb.times.k.sub.v.times.k.sub.pr.times.k.su-
b.pa from sampled temperature and relative humidity readings and
from patient data entered via data entry means by the operator; and
d. display index Qi to the operator via display means over the
course of a monitoring interval.
7. An automated diagnostic method for assessing and monitoring the
coupling between lung perfusion and ventilation in a patient who is
mechanically ventilated or who is breathing spontaneously through a
conventional artificial airway by use of the apparatus of claim 6,
the method comprising: by a computer system of a monitoring centre:
a. detecting the breathing phases of the patient by timing the
interval between the low and/or high temperature and/or humidity
plateaus between individual inhalations and/or exhalations as
measured by the temperature and/or relative humidity sensors; b.
obtaining base heat exchange values from the measured temperature
and relative humidity of the inhaled and/or exhaled gases and then
repeatedly sample the temperature and relative humidity of the
inhaled and/or exhaled gases at the prompt of the operator or
according to a pre-determined interval; c. automatically
calculating coupling index Qi of the form
Qi=k.sub.1.DELTA.H.times.k.sub.nb.times.k.sub.v.times.k.sub.pr.times.k.su-
b.pa from sampled temperature and relative humidity readings and
from patient data entered via data entry means by the operator; and
d. displaying index Qi to the operator via display means over the
course of a monitoring interval.
Description
TECHNICAL FIELD
[0001] The presently disclosed subject matter relates to methods,
systems and apparatus for measuring the temperature and humidity of
inhaled and exhaled gases in the respiratory tract.
BACKGROUND
[0002] Taken in isolation, the clinical assessment of physiological
variables used to monitor patient condition (e.g. requirements for
supplemental oxygen, composition of exhaled gases, blood pressure,
heart rate, etc.) is often open to misinterpretation. These
variables are frequently interdependent, and misinterpretation of
their individual variations may result in delay in the timely
detection of a change in status and subsequent diagnosis, and in
the appropriate treatment of a patient. Wrong clinical management
decisions may also be made when changes in vital signs are
misleading due to diseases or injuries having similar clinical
manifestations.
[0003] Several devices have been developed to measure temperature
and humidity in the tracheo-bronchial tree and in the upper airways
in humans, and some of these have attempted to derive specific
quantitative values such as, for example, cardiac output. However,
prior efforts in this area have primarily addressed specific
problems related to the way that ambient temperature and humidity
affect long-term ventilation via tracheostomy, and have generally
produced devices and methods suitable for laboratory research
purposes only. Consequently, such devices have never become a part
of routine patient care.
SUMMARY
[0004] The function of the heart and the lungs are interdependent
and are affected by the changing conditions in the rest of the
body. A reliable, easy to use, real-time, non-invasive or minimally
invasive system for assessment of cardio-pulmonary status by an
analytical and predictive instrument that does not require expert
interpretation of physiological parameters would accordingly be of
high clinical value. Making this kind of artificial intelligence
available to those who care for hospitalized and ambulatory
patients would represent a significant advancement in the
improvement of clinical outcomes.
[0005] The presently disclosed and claimed subject matter
accordingly provides a method, system and apparatus for assessing
the coupling between lung perfusion and ventilation in a patient
who is mechanically ventilated or who is breathing spontaneously
through a conventional artificial airway (such as an endotracheal
tube or tracheostomy tube). Embodiments of the present apparatus
comprise an adaptor configured to fit between the artificial airway
and mechanical ventilator (or simply to attach to the free end of
the artificial airway in cases where the patient is breathing
spontaneously), a measuring chamber in constant fluid communication
with the adaptor via one or more measuring chamber sampling ports,
and a monitoring unit where data obtained from temperature and
relative humidity sensors located in the measuring chamber (and in
some embodiments together also with data obtained from spirometry
and/or reference temperature and reference relative humidity
sensors associated with the monitoring unit) is calibrated,
sampled, logged and analyzed together with anthropometric patient
data provided by the operator in order to, inter alia, calculate
and/or derive a novel cardio-pulmonary coupling index termed "Qi"
as described hereinbelow, and to enable ongoing diagnostic
cardio-pulmonary monitoring of a patient by comparing changes in
the patient's Qi index during a monitoring interval. The Qi index
is expressed in non-dimensional units, and is displayed relative to
a range of "normal" values defined with reference to values that
are commonly observed at rest in persons in good general health and
who generally match a given patient in gender, age and body size,
and/or as a specific patient's baseline values at rest or under
stress at the outset of a monitoring interval.
[0006] The measuring chamber is preferably located adjacent to (or
as close as possible to) the end of the artificial airway in order
to minimize heat losses, and is disposed out of the main path of
airflow through the adaptor into and from the lungs to reduce the
possibility of mucosal secretions or other substances interfering
with the functioning of the sensors. In preferred embodiments, the
measuring chamber is positioned above the adaptor during use to
further reduce the possibility of such interference.
[0007] To optimize the response time of the sensors and to further
reduce heat losses, measuring chamber architecture may comprise one
or more ducted paths through which air that is drawn through the
sampling port or ports enters the measuring chamber. Ideally, the
ducted paths are pointed directly at the sensors and (to simplify
calculations) are sized to maintain the same gas/air flow speed as
in the main artificial airway, or a predetermined ratio thereof.
Heating resistors located in the ducted paths may also preferably
be used to compensate for minor heat losses that may occur during
the transfer of air from the adaptor to the measuring chamber, to
intercept and evaporate mucous reaching the ducts, to remove
condensation that may have occurred inside the measuring chamber
before a sensor reading is taken (in order to minimize
evaporation-induced measurement errors), to remove condensation
from the tubing that links the measuring chamber and the monitoring
unit (in order to prevent a build-up of moisture in the tubing that
could interfere with pump operation), and/or to displace (i.e. to
lower) the relative humidity levels of the air in the measuring
chamber by a specific selected amount to improve the performance of
the relative humidity sensor.
[0008] The adaptor and measuring chamber may be formed as a single
unitary assembly, or may be formed from separate moldings or
castings, and in preferred embodiments both adaptor and measuring
chamber are formed of clear rigid plastic and provided in a clean
or sterile single-use package to prevent or reduce the risk of
patient cross contamination. The measuring chamber walls preferably
include one or more molded-in plano-convex or double-convex lenses
positioned to provide an enlarged view of the temperature sensor,
the measuring surface of the relative humidity sensor, and the
heating resistors. A Light Emitting Diode (LED) may also be
positioned within the measuring chamber to illuminate the
temperature and relative humidity sensors. These features allow an
operator to readily check for the presence of mucous or other
undesirable matter on the sensors or resistors. The intensity of
the LED may be also modulated to provide some heating to compensate
for heat losses across the measuring chamber walls.
[0009] In some embodiments, an optional auxiliary adaptor that
includes a flexible membrane to create pressure differentials by
resisting airflow therethrough, as well as an outlet for draining
away airway secretions, is fitted to the airway side of the main
adaptor. The pressure differentials generated by the airflow
against the flexible membrane are monitored and utilized by a
conventional spirometry module located in the monitoring unit to
calculate tidal volume and/or minute volume (i.e. the volume of gas
moved into and out of the lungs in one minute). In cases where the
patient is being mechanically ventilated, these volumes may
alternatively be calculated or obtained directly from the
mechanical ventilator. In further alternative, these volumes may be
obtained or estimated in other ways known to those of skill in the
art, and manually inputted into the system by the operator.
[0010] The measuring chamber and the optional auxiliary adaptor are
connected to the monitoring unit by single use or reusable (e.g.
autoclaveable) tubing, and by conventional wiring and connectors
for connecting the sensors and other components of the measuring
chamber and the optional auxiliary adaptor to corresponding
componentry of the monitoring unit. The monitoring unit comprises a
suction system; processing and control circuitry under the control
of software instructions for the calibration, sampling, logging and
analysis of data obtained from the temperature and relative
humidity sensors, from the optional auxiliary adaptor, and from the
operator of the apparatus; display and data entry means such as an
LCD touch screen or a more conventional display and keyboard; and
associated electromechanical controls including relays and
solenoids as described further hereinbelow.
[0011] In addition to the derivation of coupling index Qi and the
general diagnostic cardio-pulmonary monitoring of a patient by
comparison of the patient's Qi index during a monitoring interval
as noted above, the processing and control circuitry of the
monitoring unit may be controlled by software instructions to:
[0012] a--carry out calibration processes in relation to the
temperature and relative humidity sensors; [0013] b--sample, log
and analyze the temperatures and humidities of inhaled and exhaled
gases as measured by the sensors, and calculate and apply suitable
correction factors to compensate for residual heat losses between
the sampling port(s) and the sensors; [0014] c--detect the
breathing cycle by, for example, detecting successive moments at
which sampled air temperatures peak and start to decrease
(indicating an inhalation start), or by detecting the moment of
pressure readings reversal from the optional auxiliary adaptor data
(indicating the switch from inhalation to exhalation or the
opposite), and synchronize the sampling therewith; [0015]
d--sample, log and analyze the pressure differentials in the
optional auxiliary adaptor and calculate the tidal and minute flows
from these values; [0016] e--detect the start of inhalation from
either the temperature and humidity profiles of prior inhaled and
exhaled gas samples, or from the differential pressure values
generated by the membrane in the optional auxiliary adaptor, and
operate the suction system of the monitoring unit for short
durations during this period in order to determine the inhaled gas
relative humidity and temperature without being affected by the
humidity sensor's time constant; [0017] f--analyze the degree of
optimization between lung perfusion and lung ventilation based on
the observed heat exchange rates and dynamic temperature profiles
of exhaled gases for a given combination of variables in the
inhaled gases. This may be done with the patient under ongoing
ventilation conditions, or subjected to an abrupt change in the
temperature and/or humidity of the inhaled gas and/or of the minute
volume; [0018] g--access and display previously recorded data and
trends therein to permit comparison to most recently collected data
and/or to typical Qi values of comparable individuals; [0019]
h--regulate the heating resistors and/or the LED within the
measuring chamber in order to remove condensation from the
measuring chamber before a reading is taken (to minimize
evaporation-induced measurement errors) or to "condition" the
relative humidity sensors when required prior to data acquisition.
Humidity sensor conditioning entails the heating thereof during the
inhalation phase between data sampling sessions in order to restore
optimal sensor response characteristics; and, [0020] i--regulate
the heating resistors and/or an LED within the measuring chamber to
remove condensation from the tubing linking the measuring chamber
to the monitoring unit to prevent a build-up of moisture in the
tubing, which may interfere with suction pump operation.
[0021] In preferred embodiments, a self-diagnostic application is
additionally embedded in the processing and control circuitry to
warn users when device operating parameters are outside of
specified limits. Standard health care protocol may also be
provided to facilitate the transmission of acquired patient data to
a central monitoring and data storage system within medical
facilities such as hospitals, clinics, etc.
[0022] All of the methods and tasks described herein, excluding
those identified as performed by a human, may be performed and
fully automated by a computer system, and may be embodied in
software code modules executed by one or more general purpose
computers. The code modules may be stored in any type of
computer-readable medium or other computer storage device. Some or
all of the methods may alternatively be embodied in specialized
computer hardware. The computer system may, in some cases, include
multiple distinct computers or computing devices (e.g., mobile
devices, physical servers, workstations, storage arrays, etc.) that
communicate and interoperate over a network to perform the
described functions. Each such computing device typically includes
a processor (or multiple processors) that executes program
instructions or modules stored in a memory or other non-transitory
computer-readable storage medium. Where the system includes
multiple computing devices, these devices may, but need not, be
co-located. The results of the disclosed methods and tasks may be
persistently stored by transforming physical storage devices, such
as solid state memory chips and/or magnetic disks, into a different
state.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] For a fuller understanding of the nature and advantages of
the disclosed subject matter, as well as the preferred mode of use
thereof, reference should be made to the following detailed
description, read in conjunction with the accompanying drawings. In
the following drawings, like reference numerals designate like or
similar parts or steps.
[0024] FIG. 1 is a schematic functional diagram of an apparatus in
accordance with an embodiment of the disclosed subject matter,
showing the main components thereof in relation to a patient.
[0025] FIG. 2 is an enlarged cross-sectional side elevation of the
adaptor/measuring chamber element of the apparatus of FIG. 1.
[0026] FIG. 3 is a schematic diagram of the monitoring unit element
of the apparatus of FIG. 1.
DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS
[0027] Referring to FIG. 1, a system and apparatus for assessing
the coupling between lung perfusion and ventilation in a patient
100 who is mechanically ventilated or who is breathing
spontaneously through a conventional artificial airway 102 is
provided and generally designated with reference numeral 110. The
apparatus generally comprises an adaptor/measuring chamber 1
configured for connection to artificial airway 102, either directly
or, as illustrated, via auxiliary adaptor 200, and to a remote
monitoring unit 3 via conventional plastic tubing 2a and electrical
wiring 2b. In typical embodiments, the plastic tubing 2a is of
conventional 2- or 3-lumen configuration and has an internal
diameter of 2.4 mm or less, and the electrical wiring comprises 7
to 12 discrete wires, all of which are fitted with conventional
mechanical and electrical connectors at each end.
[0028] The illustrated embodiment of adaptor/measuring chamber 1 is
shown as being formed from a single molded piece, but the adaptor
and measuring chamber portions thereof may alternatively be formed
from separate moldings or castings. Inlet 4 and outlet 5 of
adaptor/measuring chamber 1 are shaped and configured to connect,
respectively, to conventional artificial airway 102 (or to
auxiliary adaptor 200) and to a conventional mechanical ventilator,
and define a main airflow path 4-5 therebetween through the adaptor
portion of adaptor/measuring chamber 1.
[0029] Sampling port or ports 6 permit gases to be drawn from the
main airflow path 4-5 into the measuring chamber portion 7 of
adaptor/measuring chamber 1 via one or more ducts 8 integrated into
the molding and sized to maintain the same gas/air flow speed as in
the artificial airway 102, or a selected ratio thereof. A thin-wire
fast response (typically 2 mS) temperature sensor or thermocouple 9
and a fast response (typically 3 sec) relative humidity ("RH")
sensor 10 are positioned adjacent the outlet of the ducts 8 to
optimize response time. Surface mounted and mechanically secured
heating resistors 11 may be located in the ducts 8, and when
present may be used to compensate for heat losses incurred during
the transfer of gases into the measuring chamber 7, and to displace
(i.e. lower) the relative humidity levels of the gases by a
selected specific amount to improve the performance of the RH
sensor. Heating resistors 11 may also act as mucous interceptors,
evaporators or measuring chamber 7 driers, and may also be used to
verify the gas flow rate passing through the measuring chamber 7 by
comparing the time that it takes the thermocouple 9 to detect a
given temperature rise vis-a-vis the time taken for a corresponding
temperature rise to occur during calibration with a known gas flow
rate.
[0030] Gases drawn through the measuring chamber 7 exit to tubing
2a and thence on to monitoring unit 3 through a chamber outlet 12
that is preferably located in a position remote from the sampling
port(s) 6, and that may comprise a Lure Lock.TM. male connector. In
embodiments where an optional auxiliary adaptor 200 is used,
outlets 104 and 105, also comprising male connectors and located
remote from the sampling port(s) 6, are also be provided for
transmitting pressure signals via tubing 2a to a spirometry module
32 in the monitoring unit 3.
[0031] The adaptor/measuring chamber 1 is preferably constructed of
clear rigid plastic material, and may additionally comprise up to
three photo sensors 106 orthogonally aligned in three dimensions
and associated circuitry to enable the automatic detection of
inclination of the adaptor/measuring chamber 1 by comparing the
difference in the ambient light reaching each of the photo sensors
106. In alternative embodiments, photo sensors 106 may be replaced
with a 3-axis accelerometer to achieve the same purpose. Optional
one-way flap 107 may also be provided between the main airflow path
4-5 and measuring chamber portion 7 of the adaptor/measuring
chamber 1 to minimize humidity migration into measuring chamber 7
during the exhalation phase.
[0032] The measuring chamber 7 may also include one or more
molded-in plano-convex or double-convex lenses 13 suitably
positioned to provide an enlarged view of the temperature sensor
(i.e. thermocouple) 9, the measuring surface of the relative
humidity sensor 10, and the heating resistors 11. An LED 14 may
also be mounted within measuring chamber 7 to illuminate the
thermocouple 9, the relative humidity sensor 10 and the heating
resistors 11. Lenses 13 and LED 14 thereby permit, where present,
an operator to readily check for the presence of mucous or other
undesirable matter on the sensors 9, 10 and/or resistors 11. The
intensity of LED 14 may be also modulated to provide heating to
compensate for heat losses across the walls of measuring chamber 7.
All chamber component wiring terminates at an electrical connector
15 for connection to monitoring 3 via wiring 2b.
[0033] Auxiliary adaptor 200 comprises a length of molded clear
rigid plastic tubing with an inlet 202 and an outlet 204 shaped and
configured to connect, respectively, to artificial airway 102 and
to inlet 4 of adaptor/measuring chamber 1, and define a main
airflow path 202-204 therebetween through auxiliary adaptor 200. A
membrane 206 comprising a flexible flap provides resistance to the
airflow through auxiliary adaptor 200, and the relative pressures
generated by this resistance are transmitted via outlets 104 and
105 and flexible tubing 2a to spirometry module 32 in the
monitoring unit 3. A drain 208 molded in the auxiliary adaptor
intercepts mucous and fluids, and allows them to be readily removed
via drain outlet 210. Outlet 204 of auxiliary adaptor 200 is
preferably keyed to fit the adaptor/measuring chamber 1 with drain
208 positioned at 180 degrees relative to the vertical orientation
of the measuring chamber 7 to further facilitate proper drainage of
mucous and fluids. Drain outlet 210 is connected to tubing 212 and
a manually or automatically operated drain valve 214. In preferred
embodiments, the automatic drain valve 214 is actuated during an
exhalation cycle and when the system is not sampling data.
[0034] Schematically illustrated in FIG. 3, monitoring unit 3
comprises a small capacity diaphragm suction pump 16 with an
optional heated head 16a, flow meter or thermocouple 17, data
acquisition, conversion, storage and display module 18, control
module 19, LCD touch screen display and driver 20, keypad 21,
solenoid shut off valve 22, air inlet connection 23 for receiving
gases drawn through tubing 2 from measuring chamber outlet 12, air
outlet connection 24, wire connector 25 for communication via wires
2b with electrical connector 15 of measuring chamber 3, reference
thermistors 26 and 36, reference relative humidity sensor 27, and
conventional power supply module 28 to provide DC power thereto. AC
power is provided to the power supply module 28 via receptacle 29,
and to the pump 16 via relay 30. For calibration at start-up, a
bracket 31 is provided on monitoring unit 3 to hold the
adaptor/measuring chamber 1 in a suitable position for directing
airflow over the reference thermistors 26 and 36 and relative
humidity sensor 27. In some embodiments, a spirometry module 32 is
also included and is connected to pressure ports 34 and 35.
[0035] If present, the heated head 16a of pump 16 reduces the
mechanical deterioration of pump 16 components due to high humidity
and condensation. Air outlet 24 is preferably connected to a
conventional gas reclamation or scavenging system 38.
[0036] The monitoring unit 3 is typically located at the site of
patient care and is connected to the electrical mains via
receptacle 29. The display and operator input portions 20, 21 of
the monitoring unit 3 can be duplicated or physically separated
from the remaining components of monitoring unit 3, and may, for
example, be mounted at a clinical work station, which may be
located remote from the site of patient care.
[0037] The data acquisition, conversion, storage and display module
18 of monitoring unit 3 preferably comprises an electronic circuit
board (referred to herein as the "Data Acquisition Conversion
Storage and Display" or "DACSD" board) configured to receive
signals from the thermocouple 9 and relative humidity sensor 10 of
measuring chamber 7, as well as from reference thermistors 26 and
36, reference relative humidity sensor 27, flow meter or
thermocouple 17, spirometry module 32, touch-screen display 20 and
keypad 21, and to automatically calculate Qi under control of
software instructions as a weighted function of heat gain in one or
more breathing cycles, the tidal or minute volume entered by the
operator or determined by other means (such as by use of a
spirometry module as herein described), the type of ventilation
change introduced (or not) by the operator, anthropometric patient
data entered manually by the operator, and the parameters of the
exhaled air temperature profile.
[0038] In general form,
Qi=k.sub.1.DELTA.H.times.k.sub.nb.times.k.sub.v.times.k.sub.pr.times.k.su-
b.pa, where H is air flow enthalpy, and k.sub.1, k.sub.nb, k.sub.v,
k.sub.pr, and k.sub.pa are weighing factors stored in system memory
or calculated from manually entered or sensor acquired data. Any
change in any of the weighing factors will accordingly have a
direct impact on the Qi. k.sub.1 is calculated as a function of
tidal volume; k.sub.nb as a function of breathing rate; k.sub.v as
a function of the ventilation change, if any, introduced by the
operator of a mechanical ventilator; k.sub.pr as a function of
anthropometric patient data entered by the operator; and k.sub.pa
as a function of exhaled air temperature profile.
[0039] Since the Qi index is expressed in non-dimensional units and
is displayed relative to a range of "normal" values (defined with
reference to values that are commonly observed at rest in persons
in good general health and who generally match a given patient in
gender, age and body size, and/or as a specific patient's baseline
values at rest or under stress at the outset of a monitoring
interval), and since ongoing diagnostic cardio-pulmonary monitoring
of a patient is carried out by comparing changes in the patient's
Qi index during a monitoring interval, the specific methodology
utilized in the derivation of numeric values for each of the
weighing factors k.sub.1, k.sub.nb, k.sub.v, k.sub.pr, and k.sub.pa
is not critical, so long as whatever methodology is chosen is
consistently applied as between the derivation of the patient's
values and the reference values against which the patient's Qi
index is evaluated.
[0040] For artificially ventilated patients, ventilation may
typically include one or more of: (a) switching from heated and
humidified gas to gas of a different composition, (b) changing the
tidal volume, and (c) changing the ventilation rate. The tidal
volume k.sub.1 in this implementation may be entered by the
operator or determined by other means as previously described.
[0041] Additional functions of the DACSD module 18 may include:
[0042] a--the conversion of the sampling data generated by the
relative humidity sensors 10, 27; thermocouples 9, 17; and
thermistors 26, 36 into temperature and humidity readings; [0043]
b--the calculation and application of correction values for the
readings of the measuring chamber relative humidity sensor 10 by
comparison with the readings of the reference relative humidity
sensor 27 and the heating resistors' 11 operation; [0044] c--the
conversion of data from the spirometry module 32 into tidal and
minute volume values; [0045] d--monitoring of the inclination of
the measuring chamber 7 relative to its preferred position along a
vertical axis atop the adaptor portion of adaptor/measuring chamber
1 by comparison of readings from each of the photo sensors (or
accelerometer) 106, and preferably including the triggering of an
alarm if the inclination exceeds a predetermined maximal value;
[0046] e--checking for the sampling gas flow value at start-up and
periodically thereafter via the direct flowmeter 17, or by
measuring the temperature rise when the heating resistors 11 are
activated and comparing it to the expected temperature rise for a
given suction pump 16 airflow level; [0047] f--determining the
sequence of operation of the suction pump 16, the solenoid valve 22
and the heating resistors 11 using data received from the sensors
of the measuring chamber 7 and of the monitoring unit 3, the keypad
21 the touch screen 20 and an internal timer; [0048]
g--transmission of converted data to the display driver 20; [0049]
h--retrieving and displaying previously calculated Qi's, Qi trends,
and other derived value profiles for the patient undergoing
testing, or for typical cases stored in memory; [0050] i--detecting
and initiating recovery measures when an abnormal condition
involving condensation or mucosal secretions occurs, and shutting
down the system if the recovery attempt fails; [0051]
j--determining the additional heating required to compensate for
heat loss of the gas in transit from the airway to chamber 7 with
respect to ambient temperature, and transmitting this data to the
control board 19; [0052] k--determining the RH displacement when
the heating resistors 11 are in operation; [0053] l--determining
the level and duration of the condensation clearing cycle prior to
logging of the sampled gas flow data, and transmitting this the
data to the control board 19; [0054] m--determining the timing of
the fluid clearing routine from the auxiliary adaptor 200 with
respect to sampling cycles and preset or automatically determined
time intervals; [0055] n--monitoring the moisture content in
suction pump 16 during shut down of the monitoring unit 3 to ensure
the pump 16, solenoid 22 and flow meter or thermocouple 17 are
clear of moisture before power is turned off; [0056] o--issuing
warning messages when unusual data (such as, for example, a
humidity drop to 0%, or a temperature reading below ambient)
indicates a fault in the equipment or its performance; [0057]
p--issuing a visual and audio warning message if a trend consistent
with a deterioration of a patient's condition (signaled by a
decreasing Qi index number) is detected; and, [0058] q--optionally
transmitting display data and alert messages to a remote/central
monitoring station.
[0059] The control board 19 receives data from the DACSD 18, the
keypad 21 and the touch-screen display 20. The functions of the
control board 19 include: [0060] a--conditioning and providing the
required DC power to the DACSD 18, the display 20, the keypad 21,
the solenoid valve 22, the RH sensors 10, 26, 36, the heating
resistors 11, the LED 14 and the pump-head heater 16a; [0061]
b--controlling and monitoring the AC or DC power going to the pump
16, and signal a warning if a set current threshold is crossed or
if a suspicious trend (such as an unexpected incremental decrease
of power consumption, likely indicating pump diaphragm failure, or
an unexpected incremental increase in power consumption, likely
indicating blockage of tubing 2a or a failing pump motor) develops;
[0062] c--pulsing the power supply to the pump 16 in synchronicity
with inhalation periods in order to operate pump 16 for typically
1.0 seconds after a short initial delay of typically 0.2 seconds
following the start of inhalation, thereby to synchronize the
apparatus for sampling of only inhaled air conditions (as required
where inhaled air parameters are not keyed in manually); [0063]
d--monitoring the wiring 2b between the measuring chamber 7 and
monitoring unit 3, and shut down all power if a ground fault is
detected; [0064] e--providing routine electrical safety monitoring
and response; and, [0065] f--opening and closing the fluid removal
solenoid valve at the auxiliary adaptor outlet.
[0066] In use of the subject system and apparatus 110, the power is
turned on and a fully connected adaptor/measuring chamber 1 is
first fitted over bracket 31 of monitoring unit 3 (prior to the
connection of the adaptor/measuring chamber 1 to the artificial
airway 102) for initial calibration of measuring chamber
temperature sensor 9 and relative humidity sensor 10 as against
reference thermistor 26 and reference relative humidity sensor 27
of monitoring unit 3. Reference relative humidity sensor 27 may
itself be calibrated periodically by running the standard
calibration procedure and using one of the reference thermistors
26, 36 for wet bulb readings (by using a wet sleeve fitted to it)
against a dry bulb reading provided by the other reference
thermistor 26, 36. Bracket 31 additionally holds the
adaptor/measuring chamber 1 in a suitable position to permit the
operator to check for defects and for correct gas flow through
adaptor/measuring chamber 1.
[0067] Once initial calibration is complete, the adaptor/measuring
chamber 1 is removed from bracket 31, and in embodiments that
include an auxiliary adaptor 200, the adaptor/measuring chamber 1
is then connected to the auxiliary adaptor 200 before the auxiliary
adaptor 200 is connected to the artificial airway 102. In
embodiments where no auxiliary adaptor 200 is used, the
adaptor/measuring chamber 1 is connected directly to the artificial
airway 102.
[0068] The operator then initiates the sampling sequence manually
or automatically via a timer set from the keypad 21 or from the
display touch-screen 20. The sampling sequence starts the suction
pump 16 and the flow of gases through the measuring chamber 7. By
timing the interval between the low and/or high temperature and/or
humidity plateaus between inhalations and/or exhalations (or the
pressure reversal points in embodiments that employ auxiliary
adaptor 200), the apparatus detects the breathing phases (i.e. the
duration of inhalation and exhalation), initiates the inhaled gas
measurement cycle followed by the full measurement cycle and logs
the contemporaneous sensor readings.
[0069] A typical sequence of events experienced by a patient during
a testing session using the subject system and apparatus 110 may
comprise: [0070] a--An initial keying-in via keypad 21 and/or
touch-screen display 20 of patient data including, among other
potential characteristics, the weight, height, gender, and age of
the patient, and in some preferred embodiments where the apparatus
is set up to send data to a patient data storage location (e.g. to
a hospital information system), a unique patient identifier; [0071]
b--If clinical circumstances permit, obtaining "baseline" samples
of the patient's Qi and storing these in DACSD module 18; [0072]
c--Next, sampling at pre-determined intervals and/or at the prompt
of the operator with or without a concurrent transient change in
the hydrothermal profile of the inhaled gases is carried out. The
apparatus 110 tracks the type of changes, if any, induced in the
inhaled gases, and the type of ventilation change that is induced
is keyed in or left to the system to track; [0073] d--The sampling
sequence typically starts with determining the inhaled gas
temperature and humidity by running the suction pump 16 for
typically one or two seconds within several inhalation periods. A
full sampling then follows (typically for roughly 30 seconds), and
the acquired temperature and humidity data is continuously logged
and used for the generation of graphical displays and for
calculating the heat exchange values in the patient's lungs with
respect to the inhalation parameters; [0074] e--The inhaled gas
sampling procedure outlined in step (d) above may also be used to
determine the exhaled gas temperature and humidity, and this data
may alternately be used to calculate the heat exchange values, or
as a cross-check for the heat exchange values calculated in
accordance with step (d); [0075] f--The values of the Qi over the
course of the patient observation period are calculated, monitored
and analyzed by the system and presented visually to the operator.
The apparatus will provide an alarm signal if a trend in the Qi or
in the temperature or humidity profiles shows a deterioration in
the patient's clinical status. [0076] g--The apparatus also
calculates and measures trends (salutary or otherwise) and displays
these in a color coded manner. Improvement or deterioration coding
will be relative to previous readings for the same patient, or
relative to "in good health" values for persons of similar stature,
gender and age.
[0077] The present description includes the best presently
contemplated mode of carrying out the subject matter disclosed and
claimed herein, and is made for the purpose of illustrating the
general principles of the subject matter and not be taken in a
limiting sense; the subject matter can find utility in a variety of
implementations without departing from the scope of the disclosure
made, as will be apparent to those of skill in the art from an
understanding of the principles that underlie the subject
matter.
* * * * *