U.S. patent application number 09/341975 was filed with the patent office on 2002-12-12 for controlled gas-supply system.
Invention is credited to KREBS, CHRISTIAN.
Application Number | 20020185126 09/341975 |
Document ID | / |
Family ID | 43466707 |
Filed Date | 2002-12-12 |
United States Patent
Application |
20020185126 |
Kind Code |
A1 |
KREBS, CHRISTIAN |
December 12, 2002 |
CONTROLLED GAS-SUPPLY SYSTEM
Abstract
The invention relates to a gas-supply system for patients
receiving artificial respiration or breathing spontaneously, in
which one or several gases (for example NO, oxygen) are added to
the respiration gas at varying proportions (continuously or
intermittently) by means of a control device (program control,
sensor control or combined program/sensor control). This gas-supply
system allows for adaptive dosing of the gas to suit individual
patients.
Inventors: |
KREBS, CHRISTIAN; (VIENNA,
AT) |
Correspondence
Address: |
CONNOLLY BOVE LODGE & HUTZ, LLP
1220 N MARKET STREET
P O BOX 2207
WILMINGTON
DE
19899
|
Family ID: |
43466707 |
Appl. No.: |
09/341975 |
Filed: |
August 26, 1999 |
PCT Filed: |
January 15, 1998 |
PCT NO: |
PCT/EP98/00202 |
Current U.S.
Class: |
128/200.24 |
Current CPC
Class: |
A61M 2206/14 20130101;
A61M 2202/0275 20130101; A61M 2202/03 20130101; A61M 16/107
20140204; A61M 16/12 20130101; A61M 2016/0021 20130101; A61M
2202/0208 20130101; A61M 2202/0208 20130101; A61M 16/202 20140204;
A61M 2202/0007 20130101; A61M 2202/0291 20130101 |
Class at
Publication: |
128/200.24 |
International
Class: |
A62B 007/00; A62B
009/00; A61M 015/00; A61M 016/00; A62B 018/00; F16K 031/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 17, 1997 |
DE |
197 01 617.0 |
Oct 23, 1997 |
DE |
197 46 742.3 |
Claims
1. Gas supply system for treating humans or mammals by inhalation,
having a controlled gas metering of at least one gas, characterized
by a program control unit, a sensor control unit or a combined
programme/sensor control unit for inspiration-synchronized gas
metering which is carried out in a pulse-modulated manner or in
sequences.
2. Gas supply system according to claim 1, characterized in that
pulse width, pulse height and number of pulses within one breath
are preset or variable.
3. Gas supply system according to claim 1 or 2, characterized in
that the gas metering is carried out by means of a basic metering
and an additional metering of the gas.
4. Gas supply system according to one of claims 1 to 3,
characterized in that the gas metering is controlled by means of a
response curve.
5. Gas supply system according to one of claims 1 to 4,
characterized in that the gas supply system contains a pressure
vessel containing compressed gas, a vessel containing
cold-liquefied gas or a gas generator as the gas source.
6. Gas supply system according to one of claims 1 to 5,
characterized in that oxygen and an NO-containing gas; an
NO-containing gas and hydrogen; oxygen and hydrogen; oxygen and
helium; oxygen, an NO-containing gas and hydrogen; oxygen, an
NO-containing gas and helium; oxygen, carbon dioxide and helium; or
oxygen, an NO-containing gas, carbon dioxide and hydrogen are
metered in parallel.
7. Gas supply system according to one of claims 1 to 6,
characterized in that the gas supply system contains a gas-specific
sensor, a gas sensor, a gas analyser, a pressure sensor, a pressure
sensor and a gas sensor, a sound sensor, a sound pressure sensor, a
gas volumetric flow sensor, a gas volume sensor, a sensor for
measuring the oxygen saturation in the peripheral blood, for blood
gas analysis, for measuring the oxygen saturation in the peripheral
blood, for measuring blood pressure, for measuring pulmonary blood
pressure, for measuring heart rate or for measuring cardiac
output.
8. Gas supply system according to one of claims 1 to 7,
characterized in that the gas supply system contains one or more
sensors for simultaneously measuring at least two variables, the
variables being used to control the gas metering.
9. Gas supply system according to one of claims 1 to 8,
characterized in that the gas supply system contains one or more
sensors for simultaneously measuring heart rate and oxygen
saturation in the peripheral blood or pulmonary vessel pressure and
oxygen saturation in the peripheral blood.
10. Gas supply system according to one of claims 1 to 9,
characterized in that the gas supply system contains a system for
controlling the gas metering of at least one gas, which system is
adaptive or related to the human or mammal being treated.
11. Gas supply system according to one of claims 1 to 10,
characterized in that the gas supply system contains a sensor for a
warning system or for controlling a safety shut-off for gas
metering.
12. Gas supply system according to one of claims 1 to 11,
characterized in that the gas supply system contains a program
control unit and/or sensor control unit for the continuous or
discontinuous temporal change in the gas volume or gas
concentration of a gas in the respiratory gas.
13. Gas supply system according to one of claims 1 to 12,
characterized in that the gas supply system, after one or more
metered gases have been fed in, contains a mixing path and/or a
mixing member in the respiratory gas line.
14. Method for metering gas for treating humans or mammals by
inhalation with one or more gases, characterized in that the gas
metering takes place in an inspiration-synchronized manner and by
means of a program control unit, a sensor control unit or a
combined program/sensor control unit, in a pulse-modulated manner
or in sequences.
15. Method according to claim 14, characterized in that the
sequence of the program for controlling the metering of a gas is
dependent on a measured variable being reached, and program
sequences of the gas metering are triggered in the event of a
threshold of a measured variable being exceeded or undershot.
16. Method according to claim 14, characterized in that measured
values from the previous breath are used to control the metering of
a gas.
Description
[0001] The invention relates to an apparatus for the controlled
metering of gases, in particular for the controlled addition of NO
or oxygen to a respiratory gas in apparatus for artificial
respiration or respiratory donation.
[0002] Artificial respiration apparatus are used for mechanical
artificial respiration, for anesthesia and for respiratory therapy
by treatment with gases, e.g. oxygen donation or treatment with
nitrogen monoxide (NO).
[0003] An inhalation-anesthesia apparatus is described, for
example, in DE 37 12 598 A1. It is used to meter anesthetic gas
into the respiratory gas.
[0004] DE 43 25 319 C1 describes an apparatus for continuously
metering NO to the respiratory air of patients, containing a
respirator, an NO metering vessel, a metering unit with control
unit and an analyser for determining the NO concentration in the
respiratory air. The control unit (monitoring and regulating unit)
is responsible for metering the NO to be metered by determining the
volumetric flow rates of respiratory gas and NO, taking into
account the NO analysis parameter. The NO metering is proportional
to volume or to volumetric flow rate, so that the NO concentration
in the respiratory gas is always kept constant. The essential
technical principles involved in metering NO in NO therapy are
described in: "C. Krebs et al., Technological basis for NO
application and environmental security, Acta Anaesthesiologica
Scandinavica Supplement 109, Vol. 40, 1996; pp. 84-87".
[0005] Patients with chronic breathing difficulties (e.g. asthma
and COPD (Chronic Obstructive Pulmonary Disease)) are assisted by a
generally movable oxygen donor in the oxygen supply to the body.
Such patients are referred to as spontaneously breathing patients,
in contrast to patients who are connected to an artificial
respiration apparatus by in-patient intubation. Thus, spontaneously
breathing patients are given, for example, an additional oxygen
donation (LOT=Long-term Oxygen Therapy) or respiratory assistance
(via CPAP=Continuous Positive Airways Pressure). The gases are
administered either via so-called nasal spectacles or a nasal probe
(nasal application: in the most simple case, a gas supply tube, the
opening of which is arranged to be open beneath the nasal orifices
of the patient) or by means of a breathing mask (particularly in
the case of CPAP).
[0006] An apparatus for feeding respiratory gas or oxygen to a
patient is described in DE 43 09 923 A1. A pulse-oxymeter is used
to adapt the respiratory gas volume to be fed to the patient to the
blood gas saturation level determined.
[0007] The invention is based on the object of providing an
apparatus for supplying patients with one or more gases, the gas
metering into a respiratory gas being individually adapted to a
patient by means of a control unit of the apparatus.
[0008] The object is achieved by means of a program-controlled or a
program- and sensor-controlled gas supply system, in particular by
means of a gas supply system with controlled metering of at least
one gas, in which system the gas is a pure gas or a gas mixture,
the gas is metered in an inspiration-synchronized,
program-controlled and/or sensor-controlled manner, and the volume
of gas metered in one respiratory cycle is dependent on the
respiratory gas volume.
[0009] Gas supply systems are arrangements or devices which feed
one or more gases to a patient or provide one or more gases to a
patient for respiration. The gases, in particular medical gases,
are preferably mixed with air, a respiratory gas or oxygen, so that
gas mixtures which maintain respiration are obtained. A gas supply
system is, for example, an artificial respiration system comprising
artificial respiration apparatus and gas metering device for one or
more gases. An artificial respiration system comprises, for
example, hose connections or gas lines, gas source, gas metering
device (gas metering unit), breathing mask, preferably a
respiratory gas humidifier and, if appropriate, one or more gas
filters (e.g. NO.sub.2 filter). Artificial respiration systems
having an artificial respiration apparatus are generally used for
the in-patient treatment of patients. Gas-supply systems may be
stationary or mobile, in particular portable, apparatus. Gas supply
systems according to the invention are preferably used to treat
humans or mammals with one or more gases, in particular for
inhalation treatment of the lungs.
[0010] An artificial respiration system which, with modifications,
can be used as a gas supply system is described, for example, in DE
43 25 319 C1, to which reference is made.
[0011] Gas supply systems are, for example, also gas-donating
apparatus for spontaneously breathing patients. Such a gas supply
system is described in DE 43 09 923 A1, to which reference is
made.
[0012] The gas supply system generally contains a breathing mask or
nasal spectacles. The gas supply system preferably contains a
humidifier for the respiratory gas and/or gas.
[0013] The gas supply system preferably contains one or more gas
sources. Gas sources are, for example, compressed-gas sources
containing a compressed gas, such as compressed-gas vessels,
compressed-gas cylinders, pressure boxes, compressed-gas lines or
vessels containing cold-liquefied gas (e.g. for delivering
evaporated, gaseous oxygen). A gas generator may also serve as a
gas source. A gas generator is, for example, an on-site gas
generator, e.g. for producing nitrogen monoxide (NO), in particular
NO in nitrogen, by low discharge in a nitrogen/oxygen gas mixture.
Further gas generators are, for example, electrolysis cells (e.g.
for generating hydrogen) or chemical reactors (e.g. reaction
chambers in which chemical reactions take place in order to
generate gas). The gases are preferably medical gases. Medical
gases are gases or gas mixtures which are used in the medical
sector, for example for treating disorders; therapy, prophylaxis,
anesthesia, diagnostics, improving the respiratory function or
state of health of humans or mammals. Medical gases often have a
pharmacological action. However, medical gases may also be used for
other properties (e.g. as contrast agents for tomography, in
particular NMR computer tomography of the lung or other
image-generating procedures). Medical gases are, for example,
oxygen, anesthetic gases such as laughing gas (N.sub.2O) or xenon,
hydrogen, noble gases such as helium, carbon dioxide (CO.sub.2),
nitrogen monoxide (NO) or gas mixtures containing one or more of
the abovementioned gases as a constituent, e.g. helium/oxygen gas
mixtures, helium/oxygen/NO gas mixtures or helium/oxygen/CO.sub.2
gas mixtures. As an alternative to metering a gas mixture, the
individual components or individual components and partial gas
mixtures may also be metered in parallel (simultaneously or at
different times) to, for example, a respiratory gas. Medical gases
generally have a high purity.
[0014] The metering of one or more gases advantageously takes place
only during inspiration phases. No gas metering takes place during
expiration. Gas metering which is synchronized to the respiratory
cycles is achieved by means of a trigger effect with the aid of a
sensor. The start of inspiration or the start and end of
inspiration is detected by a control unit on the basis of sensor
measured values. Gas metering takes place continuously (e.g. with a
fixed volume or concentration of the metered gas per inspiration
over the entire operating time) or discontinuously (e.g. with
metering breaks), preferably
[0015] a) program-controlled (e.g. time program),
[0016] b) sensor-controlled, or
[0017] c) with a combined program control and sensor control.
[0018] The control unit (e.g. microprocessor control, computer
control) receives the measurement signal from the sensor for
triggering the gas metering and preferably uses a program and/or
sensor control to determine whether the gas is metered, and for
what duration (pulse width ti), at what volumetric flow rate
V.sub.i' (differential change in the gas volume V.sub.i with
respect to time t: V.sub.i'=dV.sub.i/dt=pulse height) and with what
number n.sub.i of metering operations (n.sub.i: number of pulses)
the gas i is metered. This type of gas metering is referred to as
pulse-modulated gas metering. The duration t.sub.max of inspiration
and the beginning and end of inspiration are advantageously
determined by means of a sensor. The pulse width t.sub.i is less
than or equal to the duration t.sub.max. The metered gas volume
V.sub.i of a pulse is calculated on the basis of the equation
V.sub.i=V.sub.i'*t.sub.i, and the volume of gas metered during an
inspiration is calculated on the basis of the equation
V.sub.i=V.sub.i'*t.sub.i*n.sub.i.
[0019] The concentration C.sub.i of a metered gas, based on the
respiratory gas volume V.sub.ges (V.sub.ges=sum of all the gas
volumes V.sub.i), can be calculated, given n.sub.i=1, according to
the equation
C.sub.i=V.sub.i/V.sub.ges=V.sub.i'*t.sub.i/V.sub.ges.
[0020] The values of pulse width, pulse height and number of pulses
within one inspiration may be fixed in advance or variable.
[0021] In many applications, a gas is advantageously metered by the
combination of a basic metering, preferably with constant settings
for V.sub.i', n.sub.i and t.sub.i, and an additive metering with
variable (controlled) settings of V.sub.i', n.sub.i and t.sub.i.
Basic metering and additive metering of a gas are preferably
carried out using separate metering devices (e.g. controlled
solenoid valves). The basic metering may in this case provide a
basic supply of a gas and the gas volume and gas concentration are
regulated by the additive gas metering. In this case, the additive
gas metering may be program- or sensor-controlled.
[0022] Measured values from the preceding inspiration, e.g. the
duration of inspiration (t.sub.max) and/or the respiratory gas
volume (V.sub.ges), are used to control the metering of a gas.
Controlled variables are, for example, the gas concentration
C.sub.i or the mixing ratio of gases (e.g. V.sub.1/V.sub.2).
[0023] By means of a program, the gas metering can be varied
between a lower limit value and an upper limit value, e.g. the gas
concentration can be increased and reduced over a series of
inspirations (e.g. in a regular sequence with an even or uneven
ratio of raising and lowering the gas concentration; advantageous
for NO metering). The gas metering may also advantageously be
controlled on the basis of a response curve previously determined
on the patient. To determine the response curve, a sensor is used
to measure a body parameter of the patient (e.g. oxygen saturation
in the peripheral blood and/or heart rate, determined by means of
pulse-oxymeter) as a function of the metered volume of gas or gas
concentration, and the temporal gas demand required to establish a
uniform body condition is determined.
[0024] In a further process variant of the gas metering, the
sequence of the program used to control the metering of a gas is
dependent on certain measured variables, which are detected by one
or more sensors, being reached. For example, if a measured variable
falls below or exceeds a threshold, program sequences of the gas
metering may be triggered. One threshold may activate a program
section which brings about a metering sequence for high, average or
low gas metering.
[0025] The gas metering is advantageously a metered addition of the
gas (e.g. oxygen or NO or NO-containing gas) to the respiratory gas
in metering intervals of a defined sequence (sequential gas
metering). Thus, the gas metering is carried out, for example, via
a repeating sequence of inspiration cycles with gas metered to the
respiratory gas (gas metering) and inspiration cycles without gas
being added (exclusion).
[0026] The sequential gas metering is, for example, a repetition of
the following sequences (regular sequences) with an equal duration
of the metering intervals (e.g. metered addition of oxygen or NO
during artificial respiration or for spontaneously breathing
patients):
[0027] a) one metered gas addition and one exclusion,
[0028] b) 2 metered gas additions (e.g. 2 inspiration phases with
metered gas addition) and 25 following exclusions (i.e. 25
following inspiration phases without metered gas addition),
[0029] c) 10 metered gas additions and 30 following exclusions,
or
[0030] d) 3 metered gas additions and 80 following exclusions.
[0031] A metered gas addition may also comprise variable
(irregular) sequences, e.g. a succession of sequences with
increasing or decreasing numbers of metered gas additions.
[0032] The most simple sequence is the sequence comprising one
metered gas addition and one exclusion. The repetition of the
sequence provides the overall cycle of metering steps (of gas
metering) . Examples of different forms of sequential gas metering
are listed in the table.
1 Forms of sequential gas metering (where n.sub.i = 1) Gas
concentration or gas volume in Duration of Sequence of Type of the
metering the metering the metering metering interval interval
intervals 1. Constant Constant Constant 2. Constant Constant
Variable 3. Constant Variable Constant 4. Constant Variable
Variable 5. Variable Variable Constant 6. Variable Constant
Variable 7. Variable Constant Constant 8. Variable Variable
variable
[0033] The sequential gas metering has the advantage that for a
time high levels of gas can be metered, while nevertheless on
average, over a period of time, a very low concentration or volume
of gas is added. For example, a sequence of one or more (two,
three, four, five, six, seven, eight, nine, ten or more)
inspirations can be used to administer a standard NO dose (e.g. up
to 80 ppm NO in the respiratory gas for extremely severe pulmonary
failure), and then a sequence of inspirations (one, two, three,
four, five, six, seven, eight, nine, ten or twenty, thirty, forty,
fifty or more inspirations) can be used to administer a very low
quantity of NO, so that the result is an average NO concentration
which lies, for example, in the ppb or ppt range. The sequential
gas metering of two, three or more gases can be combined.
[0034] The controlled gas metering leads to a lower consumption of
gas, in particular to a lower overall volume of gas administered,
so that side-effects from the gas (e.g. NO) on the patient can be
reduced. A further advantage is that discontinuation and withdrawal
of the gas therapy (e.g. NO therapy) are made easier. It is
generally advantageous when withdrawing artificially respirated
patients who need NO to continuously reduce the amount of NO
administered. When using an artificial respiration system with
controlled NO metering, a further significant advantage is that the
level of toxic NO.sub.2 formed overall from NO in the artificial
respiration is lower.
[0035] Control equipment for gas metering can advantageously be
controlled electrically. Control equipment used is, for example,
time- and/or sensor-controlled solenoid valves (e.g. solenoid valve
with upstream-connected electronics, sold by Burkert, Germany),
mass throughput regulators (e.g. appliance type MFC from Brooks,
the Netherlands), automatically adjustable pressure regulators
(e.g. adjustable by means of stepper motor or electric motor) or
control valves for the direct, in particular automatic, adjustment
of the gas pressure. In the case of gas sources containing
cold-liquefied gas, the evaporation of the gas is advantageously
regulated by means of a heating device in the storage vessel. The
heating device is preferably an electrical resistance heater which
is controlled by switching the heating current on or off or by
continuously varying the heating output. In addition, the gas can
be metered by means of a solenoid valve in the gas supply line.
[0036] Sensors are generally measurement sensors. The term also
comprises (in a broad sense) measurement appliances and analysis
devices. The use of sensors can be divided into sensors for
triggering the gas metering (trigger sensors), sensors for
controlling the sequence of gas metering (regulating sensors) and
sensors for monitoring the safety of the gas supply system (e.g.
for triggering an alarm or for safety shut-off of apparatus
functions, in particular by means of gas sensors).
[0037] A suitable trigger sensor is a pressure sensor which
measures the gas pressure, in particular a low-pressure sensor. The
measured signal from the sensor can itself be used as a control
signal (e.g. in the case of a so-called "smart sensor") or can be
converted into a control signal by means of an electronic
processing and control unit. The sensor may, for example, measure
the pressure (gas pressure) in or in front of the nose (e.g. by
means of a sensor which is integrated in the breathing mask or
nasal spectacles). A pressure sensor is also suitable for detecting
the profile of the inspirational reduced pressure and can be used
to control a gas metering which is adapted to requirements (e.g.
higher gas metering for deep inspirations, lower gas metering for
shallow inspiration). It is also possible to measure differential
pressures and use these for control purposes (e.g. differential
pressure with respect to pressure at corresponding phase of
preceding inspiration), since at a defined setting these pressures
indicate the square of the flow rate.
[0038] Regulating sensors are, for example, pressure sensors,
gas-specific sensors or gas sensors (e.g. electrochemical gas
sensors for O.sub.2, NO or NO.sub.2) and, in particular, sensors
for detecting physical reactions, body functions or body states of
the patient (patient-oriented measured values), sensors for
measuring the oxygen saturation in the peripheral blood, e.g.
pulse-oxymeters (e.g. ASAT appliance from Baxter, USA), sensors for
blood gas analysis (e.g. 995 HO appliance from AVL, Austria;
"Perotrend" appliance from Crosstec), sensors for measuring blood
pressure or sensors for measuring pulmonary blood pressure (also
pulmonary pressure or pulmonary artery pressure; by means of a
catheter floating in the pulmonary artery, e.g. type SWAN-Ganz from
Baxter, USA, with electrical conversion by means of the "Explorer"
appliance from Baxter), sensors for measuring the cardiac output or
cardiac rate or sensors for detecting artificial respiration
parameters, such as artificial respiration pressure, artificial
respiration volume or compliance (expansibility of the lung).
[0039] Heart rate and oxygen saturation in the peripheral blood can
be measured by means of pulse-oxymeters. The simultaneous detection
of both parameters is advantageously used to control the gas
metering, e.g. when metering oxygen and/or NO in artificial
respiration systems or systems for spontaneously breathing
patients, in particular in the gas therapy of COPD patients.
[0040] Preferably, highly miniaturized sensors (in particular
pressure sensors), which allow positioning directly at the
measurement site (e.g. on the nose, on or in the patient's body)
are used. However, the sensor may also be arranged at a distance
from the actual measurement site, e.g. may be positioned in the
metering line, or may be connected to the measurement site by means
of a suitable hose line. This may, for example, be the case when
vacuum measurement apparatus (pressure measuring apparatus) are
used as sensors or in the case of sensors (measurement apparatus,
analysis apparatus) for determining the concentration of a gas
component, e.g. NO concentration, carbon dioxide concentration or
oxygen concentration. It is also possible to combine different
sensors in order to control the gas metering and/or gas mixture.
For example, it is possible to use a combination of pressure
sensors and gas sensors.
[0041] The use of the sensors allows automatic, patient-oriented
gas metering.
[0042] The invention is explained below on the basis of NO
metering, oxygen therapy and the combined metering of NO-containing
gas and oxygen.
[0043] The NO metering is advantageously controlled using a curve
indicating the response of the patient to NO. The response curve of
the patient is determined in advance, i.e. the temporal dependence
of a measured variable (a parameter) on the quantity or
concentration of NO administered. The response curve may, for
example, be determined by measuring the increasing oxygen content
in the peripheral blood which is brought about by the NO metering
and/or by the pulmonary pressure, which falls during NO metering.
This response curve can be used to determine the most suitable NO
metering. An empirically determined set value can be compared with
the measured variable in order to control the NO metering and, on
this basis, a control unit (e.g. flow regulator or solenoid valve)
can be actuated, the NO quantity, for example, being controlled in
such a way that the temporal change in the measured variable
measured on-line comes closer to the response curve.
[0044] Limit values for the NO concentration to be set (minimum,
maximum concentration), number of respiratory cycles with and
without metered addition and optimum parameters for controlling the
gas metering can be determined in a preceding determination or
during the therapy itself (determination of the control parameters:
desired gas concentration profile over the course of time). The
following procedure can be used to optimize the NO metering
(automatic detection and adaptation of the most favorable (minimum
required) NO quantity): 1. Constant increase in quantity of NO (NO
increase) from lower limit (e.g. 0.1 ppm NO) to upper limit (e.g.
100 ppm), involving measuring the oxygen saturation in the
peripheral blood and/or the pulmonary pressure (observing the
reaction of the patient=response). Determining the appropriate NO
concentration (becomes set value for control) . Monitoring the set
value by means of second response measurement (passing through the
NO concentration lower limit/upper limit/lower limit=triangular
measurement). The optimum NO profile (NO concentration curve in the
respiratory gas) is achieved when a constant oxygen saturation in
the peripheral blood or a minimum, constant pulmonary pressure is
established (adaptive control of gas metering).
[0045] The gas supply system is used, for example, in the treatment
of hypoxia or high lung pressure with NO. It is also advantageously
used for the following disorders/clinical pictures: ARDS (Adult
Respiratory Distress Syndrome), asthma, PPH (Primary Pulmonary
Hypertension), COPD (Chronic Obstructive Pulmonary Disorder), heart
malformation, immature lungs in the case of premature and newborn
infants.
[0046] In the case of gas supply systems for oxygen therapy, it is
advantageous to use the measurement of the oxygen saturation of
hemoglobin in the peripheral blood (e.g. measurement by means of a
pulse-oxymeter). The oxygen concentration in the respiratory gas or
the oxygen volume is controlled. The control range of the oxygen
concentration extends to up to 100% by volume. In the same way as
for the NO metered addition, in this procedure for which the gas
supply system is being used the metered addition of oxygen is
regulated in a controlled manner.
[0047] In oxygen therapy, discontinuous measurement methods for
determining the oxygenation in the circulation can be used as
measured and regulating variables, e.g. by means of the HO 995
apparatus from AVL (Austria), or alternatively continuous
measurement methods, e.g. using the "Perotrend" appliance from
Crosstec, can be used. Blood gas analysis generally determines
arterial blood gas, venous blood gas or mixed-venous blood gas.
[0048] The gas supply system for automatic oxygen metering in
oxygen therapy is advantageously suitable for use in both
spontaneously breathing and artificially respirated patients. In
particular, pulse-modulated metering of oxygen or other additional
gases is advantageously controlled on the basis of measured
variables such as blood oxygen content and/or pulmonary blood
pressure or blood oxygen content and/or heart rate.
[0049] Program control for the oxygen metering and, if appropriate,
further metered gases allows a gas supply system to have a
particularly simple design, in particular to be a portable gas
supply system for chronically ill patients (e.g. COPD
patients).
[0050] The gas supply system is particularly advantageously suited
to controlled, adapted gas metering of two or more gases, e.g.
selected from the gases NO, oxygen, hydrogen gas, helium and carbon
dioxide. The controlled metering of helium is used to improve the
airing of the lungs, while carbon dioxide stimulates respiration. A
sensor control system and/or a program control system may be
provided for each gas. Two or more gases can be metered on the
basis of the determination of overall volumetric flow rate or
partial volumetric flow rates of the individual gases. In
principle, the gases can be metered in the same way as one
individual gas is metered. A mutually adapted metering of the gases
is preferred. For example, the gas mixing ratio may be selected as
a control parameter. When metering a plurality of gases, it is, of
course, possible to use different control types for the individual
gases, e.g. to control some of the gases using a sensor control
unit and some using a program control unit or some using a combined
program/sensor control unit. By suitably selecting one or more gas
sources (e.g. liquid oxygen, NO-containing gas, in particular
NO-containing gas from an on-site generator) and providing a
suitable control unit, the power required to operate the gas supply
system can be considerably reduced (advantageous for
battery-operated mobile systems).
[0051] For pulse-modulated gas metering, in particular for metering
two or more gases, it is important for the respiratory gas to be as
homogeneously mixed as possible, in order to avoid concentration
peaks of a gas in the respiratory gas. It is advantageous to
homogenize the gas mixture by means of a mixing body in the hose
system, preferably in the respiratory tube. Preferably, a
hollow-cylindrical part which has a helically twisted part (e.g.
metal strip or plastic strip with ends rotated through 180.degree.
with respect to one another) is fitted in the tube system as the
mixing body.
[0052] The mixing path is both for tube systems used in the
intensive care sector (22 mm tube diameter for artificial
respiration of adults, 15 mm for children, 10 mm for newborn
infants) and, for example, for 8 mm or 10 mm tube systems for home
therapy of the chronically ill, in particular COPD patients.
[0053] Filters, absorbers or humidifiers, e.g. in a respiratory
tube, also improve the homogenous mixing of gases.
[0054] Use on patients for NO application, e.g. for the chronically
ill, is improved by fitting a filter for nitrogen dioxide
(NO.sub.2), e.g. filters containing polyphenylene sulfide as filter
material or sodium carbonate cartridges (Sodalime). It is also
advantageously possible to combine an on-site generator for NO with
a NO.sub.2 filter.
[0055] The following figures explain the invention and describe gas
supply systems for spontaneously breathing patients (e.g. COPD
patients).
[0056] FIG. 1 diagrammatically shows a breathing mask 2 with sensor
1 (e.g. pressure sensor) and gas supply tube 3 (e.g. oxygen) as
parts of a gas supply system.
[0057] FIG. 2 diagrammatically shows nasal spectacles 4 with sensor
1 (e.g. pressure sensor) and gas supply tube 3 (e.g. oxygen). A
plurality of nasal spectacles 4 may be arranged on the patient in
order to supply the patient with different gases. As an alternative
to a plurality of nasal spectacles, it is also possible to use
coaxial tubes, in which a different gas flows through each
lumen.
[0058] FIG. 3 shows a schematic diagram of the nasal pressure
P.sub.N as a function of time t without gas metering, measured by
means of a pressure sensor in front of the nasal orifice. The marks
a and b indicate the start and end of an inspiration interval.
[0059] FIG. 4 shows a schematic diagram of the measured nasal
pressure P.sub.N as a function of time t when metering oxygen. The
bottom diagram (figure) shows the volumetric flow rate of metered
oxygen in the metering interval a to b (inspiration interval).
[0060] FIG. 5 shows a schematic diagram of the measured nasal
pressure P.sub.N as a function of time t with pulsed metering of
oxygen. The bottom diagram (figure) shows the volumetric flow rate
of pulsed, metered oxygen in the metering interval a to b
(inspiration interval).
[0061] FIG. 6 diagrammatically shows a sensor-controlled gas supply
system with a plurality of sensors 1 (P1: pressure), 1' (P2:
pressure) and 1" (T: temperature) and a gas source 7 (e.g. oxygen)
. If the pressure of the gas (e.g. oxygen) is known either from a
one-off or a continuous measurement of the pressure (P1) and of the
diameter of one or possibly more nozzles 5 or constrictions (may
also, for example, be the diameter of the valve inlet or valve
seat), it is thus possible to determine on a one-off or continuous
basis the volumetric flow administered to the patient and, if the
duration is known, to determine the volume of gas administered. It
is also possible, by means of the temperature (temperature sensor),
to determine the volumetric flow rate by means of a
pressure/temperature back-calculation for the precise standard
volumetric flow rate. The trigger of the start of the inspiration
phase and hence the beginning of opening of the solenoid valve can
be triggered by the low-pressure sensor P2. The duration of opening
and therefore the volume to be administered is displayed or
adjusted by means of a volume assigned to a potentiometer on the
control unit 6 (or by input/display of a more highly electronicized
system, such as for example microprocessor/controll- er).
[0062] FIG. 7 diagrammatically shows a gas supply system with
pressure-reducing device at the gas source 7. By varying the
pressure of the supply gas, this may be a compressed-gas vessel
with pressure-reducing device or a liquefied-gas vessel with
evaporation device, with or without pressure-reducing device, the
volumetric flow rate can be altered. This is detected by means of
the pressure measurement and the new time or the new volume
administered can be displayed and calculated/controlled.
[0063] FIG. 8 diagrammatically shows the profile of the total
volumetric flow rate analogously to the nasal pressure P.sub.N
(bottom diagram) when metering a plurality of gases with the
respective volumetric flow rates V.sub.1, V.sub.2, V.sub.n. A
suitable gas supply system is shown in FIG. 11.
[0064] Analogously to FIG. 8, FIG. 9 shows the profile of
volumetric flow rates produced for various gases. FIGS. 8 and 9 are
examples of different mixing ratios produced for a plurality of
gases.
[0065] FIG. 10 diagrammatically shows a gas supply system with a
plurality of gas sources 7, 7' and 7" and assigned pressure sensors
1, 1' and 1".
[0066] FIG. 11 diagrammatically shows a gas metering system with a
plurality of gas sources 7, 7' and 7" and associated
pressure-reducing devices (e.g. nozzles) 5, 5' and 5" and a sensor
1 for controlling the solenoid valves by means of a control unit
6.
[0067] FIG. 12 shows the delivery of gas from the gas sources 7
(e.g. oxygen) and 7' (e.g. NO source) via a sensor 1 and/or a gas
analysis unit.
[0068] FIG. 13 shows a gas supply system with a plurality of gas
sources 7 to 7'" (e.g. oxygen, NO source, helium, carbon dioxide)
using sensors 1 to 1'" and patient-mounted sensor 1.sup.IV and
filter element 9.
[0069] FIG. 14 diagrammatically shows a gas supply system for
liquid oxygen and NO-containing gas. The valves V1 and V2 (e.g.
solenoid valves) are controlled by means of the patient-mounted
sensor 1 (e.g. pressure sensor) in conjunction with the control
unit 6.
[0070] FIG. 15 diagrammatically shows the temporal profile of
volumetric flow rates of oxygen and NO-containing gas and of the
measured nasal pressure P.sub.N.
[0071] FIG. 16 shows a mixing device for gases, comprising
hollow-cylindrical part 11 and mixing body 10, which is formed by a
twisted flat body (e.g. made from metal, plastic or glass; ends of
the flat body rotated with respect to one another, e.g. 180.degree.
or 360.degree.). The mixing device, as mixing path, is preferably
fitted in the respiratory tube of the gas supply system.
EXAMPLE
NO Metering as a Function of Oxygen Volume
[0072] A portable unit for the combined metering of oxygen and NO
(in nitrogen) contains a storage vessel for cold-liquefied oxygen
with integrated evaporation system (capacity: 0.5 liters), a
compressed-gas vessel for NO-nitrogen gas mixture (typically 800 to
1000 ppm NO in N.sub.2; geometric cylinder volume: 0.2 to 1.0
liter; filling pressure: 150 to 200 bar), a control unit for
controlling the metering of oxygen and NO gas mixture, at least 2
electrically controllable solenoid valves, gas hoses and nasal
spectacles with pressure sensor, NO sensor and NO.sub.2 sensor in
the respiratory gas line, a warning system and safety device
(alarm: when NO gas mixture cylinder empty, when oxygen storage
vessel empty, excessive oxygen, NO or NO.sub.2 concentration in the
respiratory gas).
[0073] The pressure sensor is used to trigger the gas metering
(inspiration-synchronized gas metering). At the start of
inspiration, the solenoid valve for oxygen metering and the
solenoid valve for NO gas mixture metering are opened. The volume
of oxygen metered per inspiration is preset, e.g. V.sub.O2=50 ml. A
set oxygen volumetric flow rate V.sub.O2' of 3000 ml/minute results
in a pulse width t.sub.O2 of 1 second. The NO concentration to be
set in the respiratory gas volume V.sub.ges
(V.sub.ges=V.sub.O2+V.sub.NO) is to amount to C.sub.NO=35 ppm. The
NO gas mixture contains 1000 ppm NO. The preset NO gas mixture
volumetric flow rate V.sub.NO' amounts to 500 ml/minute. The
metered volume of NO gas mixture V.sub.NO required to set the NO
concentration C.sub.NO=35 ppm (volume/volume) in the respiratory
gas is calculated as follows:
C.sub.NO=(V.sub.NO*F)/V.sub.ges=(V.sub.NO*F)/(V.sub.O2+V.sub.NO)
[0074] where F: NO concentration in the NO gas mixture.
[0075] It follows that
V.sub.NO=(V.sub.O2*C.sub.NO)/(F-C.sub.NO).
[0076] Where V.sub.O2=3000 ml, C.sub.NO=35 (ppm) and F=1000 (ppm),
V.sub.NO=1.8 ml.
[0077] The opening time of the NO metering valve (in this function
open/shut function) is fixed by V.sub.NO=V.sub.NO'*t.sub.NO. The
opening time of the solenoid valve for NO gas mixture metering is
therefore 218 milliseconds (where V.sub.NO'=500 ml/minute). For
reasons of homogeneity, it is advantageous for the metering
conditions to be selected in such a way that the NO metering time
is t.sub.NO=1/2t.sub.O2. This is achieved by reducing the
volumetric flow rate V.sub.NO' by lowering the preliminary pressure
in the gas metering line. The preliminary gas pressure is
advantageously reduced by means of a controllable diaphragm or
nozzle incorporated in the gas metering line (automatic adjustment
of the diaphragm aperture or nozzle aperture).
[0078] In order to simplify illustration, the calculation example
contains only one predetermined NO concentration. It is preferable
for the NO concentration to be varied by means of a control program
or a sensor control system.
* * * * *