U.S. patent number 3,662,751 [Application Number 05/038,948] was granted by the patent office on 1972-05-16 for automatic respirator-inhalation therapy device.
This patent grant is currently assigned to Michigan Instruments, Inc.. Invention is credited to Clare E. Barkalow, Ilden R. Folkerth.
United States Patent |
3,662,751 |
Barkalow , et al. |
May 16, 1972 |
AUTOMATIC RESPIRATOR-INHALATION THERAPY DEVICE
Abstract
A primary control valve when open permits the flow of a
pressurized oxygen containing gas from a source to a patient
adapter for use by the patient. A pressure control means controls
the opening of the primary valve and is responsive to a sub-ambient
pressure in the adapter caused by initial patient inhalation to
actuate the primary valve to an open position. A pair of adjustable
timing mechanisms control the lapse time for the primary valve in
the open or closed position. The timing mechanism controlling the
time during which the primary valve is closed is subservient to the
pressure control means so that patient inhalation causes the valve
to open prior to the preselected lapse time. It may also be turned
off to permit gas flow only as a result of patient inhalation. A
pressure regulator is also provided to prevent flow pressures in
the adapter above a predetermined level. A mechanism is also
provided to adjust the level of output flow to meet varying patient
needs.
Inventors: |
Barkalow; Clare E. (Comstock
Park, MI), Folkerth; Ilden R. (Sparta, MI) |
Assignee: |
Michigan Instruments, Inc.
(Grand Rapids, MI)
|
Family
ID: |
21902840 |
Appl.
No.: |
05/038,948 |
Filed: |
May 20, 1970 |
Current U.S.
Class: |
128/204.25;
128/204.26 |
Current CPC
Class: |
A61M
16/00 (20130101); A61M 11/06 (20130101); A61M
16/0833 (20140204) |
Current International
Class: |
A61M
16/00 (20060101); A61M 11/06 (20060101); A62b
007/04 () |
Field of
Search: |
;128/145.8,145.5,145.6,145.7,142-142.3 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Gaudet; Richard A.
Assistant Examiner: Mitchell; J. B.
Claims
The embodiments of the invention in which an exclusive property or
privilege is claimed are defined as follows:
1. An automatic respirator-inhalation therapy device comprising, in
combination: a patient adapter;
a primary pressure supply conduit means adapted to receive
pressurized gas from a source and deliver said gas to said patient
adapter for use;
a primary control valve means in said supply conduit means and
operative when open to permit flow of said gas to said adapter, and
operative when closed to prevent said gas flow;
first control means operatively associated with said control valve
means and adapter, said control means being responsive to the
pressure in said adapter so that when there is a predetermined
sub-ambient pressure condition in the adapter, such sub-ambient
pressure is communicated to said control means causing it to open
said control valve means; and
second control means operatively associated with said primary
control valve means to maintain said primary control valve means
open a predetermined time and to close said control valve means
after a predetermined time has elapsed, said second control means
including adjustment means for adjusting said predetermined elapsed
time.
2. The combination according to claim 1 wherein said combination
further includes a pressure regulator means responsive to the flow
pressure in said adapter so as to prevent said flow pressure from
attaining a pressure higher than a predetermined level, said
regulator means including adjustment means for selecting a
predetermined pressure level.
3. The combination of claim 2 in which a means is provided for
varying the flow rate to said adapter to substantially match the
flow intake impedances of different patients.
4. The combination of claim 3 in which said primary control valve
is actuated into closed and opened position in response to
pneumatic pressure from said primary pressure supply conduit
means.
5. The combination according to claim 4 in which the first control
means is a pressure responsive valve means actuated in response to
the pressure in said adapter and connected between said primary
pressure supply conduit means and said primary control valve
means.
6. The combination of claim 4 in which said second control means is
a manually adjustable restrictor valve means connected to said
supply conduit means, the degree of restriction controlling the
said predetermined time required to build up sufficient pressure to
actuate said primary control valve closed.
7. The combination of claim 1 in which a means is provided for
varying the flow rate to said adapter to substantially match the
flow intake impedances of different patients.
8. The combination of claim 1 in which said primary control valve
is actuated into closed and opened position in response to
pneumatic pressure from said primary pressure supply conduit
means.
9. The combination according to claim 8 in which the first control
means is a pressure responsive valve means actuated in response to
the pressure in said adapter and connected between said primary
pressure supply conduit means and said primary control valve
means.
10. The combination of claim 8 in which said second control means
is a manually adjustable restrictor valve means connected to said
supply conduit means, the degree of restriction controlling the
said predetermined time required to build up sufficient pressure to
actuate said primary control valve closed.
11. An automatic respirator-inhalation therapy device comprising,
in combination:
a primary pressure supply conduit means adapted to receive
pressurized gas from a source and deliver said gas to a patient
adapter for use;
a primary control valve means in said supply conduit means and
operative when open to permit flow of said gas to said adapter, and
operative when closed to prevent said gas flow, said primary
control valve means being actuated into closed and opened positions
in response to pneumatic pressure from said primary pressure supply
conduit means;
first control means operatively associated with said control valve
means and adapter, said first control means comprising a bi-stable
pressure responsive valve means actuated in response to the
pressure in said adapter and connected between said primary
pressure supply conduit means and said primary control valve means,
said bi-stable valve means being actuated into a closed position by
a vacuum created by a venturi means operatively connected to said
primary pressure conduit means through said pressure responsive
valve means and said primary control valve means, said first
control means being responsive to the pressure in said adapter so
that when there is a predetermined sub-ambient pressure condition
in the adapter, such sub-ambient pressure is communicated to said
control means causing it to open said primary control valve
means;
and second control means operatively associated with said primary
control valve means to close said control valve means after a
predetermined time has elapsed, said second control means including
adjustment means for adjusting said predetermined elapsed time.
12. The combination of claim 11 in which a third control means is
operatively associated with said primary control valve means to
open said primary control means after a predetermined time has
elapsed.
13. The combination of claim 12 in which said third control means
is a manually adjustable restrictor valve means connected to said
supply conduit means, the degree of restriction controlling the
said predetermined time required to build up sufficient pressure to
actuate said primary control valve open.
14. The combination of claim 13 in which said second control means
is a manually adjustable restrictor valve means connected to said
supply conduit means, the degree of restriction controlling the
said predetermined time required to build up sufficient pressure to
actuate said primary control valve closed.
15. The combination of claim 11 wherein said combination further
includes a pressure regulator means responsive to the flow pressure
in said adapter so as to prevent said flow pressure from obtaining
a pressure higher than a predetermined level, said regulator means
including adjustment means for selecting a predetermined pressure
level, and means are provided for varying the flow rate to said
adapter to substantially match the flow intake impedances of
different patients.
16. The combination of claim 15 in which a third control means is
operatively associated with said primary control valve means to
open said primary control means after a predetermined time has
elapsed.
17. The combination of claim 16 in which said third control means
is a manually adjustable restrictor valve means connected to said
supply conduit means, the degree of restriction controlling the
said predetermined time required to build up sufficient pressure to
actuate said primary control valve open.
18. The combination of claim 17 in which said second control means
is a manually adjustable restrictor valve means connected to said
supply conduit means, the degree of restriction controlling the
said predetermined time required to build up sufficient pressure to
actuate said primary control valve closed.
Description
BACKGROUND OF INVENTION
This invention relates to therapeutic inhalation devices and, more
specifically, to an automatically intermittent positive pressure
ventilator providing pressure limited, full-volume ventilation.
Various respirators or intermittent pressure ventilators have been
proposed, the more common consisting of a magnetic toggle valve
which opens upon inhalation by a patient and which closes when a
predetermined pressure is present in the face mask or adapter.
During ventilation, back pressure is created essentially by
ventilatory resistance and compliance. Back pressure due to
resistance to air passage to the lungs tends to be a maximum at the
initiation of ventilation while that due to compliance becomes a
maximum at the end of ventilation when the lungs are full.
A critical problem in the prior art has been the immediate
cessation of flow when the predetermined pressure level is reached.
This can occur many times at the initiation of ventilation when the
patient attempts to inhale causing the back pressure due to
resistance to reach the predetermined pressure level, shutting the
flow off. This is particularly likely if the patient's airway
resistance is high, and the inhalation device setting of flow rate
is excessive. This is extremely undesirable since the patient has
not achieved proper ventilation. Thus, if the patient desires to
use these devices, he must learn to control air flow during
inhalation so that the back pressure does not reach the shut-off
level until adequate ventilation is achieved. This problem is also
critical when used on apneic patients since constant care and
adjustment by the technician is required. In these cases, premature
shut-off causing inadequate ventilation may be corrected by
reducing output flow -- an unnatural and confusing adjustment.
One alternative has been suggested which incorporates a bellows
into the system which will provide variable volume delivery at a
constant pressure level. These and other alternatives to date have
proven to be very complex and costly and they require constant
adjustment by a skilled technician and hence are not easily adapted
to home use. In addition, none of the prior art suggests a simple
way of timing the ventilation cycle while providing variable flow
at a preselected pressure level. Such an accomplishment would
provide maximum supportive therapy to any patient having pulmonary
deficiencies requiring attention and in the automatic mode, would
provide respiration for the apneic patient.
SUMMARY OF INVENTION
It is a principle object of this invention to provide an
intermittent positive pressure ventilator means capable of
providing variable full-volume ventilation at a preselected
pressure level over an adjustable predetermined length of time.
It is a further principle object of this invention to provide an
apparatus having the capabilities aforementioned which is at all
times responsive in operation to initial patient inhalation to
trigger the ventilation cycle and in addition provide a means for
automatically triggering the ventilation cycle in the event the
patient becomes apneic, or in pulmonary arrest.
It is yet another object of this invention to provide an automatic
intermittent positive pressure ventilator which includes adjustment
means capable of operation by an unskilled patient which will vary
both the on and off time cycle of the ventilator as well as the
pressure level of the oxygen containing supply gas.
For achievement of these and other objects apparent to those
skilled in the art, this invention provides a primary pressure
supply conduit means adapted to receive a pressurized oxygen
containing gas from a source and deliver the gas to a patient
adapter for ventilatory use by the patient. A primary control valve
in the supply conduit permits flow to the adapter when open and
prevents flow when closed. The primary valve may be actuated to
open by two separate and adjustable control means. The first
control means is responsive to a sub-ambient pressure in the
adapter -- caused by the instance of patient inhalation -- and the
second control means automatically opens the primary valve after a
predetermined time lapse, this latter mentioned means being at all
times subservient to voluntary instigation by the patient. A third
adjustment control means causes the primary valve to close after a
predetermined time has elapsed. Means are also provided for
selecting and maintaining a maximum pressure level in the patient
adapter so that excessive ventilation cannot occur. Other means are
provided for selecting a range of output flow rates for best
matching of the patient's needs.
The advantages of the apparatus briefly described above are
significant. Individual patients have multifarious needs and
requirements based on such factors as individual ventilatory
compliance and resistance, flow rate requirements, volume
requirements, pressure requirements, and other variables too
numerous to mention as for example physician technique. In
addition, the supportive therapy requirements for one patient do
change as the patient improves his breathing habits and
capabilities, and responds to therapy. The apparatus provided by
this invention permits easy adjustment by either a skilled
technician or the patient himself in order to adjust to changing
needs. In addition, the automatic cycling means provided by the
invention permits maintenance of ventilation for the apneic patient
in a device which is extremely attractive from both economical and
reliability viewpoints.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a pneumatic circuit diagram of the intermittent positive
pressure ventilator provided by this invention;
FIG. 2 is a cross-sectional view of the pressure valve provided by
this invention; and
FIG. 3 is a cross-sectional view of the primary control valve
provided by this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the drawings, reference is particularly made to
FIG. 1 showing the pneumatic circuit which makes up the invention.
The major components of this circuit are the input line 10 (far
left), leading to a patient adapter 34 (far right) through the
lines 18, 22, 26, and 28 and venturi gain mechanism 30. The flow of
the gas or air through these lines is indirectly controlled by the
bi-stable pressure sensitive control valve 60. Regulator means 24
is provided in the lines to the adapter 34 for regulating the
pressure therein. An important aspect of this invention is the
timing mechanism designated by reference numeral 92, which controls
the time during which the primary control valve is open and closed
so as to time-control the feeding of compressed air or oxygen to
the adapter.
Referring more specifically to the details of FIG. 1, input line 10
which is in communication with an oxygen containing gas source or
other source of air (not shown), leads to a manual on-off switch
valve 12 which must be in the on position as shown for the system
to operate. The gas passes through valve 12 directly into a filter
14 provided to improve overall system reliability. A pressure gauge
16 is preferably provided downstream of the switch outlet providing
a visual readout of the source pressure.
The gas flow leaving filter 14 in line 10 is diverted into two
separate lines 18 and 62. The primary line 18 feeds directly into
the primary control valve 20, and when valve 20 is open, the gas
flow feeds directly through valve 20 into a primary line 22
connected directly into regulator means 24. Regulator means 24
permits flow of the gas source through primary lines 26 and 28
directly into a venturi gain mechanism 30, through a throttle valve
orifice 32 directly into the patient adapter 34 for use by the
patient as a ventilation aid. Adapter 34 is shown to include a
conventional mouthpiece 36 well-known in the art and it will be
appreciated that in lieu of a mouthpiece, a face mask or other
desirable means could be used. The primary flow of the oxygen or
compressed air is thus established.
Turning briefly to the venturi gain mechanism 30 and throttle valve
orifice 32, the venturi gain mechanism 30 is described in detail in
copending application entitled Inhalation Positive Pressure
Breathing Apparatus filed Oct. 7, 1968, Ser. No. 765,468, issued as
U.S. Pat. No. 3,610,237, which application is incorporated herein
by reference.
Herein, however, provision is made to switch in several different
venturi configurations whereby the output flow characteristic can
be more closely matched to the patient's needs. These different
combinations of venturi geometrical configurations are shown to be
carried in a slide 37 which would be positioned by the physician or
technician to best match the patient's needs. Another, more
scientific, concept is the matching of the internal venturi
resistance to the resistance of the patient to achieve more
efficient and uniform performance.
The venturi gain mechanism 30 also provides a mixing mechanism.
Thus, if primary oxygen is used, the ambient air drawn into the
venturi opening 38 mixes with the primary oxygen, and the diluted
mixture is delivered to the patient, representing a first step in
oxygen enrichment over pure air. If further enrichment is desired,
a bleed conduit 40 off the primary line source 26 can provide a
flow of O.sub.2 into the interior of the venturi for additional
enrichment. An adjustable bleed valve 42 is provided to regulate
the degree of enrichment.
In addition, throttle valve orifice 32 which is regulated by a
throttle valve 44 provides a controlled rate of acceleration of the
flow to the patient during the inspirational phase. That is, it has
been found that a gradual increase in the flow rate and
inspirational pressure during inspiration decreases turbulance so
that a more uniform difusion of breathing gas into the pulmonary
alveoli is promoted. A more efficient pulmonary gas exchange is
then realized. It is therefore desirable to gradually increase the
pressure and flow rate of air entering the lungs. Throttling valve
44 provides this controlled rate of acceleration of flow to the
patient during the inspirational phase. Also, when the primary
control valve 20 is closed, the throttle valve 44 isolates the
primary flow lines from the patient adapter 34 in order that a
slight inhalation by the patient will create a sub-ambient pressure
in the adapter, the purpose of which will be discussed hereinafter.
The details of throttle valve 44 and throttle valve orifice 32
omitted in that they are likewise described in detail in the
above-identified copending application.
In addition to the primary line flow, an auxiliary line 46 is in
communication with the primary line 22 downstream of the primary
control valve. Line 46 communicates directly from primary line 22
into pressure regulator 50 and thence to the patient adapter
through a nebulizer 48 permitting the patient to receive medication
mixed in with the oxygen containing gas. Along with nebulizer 48, a
non-rebreathing valve 49 is provided to permit exhalation by the
user to atmosphere without retrograde flow of exhaled air back
through the breathing hose. The operation of the nebulizer and
non-rebreathing valve are also described in the above-identified
application.
As mentioned previously, primary line 22 upon leaving the primary
control valve feeds into a regulator means 24 which permits
regulated flow through primary line 26, 28 into the patient
adapter. The regulator means includes a valve positioned on the
primary line between the primary control valve and the patient
adapter in order to regulate and maintain a preselected flow
pressure in the adapter and likewise prevent that pressure from
exceeding a preselected maximum. An adapter pressure feedback line
52 is connected to adapter 34 for feeding back the exact pressure
in the patient adapter to the regulator means 24 and the pressure
sensitive control valve 60. Line 52 feeds branches into line 54
which communicates directly with regulator valve 24 and line 70
which communicates directly with pressure sensitive control valve
60. Valve 24 is also in direct communication with the primary line
downstream of the primary control valve 20 via line 56. An
additional regulator 58 is provided to control the pressure on
regulator valve 24 off the primary line. Resistors 23, 25 and 27
provide smooth flow during the on and off cycling of the regulator
and in addition, resistor 25 takes care of any spool leakage to
maintain regulator accuracy.
Preferably, regulator valve 24 is a diaphragm valve responsive to
both the pressure derived from main flow of oxygen containing gas
through the system and the pressure of the oxygen containing gas in
the patient adapter. This is accomplished by means of bleeding off
from the primary line 22 a line 56 which has its own pressure
regulator 58, and also feeding back the pressure from adapter 34
through the feedback lines 52 and 54. The valve 24 is responsive in
a well-known conventional way to the differential between these
pressures in order to regulate the pressure of the gas or air
flowing into line 26. The details of this regulator valve 24 are
omitted in this specification in that they are fully described in
U.S. Pat. No. 3,461,860 issued Aug. 19, 1969 and assigned to the
assignee of record herein.
The pressure sensitive control valve 60, as previously stated, is
provided in the system for actuating the primary control valve 20
from a closed to open position. Pressure sensitive control valve 60
is in direct communication with the primary line 10 which is
upstream of the primary control valve 20 as well as in
communication with the control valve itself. This is accomplished
by an input line 62 which brings the gas directly from its source
through a regulator 64 into the pressure sensitive control valve
60. The regulator 64 is provided in line 62 since it is undesirable
to have full source pressure operating through the pressure valve.
In addition, a more precise control of pressure is desired. Line 66
is provided between the pressure sensitive control valve 60 and
primary control valve 20 so that when the pressure sensitive
control valve is in an open position, the flow through line 62a
passes through the pressure sensitive control valve into line 66
which flow, as will be described hereinafter, acts on the primary
control valve to open it. A one-way check valve 68 is provided in
line 66 to permit one-way flow to the primary control valve.
Pressure sensitive control valve 60 is also in direct communication
with the patient adapter 34 through feedback line 70 which is
connected directly to line 52. The details of pressure sensitive
control valve 60 will be described in more detail hereinafter but
the essential operation is that when a sub-ambient pressure is
registered in adapter 34, it is fed back through lines 52, 70 to
pressure sensitive control valve 60, in which sub-ambient pressure
acts upon a diaphragm in the pressure valve causing the valve to
open. Upon opening, gas flow is permitted from the source through
lines 62, 66 and 67 into the primary control valve causing it to
open. Once the primary control valve is opened, the flow through
lines 66 and 67 passes directly through the primary control valve
into a return line 72 which feeds into a venturi pump 74 attached
to the pressure sensitive control valve 60. The function of venturi
pump 74 is to immediately reset pressure control sensitive valve 60
into a closed position rendering it ready for use on the next
cycle, i.e. after complete ventilation has occurred and the primary
control valve is once more closed. Venturi pump 74 also provides an
exhaust to atmosphere for line 72 to prevent any pressure remaining
in line 72 which might oppose the operation of pressure sensitive
control valve 60. An exhaust bore 76 is also provided in pressure
sensitive control valve 60 for bleeding any pressure in line 66
which might remain after the primary control valve is closed.
Turning now to a more detailed description of the pressure
sensitive control valve 60, FIG. 2 shows in detail the preferred
construction of the control valve which produces the function just
described.
Pressure sensitive control valve 60 is a bi-stable valve in the
sense that it is actuated into a completely open or closed
position. Valve 60 is generally T-shaped in cross section with the
horizontal portion 100 defining a pressure chamber 102 while the
vertical portion 104 includes an annular tube section 106 for
receipt of a spool-type valve 108. Spool 108 is positioned within
the annular tube 106 and adapted to reciprocate with respect
thereto. A reduced diameter portion 110 is provided to establish
communication between lines 62 and 66 via ports 112 and 114 when
spool 108 is in the uppermost (open) position with respect to tube
106. A plate 116 is fixed to the top of spool 108 and secures a
flexible diaphragm 118 which divides pressure chamber 102 into
upper and lower portions. The vertical portion 104 of valve 60 also
includes an enlarged annular tube 120 extending from annular tube
106. Tube 120 defines a pressure chamber 122 in the vicinity of the
lower portion of spool 108. A dipole magnet 124 is adjustably
mounted to the bottom portion of tube 120 within pressure chamber
122 and aligned with a second dipole magnet 126 permanently affixed
to the bottom end portion of spool valve 108. Dipole magnet 124 is
mounted for adjustment in the rotational sense about the axis of
annular tubes 106 and 120. When the poles of the adjacent magnets
124 and 126 are lined up, a maximum attractive force is provided
between them. When however, magnet 124 is rotated with respect to
magnet 126, the attractive force between the magnets decreases.
This provides a simple means for adjusting the magnetic impact of
the dipole magnets. A port 128 is provided into chamber 122 and
connects line 66a to line 66 so that when the pressure sensitive
control valve 60 is open, flow communicated between lines 62 and 66
will also be directed into pressure chamber 122. The purpose for
this and the operation of valve 60 will now be explained.
To begin with, pressure sensitive control valve 60 is shown in FIG.
2 in a neutral position which it is incapable of achieving since it
is a bi-stable valve. This is done for the sake of clarity of
description. Assuming for the moment that the valve is in a closed
position, spool 108 would be in its lowermost position with magnets
124, 126 in coercive proximity with each other. In this position,
the upper non-reduced portion 130 of spool 108 would block flow
from line 62 through port 112. The exhaust port 128 is open
providing a bleed for lines 66, 66a which bleeds off any trapped
air upstream of check valve 68. The travel of spool 108 is such
that a portion of the reduced diameter portion 110 of the spool
will always be exposed to line 66 so that line 66 is either
communicating directly with line 62 when the pressure valve is open
or it is communicating with the exhaust port 128 when the valve is
closed.
As stated previously, the function of pressure sensitive control
valve 60 is to actuate the primary control valve 20 when patient
inhalation begins. When the user begins to inhale on adapter 34, a
sub-ambient pressure is created on the order of one centimeter of
H.sub.2 O referring to a water manometer. A negative pressure on
the order of one centimeter of water is sufficient to actuate the
pressure sensitive control valve. This negative pressure is
communicated through lines 52, 70 and port 132 into pressure
chamber 102 on the upper side of diaphragm 118. This negative
pressure acting on the entire area of diaphragm 118 is sufficient
to overcome the coercive force of the dipole magnets. Once spool
displacement occurs, and there is communication between pressure
lines 62, 66, the flow through line 66 also flows through line 66a
into pressure chamber 122 contributing towards complete
displacement of spool 108 into the open position by virtue of the
pressure applied over the area of the spool end. With spool 108 in
its uppermost position, exhaust port 128 is closed, and there is
direct communication between line 62, 66 to actuate the primary
control valve 20.
Before turning to the details of the primary control valve 20, a
description of the reset venturi 74 would be helpful. Once the
primary control valve 20 is open, the flow through line 66, 67
feeds into line 72 directly into reset venturi 74. The function of
the reset venturi is two-fold. One, it provides an exhaust to
atmosphere for the flow just described and two, it closes the
pressure control valve in preparation for the next breathing cycle.
Venturi 74 has a straight through feed line 136 providing the
exhaust to atmosphere for flow through line 72 and a port 138
normal to line 72, 136 which port feeds into the lower portion of
pressure chamber 102 providing a sub-ambient pressure when there is
flow through line 72. The sub-ambient pressure created by reset
venturi 74 acting on diaphragm 118 is sufficient to overcome the
force which maintains valve 60 in the open position. This force is
essentially created by the flow through line 66a into pressure
chamber 122. Once spool 108 begins its downward or closing movement
the coercive force of dipole magnets 124 and 126 along with the
sub-ambient pressure created by reset venturi 74 completely closes
pressure sensitive control valve 60. As this pressure sensitive
control valve 60 is closed, flow ceases through lines 66, 72, and
the force of the dipole magnets is sufficient to insure full
closure of the valve. Since there is flow through line 28 into the
adapter 34, positive pressure will be registered through feed back
lines 52, 70 so that the pressure control valve 60 will not open
until ventilation has ceased and the next inhalation cycle
begins.
For convenience, a pressure gauge 78 provides a visual readout of
the pressure in line 52 which indicates the pressure in the patient
adapter 34 and line 54 and 70. Gauge 78 preferably registers both
positive and negative ambient pressures so that one can immediately
ascertain whether a sub-ambient pressure is being registered for
purposes of activating pressure sensitive control valve 60 through
line 70 while on the other hand gauge 78 also permits a visual
registration of the positive pressure during flow which pressure is
important for purposes of control of the regulator valve 24 and the
selection of proper venturi characteristic by adjustment of slide
37.
The regulated source pressure feeding in through line 62a into the
pressure sensitive control valve 60 is also routed through two
timing mechanisms 84 and 92. Line 82 feeds the timer mechanism 84
and line 80 feeds timer mechanism 92.
Mechanism 84 automatically turns the primary valve 20 on after a
preselected time has elapsed in the event that the primary valve is
not triggered by pressure sensitive control valve 60. The automatic
triggering of primary valve 20 is especially important in
situations where the patient is apneic or there is a possibility of
pulmonary arrest. It assures the ventilation at selected time
periods if the patient is incapable of initiating it himself.
Mechanism 84 includes a manual on-off switch valve 86 which permits
elimination of control means 84 from the system if it is desired.
Many users requiring ventilation assistance are in no danger of a
pulmonary arrest and would prefer not having a timed "off" control
in the system.
Various timing mechanisms could be employed, however, it is
preferred that in a pneumatic system as described, the combination
of a needle valve 88 and accumulator 90 be used. Needle valve 88
permits varying the flow volume through line 82 into the
accumulator. The accumulator, somewhat analagous to an electrical
capacitor is a fixed volume chamber which retards the buildup of
internal pressure needed to activate the primary control valve, as
will be described hereinafter. It will be appreciated that the
regulated air passing from the source into line 62a has more than
sufficient pressure to open the primary control valve 20 when the
pressure sensitive control valve 60 opens. This same regulated air
passes from line 62, 62b into line 82 and the accumulator 90 is
capable of reaching substantially the same pressure as the
regulated pressure in line 62a. This is more than sufficient to
open the primary control valve 20, and thus controlled flow in 82a
through needle valve 88 determined the time of opening of valve 20.
Check valve 68 prevents flow from the accumulator back up to the
control valve 60 through line 66 during this process.
The regulated air passing through line 62b also controls the timing
mechanism 92 comprising line 80, needle valve 94, lines 96a, 96b
and 96c which communicate through valve 20 and accumulator 98. Line
96c feeds into the top of the primary control valve 20 to provide a
control as will be explained in detail hereinafter. Timing
mechanism 92 is constantly effective in the system and performs the
very important function of timing the ventilation cycle; i.e., the
time during which the primary control valve 20 is open. The
operation of timing mechanism 92 is somewhat similar to that
described previously with respect to timing mechanism 84. That is,
an adjustable needle valve 94 controls the rate of flow through
line 80. When the primary control valve 20 is closed, flow is
prevented through control valve 20. However, when control valve 20
is open, flow is permitted from line 96a directly through control
valve 20 to line 96b feeding into accumulator 98. When accumulator
98 is sufficiently filled, its pressure is communicated through
line 96c, to close valve 20 thus stopping further ventilation. Any
air entrapped in lines 96b, 96c and accumulator 98 are exhausted
through port 182 in valve 20, the details of which will be
described shortly. The time duration during which primary control
valve 20 is open is easily adjustable by simply adjusting needle
valve 94 to control the volume flow into accumulator 98 when the
primary control valve is open. It is significant to control the
elapsed time during which the primary control valve 20 is open
supplying ventilation to the patient. It prevents premature
cessation of the flow to the patient, and, in addition, assists the
patient in developing good breathing habits. Should the patient
reach complete ventilation prior to the primary control valve being
closed, the ventilatory back pressure and compliance will be
substantially equal to the primary source pressure and hence flow
will cease. Thus, no patient discomfort is felt.
The details of the primary control valve 20 will now be described
and reference is made in particular to FIG. 3. Valve 20 is formed
from an annular body 140 having enlarged ends 142, 144. The
enlarged ends are hollow and define cylindrical chambers 146, 148.
An elongated spool 150 is positioned within the hollow central
portion of the annular body 140 and adapted to slide longitudinally
with respect thereto. Valve 20 is a bi-stable valve similar to
pressure valve 60 in that it is adapted to function in either a
completely closed or open position. In order to achieve this, a
pair of magnets 152 and 154 are positioned in each enlarged end of
the valve. A cylindrical armature 156 is affixed to the upper end
of spool 150 with a somewhat similar armature 158 affixed to the
lower end. The spool 150 is shown for the sake of clarity in FIG. 3
as being in a neutral position. In reality, the spool except when
actuated will always be in either an uppermost (open) position
wherein armature 156 is in coercive proximity with magnet 152 or
armature 158 is in coercive proximity with magnet 154 in the
downwardmost (closed) position. Armature 156 is slightly different
than armature 158 in that it functions also as a piston which moves
up and down as the spool moves. Thus, chamber 146 is a pressure
chamber with an "O" ring 160 sealing pressure chamber 146 into an
upper and lower portion.
Spool 150 has a plurality of reduced diameter portions 162, 164,
166, defining a plurality of communicating chambers 168, 170 and
172. Inlet and outlet ports are provided through the annular body
140 with respect to each communication chamber 168, 170 and 172.
The inlet and outlet ports are as follows: with respect to chamber
168, inlet port 174 is connected to line 67a while outlet port 176
is connected to line 72; with respect to chamber 170, inlet port
178 is connected to line 96a while outlet port 180 is connected to
96b. In addition, an exhaust port 182 communicates with chamber 170
and leads to atmosphere, the significance of which will be
explained hereinafter. With respect to chamber 172, an inlet port
184 leads to line 18 while the outlet port 186 leads to line 22.
When valve 20 is closed, spool 150 is in the downwardmost position
with armature 158 in coercive proximity with magnet 154. In this
position, spool portion 188 prevents line 18 from communicating
with line 22; spool portion 190 prevents line 96a from
communicating with line 96b although communication between line 96b
and exhaust port 182 is established; and spool portion 192 prevents
communication between lines 67a and 72. When valve 20 is open,
spool 150 is in the upwardmost position with armature-piston 156 in
coercive proximity with magnet 152. In this position, communication
is established between the lines referred to previously except that
spool portion 188 now prevents exhaust port 182 from communicating
with chamber 170, permitting only communication between lines 96a
and 96b through chamber 170.
Having established the various communicating lines feeding into and
out of the central portion of valve 20, it is desirable at this
time to describe in detail how valve 20 is opened and closed. When
valve 20 is closed, the volume of the lower portion of pressure
chamber 146 is a minimum. The port 194 communicates with the lower
portion of pressure chamber 146 and leads to a line 67b which
connects with line 67. To open valve 20, it is necessary to
establish sufficient pressure in the lower portion of pressure
chamber 146 to act on piston 156 and overcome the coercive force
between magnet 154 and armature 158 to move piston 156 and spool
150 upwards into coercive proximity with magnet 152 and armature
156. This is accomplished by feeding pressurized flow through line
67 into branch 67b through port 194 into the lower portion of
pressure chamber 146. Flow through line 67 is provided from two
sources: timing mechanism 84 and/or pressure valve 60 when
activated to permit flow through line 66. Both of these sources
have been described in detail before and hence will not be
repeated. Once valve 20 is opened, flow is established through
primary lines 18, 22 through chamber portion 172.
In order to close valve 20, it is necessary to provide sufficient
pressure in the upper portion of pressure chamber 146 to act on
piston 156 and overcome the coercive force of magnet 152 to move
the piston and spool down until armature 158 is in coercive
proximity with magnet 154. A port 196 leads into the upper portion
of chamber 146 and is connected to line 96c which communicates the
pressurized flow to the upper portion of chamber 146. Flow into the
upper portion of chamber 146 is provided by timing mechanism 92
described herein before. Briefly, this flow passes from the
regulated air through line 62 to line 80, through needle valve 94
and line 96a. When primary control valve 20 is open, the flow in
line 96a passes through chamber 170 in the control valve into line
96b dumping into accumulator 98. When sufficient pressure has built
up in accumulator 98, the pressurized air in line 96c will pass
into the upper portion of chamber 146 actuating the piston 156 and
spool 150 into a closed position. Once valve 20 is closed,
communication between lines 96a and 96b is prevented. In order to
bleed off any excess or entrapped pressurized air in lines 96b,
96c, accumulator 98 and upper portion of chamber 146 so that the
timing cycle is precise, an exhaust port 182 is provided in valve
20 for communication with line 96b when the spool valve is closed.
Port 182 simply dumps this entrapped air to atmosphere.
Finally, means are provided for manually operating valve 20 when
desirable. A handle 200 is mounted through end 144 and affixed to
armature 158. Simple exertion upwards or downwards will manually
open or close the valve.
OPERATION
Referring now to FIG. 1, input line 10 in operation is connected to
a source of pressurized oxygen containing gas and, when valve 12 is
in the open position as shown, filtered air through filter 14 is
provided for use. Flow through the primary line 18 is prevented
until the primary control valve 20 is opened. The alternative flow
route of filtered air through line 10 is through line 62 which is
regulated by regulator 64. Flow of regulated air through line 62 is
prevented through line 62a by the pressure valve 60 when it is
closed. Flow through line 62b leads into lines 80 and 82 with the
former being blocked by the primary control valve 20 when it is
closed and the latter being fed into the automatic timing mechanism
88 which operates only when the switch 86 is in the "on" position
as shown.
Assuming for the moment that the user or patient is apneic or that
there is a good chance of pulmonary arrest, it will be desirable
that the automatic actuation of valve 20 be achieved. With switch
86 in the "on" position as shown in FIG. 1, regulated air passes
through needle valve 88 which is adjustable by the physician or
technician into accumulator 90. When the pressure build-up in
accumulator 90 is sufficient, communicating through line 82b into
line 67, 67b, into the lower portion of chamber 146 in control
valve 20, it opens the valve. Once this happens, flow through the
primary line 18 is communicated through control valve 20 to line 22
on through the regulator 24 into line 26, 28, through the venturi
30 and throttling orifice 32 into the patient adapter 34 for use by
the patient. At the same time, regulated air flow is permitted
through line 80 through timing mechanism 92 which times the
ventilation cycle. Air in line 80 passes through needle valve 94
(again adjustable by the physician or technician) into line 96a,
through control valve 20 into line 96b into accumulator 98 into
line 96c and upper portion of chamber 146. When the pressure
build-up in the upper portion of chamber 146 reaches the
preselected level, valve 20 is actuated into a closed position.
Immediately thereafter, timing mechanism 84 begins to take effect
again with pressure building up in accumulator 90 to time the
period valve is to remain closed.
If at any time the patient begins the ventilatory cycle himself by
inhaling, the control valve 60 comes into play. This will happen
regardless of whether or not switch 86 is in the "on" or "off"
position. When the primary control valve 20 is closed, the spring
biased throttle valve 44 is extended into throttle orifice 32
blocking flow past the orifice. In this position, when the patient
begins to inhale, a static sub-ambient pressure is created in the
adapter line 34 up to the throttle orifice 32. This sub-ambient
pressure is communicated through feed back lines 52, 70, to control
valve 60. When a sub-ambient pressure is recorded, it acts on
diaphragm 118 to open the pressure sensitive control valve. Upon
opening, flow is permitted from regulated air line 62 through line
62a into line 66, which in turn feeds through line 67 and 67b
actuating the primary control valve 20 into an open position. Once
this occurs, timing mechanism 92 begins functioning to time the
ventilation cycle. When valve 20 is open, flow through line 67, 67a
is directed through line 72 into reset venturi 74 to reset the
control valve 60 into a closed position.
Once valve 20 is open and flow is established through primary lines
18, 22, the pressure regulator valve 24 controls flow through lines
26, 28 into adapter 34 to prevent excessive pressure levels from
being attained and yet permitting the proper volume flow in order
to meet the patient's needs. It is important to note that should
the patient or user be properly ventilated prior to timing
mechanism 94 turning the system off, no damage or discomfort is
felt by the user. When the patient has finished his breathing
cycle, the ventilatory back pressure and compliance pressure
reaches the maximum permissable pressure selected by the pressure
regulator 24. When this occurs, flow through primary lines 18, 22,
26 and 28 simply reduce, although the pressure level remains until
timing mechanism 84 closes valve 20. Herein lies the advantage of
being able to manually adjust the timing mechanisms 84 and 92. If
after several ventilation cycles, it is apparent that either phase
is too long or too short, the physician or technician, or user
himself may simply adjust needle valves 88 or 94, respectively.
It will be obvious to those having ordinary skill in this art that
the details of construction of this particular preferred embodiment
may be modified in a great many ways without departing from the
unique concepts presented. It is therefore intended that the
invention is limited only by the scope of the appended claims
rather than by particular details of construction shown, except as
specifically stated in the claims.
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