U.S. patent number 3,916,889 [Application Number 05/401,739] was granted by the patent office on 1975-11-04 for patient ventilator apparatus.
This patent grant is currently assigned to Sandoz, Inc.. Invention is credited to George K. Russell.
United States Patent |
3,916,889 |
Russell |
November 4, 1975 |
Patient ventilator apparatus
Abstract
Disclosed herein is a patient ventilator apparatus having a
pneumatic control system operable in three different modes wherein
the apparatus assists the breathing of the patient, controls the
patient's breathing in a timed manner, or operates in a combination
assist/control mode according to certain predetermined conditions.
Fluidic circuitry controls a valved bellows apparatus, which in
turn supplies air to a patient subject to limitations of time,
volume, and pressure, wherein the gas supplied to the bellows
comprises an adjustable oxygen/air mixture. Fluidic timers are
provided for use in the control mode of the circuitry, and
identical fluidic circuitry combinations are provided for use in
the assist mode to automatically trigger the ventilator apparatus
into an inspiratory state according to the patient's breathing
requirements and to trigger such apparatus into an exhalation state
when a predetermined inspiratory pressure is attained.
Inventors: |
Russell; George K. (Castle
Rock, CO) |
Assignee: |
Sandoz, Inc. (E. Hanover,
NJ)
|
Family
ID: |
23589024 |
Appl.
No.: |
05/401,739 |
Filed: |
September 28, 1973 |
Current U.S.
Class: |
128/204.24;
128/205.11; 128/205.15 |
Current CPC
Class: |
A61M
16/00 (20130101); A61M 16/0012 (20140204); A61M
16/0009 (20140204); A61M 16/0081 (20140204); A61M
16/0075 (20130101); A61M 16/107 (20140204); A61M
2205/42 (20130101) |
Current International
Class: |
A61M
16/00 (20060101); A62B 007/04 () |
Field of
Search: |
;128/145.8,145.7,145.6,145.5,142,188 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Gaudet; Richard A.
Assistant Examiner: Recla; Henry J.
Attorney, Agent or Firm: Sharkin; Gerald D. Honor; Robert S.
Jewell; Walter F.
Claims
What is claimed is:
1. A fluidically controlled patient ventilator apparatus
comprising:
a patient breathing hose;
means for supplying a predetermined quantitiy of air to the patient
breathing hose;
a fluidic flip flop circuit switchable into first and second
states, said flip flop circuit having opposed input ports for
controlling said switching, and having at least one output port
providing a pressure signal while said flip flop circuit is
switched into said first stable state;
means coupled between said flip flop circuit output port and said
air supply means to actuate the latter to supply air to the
breathing hose in reponse to said pressure signal, thereby defining
an inspiratory period of operation;
a first fluidic timing means actuable during said inspiratory
period and a second fluidic timing means actuable during an
exhalation period, said first and second timing means having
respective output ports coupled to said opposed input ports of said
flip flop for controlling said flip flop to switch between said
stable states, wherein an output signal from said first timing
means actuates said flip flop to switch from its first to its
second stable state, nd an output from said second timing means
actuates said flip flop to switch from its second to its first
stable state;
a fluidic trigger circuit having an input coupled to said patient
breathing hose for providing a trigger signal at an output port
thereof in reponse to a minimum pressure in said patient breathing
hose corresponding to the termination of a patient exhalation cycle
and means coupling said trigger signal to one of said input ports
of said flip flop to control said flip flop to switch from its
second to its first stable state to initiate said inspiratory
period;
a fluidic pressure limit circuit having an input port coupled to
said patient breathing hose for providing a limit signal at an
output port thereof in reponse to a predetermined maximum pressure
in the patient breathing hose, and means coupling said limit signal
to one of said input ports of said flip flop to control said flip
flop to switch from its first to its second stable state to
terminate said inspiratory period;
a volume limit signal generating means coupled to said patient
breathing hose for providing a trigger output signal in response to
the sensing of a predetermined quantity of air supplied to the
patient breathing hose by the air supply means, and means coupling
said trigger signal to one of said input ports of said flip flop to
control said flip-flop to switch from its first to its second
stable state to terminate said inspiratory period;
and mode selecting means for selectively deenergizing said trigger
circuit and said first timing means, one at a time.
2. A fluidically controlled patient ventilator apparatus as set
forth in claim 1 further comprising an adjustable oxygen/air mixing
valve means coupled between said inlet valve and said bellows
element for selective positioning to control the oxygen content of
the air within the bellows, element wherein said mixing valve means
is coupled to a source of room air, and is coupled through said
inlet valve means to a source of oxygen.
3. A fluidically controlled ventilator apparatus as set forth in
claim 2 wherein said bellows chamber comprises a fixed volume
surrounding said bellows element, and further comprising means
responsive to said pressure signal from said one output port of
said flip flop circuit for charging said bellows chamber with
oxygen to collapse said bellows and discharge the air therein
through said outlet valve means;
said bellows element having a weight mounted therein for causing
its expansion upon depressurization of said bellows chamber; and
further comprising conduit means interconnecting said bellows
chamber and said inlet valve means wherein said oxygen charged into
said bellows chamber escapes through said inlet valve for selective
coupling through said mixing valve means to said expanding bellows
element.
4. A fluidically controlled patient ventilator apparatus as set
forth in claim 1 wherein said flip flop circuit has a second output
port for generating a pressure signal while said flip flop is
switched into its second stable state defining an exhalation period
of the apparatus, and wherein said first and second timing means
comprise respective first and second fluidic logic switching
circuits, first and second sealed cannisters, and first and second
pressurized bellows members disposed within said sealed cannisters,
said first switching circuit having output port means coupled for
actuation by the pressure signal from said second output port of
said flip flop circuit to charge a regulated quantity of air into
said first cannister, and said second switching circuit having
output port means coupled for actuation by the pressure signal of
said first output port of said flip flop circuit to charge said
second cannister, wherein said charging of said cannisters causes
the bellows members therein to collapse, and first and second
sensing means for generating said timing means output signals in
response to said collapse of said respective bellows after a
predetermined air charging time of said cannisters, said sensing
means being coupled to said opposed input ports of said flip flop
circuits.
5. A fluidically controlled patient ventilator apparatus as set
forth in claim 4 wherein said first and second sensing means are
movably mounted, and wherein movement thereof changes said
predetermined air charging times at which said output signals are
generated, and further comprising a rotatable shaft having a pair
of cams mounted thereon in a spaced relation for engaging said
first and second sensing means, whereby rotation of said shaft and
cams moves said sensing means and changes the timing periods of
said first and second timing means.
6. A fluidically controlled patient ventilator apparatus as set
forth in claim 5 further comprising an adjustable by-pass valve
connected to change the charging time of said first cannister for
independently adjusting the timing period of said first timing
means.
7. A fluidically controlled patient ventilator apparatus as set
forth in claim 6 further comprising first and second dump valve
means mounted respectively on said first and second cannisters for
depressurizing said cannisters in response to input signals
received respectively from said second output port and said one
output port of said flip flop circuit.
8. A fluidically controlled patient ventilator apparatus as set
forth in claim 1 wherein said trigger circuit and said pressure
limit circuit are constructed identically and comprise three
proportional amplifiers connected in series, and three fluidic flip
flops connected in series with each other and in series with an
output of said three fluidic amplifiers, and wherein said trigger
circuit further comprises means for connecting inputs of one of
said three fluidic amplifiers to a pressure source for adjusting
the sensitivity thereof, and for connecting inputs of another one
of said fluidic amplifiers to a positive end expiratory pressure
signal and to said patient breathing hose.
9. A fluidically controlled patient ventilator apparatus as set
forth in claim 1 further comprising a positive end expiratory
pressure circuit having an output coupled to an input port of said
patient trigger circuit for providing a bias signal thereto, said
end expiratory pressure circuit including a fluidic capacitance
having an output port coupled as said input to said trigger
circuit; an adjustable offset pressure valve having an output
coupled as an input to said fluidic capacitance; a pressure
actuated gate valve having an output coupled to the input of said
offset valve, having an input coupled to a source of positive end
expiratory pressure sinals, and having a gate input coupled for
actuation by said flip flop circuit during said inspiratory
period.
10. A fluidically controlled patient ventilator apparatus as set
forth in claim 1 further comprising first and second manually
operable pressure switches connected respectively to said opposed
inputs of said flip flop for switching said flip flop from one of
its stable states to its other stable state, and first, second and
third indicator displaymeans coupled respectively to the outputs of
said patient trigger circuit, said pressure limit circuit, and said
first timing means for indicating the presence of signals at the
outputs thereof.
Description
BACKGROUND OF THE DISCLOSURE
Certain respiratory apparatus is known in the art wherein fluidic
circuits are provided for controlling the exhalation and inhalation
cycles of a patient. However, the instant disclosure relates to an
improved patient ventilator apparatus utilizing totally pneumatic
control circuitry for operating the ventilator apparatus in a
plurality of desired modes wherein the breathing of the patient is
assisted, completely controlled, or subjected to a combination
assist/control operation according to predetermined parameters.
SUMMARY OF THE INVENTION
In accordance with the invention there is provided a pneumatic
ventilator apparatus utilizing a pressurized source of gas for
operating fluidic circuitry, which in turn controls a source of gas
supplied to a patient. During the inspiratory cycle air is
exhausted from a bellows apparatus, and supplied through an outlet
value to a patient breathing hose. The bellows is surrounded by a
confined volume, and it is evacuated by supplying oxygen to that
confined volume, thus causing the bellows to collapse. A weight is
provided in the free lower end of the bellows, so that upon release
of the oxygen pressure in the confined area surrounding the
bellows, the latter will automatically be exposed under the
influence of the weight, thereby pushing the oxygen out from the
confined area and through a mixing valve, wherein the oxygen is
either vented to the atmosphere or mixed with a supply of room air
and then injected into the expanding bellows for use in the next
succeeding inhalation cycle. An inlet valve couples the mixing
valve to the confined volume surrounding the bellows, and the inlet
and outlet valves for the bellows apparatus are actuated
alternately during the exhalation and inhalation cycles,
respectively, by means of a logic circuit having its input coupled
to one output of a master flip flop which in turn is controlled at
one input by an exhalation timer signal and an automatic patient
trigger signal, and controlled at its other input side by an
inspiration timer signal, a pressure limit triggering circuit
signal, and a volume limit signal coupled from the bellows
apparatus.
The ventilator apparatus is provided with three different modes of
operation selectable by means of a manually operable pneumatic
switch. First, in an ASSIST mode the selecting switch is connected
to activate the patient trigger circuit which, together with the
pressure limit circuit, is responsive to the air pressure in a
patient reference line, so that the master flip flop switches
states to control the exhalation and respiration cycles of the
bellows apparatus in accordance with the patient's breathing
demands. That is, when the air pressure in the patient reference
line drops to a low level indicating the completion of an
inspiratory cycle, that low level pressure is detected by the
patient trigger circuit which then triggers the master flip-flop to
initiate the inspiratory cycle of the bellows apparatus. Then,
during the ASSIST mode the pressure limit circuit provides a
trigger signal to the master flip-flop to terminate the inspiratory
cycle if the pressure in the patient reference line exceeds a
predetermined value, while the volume limit detector device in the
bellows apparatus also provides a trigger signal to the master
flip-flop to terminate the inspiratory cycle after a predetermined
maximum amount of air has been supplied to the patient from the
bellows apparatus, or a fluidic timing device provides a trigger
signal to the master flip-flop to terminate the inspiratory cycle
after a predetermined amount of time. Therefore, the first one of
the pressure, volume, or time signals to reach its predetermined
maximum value is the signal which triggers the flip-flop to
terminate the inspiration cycle; and the command from the patient
trigger circuit terminates the exhalation cycle.
When the manually operable mode switch is positioned to select a
CONTROL mode, the exhalation timer is activated and the patient
trigger circuit is deactivated, so that the master flip-flop is
controlled at one input by the output of the exhalation timer,
while it is controlled at its other input by the pressure limit
circuit, the inspiration timer, and the volume limit detector.
Accordingly, in the CONTROL mode the exhalation cycle is
automatically timed, as is the inspiration cycle, but the latter is
also terminated prematurely of the inspiration timer output if the
pressure limit signal or volume limit signal reach their
predetermined maximum values.
The bellows for supplying air to the patient has an adjustable
volume which is determined by a movable plate positioned to control
the expansion of the bellows and which also contributes to defining
the confined volume surrounding the bellows. During the inspiration
cycle, the master flip flop controls a power valve which supplies
oxygen under pressure to the confined volume thereby causing
contraction of the bellows. Then, upon releasing the pressure in
the confined volume, the bellows starts to expand under the force
of a weight carried therein and the oxygen is forced out of the
confined area and through the inlet valve which is actuated to an
open condition by the logic circuit. A mixing valve which receives
the oxygen from the inlet valve is adjustable to conduct a
controlled amount of the oxygen through to the bellows along with a
partial supply of filtered room air. The room air is received at
ambient pressure and is drawn into the bellows due to a vacuum
caused by its expansion. However, the oxygen is supplied under
pressure as a result of its forced expulsion from the confined area
so that the mixing valve permits the oxygen content of the gas
supplied to the bellows to be varied from 21-100%.
Each of the timer devices comprises a bellows housed within a
chamber having an input orifice for receiving oxygen at a
predetermined pressure to cause a timed contraction of the bellows.
A shaft has one end fixed to the movable end of the bellows, while
the opposite end of the shaft closes a vent on a back pressure
detector which is coupled to the input of the master flip-flop.
Therefore, a pair of opposed inputs to the master flip-flop are
controlled respectively by the movable shafts on the two timer
bellows. Furthermore, each of the chambers surrounding the timer
bellows have dump valves mounted therein, such valves being
actuable by opposed outputs of the master flip-flop, so that as
soon as the back pressure detector of one of the bellows provides
an output for switching the master flip-flop, the resultant output
of the flip-flop is coupled back to that bellows chamber to cause
its depressurization, and to prepare it for its next timing cycle.
The two bellows devices and their surrounding chambers are mounted
side by side and their back pressure sensing elements are movable
mounted movably springs, so that they are adjustably positioned by
means of a pair of cams fixed on a shaft, so that rotation of the
shaft causes movement of the cams and adjustable movement of the
two sensing devices. Thus, this movement of the sensing devices
changes the timing periods for both the exhalation and inspiration
timers which can be adjusted in unison by rotation of the shaft.
Furthermore, a by-pass valve is provided in parallel with the input
orifice to the inspiration timer, and that by-pass valve can be
opened to decrease the inspiration time, thus adjusting the
inspiration/exhalation (I/E time ratio. However, the timing devices
are constructed so that the I/E ratio has a maximum value of
unity.
The patient trigger circuitry, and the pressure limit circuit have
identical configurations, and each comprises a more universal
trigger circuit for automatic operation in a patient ventilator. In
particular, the universal trigger circuit consists of a six-gate
fluidic circuit having three proportional amplifiers connected in
series with each other and with three serially connected fluidic
flip-flops. In accordance with the invention the universal circuit
can be used as the patient trigger and the pressure limit circuit
as described above, and depending on the input connections thereto
it can function to provide an output in response to a small
differential pressure at its inputs; it can function to provide an
output in response to pressures slightly below ambient, as would be
caused by a patient's breathing efforts; it can function to provide
an output in response to pressure levels above or below
atmospheric, wherein the device is automatically biased so that it
can be used in conjunction with end expiratory pressure signals; it
can function to provide an output in response to air pressure
inputs indicating maximum levels; and it can function to provide an
output in response to flow signals, or rate of change of pressure
as is sometimes desirable.
In accordance with the use of the universal trigger circuits, as
controlled in part by end expiratory pressure signals, the circuit
is utilized to provide an output in response to small differential
pressures. To allow the Positive End Expiratory Pressures (PEEP) to
be used during assisted breathing, without the need for the
patient's inhalation effort to return the patient hose to ambient
pressure, the PEEP pressure is fed through a diaphragm valve to the
patient trigger module, to bias that module so that it can be
triggered while the patient reference line is still above the
ambient pressure level.
BRIEF DESCRIPTION OF THE DRAWINGS
One embodiment of the invention is described herein in conjunction
in the accompanying drawings. In such drawings:
FIG. 1 shows a block diagram of a patient ventilator apparatus
according to the invention;
FIG. 2 is a schematic view of the fluidic circuitry illustrated in
FIG. 1;
FIG. 3 is a front elevation of the mixing device mounted on the
bellows apparatus disclosed in FIG. 1;
FIG. 4 is a sectional view taken along the line 4--4 of FIG. 3;
FIG. 5 is a sectional view taken along the line 5--5 of FIG. 3;
FIG. 6 is a sectional view taken along the lines 6--6 of FIG.
3;
FIG. 7 is a perspective view of the mixer valve stem illustrated in
FIGS. 3--5;
FIG. 8 is a sectional view of the timer devices illustrated
schematically in FIG. 2; and
FIG. 9 is a sectional view of a dump valve used with the timer
devices of FIG. 4.
DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION:
An embodiment of the invention is depicted in block diagram form in
FIG. 1 of the drawings, and includes a bellows apparatus 10 having
a bellows element 12 fixedly held at its upper end within a
cylindrically formed chamber 14. The chamber 14 is provided at its
upper end with a connecting conduit 16, and is provided at its
lower end with an adjustable plate 18 having a seal 20 connected at
its periphery for sealing the plate against the sidewalls of the
chamber 14. The plate is adjustably movable through the chamber 14
by means of an adjusting device 15, so that when the plate is moved
upwardly the confined volume of the chamber within which the
bellows can expand and contract is decreased, while such volume is
increased when the plate 18 is moved downwardly within the chamber
14. In operation, the bellows element 12 is charged with air
through an input duct 22 having a check valve 24 mounted thereon,
and the bellows element is connected in communication with an
outlet valve 26 for actuation to allow air within the bellows
element to be discharged to the patient during the inspiration
cycle. The discharge of air from the bellows element 12 is effected
by pressurizing the chamber 14 with oxygen supplied through the
conduit 16. When the chamber 14 is so pressurized with oxygen, it
causes the bellows element 12 to collapse to expel the air
previously charged therein.
Accordingly, the tidal volume of the system is determined by the
placement of the plate 18 which plate also minimizes gas
consumption by limiting the confined volume surrounding the bellows
element 12. As illustrated, the check valve 24 closes off the input
port to the bellows element during its collapse. The output valve
26 also includes a check valve to prevent air from the patient hose
28 from being injected into the bellows element, and the valve 26
is controlled by a diaphragm 30, which in turn is controlled by the
fluidic circuitry described below.
The bellows element 12 continues its collapsing movement until the
chamber 14 is depressurized in response to one of four different
control signals which are adapted to terminate the inspiration
cycle. One of these four control signals is initiated by a rod 32
mounted above the bellows element 12 and spring loaded in a
downward direction, but movable upwardly due to pressure exerted by
the upward movement of the lower portion of the bellows element
wherein such upward movement of the rod indicates the total
exhaustion of the air previously charged into the bellows element.
The rod 32 closes a vent in a pressurized conduit 34, thus
providing a back pressure signal along a volume limit conduit 36.
The conduit 34 is pressurized by a regulated supply of oxygen fed
through an orifice 37.
As stated above, the inspiration cycle is terminated when the
chamber 14 is depressurized, and at that time the bellows element
12 automatically expands under the force of a weight 38 housed in
its lower extremity. As the bellows element expands it creates a
partial vacuum which opens the inlet check valve 24 and draws air
inwardly through the conduit 22 which has a filter 40 connected
thereto and disposed in communication with room air.
Depressurization of the chamber 14 is obtained by opening a bellows
inlet valve 42 so that the oxygen which is forced out of the
chamber 14 by the expanding bellows element 12 is coupled through
the inlet valve 42 to a three port mixing valve 44 as described in
detail below in conjunction with FIGS. 3-7. In operation, the
oxygen discharged from the chamber 14 through the valve 42 is
vented to atmosphere by the valve 44, or is directed in an
adjustably controlled volume to the conduit 22 which supplied air
to the bellows element 12. Since the oxygen is discharged under
pressure from the chamber 14, due to the expansion of the bellows
element 12, the pressure of the oxygen exiting the mixer valve 44
is greater than the ambient pressure of the room air coupled
through the filter 40, and therefore the oxygen/air mixture can be
varied by positioning the valve 44 to a desired position.
The input and output valves 26 and 42 of the bellows apparatus 10,
and the supply of oxygen to the chamber 14, are controlled by the
fluidic circuitry shown in block diagram form in FIG. 1, such
circuitry being energized by a 50 psig oxygen supply source
indicated at reference numeral 46. The pressurized oxygen is
coupled through a filter 48 to a power valve 50 which is gated to
supply oxygen through an adjustable flow valve 52, and through a
silencer-filter 54 to the input conduit 16 for the bellows chamber
14. The output of the filter 48 is also coupled to a regulator 56
wherein the oxygen pressure is reduced so that the oxygen emanating
from the regulator 56 can be used as a supply source for the active
elements of the fluidic circuitry. The regulated oxygen, which may
be at a pressure of about 5 psig, is also coupled through a three
position mode selector switch 58, which permits the selection of
three modes of operation, including an ASSIST mode, a CONTROL mode,
and an ASSIST/CONTROL mode.
The fluidic circuitry includes a master flip flop 60 having a
principle output 62 which actuates the power valve 50, and which
operates a dual OR/NOR circuit 64 to provide regulated oxygen
pressure signals along the respective conduits 66 and 68 to the
inlet and outlet valves 42 and 26 of the bellows apparatus 10. In
particular, when the output 62 of the flip flop 60 provides a
positive pressure, the dual OR/NOR circuit provides a positive
signal on the output conduit 66 to close the inlet port to the
bellows apparatus, while the outlet port 26 is allowed to open so
that the inspiration cycle will commence due to collapsing movement
of the bellows element 12, which in turn results from
pressurization of the chamber 14. Similarly, upon completion of the
inspiration cycle, the flip flop 60 will switch to its opposite
stable state whereby a positive regulated pressure signal will be
coupled along conduit 68 to close the outlet valve 26 while the
pressure on conduit 66 will be decreased to allow the valve 42 to
open so that he oxygen discharged from the bellows chamber 14 will
pass through that input valve 42 to the mixing valve 44.
The flip flop 60 has three inputs which cause it to switch to its
inspiration command state wherein it provides an output to conduit
62, and those three inputs are supplied from a manually operable
input signal device 70, a patient trigger device 72, and an
exhalation timer device 74. On the other hand, the flip flop has
four inputs for causing it to terminate its inspiration command,
and those inputs are coupled from a manually operable exhalation
triggering device 76, a pressure limit circuit 78, an inspiration
timer device 80, and the volume limit detector device formed by the
elements 32, 34, and 36 disposed in the bellows apparatus 10. A
pressure limit display device 82 is actuable to exhibit a red
display in response to an indicator signal from a driver device 84
which in turn is energized by the output of the pressure limit
circuit 78. The display device 82 utilizes reflected light.
Similarly, a red display device 86 is operated by a driver 88 in
response to an output from the inspiration timer 80, while a green
display light 90 operates in a similar manner under the control of
an indicator driver 92 which is energized by an output from the
patent trigger circuit 72.
In the operation of the circuitry, when the ASSIST mode is
selected, a regulated oxygen pressure signal is applied to the
patient trigger circuit through a conduit 93 to put it in an
energized condition, and an input control port for the patient
trigger circuit is coupled through a patient reference line 94 to
the patient hose line 28, so that the patient trigger circuit
provides an output to switch the master flip flop 60 to its
inspiration state when the pressure in the patient reference line
94 decreases to a minimum indicating the completion of an
exhalation cycle. While the system is operating in its ASSIST mode,
the green light 90 will be actuated at each instance of a patient
trigger output signal, which in turn is controlled by the patients
breathing in response to a signal coupled along the patient
reference line 94.
An additional input to the patient trigger device 72 includes a
regulated oxygen signal coupled through an adjustable input port 96
to control the sensitivity of the trigger device 72, and an input
signal from a Positive End Expiratory Pressure (PEEP) 98, wherein
the patient trigger device 72 is adaptable to provide an output in
response to a small differential input pressure between the input
coupled along the conduit 94 and the PEEP input. The PEEP circuit
98 has a gate input coupled from an output conduit 100 of the dual
OR/NOR circuit 64, and the gate is maintained in a closed condition
by the positive regulated oxygen supply coupled through a small
orifice 102, an adjustable orifice 104, and a one way valve 106, to
the gate input, wherein the junction of the adjustable orifice 104
and the one way valve 106 are vented to the atmosphere through an
orifice 108. However, during an exhalation cycle, the pressure in
the conduit 100 opens the PEEP driver circuit to permit the
regulated pressure coupled through the orifices 102 and 104 to be
applied though an offset adjust orifice 110 and a spike -- damping
volumetric chamber 112 to the patient trigger device 72.
The pressure limit circuit is identical in construction to the
patient trigger circuit, but provides an output in response to a
high pressure sensed on the patient reference line 94, and the
sensitivity of the device is adjustable by means of a variable
orifice 114 coupled as a second input thereto. Also, a pressure
gauge 116 is connected at the second input to the pressure limit
circuit 78 for displaying the selected pressure limit adjustment to
which the circuit is sensitive, and a second pressure gausge 118 is
connected to the patient reference line so that the actual pressure
such line can be monitored. An adjustment is provided but not shown
in FIG. 1 wherein the periods of the exhalation timer and the
inspiration timer can be simultaneously adjusted, and an adjustable
orifice 120 is provided in the input line to the inspiration timer,
so that the inspiration/exhalation (I/E) ratio can be adjusted.
These adjustments are desireable since medical ventilation systems
require a matching of the I/E ratio to the needs of individual
patents, and since it is usually considered detremental to use I/E
which is greater than unity. Also, controlled breathing required
uniform cycle rates, but such rates should be adjustable to permit
changes in the minute-volume, without disturbing the selected I/E
ratio. The above-mentioned controls satisfy these requirements.
An additional function of the ventilator apparatus disclosed herein
is provided by a conduit 122 for coupling to a nebulizer device
wherein that conduit 122 is connected through an adjustable orifice
124 to an OFF position, an INTERMITTENT position wherein the
nebulizer is operated by the output of the power valve 50, and a
CONTINUOUS position wherein the nebulizer is operated by the supply
source of oxygen as coupled through an orifice 128.
In summary, in the ASSIST mode the inspiration cycle is terminated
by the pressure limit circuit 78, by the manually operable signal
device 76, by the volume limit signal coupled along the conduit 36,
or by the inspiration timer 80, and the exhalation cycle is
terminated by the patient trigger circuit 72, or the manually
operable signal device 70.
In the CONTROL mode the regulated oxygen supply is coupled throgh
the selecting switch 58 to energize the exhalation timer, while the
patient trigger circuit 72 is deenergized. Therefore, in the
CONTROL mode the inspiratory command generated in the conduit 62 is
initiated by the exhalation timer 74 or the manual signal device
70, while the inspiratory cycle is terminated by any one of the
four inputs to the master flip-flop 60 from the manually operable
device, such inputs including signal pressure limit circuit 78, the
inspiratory timer 80, or the volume limit signal conducted along
conduit 36. During normal operation of the CONTROL mode, the master
flip-flop may be operated during both the inspiratory and
exhalation cycles in a timed manner determined by the timers 74 and
80, respectively. However, the inspiratory cycle is terminated
prematurely of its timed duration if either pressure limit or the
volume limit exceeds its maximum predetermined value.
Then, in the ASSIST/CONTROL mode, the selector switch 58 energizes
both the patient trigger circuit 72 and the exhalation timer 74
through the use of a pair of one way valves 58A and 58B, so that
the circuitry operates as described above with respect to the
CONTROL mode with the exception that flip-flop 60 will be triggered
to generate its inspiratory command along conduit 62 by the patient
trigger signal from the device 72, as well as by the exhalation
timer 74.
The actual circuitry included in the blocks of FIG. 1 is shown in
greater detail in FIG. 2, wherein a preferred form of the patient
trigger circuit 72 is shown as comprising a six section fluidic
device incorporating three proportional amplifiers 130A, 130B,
130C, connected in series with each other and in series with three
serially connected flip flops 132A, 132B, 132C. Each of the six
circuits has its supply input coupled along the conduit 73 to the
mode selector switch 58 while each of circuits 130B, 130C, 132A,
132B, and 132C, have their control inputs coupled to the respective
outputs of the preceeding stage; while the control inputs to the
first proportional amplifier 130A are coupled respectively to the
output of the PEEP circuit 98 and to the patient reference line 94.
Furthermore, the adjustable sensitivity orifice 96 is coupled to a
second control input to the proportional amplifier 130B, and this
configuration permits a stable sensitivity adjustment from +1 to
more than -10 cm H.sub.2 O with respect to ambient pressure. The
fourth input to the amplifier 130B is vented. The gating device for
the PEEP driver 98 which is shown schematically in FIG. 2 comprises
a diaphragm 134 which closes off the conduit leading to the PEEP
input for the proportional amplifier 130A, and it is seen that the
PEEP driver 98 is maintained in a closed condition by that
diaphragm 134 due to pressure from conduit 100 during inspiration.
The pressure through the one way valve 106 is negated by a signal
from the dual OR/NOR circuit 17 during the inspiration cycle.
Diaphragm 134 permits oxygen flow from the valves 102 and 104 and
then through the adjustable valve 110 and the damping chamber 112
through to the proportional amplifier 130A during exhalation. Also,
during exhalation the pressure through 106 is delivered to conduit
100 where it is used to hold the patient circuit exhalation valve
at the PEEP pressure.
In operation, an end expiratory pressure which remains higher than
ambient pressure is generated by bleeding a small amount of the
driving gas into the exhalation exhaust line through the one way
valve 106. This keeps the diaphragm 134 of the PEEP device 98 at a
slight positive pressure. Then, since most exhalation valves hold
patient hose pressures slightly higher than their actuation
pressures, the OR/NOR output pressure with PEEP will usually be
less than the PEEP pressure shown on the patient pressure gauge.
Therefore, variations in the obtainable PEEP pressures will be
experienced with exhalation manifolds of different manufacturers.
To allow PEEP to be used during assisted breathing, without the
need for the patient's inhalation effort to return the patient hose
to ambient conditions, the PEEP pressure is fed to the patient
trigger module to bias that module so that it can be triggered
while the patient hose pressure is still above the ambient pressure
level. The amount of pressure difference required to switch the
trigger module is preset by the offset-adjust valve 110. During
inspiration, the diaphragm 134 is closed to remove the bias signal
from the patient trigger module so that high exhalation valve
pressures will not hold the ventilator in an inspiration condition.
However, during exhalation, the diaphragm 134 opens and allows the
PEEP pressure to reach the patient trigger module circuit 130A. The
system is ususally preset so that the pressure difference required
to trigger the patient trigger module is relatively large as
compared to that normally required without PEEP to compensate for
leaks. The offset-adjust valve 110 is provided to function as a
leak compensator for desensitizing the patient trigger module
during PEEP operation.
The pressure limit circuit 78 is identical to the above-described
patient trigger circuit 72 in its construction, with the exception
that the source supplied for each of the six individual circuits is
coupled to the regulated source of oxygen provided at the output of
the regulator 56, while the control inputs to the pressure limit
circuit 78 are as described above in conjunction with FIG. 1.
It is seen, therefore, that the circuits 72 and 78 as illustrated
in FIG. 2 of the drawings are identical, although their input
signals may be connected in different ways to make the circuit
responsive to different input parameters. In addition to the
responses described above with respect to FIG. 2 of the drawings,
the inputs to the six-state circuit can be coupled in at least
three different configurations so that the circuit may be described
as a universal trigger circuit. In this regard, for example, the
inputs can be connected as illustrated at 72 in FIG. 2, while the
PEEP input is replaced by an ambient pressure input so that the
circuit will be sensitive to small negative pressures. As another
example, the PEEP input to the circuit 72 as illustrated in FIG. 2
may be connected to be automatically biased to allow triggering at
pressure levels above or below atmospheric pressure. For example,
the input may be connected to a three-position switch so that when
PEEP pressures are used, a pressure slightly above atmospheric is
applied, while with negative end-expiratory pressures (NEEP), a
pressure slightly below atmospheric is applicable through a second
position of the switch. In such NEEP applications, the
reference-adjust gas is used to drive a venturi for evacuating the
patient hose, thereby generating the vacuum necessary for the
negative bias. The third position of the switch may provide for
normal operation so that the universal trigger circuit may be
switched from NORMAL, to PEEP, to NEEP without requiring
readjustment of the sensitivity control. A further example of the
responsiveness of the universal circuit results when a suitable
restriction is placed in the patient hose input, while a feedback
connection is coupled to the circuit 72 in place of the PEEP input
so that the ventilator will be cycled as a function of flow, or as
a function of the rate of change of pressure. That is, the feedback
connection can be used to sense flow since the pressure
differential across the restriction in the patient hose will give
an indication of such flow. This last-described configuration can
be used to turn on the ventilator due to a slight patient breathing
effort, and if a time delay circuit such as a fluidic RC circuit is
provided in a parallel feedback line, the patient trigger signal
can be extended.
The OR/NOR circuit 64 is also depicted in schematic form in FIG. 2
and comprises a two stage device, wherein the first stage 136
provides a positive pressure output along the conduit 66 in
response to an input signal received from the flip flop 60 along
the conduit 62. Similarly, the second stage 138 provides an output
along conduit 100 during the inspiration cycle to maintain the
exhalation valve on the patient hose in a closed condition during
such inspiration cycle.
In the past, fluidic timers for respiratory equipment have been
constructed to allow a certain volume (capacitance) of fluid to
slowly increase or decrease to a desired switching pressure level.
However, it is difficult to repeat such pressures, and elaborate
circuitry is usually required to provide the necessary
repeatability. Another type of known timer comprises a fluidic
oscillator combined with complex digital counter stages, and this
configuration also has obvious drawbacks.
In the present invention accurate and relatively simple timers are
provided wherein each of the timing devices 74 and 80 comprises a
logic circuit 74A and 80A, and a bellows device 74B and 80B,
respectively. When the flip flop 60 is switched to provide an
inspiration command along the conduit 62 the logic circuit 80A
provides a regulated pressure output coupled through an orifice 80C
to the chamber of the bellows device 80B, and causes the bellows
element thereof to collapse. A rod 80D is fixed to the moveable
portion of the bellows element, and is mounted to engage a sensor
80E for causing a back pressure along a conduit 80F which is
connected as an inspiration cycle terminating signal of the flip
flop 60. Similarly, the timing device 74 has the input of its logic
circuit 74A connected for actuation by the opposing output of the
flip flop 60 while the sensor device 74E couples a signal along the
conduit 74F to terminate the exhalation cycle of the apparatus by
switching the flip flop 60. Additionally, the adjustable orifice
120 is connected in parallel with the orifice 80C to vary the I/E
ratio as described above.
Various additional details of the construction of the valving
apparatus are shown in FIGS. 3-7. Particularly, FIG. 3 shows an
embodiment of the valve construction utilized with the bellows
apparatus 10 wherein the room air is drawn through the filter 40,
the oxygen/air mixture is controlled by the valve knob 44A, and the
patient output hose is connected to the output port 28A. The
internal configuration of the valve apparatus is shown in FIGS. 4-6
which comprise sectional views wherein the opening 140, as shown in
FIG. 4, comprises the port opening of the bellows element 12, while
the input check valve 24 is shown in communication with a duct 22
corresponding with the duct 22 illustrated in FIGS. 5 and 6.
Similarly, the air filter 40 is also shown in FIG. 4, and the duct
16, communicating with the bellows chamber 14 and valve 42, is
shown in FIG. 5. Also, the adjustable flow control orifice 52, and
the oxygen filter 54 are shown in FIG. 6, while the valve stem for
the mixing valve 44 is shown as element 44B in FIGS. 5 and 7. When
the valve stem 44B is rotated by means of the valve knob 44A to its
extreme counterclockwise position, all of the oxygen forced out of
the chamber 14 by the expanding bellows element 12 is vented to the
atmosphere through a vent opening 142 as illustrated in FIG. 3. As
the knob 44A is rotated clockwise, however, increasing quantities
of oxygen are permitted to flow through the conduit 22, first
through a slit portion 44C in the valve stem 44B, and then through
the full open orifce 44D thereof so that when the valve knob 44A is
turned completely clockwise, the entire quantity of oxygen forced
out of the chamber 14 is drawn into the bellows element 12. The
bladder elements 26A and 42A shown respectively in FIGS. 4 and 5
are controlled by the pressure signals coupled through conduits 68
and 66, respectively, as described above in conjunction with FIG.
1.
Since the oxygen/air mixture is effected by the expanding bellows,
and proportioned by the valve 44, the oxygen concentration is
unaffected by the patient's breathing, the inspiratory flow rate,
the tidal volume, the patient hose pressure, or the cycle time,
thereby providing an accurately controllable system in this
regard.
The timing devices 74B and 80B, shown schematically in FIG. 2, are
illustrated in FIG. 8, wherein the device 74B, is depicted in a
partially sectional view. The timing devices include sealed
cannisters 150, 151, each having a sealed collapsible bellows
device 152 mounted therein. As shown, the sensor device 74E is
supported on a spring 154 and its elevation position is determined
by the pressure exerted thereon by a cam 156 mounted on a shaft
158. Similarly, the sensor device 80E is positioned by a
corresponding cam 160 mounted on the shaft 158. In the operation of
the timers, a regulated air pressure is selectively applied through
one of the orifices 74C and 80C to the cannisters 150 and 151.
Then, for example, if the cannister 150 is charged, the bellows 152
will collapse causing the spring-loaded rod 74D attached thereto to
move upwardly until it engages the sensor 74E, thus closing a vent
in the line 74F so that the flip flop 60 receives an input signal
for switching it to provide an inspiratory command along conduit 62
as shown in FIGS. 1 and 2. The bellows 152 and the spring loading
on the rod 74D are so proportioned that the movement of the rod
does not require a large pressure change, so that the travel time
for the rod can be accurately established. During calibration
procedures, the adjustable orifice 120, as shown in FIGS. 1 and 2
is completely closed, whereupon the cam 156 and 160 are adjusted to
provide the necessary exhalation and inspiratory time periods so
that the desired maximum value for the quantity I/E is defined.
Then, the timing periods for both of the timers 74B and 80B can be
simultaneously adjusted by rotating the shaft 158 to reposition the
sensing devices 74E and 80E by means of the cams 156 and 160.
Subsequently, the I/E ratio can be decreased by opening the valve
120 to a desired position.
The dump valves described above in conjunction with FIG. 2, are
shown in FIG. 8, and a sectional view of the dump valve 74G is
illustrated in FIG. 9 wherein it is seen that a bladder 162
maintains a valve seat 164 in a closed position on a discharge
opening in the side wall of the cannister 150. Then, when the
master flip flop is actuated by the exhalation timer 74 to provide
an inspiratory command along the output conduit 62, the opposing
output of the flip flop 60 is coupled to the bladder 162 to provide
a slight negative pressure thereto so that the oxygen stored in the
timer cannister 150 is exhausted to the atmosphere through the port
166 by the released valve seat 164.
The dump valve seals the outlet opening in the cannister 150 when
the flip flop is switched out of its inspiratory command state.
In summary, the apparatus disclosed in the foregoing specification,
and in the accompanying drawings, provides a patient ventilator
which is controlled solely by fluidic circuitry to function
manually, automatically, or semiautomatically, in response to the
breathing requirements of a patient.
* * * * *