U.S. patent number 3,871,371 [Application Number 05/313,978] was granted by the patent office on 1975-03-18 for respiration supply and control.
This patent grant is currently assigned to Puritan-Bennett Corporation. Invention is credited to James Weigl.
United States Patent |
3,871,371 |
Weigl |
March 18, 1975 |
Respiration supply and control
Abstract
A system including apparatus and method for supplying and
controlling a selected breathing gas mixture in proper amounts at a
selected cycle rate with a high degree of accuracy including a
console with gas supply and control units at a substantial distance
from the patient and a transfer unit in proximity to the patient.
The gas supply hose from the console to the transfer unit is long
and of large volume, while the delivery hose from the transfer unit
to the patient is very short and of relatively small volume.
Control valves for the supply and return flow paths are in the
transfer unit and are actuated by remote control means in the
console. Thus, the major part of the machine compliance is
eliminated, and the system makes it possible to accurately control
the volume of gas delivered to a patient. The transfer unit
includes a pressure sensor for continually monitoring pressure and
a temperature sensor.
Inventors: |
Weigl; James (Santa Monica,
CA) |
Assignee: |
Puritan-Bennett Corporation
(Kansas City, MO)
|
Family
ID: |
23218012 |
Appl.
No.: |
05/313,978 |
Filed: |
December 11, 1972 |
Current U.S.
Class: |
128/204.17;
128/205.23 |
Current CPC
Class: |
A61M
16/024 (20170801); A61M 16/206 (20140204); A61M
16/204 (20140204); A61M 16/00 (20130101); A61M
16/209 (20140204) |
Current International
Class: |
A61M
16/00 (20060101); A61M 16/20 (20060101); A61m
016/00 () |
Field of
Search: |
;128/145.8,145.7,145.6,145.5,145,142,142.2,188,2C,2.08 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Gaudet; Richard A.
Assistant Examiner: Dunne; G. F.
Attorney, Agent or Firm: Fulwider, Patton, Rieber, Lee &
Utecht
Claims
I claim:
1. A respiration supply and control system comprising:
a console provided with a volume generator to supply a desired
respiration gas mixture at a selected cycle rate for use by a
patient located at a substantial distance from the console;
a transfer unit to receive the gas and transmit it to the
patient;
an elongate, large volume, gas supply hose interconnecting the
volume generator and the transfer unit;
a relatively short, small volume, delivery hose extending from the
transfer unit and adapted to be placed in flow communication with
the patient;
valve means in the transfer unit to control the flow of gas
therefrom to the patient;
an actuator on the transfer unit for the valve means;
and control means on the console and connected to the actuator to
control its operation.
2. A system as claimed in claim 1 further including:
an elongate, large volume, gas return hose interconnecting the
transfer unit and the console;
a relatively short, small volume, expiration hose extending from
the transfer unit and also adapted to be placed in flow
communication with the patient;
second valve means in the transfer unit to control the flow of gas
from the expiration hose to the gas return hose;
and control means on the console and connected to the second valve
means to control its operation.
3. A system as claimed in claim 2 further including:
a spirometer on the console flow connected to the downstream end of
the gas return hose.
4. A system as claimed in claim 2 further including:
a pressure sensor is flow connected to the expiration hose upstream
of the second valve means; and
means for displaying sensed pressure versus time.
5. A respiration supply and control system, comprising:
a console provided with a volume generator to supply a desired
respiration gas mixture at a selected cycle rate for use by a
patient located at a substantial distance from the console;
a transfer unit to receive the gas and transmit it to the
patient;
an elongate, large volume, gas supply hose interconnecting said
volume generator and said transfer unit;
a relatively short, small volume, delivery hose extending from said
transfer unit and adapted to be placed in flow communication with
the patient;
valve means in said transfer unit to control the flow of gas
therefrom to the patient;
an actuator on said transfer unit for said valve means;
control means on said console and connected to said actuator to
control its operation;
heating means for said gas supply hose;
a first temperature sensor provided at said transfer unit in
communication with the gas flowing through the outlet end of said
hose;
a second temperature sensor provided at said console in
communication with the gas flowing through the inlet end of said
hose;
a comparator at said console, connected to both of said sensors to
determine temperature differences;
and a temperature controller located at said console and connected
to said heating means to activate it in response to an indicated
temperature drop between the inlet and outlet ends of said hose.
Description
In the method of the invention, the pressure v. time curve is
monitored to detect discontinuities in slope which are reliably
indicative of maximum and minimum lung pressure during each
breathing cycle.
BACKGROUND OF THE INVENTION
This invention resides in the field of respiration systems and
controls therefor, and is especially adapted for use with
volume-limited ventilators in which a measured volume of gas is
delivered to a patient during each inhalation phase of a positive
pressure breathing system. It is more particularly directed to the
apparatus in which the location and arrangement of parts are such
as to attain a very high degree of accuracy and consistency in the
volume and condition of the gas delivered to the patient during
each cycle and to a method for reliably ascertaining maximum and
minimum lung pressure during each breathing cycle.
Respiration apparatus for positive pressure breathing therapy is in
common use, and it has been the usual practice to determine the
volume of gas delivery and to control it in accordance with
measurements made at the respiration machine. However, the total
compliance of the system is a significant factor and one that does
not remain constant at all times. Thus, the volume of gas actually
delivered to the patient may vary relative to the desired or
selected amount.
The effectiveness of patient ventilation depends on an exchange of
ample tidal volume of gas in the lungs during each breathing cycle.
This is related to the difference between minimum and maximum
pressure in the lungs, the maximum pressure occurring at the end of
the inspiration phase and the minimum at or near the end of the
expiration phase. Should respiration apparatus be adjusted to cycle
at too fast a rate, then the lungs may not have time to force out
the gas. This could result in the residual or minimum lung pressure
climbing to an unacceptable level. Thus, it is highly desirable
from the standpoint of adjusting cycle rate, as well as for
diagnostic purposes, to know the maximum and minimum lung
pressures.
Many improvements have been made over the years in the use of
equipment and correction factors to reduce the variation in volume
delivery to a low level, and the results are generally quite
satisfactory. However, the tidal volume desired for infants is far
less than for adults and may be as low as five percent or less of
the adult requirements. Consequently, the effects of any variation
of the system and of any differences that exist in pressure between
system and the lungs are correspondingly magnified. Accordingly,
there is a need for a supply and control system which makes it
possible to very accurately control the volume of inspiratory gas
actually supplied to the patient's lungs, and to monitor the lung
pressure and especially the minimum and maximum pressures during
each cycle.
SUMMARY OF THE INVENTION
The apparatus and method of the present invention provide a simple,
convenient and highly practical arrangement for delivering a
respiration gas mixture to a patient in an accurately controlled
volume and condition, and make it possible to reliably ascertain
maximum and minimum lung pressure during each breathing cycle.
Generally stated, the system includes a console of the usual type
located at a substantial distance from the patient and provided
with a volume generator, sensing and control devices, computing
equipment, etc., and a transfer unit which is located in proximity
to the patient. The gas supply hose which is connected at its inlet
end to the volume generator is quite long and of relatively large
cross section so that it contains a relatively large volume of gas.
The transfer unit is provided with a cavity having inlet and outlet
ports and a control valve in the cavity to block or permit flow.
The gas supply hose is connected to the inlet port and a delivery
hose is connected to the outlet port.
The delivery hose is very short compared to the gas supply hose and
is also of much smaller cross section, so that its total volume or
dead space is only a small portion of that of the gas supply hose,
and is provided with a short nose tube or like delivery means for
application to the patient. Since the control valve in the transfer
unit provides the cutoff for gas delivery, it will be apparent that
the quantity of actual flow to the patient is accurately regulated.
The control valve is remotely actuated by a control unit on the
console, which coordinates the action of the volume generator and
the control valve in accordance with a predetermined program.
Pressure sensing means is provided at the transfer unit for
monitoring system pressure. In accordance with the preferred method
of the invention, pressure is continuously monitored and a pressure
v. time curve is displayed as on an oscilloscope. Discontinuities
occur in such curve substantially at the levels of the minimum or
residual lung pressure and at the maximum lung pressure during each
breathing cycle. Thus, the apparatus and method of the invention
make it possible to determine reliably this important
information.
In the illustrative system, a temperature sensor is located in the
cavity and transmits its indication to a unit on the console which
compares the outlet temperature of the gas with its inlet
temperature and activates a heating unit on the hose in response to
an indication of temperature drop from inlet to outlet. This
prevents condensation from forming in the delivery tubes, which
might adversely affect inspiratory flow. Also, by maintaining the
temperature substantially constant, the accuracy of the computing
equipment is enhanced as is the comfort of the patient.
The transfer unit may also include, as in the preferred embodiment,
a second cavity and a second control valve. In this case, a short
expiration hose of small volume is connected to the inlet port and
extends to the patient while a relatively long, large volume hose
is connected to the outlet port and extends to the console where it
may be in communication with a spirometer. The control valve is
actuated remotely by a unit at the console which coordinates its
operation with that of the volume generator and the first control
valve in accordance with the selected program.
BRIEF DESCRIPTION OF THE DRAWINGS
Various other advantages and features of novelty will become
apparent from the following description taken in conjunction with
the accompanying drawings, in which:
FIG. 1 is a schematic view in perspective of the apparatus
embodying the invention;
FIG. 2 is a schematic longitudinal sectional view of the transfer
unit; and
FIG. 3 is a pressure v. time graph illustrating the coordinated
operation of the system.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A respiration supply and control system embodying the various
features of the invention is schematically illustrated in FIG. 1,
in which a patient 10 is shown lying on a bed or other support at a
substantial distance from a consle 14 which is provided with
various supply and control components. A transfer unit 16 is
located in close proximity to the patient and may be mounted by any
suitable means or simply positioned on a support 20.
The lower compartment 22 of the console contains various items of
computer and automatic control equipment of the type disclosed in
pending application Ser. No. 283,915, entitled COMPLIANCE
COMPENSATED VENTILATION SYSTEM now U.S. Pat. No. 3,834,381 issued
June 17, 1974, and instrument panel 24 is provided with gauges,
manual control knobs and switches. The upper wall of compartment 22
serves as a base 26 to support certain components involved in the
operation of the system, and the top of the console supports others
including a spirometer 25 and an oscilloscope 27.
A volume generator 28 is mounted on the base 26 and furnishes a
desired quantity of a selected breathing gas mixture to the inlet
end 30 of a gas supply hose 32, the outlet end 34 of which is
connected to a first inlet port 36 on the transfer unit. A supply
cavity in the unit is in communication with port 36 and contains an
inspiration valve to control flow, and is also connected to a first
outlet port 38. A delivery hose 40 is connected to port 38 and
extends to a position close to the patient where, in the
illustrative case, it is connected to a small manifold 42 from
which depends nose tube 44 which is usually installed in one
nostril of the patient to deliver gas to the lungs. It will be
noted that the delivery hose 40 is very short compared to the
length of the gas supply hose 32 and is also much smaller in cross
section, so that there is a minimum amount of volume or dead space
to affect the actual delivery volume of gas.
The inspiration control valve in the cavity between ports 36 and 38
is actuated by a solenoid 54 which is connected by conductors 56 to
control means 58 on the console. This control means is further
connected by conductors 60 to the control unit 62 for the volume
generator 28, and operates in response to certain programming
equipment to actuate the volume generator 28 and the control valve
solenoid 54 in planned coordination.
In some cases, a patient may exhale directly to atmosphere, but the
system may include a return flow path to the console and to a
spirometer, such as Model No. 2642, Monitoring Spirometer, sold by
Bennett Respiration Products, Inc. As shown, an expiration hose 46,
identical to the hose 40, is connected between manifold 42 and
second inlet port 48 on the transfer unit. A second or exhalation
cavity in the unit is connected to a second inlet port 48 and to a
second exit port 50 and contains a second or exhalation valve to
control exhalation flow. A gas return hose 52 is connected to port
50 and extends to the console where it is in flow communication
with the spirometer 25. The exhalation valve means is pneumatically
actuated and is connected by a conduit 66 to control means 68 which
provides pressurized gas to close the valve at a predetermined
point in the cycle. A pressure sensor and transducer 70
communicates with the second cavity in the transfer unit and
transmits its indications through conductor 72 to the console and
thence to the oscilloscope 27. Maximum allowable system pressure
may be set by manipulation of a control knob 76.
An additional feature of the system of the invention is control of
the temperature of the delivered gas. For this purpose, the hose 32
is provided with a dual winding of a heater filament 78, which may
be molded into the hose with both ends terminating at connector 80.
A temperature sensor 82 extends into the gas flow path adjacent to
port 36 and transmits its indications through conductor 84 to
comparatory and temperature controller 86 on the console. A second
temperature sensor 88 extends into the gas flow at the inlet end 30
of the hose and transmits its indications through conductor 90 to
controller 86. The comparator reads the two indications, and the
controller supplies current through conductors 92 to connector 80
and the filament 78 in response to indication of a temperature drop
between the inlet and outlet ends of the hose. In this manner, the
temperature of the gas may be maintained constant. The temperature
indications may also be transmitted to gauge 94, and the operator
may adjust the basic temperature by manipulation of a control knob
96.
The transfer unit 16 and its various components are schematically
illustrated in FIG. 2. The body 98 may take any form but is here
shown as a two-piece block solely for purposes of illustration. A
first cavity 100 is formed in the body and is preferably circular
in cross section. A first end 102 is in flow communication with
first inlet port 36 and the second end 104 is in flow communication
with first outlet port 38 indicated in phantom lines.
A perforated diaphragm 106 is fixed in the intermediate portion of
the cavity and is provided with a flexible leaf type valve head 108
to constitute a check valve which permits flow from the inlet port
to the outlet port to supply the patient, but blocks flow in the
opposite direction. The second end 104 of the cavity is somewhat
larger than the first end and formed to define an annular valve
seat 110. The solenoid 54 is fixedly connected to the lower side of
body 98 and its armature 112 extends substantially coaxially of the
cavity through opening 114 for axial movement. The free end of the
armature carries a valve head 116 supported by a flexible diaphragm
117 for sealing purposes and arranged for movement upwards into
contact with valve seat 110 to block flow and downward out of
contact to permit flow. Tapered coil spring 118 seats on the margin
of the diaphragm and contacts head 116 to urge it to open position,
while actuation of the solenoid acts to drive it to closed
position. The valve 116 thus serves as the first or inspiration
control valve.
In operation, with valve 116 open, gas from the volume generator 28
enters port 36 into end 102 of the cavity, readily opens valve 108,
and flows into end 104 of the cavity, thence through port 38 and
through the delivery hose 40 to the patient. The machine terminates
flow and valve 116 is closed to block further flow to the patient.
After the machine dumps, valve 116 opens rather quickly, remaining
open long enough to permit pressure in the supply hose 32 to the
relieved. Even after opening, however, exhalation through hose 40
back through cavity 100 is blocked by the check valve 108.
An opening 142 is formed in the side of body 98 leading into cavity
end 102, and temperature sensor 82 extends into the gas stream. A
nut 144, engaged with threaded boss 146, retains the sensor in
position. As previously mentioned, indications from sensor 82 are
transmitted through conductor 84 to the comparator and temperature
controller 86 for use in maintaining a constant temperature in the
gas supply hose 32.
The body 98 is further provided with a second cavity 120 including
a first end 122 in flow communication with second inlet port 48,
indicated in phantom lines, and a second end 124 is in flow
communication with second outlet port 50. A partition 126 in an
intermediate portion of cavity 120 is formed with a central opening
128 having an annular valve seat 130. A fitting 132 having an
intermediate flange 134 and an external nut 136 is fixed in place
in aperture 138 and its outer end is connected to the conduit 66
which leads to control means 68. A valve head in the form of a
hollow flexible body 140 which is generally disk-like is secured on
the tubular inner end of the fitting. When pressure fluid is
introduced from control means 68 through conduit 66 and fitting
132, body 140 expands axially into contact with valve seat 130 to
block flow through the cavity. It thus serves as the second or
exhalation control valve. At the proper moment for exhalation
purposes, control means 68 relieves the pressure in body 140 to
open passage 128, and the exhaled gas flows from the patient
through expiration hose 46 and second inlet port 48 through cavity
120, second outlet port 50 and gas return hose 52 to the console
where it may flow through the spirometer 25 if desired.
As previously indicated, it is important to know the gas pressure
in the lungs during the cycle, especially at the beginning and the
end of the inspiratory phase. For this purpose, pressure sensor 70
is mounted in passage 148 which leads into the first end 122 of
cavity 120. In this position, it is upstream of valve 140 and thus
is in flow communication with the gas in the patient's lungs at all
times, even when the inspiration valve is closed. The indications
from the pressure sensor 70 are transmitted through conductor 72 to
the oscilloscope 27, and the operator may correct values at any
time by manipulation of pressure regulator knob 76, or may vary the
cycle rate.
The graph of FIG. 3 illustrates the operation of the total system
through one complete respiration cycle, including inspiration and
expiration phases, to show the interrelation of the various
components. These are pressure-time curves with the pressure in
centimeters of water and the time in milliseconds based on a
breathing rate of 40 cycles per minute, which is typical for
treatment of an infant. The line 150 represents pressures at the
transfer unit and broken line 152 represents pressures in the
lungs. It is, of course, to be understood that the values indicated
on the curve are examples of what may be encountered with an infant
patient with a restricted lung, and such values are likely to vary
considerably from patient to patient.
At the beginning of the cycle, it will be noted that the machine
pressure is zero because it has been dumped during the previous
cycle, while the residual lung in the illustrative case is assumed
to be 10 cm. of water. At this time, the first control valve 116 is
open while the second control valve 140 is closed. The system
pressure at the transfer unit builds up rapidly to the residual
lung pressure (10 cm. H.sub.2 O) and continues to climb toward its
maximum. When the machine control system, after taking the various
factors into account, determines that the desired volume of gas has
been delivered, inspiratory flow from the machine is terminated. A
brief interval later, the length of which corresponds to the
response time of the inspiratory valve 116, the latter closes to
terminate inspiratory flow to the patient. This is reflected by the
peak in a system pressure curve at a maximum pressure of 60 cm.
H.sub.2 O.
The inspiratory phase continues in a holding or plateau portion in
which both the inspiration valve 116 and expiration valve 140 are
closed, the plateau in this instance being about 200 milliseconds
in duration. With the valves in such closed condition, the
patient's lungs are in communication with the transfer unit 16
through the relatively small volume, delivery and expiration hoses
40 and 46. Communication to the remainder of the system is blocked
by the valves 116 and 140. The combined volume of these hoses and
the cavities in the transfer unit 16 is small in relation to the
lung volume and, therefore, the system pressure drops off rapidly
to the lung pressure. In the illustrative case, the lung pressure
and system pressure at the termination of inspiration is
approximately 40 cm. H.sub.2 O.
The exhalation valve 140 opens to commence the exhalation phase and
the system pressure sensed by the sensor 70 in the transfer unit
rapidly drops off to a zero level. As previously indicated, the
exhalation flow is through the path of the hoses 46 and 52 to the
spirometer 27. Because of the patient's restricted lung condition,
the pressure drop in the lung is much more gradual as reflected by
curve line 152. In addition, because of the assumed condition of
the patient, the lung pressure only drops to the residual pressure
of 10 cm. H.sub.2 O.
About 100 milliseconds after the start of expiration in the
illustrative case, the inspiratory valve 116 again opens so as to
provide for intake of air should the patient exert an inspiratory
effort prior to the conclusion of the exhalation phase determined
by the time cycle rate. It is to be understood that the exhaled gas
is still directed to the spirometer 27 because of the presence of
check valve 108 in the supply flow path.
As previously noted, the apparatus and method of the invention make
it possible to monitor the maximum and minimum lung pressure during
each breathing cycle. It is highly desirable to have this
information available, so that corrective action can be taken, if
necessary, by the medical personnel administering the treatment. In
the case of the residual or minimum lung pressure, this may involve
slowing down the cycle rate to afford a longer time period for the
patient to exhale. In the case of the maximum lung pressure, the
maximum delivery pressure of the system can be suitably adjusted by
control knob 76.
Referring to the curve of FIG. 3, a first discontinuity 154 in the
system pressure curve (see line 150) displayed on the oscilloscope
27 occurs substantially at the residual lung pressure and a second
discontinuity 156 occurs substantially at the maximum lung
pressure. The residual pressure discontinuity 154 in the curve 150
is actually seen as a slight flat in the curve for a brief
interval, as well as marking a discernible change in slope. Flow to
the transfer unit 16 initially takes place from both the
respiration apparatus and back from the patient's lungs. It will be
appreciated in this connection that the system pressure of the
transfer unit is initially atmospheric or zero, whereas some
pressurized gas is still contained in the lungs. Thus, at the very
start of inspiration, flow takes place to the transfer unit in both
directions, and the rate of pressure increase reflected by the
slope of the curve is relatively fast.
Once the system pressure builds up to equal that of the residual
lung pressure at 10 cm. H.sub.2 O, the discontinuity 154 occurs,
thereby providing a reliable indication of residual lung
pressure.
During the remainder of inspiratory flow from the machine, the
system pressure build up takes place at a reduced rate reflected by
the corresponding portion of the system curve being somewhat
flatter than the initial portion. Once inspiratory flow is
terminated and the valve 116 closes to commence the "plateau"
portion of the end of inspiration, the system curve falls at a
rapid rate. As previously explained, this occurs by reason of only
a very small volume of gas being trapped in the hoses 40 and 46
between the transfer unit 16 and the patient. Thus, the system
pressure sensed by sensor 70 and displayed on the oscilloscope 27
rapidly drops to equal the lung pressure, so that the curve
flattens out at the end or produces the second discontinuity 156
seen on the oscilloscope. This flat or discontinuity 156 is,
therefore, reliably indicative of the maximum lung pressure.
The method of the invention, as will be understood from the
foregoing description, involves sensing system pressure in the
manner described, preferably throughout both the inspiration and
expiration phases of each cycle and, in any event, during the
initial and terminal portions of inspiration. The sensed pressure
is displayed on the oscilloscope and scanned to detect the first
and second discontinuities 154 and 156, which are reliably
indicative of residual lung pressure and maximum lung pressure,
respectively. These readings provide the medical personnel valuable
information for use in administering to the patient.
* * * * *