U.S. patent number 3,834,383 [Application Number 05/313,981] was granted by the patent office on 1974-09-10 for respiration apparatus with flow responsive control valve.
This patent grant is currently assigned to Puritan-Bennett Corporation. Invention is credited to James E. P. Davis, James Weigl.
United States Patent |
3,834,383 |
Weigl , et al. |
September 10, 1974 |
RESPIRATION APPARATUS WITH FLOW RESPONSIVE CONTROL VALVE
Abstract
Intermittent positive pressure breathing apparatus having a
combined flow-responsive and control valve which is opened to
initiate the inspiration phase of a breathing cycle by a triggering
valve, monitors the decreasing flow rate resulting from
back-pressure buildup in the apparatus, and closes to terminate the
flow at a selected and adjustable terminal flow rate. The control
valve has a plunger that is carried by a piston upon which
differential pressures are applied from the inlet and outlet ends
of the valve's flow passage, and a spring assists the outlet
pressure in urging the plunger toward an annular seat which is
adjustably positioned on one side of the passage and defined as the
beveled end of a tubular seat member. The plunger is positioned in
the passage in accordance with the flow rate to maintain a constant
pressure drop, and engages the seat to shut off all flow when the
rate falls to the selected terminal flow rate.
Inventors: |
Weigl; James (Santa Monica,
CA), Davis; James E. P. (Santa Monica, CA) |
Assignee: |
Puritan-Bennett Corporation
(Kansas City, MO)
|
Family
ID: |
23218025 |
Appl.
No.: |
05/313,981 |
Filed: |
December 11, 1972 |
Current U.S.
Class: |
128/204.26;
137/115.23 |
Current CPC
Class: |
A61M
16/00 (20130101); Y10T 137/2635 (20150401) |
Current International
Class: |
A61M
16/00 (20060101); A61m 016/00 () |
Field of
Search: |
;128/142.2,145,145.5,145.0,145.7,145.8 ;137/117,509,624.11 |
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
We claim:
1. In a respiration apparatus for administering intermittent
positive pressure breathing therapy to a patient, and having
delivery means for administering gas to the patient, and conduit
means for carrying the gas from a source to the delivery means, the
combination of:
a control valve having a flow passage with an inlet end for
receiving gas from the source at a regulated, substantially
constant input pressure, an outlet end, a tubular valve seat member
adjustably mounted in said valve, said seat member having a beveled
annular end along one side of said passage and terminating in an
annular seat projecting varying distances into said passage in
different adjusted positions of said seat member, the interior of
said seat member communicating between said outlet end and said
conduit means, and a plunger slidably mounted in said valve for
movement toward and away from said seat, between open and closed
positions;
a piston carrying said plunger and slidably mounted in said valve,
said valve having first and second pressure chambers on opposite
sides of said piston, said first chamber communicating with said
inlet end and arranged to apply force to said piston determined by
inlet pressure, thereby to urge said plunger toward said open
position;
spring means urging said plunger toward said closed position with a
preselected force;
first and second signal conduits communicating respectively with
said outlet end and with said second chamber, to apply the pressure
in said outlet end to said second chamber when said signal conduits
are connected, thereby urging said plunger toward said closed
position;
pilot valve means normally connecting said signal conduits and
operable when actuated to vent said second chamber through said
second signal conduit, thereby to permit the force of inlet
pressure in said first chamber to shift said plunger to the open
position;
means communicating with said conduit means, responsive to a slight
inspiratory effort at said delivery means and operable to actuate
said pilot valve means momentarily, thereby initiating a flow of
gas through said control valve;
and means responsive to back pressure in said conduit means for
restricting the flow rate as such back pressure increases during
inflation of the patient, thereby reducing the flow rate past said
plunger and causing the latter to move toward said seat and close
against the latter when a preselected terminal flow, determined by
the adjustment of said seat, is achieved, such closure terminating
the delivery of gas from the source to said conduit means.
2. In a respiration apparatus for administering intermittent
positive pressure breathing therapy to a patient, and having
delivery means for administering gas to the patient, and conduit
means for carrying the gas from a source to the delivery means, the
combination of:
a control valve having a flow passage with an inlet end for
connection to the source and an outlet end connected to said
conduit means to deliver gas thereto, a valve seat, and a valve
member movable back and forth, toward and away from said seat
between an open position and a closed position and operable to
admit a peak flow from the source through said passage in said open
position, to block flow from the source through said passage to
said conduit means in said closed position, and to variably
restrict said passage in intermediate positions;
pressure-responsive means for positioning said valve member in said
passage in accordance with the flow rate to said delivery means and
maintaining a substantially constant pressure drop across said
valve member and between said inlet and outlet ends while gas is
flowing through said passage, said pressure-responsive means
including first means urging said valve member toward said open
position with a first force determined by the pressure at said
inlet end, second means urging said valve member toward said closed
position with a second force determined by the pressure at said
outlet end, and spring means for adding a preselected third force
to said second force and variably positioning said valve member in
said passage to maintain a preselected pressure drop across the
valve member while gas is flowing through said passage, and
normally holding said valve member in said closed position to
prevent flow through said passage;
means actuated by an inspiratory effort of the patient at said
delivery means for momentarily shifting said valve member out of
the closed position to start flow to said conduit and delivery
means at a selected peak flow rate;
and rate-control means in said conduit means responsive to the back
pressure in said apparatus during inflation of the patient, and
operable to restrict the flow rate as the back pressure builds up,
whereby increasing back pressure results in a decreasing flow rate
and a tendency to reduce said pressure drop, and said
pressure-responsive means shifts said valve member toward said seat
to maintain said pressure drop until said valve member engages said
seat to terminate the flow, said seat being disposed along one side
of said flow passage in a preselected position determined by the
position of said valve member when the desired terminal flow rate
occurs.
3. Respiration apparatus as defined in claim 2 further including
means mounting said seat for selective adjustment across said
passage, toward and away from the open position of said valve
member, thereby to vary the flow rate at which said valve member
engages said seat.
4. Respiration apparatus as defined in claim 3 in which said seat
is the annular end of a tubular member, and in which the interior
of said tubular member connects said passage to said conduit means
and is blocked by engagement of said valve member with said
end.
5. Respiration apparatus as defined in claim 4 in which said
tubular member has a peripherally beveled end forming said
seat.
6. Respiration apparatus as defined in claim 2 in which said
pressure-responsive means comprise a piston connected to said valve
member, a first chamber on one side of said piston communicating
with said inlet end to form said first means, and a second chamber
on the other side of said chamber connected for communication with
said outlet end to form said second means.
7. Respiration apparatus as defined in claim 6 in which said means
for momentarily shifting said valve member out of said closed
position comprise a pressure-operated pilot valve operable when
actuated, in response to patient suction, to vent said second
chamber.
Description
BACKGROUND OF THE INVENTION
This invention relates generally to respiration apparatus, and more
particularly to an improved apparatus for intermittent positive
pressure breathing (IPPB) therapy in which oxygen or
oxygen-enriched air is supplied to a patient cyclically, under
pressure, through delivery means such as a face mask or the like
with a flow pattern which is similar to normal breathing. Such
therapy can be used to provide life support during respiration
failure, or to relieve respiratory distress from impaired
breathing.
The cycles of an IPPB apparatus may be completely patient
controlled, that is, initiated by slight inspiratory efforts by the
patient, and also may be automatically controlled so that the
apparatus initiates the breathing cycles at a timed rate if the
patient does not breathe voluntarily. Each cycle begins with a peak
flow which inflates the patient's lungs and then decreases to a
relatively low terminal flow before the inspiration phase ceases.
Following the inspiration phase, the lungs are vented to atmosphere
during an expiration phase, which terminates when the next
inspiratory effort of the patient initiates the next cycle.
An example of a highly effective IPPB system is that illustrated in
U.S. Pat. No. 3,362,404, in which gas from a source is supplied at
relatively high pressure (for example, 50 psi) to the delivery
means through a flow-responsive valve, a pressure regulator, and a
main flow valve which is opened and closed by pressure signals
produced by the flow-responsive valve in response to changes in
rate of flow through the flow-responsive valve. In this system, the
inspiration phase is initiated by a triggering valve which
substantially increases the flow through the flow-responsive valve
in response to the initial inspiratory effort, and this increased
flow opens a signal passage from the flow-responsive valve to the
main valve to open the latter and admit the main flow from the
flow-responsive valve to the patient. The flow-responsive valve
closes the signal passage to close the main flow valve when the
flow rate drops to a preselected and adjustable terminal level.
While the foregoing system has performed satisfactorily, it was
designed for use with a high-pressure source of oxygen or air,
often from a relatively noisy piston-type pump where there is no
central supply system. Moreover, its cost is substantial in view of
the fact that two major valves are required, one for flow-rate
control and another on-off flow control, and the closing action of
the main valve was controlled by the relatively slow bleeding of
signal pressure from its actuating chamber.
SUMMARY OF THE INVENTION
The present invention resides in a respiration apparatus of the
foregoing general character which has basically the same operating
capabilities as the apparatus in the aforesaid patent, in which a
single major valve performs the combined functions of both of the
valves of the aforesaid apparatus, and which is capable of
operation with a low-pressure source of oxygen or air. Accordingly,
the apparatus is lower in cost and easier to assemble, and
eliminates the need for an expensive and noisy pump for supplying
high-pressure gas, permitting the use of a less expensive and
quieter rotary compressor.
More specifically, the respiration apparatus of the invention has a
flow control valve including a valve member that is movable back
and forth across a flow passage between open and closed positions,
a sensing or triggering valve that is operable in response to an
inspiratory effort by the patient to cause the opening of the valve
member for the initial peak flow, and a pressure-responsive
actuator for the valve member for variably positioning it in the
passage in accordance with the flow rate by maintaining a
substantially constant pressure drop between the inlet and outlet
ends of the passage. As the flow rate is reduced during the
build-up of system back pressure resulting from the inflation of
the patient's lungs, the valve member monitors the decrease and is
shifted correspondingly closer to the closed position to
correspondingly reduce the flow area through the valve. When the
desired terminal flow rate is achieved, the valve member seats and
closes with a positive, snap action, the seat being selectively
adjustable for selection of a desired terminal flow rate.
In the illustrative embodiment, the flow-responsive control valve
comprises a plunger that is guided in the valve body for sliding
toward and away from a beveled annular seat on one side of the flow
passage, and is carried by a piston that is disposed between two
pressure chambers, one communicating with the inlet end of the
passage to receive higher pressure gas which develops an opening
force, and the other connected for communication with the outlet
end of the passage to receive lower pressure gas (due to the
pressure drop occasioned by the restriction produced by the valve
member) and develop a closing force which is augmented by a light
spring force that is selected to maintain the pressure drop. The
inspiratory effort by the patient is applied as a pilot signal to
the sensing valve, which actuates a pilot valve to momentarily vent
the second chamber, permitting the inlet pressure to throw the
plunger open for the peak flow, after which the force of outlet
pressure is added to the spring force to urge the plunger toward
the closed position.
As back pressure builds up, a basically conventional
diluter/regulator progressively restricts the flow to the patient,
and thus the flow through the valve passage, tending to
correspondingly reduce the pressure drop that would occur through a
restriction of given size, so that the outlet pressure tends to
rise toward the inlet pressure. Accordingly, the plunger is shifted
progressively toward its seat and variably positioned in the
passage in relation to the flow rate, to maintain the pressure
drop, and engages the seat with a snap action to shut off all flow
to the patient at a flow rate that is selected by adjusting the
position of the seat within the passage. Thus, a single valve
performs both of the functions that formerly required two valves,
serving both as a direct "on-off" valve and as a monitor which
senses the flow rate to terminate flow at a selected terminal flow
rate.
Other objects and advantages of the invention will be apparent from
the following detailed description, taken in conjunction with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagrammatic view, partly in cross-section, of a
respiration system embodying the novel features of the present
invention;
FIG. 2 is an enlarged fragmentary cross-sectional view of parts of
the flow-responsive control valve, shown in the open position for
peak flow, with moved positions of parts indicated in broken
lines;
FIG. 3 is a fragmentary cross-sectional view taken substantially
along line 3--3 of FIG. 2;
FIG. 4 is an enlarged, fragmentary cross-sectional view
schematically illustrating the fully open condition of the
diluter/requlator;
FIG. 5 is a view similar to FIG. 4 illustrating a partially closed
condition of the diluter/regulator resulting from increasing system
back pressure as the patient's lungs are inflated; and
FIG. 6 is an enlarged cross-sectional view somewhat schematically
illustrating the structure of one of the pressure-operated pilot
valves of the apparatus.
DETAILED DESCRIPTION
As shown in the drawings for purposes of illustration, the
invention is embodied in a respiration apparatus for IPPB therapy,
as illustrated schematically in FIG. 1, for delivering an
intermittent, controlled flow of pressurized gas, typically oxygen
or air, from a source 10 such as a pump or a storage tank to a
patient (not shown) through conventional delivery means 11. The
delivery means may take various forms, for example, that of a face
mask over the patient's mouth and nose, through which the patient
receives gas during each inspiration phase of operation, and
exhales during each expiration phase of operation.
In general, the apparatus comprises a flow control means 12 which
receive gas from the source 10 through a conduit 13 and a
pressure-regulator 14, and deliver an intermittent controlled flow
of the gas to a main flow conduit 15 through which the gas is
carried to a basically conventional diluter/regulator 17 in which
air may be mixed in the gas and back pressure building up in the
system results in restriction of the flow from the flow control
means 12. From the diluter/regulator, the gas (or gas mixture)
passes through a check valve 18 and a continuation 19 of the main
flow conduit to the delivery means, and thus to the patient.
Each inspiration phase of operation normally is initiated by a
sensing valve 20 which is responsive to a pressure drop in the main
conduit 19 to produce a pressure signal for opening the flow
control means 12, and termination of the inspiration phase is
effected by the flow control means in response to a decrease of the
flow rate to the patient to the level selected for the terminal
flow. At the same time, the expiration phase is initiated by the
flow control means by opening an expiration port 21 from the main
conduit 19 so that the patient may exhale to atmosphere.
In accordance with the present invention, the flow control means
12, which heretofore has comprised a separate flow-responsive valve
and a separate main flow-control valve, is a single valve assembly
having one valve member 22 which not only opens to admit gas to the
delivery conduits and closes to shut off the flow, but also
operates during each inspiration phase to monitor the varying flow
during inspiration and shut off the flow in response to achievement
of a selected low terminal flow. In this valve, both the structure
and the assembly operations are simplified by the elimination of
the need for a separate flow-control valve, and thus are less
expensive, and the system is readily adaptable for use with
relatively low-pressure sources so that there is no need for
relatively high-pressure gas for proper operation, hereby making it
practical to operate with a less expensive and quieter pump than
the pumps that have been used in the past, in the absence of a
suitable central supply system.
More specifically, as shown in FIGS. 1 and 2, the valve 12
comprises a housing 23 on which the pressure regulator 14 is
mounted, to receive gas from the source 10 through the conduit 13
and deliver it to the valve at the proper operating pressure, for
example, 10 psi. The housing defines a flow passage 24 with an
upper, inlet end for receiving the gas from the regulator and a
lower, outlet end from which the controlled intermittent flow is
delivered to the conduit 15, and also is formed with a transverse
bore 25 which intersects the flow passage near the lower end
thereof, on the right-hand side as viewed in FIGS. 1, 2 and 3.
The valve member 22 is a plunger which is slidably guided in the
bore 25 for back and forth movement in the housing 23, toward and
away from a valve seat 27 adjacent the opposite side of the bore.
This valve seat is the annular end of an elongated seat member that
is sealed in a second bore 28 opening transversely into the
left-hand side of the passage 24, as it is viewed in FIG. 1,
coaxial with the bore 25, the seat member having a blind bore 29 in
its right-hand end portion defining an internal passage that
communicates through one or more radial ports 30 with an annular
chamber 31 outside the member, the main flow conduit 15 being
connected to this chamber to receive gas therefrom.
The left-hand end portion 32 of the seat member is fitted into the
valve housing 23 in a threaded left-hand end portion 33 of the
bore, for axial movement of the seat member upon turning of an
externally accessible knob 34 on a shaft 35 projecting to the left
from the threaded end portion. Such axial movement adjusts the
position of the seat 27 in the flow passage 24 and relative to the
left-hand side of the flow passage, as viewed in FIGS. 1, 2 and
3.
To move the valve plunger 22 back and forth relative to the passage
24, a piston 37 is mounted on the right end portion of the plunger
and is slidably fitted in an enlargement of the bore to divide the
enlargement into two pressure chambers 38 and 39 in which gas
pressure develops forces acting to urge the piston, and thus the
plunger, in opposite directions. The chamber 38 on the left side of
the piston is pressurized from the inlet end portion of the flow
passage 24, above the plunger, through a connecting conduit 40, and
the chamber 39 on the right side of the piston is connected to a
conduit 41 that is arranged to be pressurized from the outlet end
portion of the flow passage, below the plunger, when the conduit 41
is connected to a conduit 42 through a pilot valve 43.
In addition to the closing force developed by gas in the chamber
39, a light coiled spring 44 is compressed between the piston and
the right end wall 45 of the housing, thus adding a preselected
closing force to the plunger, for example, a force of about
one-half of 1 pound. Accordingly, when the gas-pressure forces are
equal, the spring will hold the plunger 22 against the seat 27, but
when the pressure develops an opening force greater than the
combined force of the spring 44 and force exerted from the chamber
39, the plunger is moved to the right, away from the seat. A
resilient end cap 47 on the end of the plunger engages, and seals
against, the seat 27 when the valve is closed.
Moreover, when the plunger 22 is in an open position, the spring 44
urges it toward the closed position, and tends to restrict the size
of the flow passage 24, so that a pressure drop is created between
the inlet and outlet ends, related directly to the cross-sectional
flow area through the restriction and to the rate of flow of gas
through the restriction. Assuming an inlet pressure of 10 psi and a
flow passage sized to produce a peak flow of from 100 to 120 liters
per minute when the valve is fully open, a pressure drop of about
one-quarter of 1 psi will be developed across the plunger.
Accordingly, a pressure differential of about one-quarter of 1 psi
will exist between the chambers 38 and 39.
This pressure drop would tend to decrease, however, as the flow
rate past the plunger decreases, so that the closing pressure in
the chamber 39 would tend to increase toward the opening pressure
in the chamber 38. As this occurs, however, the spring 44 and the
closing pressure cooperate to shift the plunger progressively to
the left, increasing the degree of restriction of the flow passage
to keep the pressure drop substantially the same.
As a result, the plunger 22 is variably positioned in the flow
passage 24 in accordance with the flow rate through the passage to
maintain a substantially constant pressure differential between the
chambers 38 and 39, in accordance with the force exerted by the
spring. The adjustable seat 27 can be set to be engaged by the
plunger in different positions of the latter, and thus when
different selected terminal flow rates are being delivered. It has
been found that variations in the position of the seat within the
passage have little, if any, effect on the response of the plunger
to different flow rates, this being attributed, in part, to the
fact that the end of the seat member is beveled toward the
seat.
The diluter/regulator 17 may be a unit similar to units that have
been sold in respiration apparatus for some time by Puritan-Bennett
Corporation, Santa Monica, Calif., identified as the 0666
Diluter/Regulator. As shown schematically in FIGS. 4 and 5, such a
unit has a main pressure chamber 48 containing gas at system
pressure and defined in part by a diaphragm 49, the chamber 50 on
the other side of the diaphragm being vented to atmosphere. The
diaphragm is urged toward a normal, balanced position (FIG. 4) by a
spring 51 having a seat 52 which is adjustable by a knob 53 to vary
the spring force, thereby calibrating the unit for different
pressure ranges, and the diaphragm is connected to a linkage 54 for
variably restricting the flow through the device in response to
system pressure changes which increase the pressure in the chamber
48 so as to move the diaphragm to the right in FIGS. 4 and 5.
Gas from the valve 12 is delivered to the diluter/regulator through
a check valve 55 and the conduit 15, which opens into a flow
chamber 57 from which a branch conduit 58 carries the gas to the
chamber 48. If air is to be mixed with the gas to dilute it, this
is accomplished by directing the gas through a venturi 59, to draw
air in through a filter 60 and inject the resulting mixture into
the chamber 48. From this chamber, the mixture passes out of the
diluter/regulator to flow to the delivery means 11 through the
check valve 18 and the conduit 19.
The linkage 54 is illustrated in FIGS. 4 and 5 by an L-shaped bell
crank having a fixed pivot 61 in the chamber 48, a first leg 62
depending from the pivot and joined to the diaphragm 49 by a
connecting rod 63 extending between the lower end portion of the
leg and the central portion of the diaphragm, and a second leg 64
projecting laterally from the pivot beneath the stem 65 of a
plunger 67 that is slidable vertically in a partition separating
the chambers 48 and 57. The head of this plunger is movable toward
and away from an inlet orifice 68 which admits gas from the conduit
15 into the chamber 57, and thus through the branch conduit 58 into
the chamber 48.
When the pressure in the chamber 48 is low, before the lungs of the
patient are inflated, the linkage 54 and the diaphragm 49 are
positioned as shown in FIG. 4 so as to leave the orifice 68 open
and unrestricted for a full flow of gas through the
diluter/regulator to the patient. As the patient's lungs become
inflated and back pressure develops in the system, the diaphragm is
shifted to the right, rocking the bell crank counterclockwise to
raise the plunger and shift its head toward the orifice, through
the position shown in FIG. 5, thereby restricting the flow through
the system.
For example, when there is virtually no back pressure, the
diluter/regulator may be set to deliver a full flow to the patient,
and to reduce the flow rate first gradually as the back pressure
begins to increase, and then more rapidly as the back pressure
approaches a selected maximum, closing the orifice completely if
that maximum (e.g., 40 centimeters of water) ever is developed in
the chamber 48.
The illustrative sensing or triggering valve 20 (FIG. 1) for
initiating each respiration cycle in response to an inspiratory
effort of the patient is a pressure-operated pilot valve which is
opened by the slight pressure drop in the conduit 19 resulting from
the inspiratory effort, and then delivers a pressure signal to the
pilot valve 43 to momentarily vent the spring chamber 39 of the
valve 12. When this is done, the inlet-pressure force in the
chamber 38 throws the plunger 22 to the fully open position to
admit the peak flow through the flow passage 24 and into the
delivery system.
As shown in FIG. 1, the sensing valve 20 comprises a main housing
69 in which a diaphragm 70 is centrally mounted to divide the
hollow interior into two chambers 71 and 72, and the diaphragm is
urged toward the centered position shown in FIG. 1 by opposed light
springs 73 and 74, the spring 73 being compressed between the
diaphragm and a seat 75 which is adjustably positioned by a
threaded screw 77 to set the sensitivity of the sensing valve. A
push rod 78 is carried by the diaphragm and normally presses a
closure ball 79 into a closed position over a port 80 opening
upwardly into the chamber 72 from a conduit 81 which normally is
connected through a pilot valve 82 (left portion of FIG. 1) to a
conduit 83. This conduit is pressurized with gas at inlet pressure
(e.g., 10 psi) through a branch conduit 84 leading to the inlet end
portion of the flow passage 24 of the valve 12.
To apply patient suction to the upper chamber 71 of the sensing
valve 20, a conduit 85 extends between this chamber and the main
delivery conduit 19 adjacent the delivery means 11. When the forces
on the diaphragm are finely balanced, a very slight pressure drop
in the upper chamber 71 is sufficient to cause the diaphragm to
rise, first cracking open the port 80, and then being opened fully
by the inlet pressure admitted into the lower chamber 72.
Mounted on the left-hand side of the housing 69 is a manifold 87
into which a conduit 88 normally delivers a continuing flow of
low-pressure gas from another conduit 89 that communicates with the
branch conduit 84 from the inlet end portion of the flow passage
24. A pair of restrictors 90 reduce the pressure in the conduit 88
to a suitably low level, such as one-quarter of 1 psi.
While the diaphragm 70 holds the high-pressure port 80 closed, the
gas flowing into the manifold 87 simply escapes to atmosphere
through a vent port 91 in the manifold. When the diaphragm 70 opens
the high-pressure port 80, however, the resulting pressure increase
in the lower chamber 72 is applied through a conduit 92 to a second
flexible diaphragm 93 covering a chamber 94 formed in the left-hand
side of the housing 69. This bulges the diaphragm 93 to the left to
block an orifice 95 through which gas flows to the vent port 91,
thus building up back pressure in the conduit 88. This back
pressure build-up is the pressure signal for initiating operation
of the valve 12, through the pilot valve 43. A manually operable
plunger 97 is disposed over the vent port 91 so that a cycle may be
initiated manually, if desired.
In this instance, the pilot valve 43 is a diaphragm-type valve
which responds to the back-pressure signal to shift from an "off"
condition to an "on" condition, both schematically illustrated in
FIG. 1 by arrows 98 and 99, respectively, indicating the flows
through the valve in the respective conditions. This connects the
conduit 41, leading to the closing chamber 39, to a vent 100,
rather than to the conduit 42 leading to the outlet end of the flow
passage 24, and thereby relieves the relatively high pressure in
the closing chamber 39 (due primarily to leakage around the piston
37). This permits the force developed in the opening chamber 38 to
shift the piston and the plunger 22 from the closed position (FIG.
1) to the right to the open position (FIG. 2), and to initiate the
flow through the valve 12 into the conduit 15 leading through the
diluter/regulator 17 to the delivery means 11.
As gas begins to flow through the main conduit 15 to the
diluter/regulator 17, signal pressure is transmitted through a
conduit 101, a restrictor 102 and a conduit 103 to the pilot valve
82 for resetting the sensing valve 20 and opening the check valve
18 between the main conduits 15 and 19. This check valve is of the
"mushroom" type, having an inflatable closure 104 which holds the
initial negative or reduced pressure in the conduit 19 for
operating the sensing valve 20, and includes a "fail safe" spring
105 for opening the check valve to pass air from the
diluter/regulator to the delivery means if the pressure system ever
should fail.
The pilot valve 82 is similar to the pilot valve 43, being actuated
by signal pressure to shift from the "off" condition to the "on"
condition, as shown schematically by the arrows 107 and 108 in FIG.
1. In the "off" condition, high pressure from the conduit 83 is
applied through the pilot valve to a conduit 108 leading to the
conduit 81 to the sensing valve port 80 and also flows through a
branch conduit 109, a restrictor 110 and an operator 111 to a
conduit 112 leading to the closure 104 of the check valve 18. This
inflates the closure to close the check valve.
In the "on" condition, high pressure is removed from the sensing
valve port 80, thereby permitting the diaphragm 70 to reseat the
closure ball 79, and is shifted to a conduit 113 which may have one
branch 114 for operating a conventional nebulizer (not shown), and
a second branch 115 leading to the check valve operator 111,
through a restrictor 117. This second branch enters an upper,
venturi-like portion of the operator so that the resulting flow of
gas past the adjacent end of the conduit 112 reduces the pressure
in the closure 104 to open the passage between the two main
conduits 15 and 19. While this is occurring, the opening of the
orifice 95 in the sensing valve manifold 87 terminates the
back-pressure signal to the first pilot valve 43, returning it to
the "off" condition in which conduits 41 and 42 communicate through
the pilot valve, to transmit the outlet pressure from the passage
24 to the closing chamber 39.
The pilot valves 43 and 82 may take various conventional forms
which respond to a pilot-pressure "input" signal to perform a
switching function with respect to "supply" pressure, one suitable
form being illustrated in FIG. 6. This pilot valve has a hollow
body 125 with an upper actuating chamber 127 to signal conduit,
such as the conduit 103, and has a flexible diaphragm 129 forming
its lower wall so as to be urged downward when the chamber 127 is
pressurized.
Below the diaphragm 129 is a second chamber 130 from which a
passage 131 leads to a "dump" port 132, this chamber being arranged
to receive gas through a central conduit 133 through the upper
partition 134 forming the bottom wall of the chamber 130. The
diaphragm 129 overlies the upper end of the central conduit 133,
and covers this conduit to close it when the upper chamber 127 is
pressurized.
Two additional chambers 135 and 137 are formed in the lower portion
of the valve body 125 and are separated by a second partition 138.
A connecting passage 139 is formed through the partition, and is
supplied with pressurized gas through a branch passage 140. A
passage 141 leads from the chamber 135 to an "off" port 142, and a
passage 143 leads from the chamber 137 to an "on" port 144.
Mounted in the passage 139 is a shuttle-type closure member having
two heads 145 and 147 above and below the partition. The upper head
145 is movably carried by a flexible diaphragm 148 forming the
bottom wall of a chamber 149 beneath the upper partition 134 and
communicating with the lower end of the central conduit 133, which
also receives pressurized gas from the branch passage 140, through
an internal passage 150 controlled by a flow restrictor 151.
With this arrangement, in the absence of signal pressure in the
upper chamber 127, pressure in the central passage 133 is relieved
through the chamber 130 and the "dump" passage 131, and supply
pressure applied through the branch passage 140 pressurizes the
chamber 135 to raise the shuttle and hold the lower head 147 over
the lower end of the connecting passage 139, so that the valve
delivers supply pressure through the branch passage 140 to the
"off" port 142.
When signal pressure is applied to the upper chamber 127, the
diaphragm 129 is pressed against, and closes, the upper end of the
central passage 133, so that the chamber 149 is pressurized to
shift the shuttle downward and cause the upper head 145 to block
the upper end of the connecting passage 139. This switches the
supply pressure in the branch passage 140 to the lower chamber 137,
and thus connects the branch passage to the "on" port 144, as long
as signal pressure is maintained in the upper chamber 127.
Various porting arrangements are possible with valves of this type,
to achieve the desired switching functions. This type of valve thus
may be used for both of the valves 43 and 82.
The exhalation port 21 normally is closed by a check valve 116,
herein having a "mushroom" closure 118 which is inflated during the
inspiration phase but depressurized during the expiration phase.
For this purpose, the inflatable closure is connected to a conduit
which leads to the signal conduit 103 that is pressurized when gas
begins to flow through the first main conduit 15, thereby inflating
the closure 118 to close the port 21. When the flow of gas to the
main conduit 15 is terminated by closing of the valve 12, pressure
in the conduits 101, 103 and 119 is bled out through restrictors
120, and the closure is depressurized so as to open and release
exhaled gas to atmosphere.
SUMMARY OF OPERATION
Although the manner of operation of the respiration system and
apparatus will be apparent to those skilled in the art from the
foregoing description of the main components and their functions, a
summary of such operation may emphasize more clearly the features
of the present invention. Assuming that the system is at rest with
the elements in the conditions shown in FIG. 1, that oxygen at a
supply pressure of 10 psi is available in the flow passage 24 of
the main, flow-responsive valve 12, the two valve chambers 38 and
39 contain gas at substantially the same pressure so the spring 44
holds the plunger 22 in the closed position.
Ten psi pressure is supplied through the conduit 83 to the pilot
valve 82, and through the "off" circuit of this valve, the check
valve 18 is closed and 10 psi gas is available at the sensing valve
port 80, which is closed by the diaphragm 70 and the closure ball
79. Similarly, 10 psi pressure is supplied to the conduit 89, and a
signal flow is passed through the restrictor 90 and the conduit 88
to the manifold 87 to bleed through the orifice 95 and out through
the vent 91.
When the delivery means 11 is applied to a patient, a slight
inspiratory effort by the patient produces a pressure drop in the
chamber 71 above the diaphragm 70 of the sensing valve 20,
sufficient to raise the diaphragm and permit 10 psi gas to
pressurize the lower chamber 72, thus pressing the diaphragm 93
against the orifice 95 to block the escape of gas from the conduit
88 and cause a back-pressure build-up therein. This actuates the
pilot valve 43 to the "on" condition, connecting the conduit 41 to
the vent 100 to relieve the pressure in the closing chamber 39, and
the valve 12 is opened.
The ensuing flow of gas through the passage 24 is at the selected
peak flow rate determined by the supply pressure and the effective
flow area of the valve, and immediately supplies gas to the
diluter/regulator while pressurizing the conduits 101, 103 and 119
to shift the pilot valve 82 to the "on" condition, terminate the
supply of the 10 psi gas to the sensing valve port 80, open the
inspiration check valve 18, and close the exhalation check valve
116. As the 10 psi pressure is relieved in the sensing valve
chamber 72 through a bleed restrictor 121, the orifice 95 is
unblocked and the pressure signal to the pilot valve 43 is
terminated. Accordingly, this pilot valve is reset to the "off"
condition in which the conduits 41 and 42 communicate with each
other through the pilot valve.
As the foregoing control functions are performed, the gas delivered
by the valve 12 floods the main conduits 15 and 19, is diluted in
the diluter/regulator 17, and flows through the delivery means 11
to the patient to begin inflating his lungs. During the initial
portion of the inspiration phase, the peak flow rate is delivered
by the valve and back pressure in the chamber 48 of the
diluter/regulator is negligible, so the orifice 68 is unrestricted,
as shown in FIG. 4.
As soon as the pilot valve 43 is reset, the pressure at the outlet
end of the passage 24 is applied to the closing chamber 39 and its
force is added to that of the spring 44, to oppose the force
developed by inlet pressure in the opening chamber 38. With the
relatively high peak flow rate that exists prior to build-up of any
substantial back pressure, the desired pressure drop is produced
while the plunger 22 is maintained in a relatively wide-open
position. When the back pressure begins to build up, the
diluter/regulator reduces the flow rate correspondingly, as
illustrated in FIG. 5, and the reduced flow rate through the flow
passage 24 results in movement of the plunger to the left to
restrict the flow area and maintain the pressure drop, so that the
position of the plunger continues to correspond to the flow
rate.
The position of the seat 27 is adjusted initially, based upon an
empirical determination of valve characteristics, so that the
plunger 22 will engage the seat and terminate the flow of gas at
the desired terminal flow rate. It has been found that the plunger
closes with a snap action after it has come within a few
thousandths of an inch of the seat, regardless of the particular
position selected for the seat, and that the seat position has, at
most, a negligible effect on the response of the plunger to changes
in the flow rate.
When the plunger 22 shuts off the flow, the supply of gas to the
patient ceases, the pressure in the conduits 101, 103 and 119 is
bled out of through the restrictor 120, and the pilot valve 82 is
therefore reset to close the check valve 18 as the pressure in the
exhalation check valve 116 is relieved to permit the patient to
exhale. The reduction in the pressure in the chamber 48 of the
diluter/regulator restores the diaphragm 49 to the position shown
in FIG. 4, and the system is ready to initiate another cycle in
response to the next inspiratory effort by the patient.
From the foregoing, it will be apparent that the present invention
provides an IPPB apparatus in which the flow-responsive monitoring
function and the "on-off" flow control function are accomplished
with a single valve that is relatively simple in construction and
effective in construction, so as to achieve the same basic
operating characteristics as the apparatus of the aforesaid patent,
but with less expensive components, and with the performance
advantages that result from direct control of the on-off function
by the flow-responsive valve.
It also will be evident that, while a preferred form of the
invention has been illustrated and described, various modifications
and changes may be made without departing from the spirit and scope
of the invention.
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