US3817246A - Flow responsive respiration apparatus - Google Patents

Abstract

Respiration apparatus for IPPB therapy in which the inspiratory effort of the patient to initiate an inspiration phase is sensed by a flow sensor which operates by directing a laminar jet of gas across a conduit of the apparatus toward a receiver, to produce a normal pressure in the receiver when there is no flow in the conduit. A second receiver establishes a reference pressure, and the change in the pressure relationship between the receivers, resulting when the patient creates a cross-flow across the jet, is used as a pilot signal to operate an actuator for opening a flow control valve. Similarly, as the flow rate is reduced near the end of the inspiration phase, the pressure relationship is restored and the actuator closes the control valve. One embodiment uses a laminar jet that is directed into an aligned receiver to raise the pressure therein relative to a receiver spaced from the jet, and referenced to actual patient delivery pressure, until a cross-flow disturbance changes the jet to turbulent, thereby reducing the pressure in the aligned receiver. Another embodiment uses a turbulent jet directed between two longitudinally spaced receivers, disposed in close proximity to one another, to establish equal pressures therein until the jet is deflected longitudinally toward one of the receivers and away from the other in response to a cross-flow.

Description

in 3,817,246 3 [451 June 18, 1974 1 FLOW RESPONSIVE RESPIRATION APPARATUS [75] Inventor: James Weigl, Santa Monica, Calif.

[73] Assignee: Puritan-Bennett Corporation,

Kansas City, Mo.

22 Filed: Dec. 11, 1972 211 App]. No.: 313,983

[52] US. Cl. 128/1458, 137/842 [51] Int. Cl A6lm 16/00 [58] Field ofSearch 128/1458, 145.6, 145.7, 128/1455, 145; 137/842 [56] References Cited UNITED STATES PATENTS ,7 3,385,295 5/1968 Beasley 128/1458 3,413,993 12/1968 Ziemer 137/842 3,428,068 2/1969 Howie .1 137/842 3,429,323 2/1969Mott 137/842 3,537,449 11/1970 Foxwell..... 128/1455 3,669,108 6/1972 Sundblom 1 128/1458 Primary Examiner-Richard A. Gaudet Assistant Examiner-G. F. Dunne Attorney, Agent, or FirmFulwider Patton Rieber Lee & Utecht P1955501?! con/7201.

[ ABSTRACT Respiration apparatus for lPPB therapy in which the inspiratory effort of the patient to initiate an inspiration phase is sensed by a flow sensor which operates by directing a laminar jet of gas across a conduit of the apparatus toward a receiver, to produce a normal pressure in the receiver when there is no flow in the conduit. A second receiver establishes a reference pressure, and the change in the pressure relationship between the receivers, resulting when the patient creates a cross-flow across the jet, is used as a pilot signal .to operate an actuator for opening a flow control valve. Similarly, as the flow rate is reduced near the end of the inspiration phase, the pressure relationship is restored and the actuator closes the control valve. One embodiment uses a laminar jet that is directed into an aligned receiver to raise the pressure therein relative to a receiver spaced from the jet, and referenced to actual patient delivery pressure, until a crossflow disturbance changes the jet to turbulent, thereby reducing the pressure in the aligned receiver. Another embodiment uses a turbulent jet directed between two longitudinally spaced receivers, disposed in close proximity to one another, to establish equal pressures therein until the jet is deflected longitudinally toward one of the receivers and away from the other in response to a cross-flow.

13 Claims, 6 Drawing; Figures BACKGROUND OF THE INVENTION This invention relates to respiration apparatus, and more particularly to apparatus for administering intermittent positive pressure breathing (IPPB) therapy to a patient.

In such therapy, air, oxygen or oxygen-enriched air under pressure is supplied to a patient cyclically through delivery means such as a face mask or the like. Each inspiration phase is initiated in response to a slight inspiratory effort by the patient, and begins with a peak flow rate which inflates the patients lungs, the flow rate then being reduced to a relatively low level'at which all flow is terminated. Following the inspiration phase, the lungs are vented to atmosphere during an expiration phase, which terminates when the next inspiratory effort by the patient initiates the next cycle.

Examples of prior IPPB apparatus are shown in US. Pat. No. 3,362,404 and No. 3,368,555, illustrating two different approaches to the manner inwhich inspiration may be initiated and terminated. In US. Pat. No. 3,362,404, the patient draws air through the delivery means to create a pressure drop in the diaphragm chamber of a triggering valve, and this pressure drop is used to open a flow responsive valve which initiates the inspiration phase and eventually terminates inspiration in response to a selected low terminal flow level. In US. Pat. No. 3,368,555, a similar inspiratory effort by the patient is applied as a biasing signal to a control fluid amplifier of the monostable, lock-n type to switch a fluid flow therein from a preferred channel to another channel, thereby switching the flow through a main fluid amplifier of the bistable, lock-on type to initiate an inspiration cycle. The flow in the control amplifier switches back to the preferredchannel automatically when the biasing signal is removed, and this switches the main amplifier to terminate inspiration at a selected low terminal flow rate.

Both of these approaches are effective to initiate inspiration in response to slight inspiratory efforts, but both utilize the actual reduction of pressure caused by the patients inspiratory effort as the source of an actuating pressuresignal, with the result that there is a perceptible resistance to inspiratory effort at the beginning of inspiration until the machine overcomes its internal delays and begins to flow gas through the delivery means. A primary object and advantage of the present invention is the reduction ofthis resistance to an almost imperceptible level, to increase the comfort of the patient during IPPB therapy, in a novel manner that does not detract in any way from other performance characteristics of the apparatus.

SUMMARY OF THE INVENTION to produce a slight flow of air within the conduits of the apparatus. In other words, the sensing device of the present invention is capable of initiating the inspiration phase in response to an inspiratory effort by the patient that is virtually the same as the normal effort during in voluntary breathing, and is effective to initiate the in- 2 spiration phase with an open air circuit through the apparatus, preferably through a filter for mixing air with the primary flow of gas from the source.

This is accomplished by incorporating a fluidic flow sensor in one of the conduits of the apparatus, including means on one side of one of the conduits for directing a jet of gas under pressure across the conduit and receiver means in the path of the jet reference pressure relationship between two receivers of the receiver means, in the absence of any flow in the conduit. When a very low threshold flow is created in the conduit by the inspiratory effort of the patient, for example, a flow as low as 2 to 4 liters per minute, or even less, this cross-flow disturbs the air jet, changes the reference pressure relationship between the receivers, and produces a pressure signal that is used to initiate the inspiration phase of the apparatus. A pressure-actuated control valve responds to the signals of the flow sensor to initiate the supply of respiration gas, and a conventional regulator controls the flow rate to the patient.

As long as there is flow through the flow sensor, the changed pressurerelationship is maintained to maintain the apparatus in the inspiration phase. As flow rate is reduced during inflation of the patients lungs, however, the cross-flow through the jet is reduced to a low rate which falls below the threshold level for the flow sensor, the reference pressure signal is restored to the reference relationship, and the inspiratory phase is terminated by the control valve.

In one form of flow sensor disclosed, a turbulent jet is directed between two receivers disposed in close proximity to each: other, to establish equal pressures therein until the jet is deflected longitudinally by a cross-flow, and all flow passes through the sensor, which may have a relatively high flow area capable of handling the peak flow rate of the apparatus. In another, more sensitive form, a normally laminar jet is directed into an aligned receiver, and a reference receiver is spaced from the jet to establish a reference pressure, the jet being converted to turbulent by a cross-flow, thereby dropping the pressure in the aligned receiver sharply. The flow area in this form is restricted, and a by-pass is provided around the sensor, for carrying peak flow rates to the patient.

Other aspects and advantages of the invention will become apparent'from the following detailed description, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTIONOF THE DRAWINGS FIG. 1 is a schematic view of one embodiment of a respiration apparatus constructed in accordance with the present invention; 7

FIG. 2 is a similar schematic view of an alternative embodiment of the invention;

FIG. 3 is an enlarged longitudinal cross-sectional view of a flow sensorincorporated in the apparatusof FIG. 2;

FIG. 4 is an enlarged cross-sectional view of a flow sensor incorporated in the apparatus of FIG. 1, the view being taken in a plane indicated by line 4-4 of FIG; 5;

FIGS is a cross-sectional view talten along line 5-5 of FIG. 4; and

FIG. 6 is an enlarged cross-sectional view of a pilotoperated flow control valve suitable for use in both embodiments of the invention.

DETAILED DESCRIPTION As shown in the drawings for purposes of illustration, and with particular reference to FIG. 1, the invention is embodied in an IPPB respiration apparatus for delivering an intermittent flow of air under pressure to a patient from acompressor 11, through the various conduits and control components of the apparatus and delivery means 12 such as a face mask adapted to be worn over the patients mouth and nose. The compressor draws outside air in through a filter l3 and a silencer l4, and pumps the air through asecond filter 15 into amain flow conduit 17 in which the pressure is controlled by aregulator 18.

From thisconduit 17, the air is passed intermittently through a selectivelyoperable control valve 19 and through aconduit 20 to a conventional pressureresponsive relief valve 21 for reducing the flow rate to the patient as back pressure in the system indicates that the patients lungs are approaching full inflation. Theoutlet 22 of this relief valve is connected through twoconduits 23 and 24 to the delivery means 12. The entrance into therelief valve 21 is shown as ajet 25 for directing the gas into aventuri section 27, thus creating a pressure drop for drawing outside air through a filter 28 and entraining this air with the primary air flow from thevalve 21.

Thus, the opening and closing of thecontrol valve 19 initiates and terminates the inspiration phases of suc cessive respiratory cycles of the apparatus 10, and therelief valve 21 controls the flow rate during each such phase. The relief valve initially passes a relatively high peak flow, and then reduces this flow to a relatively low terminal flow rate before thevalve 19 is closed to terminate inspiration. Agauge 29 preferably is provided to indicate system pressure.

After termination of inspiration, the patient is permitted to exhale naturally through the delivery means 12 and anexhalation valve 30 in theconduit 24 adjacent the delivery means, this valve comprising anexhalation port 31 which is closed during inspiration by a pressure-actuatedclosure 32, herein an inflatable mushroom or balloon closure connected through aconduit 33 and a pressure divider formed by tworestrictors 34, to theconduit 35 that is pressurized during inspiration. When air is being supplied to the patient, the closure is inflated and the exhalation valve is closed. During exhalation, the pressure in the closure is relieved, and the valve opens to allow exhaled gas to escape.

If medication is to be administered to the patient as an incident to the IPPB therapy, aconventional nebulizer 36 may be included with the delivery means and supplied with nebulizing air under pressure through theconduit 35, a one-way check valve 37, and a needle valve .38. Nebulizing air also may be supplied during the expiration phase by means of aconduit 39 connected to theconduit 17 ahead of thecontrol valve 19 and having aflow restrictor 40 therein, this conduit being connected to theconduit 35 between thecheck valve 37 and theneedle valve 38.

In accordance with the present invention, the inspiration phases are initiated and terminated by afluidic flow sensor 42 in which ajet 43 is directed across one of the conduits of the apparatus, herein theconduit 23, toward receiver means which establish a reference pressure relationship and maintain that relationship as long as there is no disturbance in the conduit. When a disturbance occurs, as a result of inspiration by the patient through the delivery means 12 and the conduits of the apparatus, the pressure relationship departs from the reference, and this change is used to open thecontrol valve 19 and initiate an inspiration phase of the apparatus. Similarly, when the flow rate is reduced to the low terminal flow rate, the pressure relationship is restored to the reference level, and this change is used to close the control valve and tenninate the inspiration phase of the apparatus.

More specifically, as shown schematically in FIG. 1 and in detail in FIGS. 4 and 5, theflow sensor 42 comprises ajet tube 44 opening into one side of theconduit 23 and shaped and positioned to direct a controlled laminar jet of gas (herein air from aconduit 45 connected through a restrictor 47 to the conduit 17) across theconduit 23 and across the path of air drawn through the conduit when the patient begins to breathe through the respiration apparatus.

Directly across the conduit and aligned with thejet tube 44 to receive theair jet 43 is afirst receiver tube 48, the pressure in which is a function of the laminarity (as opposed to turbulence) of the air jet. Such a jet remains laminar for a considerably distance downstream from the orifice of the jet tube, and then breaks up into turbulence. The receiver tube is positioned closer to the jet orifice than the distance to the point of turbulence, and thus normally receives a laminar flow.

Spaced along the conduit from thefirst receiver tube 44 is asecond receiver tube 49, or reference tube, in

i which the pressure is essentially unaffected by the jet flow. Thus, a predetermined pressure differential normally exists between the tworeceiver tubes 48 and 49, the difference being the pressure increase in thetube 48 produced by thejet 43, as long as it remains laminar in character at the entrance to the tube.

When a patient begins to breathe through the apparatus, the external influence on the pressures at the tworeceiver tubes 48 and 49 is the same, but the disturbance of the air jet by the cross-flow of air in the conduit substantially reduces the distance to the point of turbulence. Thereceiver tube 48 is farther from the jet orifice than the reduced distance to the point of turbulence, and thus receives turbulent, rather than laminar, flow. The result is a marked decrease in the pressure in thereceiver tube 48, relative to original pressure. This decrease serves as a pilot pressure signal to actuate thecontrol valve 19 and initiate the inspiration phase, herein through a pressure-operated actuator 50.

Similarly, as the flow to the patient is reduced by therelief valve 21 near the end of the inspiration phase and the rate of flow through theconduit 23 declines, the disturbance of theair jet 43 is terminated, and the flow again becomes laminar at the entrance to thereceiver tube 48. When this occurs, the pressure in the tube increases markedly, and this increase serves as a pilotpressure signal which acts through the actuator 50 to close thevalve 19.

Shown in FIGS. 4 and 5 is a specific embodiment of asuitable flow sensor 42, in a fonn which may be injection molded as a small and inexpensive part, in two pieces, with thejet tube 44, thereceiver tubes 48 and 49, and theconduit 23. Basically, the sensor comprises twoflat plates 51 and 52 fitted together as shown in FIG. 5 and having adjacent recessed sides defining the tubes and the conduit.

The patient end of theconduit 23 is a port 53 in theplate 52, and the inlet end is asimilar port 54 in the same plate. Theair jet tube 44 is formed by an elongated channel in theplate 52, which channel may be rectangular in transverse cross-sectional shapefor convenience of manufacture. The two receivertubes 48 and 49 may be similar channels, permissibly of shorter length. When theupper plate 51 is clamped over the lower plate, the recesses, which may be in one or both plates, define the various ports.

It should be evident that it is very important for thejet tube 44 to be smooth-walled, to avoid premature transition to turbulent flow.Suitable connectors 55 are formed on theplate 52 withpassages 57 to carry the jet flow into thejet channel 44 and for connection of signal lines to thereceiver channels 48 and 49.

It will be seen in FIG. 4 that a plurality of elongatedparallel fins 58, 59 and 60 are formed in the left-hand portion of theconduit 23, perpendicular to the path of the jet 43across the conduit. These fins serve as flow straighteners, and also reduce the cross-sectional flow area of the conduit, to concentrate the cross-flow on the air jet. The flow area in the opposite end portion is greater by an amount equal to that occupied by the fins, and also is increased by widening of theconduit 23, the resulting restriction being indicated schematically at 61 in FIG. 1.

In addition, it will be seen in FIG. 4 that the upper fin 60, farthest from the orifice of thejet tube 44, has a downstream end 62 which is closely adjacent the normal path of thejet 43 when the flow is laminar. This fin is intended to intercept and amplify the eddy currents along the edge of the jet that are created by cross-flow, and thus to promote crisp switching of the sensor.

The sensitivity of theflow sensor 42 may be adjusted to different threshold flow rates by moving the disturbing cross-flow either closer to or farther from the jet orifice along the axis of jet flow. Accordingly, the inspiration phase can be initiated and terminated at different flow rates through theconduit 23. For example, for high sensitivity, at a threshold flow rate on the order of l to 2 liters per minute, the cross-flow is directed at the jet at a location relatively close to the supply jet orifice. For a lower degree of sensitivity, at a threshold rate of 2 to 4 liters per minute, the cross-flow is directed at the jet at a location farther away from the jet orifice and closer to the receiver orifice.

While high sensitivity is desirable for ease in initiation of inspiration, lower sensitivity can be desirable for termination at a somewhat higher terminal flow rate. Thus, a comprise may be made between these two considerations, or a by-pass may be provided so that only a portion of the flow is passed through theflow sensor 42.

The illustrative pressure-operated actuator 50, shown in FIG. ll, includes twoinflatable members 63 and 64, which may be of the mushroom type cornprising freely flexible, hollow plastic bodies. These members are disposed on opposite sides of a lever 65 to urge the lever back and forth relative to anorifice 67 through which air under pressure from aconduit 68 escapes when the lever is spaced from the orificev Themember 63 on the left-hand side is connected by aconduit 69 to thereceiver tube 48, and thus will be inflated when there is no flow through theconduit 23, to urge the lever 65 toward theorifice 67 into a blocking position. Themember 64 on the right-hand side of the lever is connected by aconduit 70 to thereceiver tube 49, to be subjected to the lower patient delivery pressure, and tending to swing the lever to an open position. A light spring 71 is positioned to exert an opening force on the lever, and to cooperate with themember 64 in developing an opening force moment that is less than the closing moment when jet flow is undisturbed, but greater than the closing moment when the jet flow is disturbed.

Amanual control 72 is shown in FIG. 1 for shifting the lever 65 into and out of its blocking position, independently of the forces exerted by themembers 63 and 64. This is simply ayoke 73 that is pivotally mounted on apin 74 above the free end of the lever, with the legs of the yoke straddling the lever and aknob 75 projecting upwardly therefrom and normally held in the centered position shown, by twosprings 77. The knob can be shifted in either direction to cause the yoke to pick up the lever and shift it into a selected position.

Air under pressure is continuously supplied to thesignal conduit 68 through thecontrol valve 19 to escape through theorifice 67 when it is unblocked by the lever 65, and to build up an actuating back-pressure signal in the conduit when the orifice is blocked. This back-pressure signal from the normally blocked orifice holds the control valve in a closed condition, indicated by the dotted-line arrow 78 in FIG. 1, and permits the valve to open when the orifice is unblocked, as indicated by the arrow 79. I

Various control valves are available to serve this function, one suitable valve construction being shown in detail in FIG. 6. This valve has abody 80 formed with twointernal diaphragm chambers 81 and 82 withdiaphragms 83 and 84 therein, theupper diaphragm 83 serving normally to close apassage 85 through apartition 87 between the chambers, and thediaphragm 84 serving normally to close apassage 88 extending out through the lower end of the body and connected to theconduit 20 leading to therelief valve 21.

Theconduit 17 from thecompressor 11 is connected to aport 89 on one side of the body, and delivers compressed air through this port to a cross-passage 90 in the body, feeding the air into thelower chamber 82 beneath thediaphragm 84, through apassage 91, and also throughrestrictors 92 and 93 into twovertical passages 94 and 95. The upper ends of these passages have ventingrestrictors 97 and 98 therein, which cooperate with therestrictors 92 and 93 in maintaining selected reduced pressures in thevertical passages 94 and 95. For example, when 10 psi air is supplied to thecrosspassage 90, therestrictors 93 and 98 may be equal in size to maintain 5 psi in thepassage 95, while thevent restrictor 97 is sufficiently larger than the restrictor 92 to maintain about one-third of 1 psi in the passage 94.

It will be seen in FIG. 6 that aconduit 99 leads from the passage 94 to theupper diaphragm chamber 81, above thediaphragm 83, to hold this diaphragm down to close the uppercentral passage 85 when thesignal conduit 68 is blocked at theorifice 67. At the same time, 5 psi pressure from the vertical passage is applied to thelower diaphragm chamber 82, above thediaphragm 84, through a passage 100. The resulting force, plus alight spring 101 above the diaphragm, holds the latter down to close thelower passage 88. This is the closed, or off, condition of thevalve 19 in which no flow is delivered from the inport 89 to theout passage 88.

When theorifice 67 is unblocked by the lever 65 in response to disturbance of theair jet 43 by the patients breathing through theconduit 23, pressure above theupper diaphragm 83 is relieved, and the higher pressure from thechamber 82 below, acting through thecentral passage 85, lifts the diaphragm and is vented through aconduit 102. This relieves the pressure above thelower diaphragm 84, so that the lifting force of the pressure beneath it overcomes thespring 101 to raise the diaphragm and open theout passage 88, conmeeting this passage to thesupply conduit 17 through thelower chamber 82, beneath thediaphragm 84, and through the cross-passage 90 and the inport 89.

Accordingly, air flows through thevalve 19 to therelief valve 21, and thus to the patient, as long as theorifice 67 is unblocked by the lever 65. When the lever is returned to the blocking position, pressure is restored above theupper diaphragm 83, closing thecentral passage 85 and thereby restoring the pressure above thelower diaphragm 84 to close theout passage 88. This shuts off the flow out of thevalve 19.

It has been stated that thepressure relief valve 21 may be of conventional construction, the valve illustrated being of the type sold by Bennett Respiration Products, Santa Monica, Calif, as the No. 1694 A Relief Valve. As will appear subsequently, the same function may be accomplished by a Bennett Respiration Products No. 0666 Diluter Regulator, which is preferred when the source supplies oxygen rather than air.

In general, therelief valve 21 defines achamber 103 into which the primary flow of air is injected through a venturi device where room air is entrained past the outside-air filter 28, one side of this chamber being formed by a diaphragm 104 adjustably loaded by a spring 105 and adjustingscrew 107 for setting the pressure control range. When ambient pressure exists in thechamber 103, aclosure 108 carried by the diaphragm covers a dump port 1109 opening out of the chamber, thus preventing escape of air except through thenormal outlet 22 leading to theconduits 23 and 24.

As back pressure builds up in thechamber 103 as a result of inflation of the patients lungs, the diaphragm 104 is raised away from thedump port 109, lifting theclosure 108 to allow air to escape from the chamber. The action of the relief valve is progressive, and eventually results in dumping of almost all of the supply flow, and delivery of only a low terminal flow to the patient.

The entrance '1 ofconduit 24 is closed during initiation and termination of the inspiration phase, by a flexible leaf-type check valve 111 which is closed initially to pass all of the flow from the patients breathing to thesensor 42, and opens in response to delivery of the peak flow of air through therelief valve 21, thus increasing the flow capacity far beyond the practical flow through therestriction 61 in theflow sensor 42. This leaf valve closes again as the flow rate is reduced by therelief valve 21, for example, when the rate drops within the range of 10 to liters per minute, and thereby routes all of the flow through the sensor as the inspiration phase nears completion.

Design criteria for theflow sensor 42 can be worked out in accordance with known principles in the art, examples of existing reference literature being the bookA flow sensor 42 specifically designed for the system shown in FIG. 1, and constructed in the manner shown in FIGS. 4 and 5, uses ajet tube 44 about 1 inch in length and about 0.018 of an inch square, with thereceiver tube 48 spaced 0.31 of an inch from the jet orifice. The effective flow area of the wider end portion of theconduit 23 is about 0.5 of a square inch, and the effective flow area of the restricted end portion is about 0.02 of a square inch.

With this sensor, a jet flow rate of about 0.3 of a liter per minute, at a pressure of 0.5 of one psi, can be used, and a pressure drop on the order of 0.05 of one centimeter H O at the port 53 creates enough flow through the conduit to trigger the sensor. In contrast, prior turbulence amplifiers have required a relatively large triggering pressure drop on the order of l centimeter H O, utilizing substantially smaller passages.

It bears emphasis that theflow sensor 42 is a highly sensitive type which is simple and inexpensive, easy to maintain, and stable in operation, and can operate with a low-pressure jet of low flow rate, sensitive to low cross-flow disturbances. This sensor can be characterized as a switching type, in which the pressure drop in thereceiver tube 48 is sharp, when the normal laminar flow at the entrance to the receiver is changed to a turbulent flow. Because its effective flow area is small, however, high peak flow rates are by-passed around the sensor through theconduit 24.

Shown in FIG. 2 is an alternative form of therespiration apparatus 112 with aflow sensor 113 of the fluid jet deflection type (FIGS. 2 and 3). In this case, all of the patient flow during the inspiration phase passes through the sensor, eliminating the need for a by-pass conduit such as theconduit 24 of FIG. 1. This type of sensor may be somewhat less sensitive and stable, however, than the type shown in FIGS. 1, 4 and 5, but is effective to control inspiration in substantially the same manner, while having the advantageous capability noted above.

In this case, thesensor 113 has atubular body 114, and ajet tube 115 opens into the body on one side thereof to direct ajet 117 of air across theconduit 118 defined by the body. This jet may travel, for example, about 0.5 inches and is directed toward a receiver formed by twotubes 119 and 120 (e.g., about 0.020 inches in internal diameter) spaced a short distance apart (e.g., about 0.040 of an inch) on opposite sides of the jets path, preferably equidistant therefrom so that the jet creates equal pressures into the two receiver tubes.

A relatively high-pressure jet is used, for example, at 10 psi, delivering about 3 liters per minute, and the reference pressure relationship established comprises meters H rather than different pressures as in the first embodiment.

As the patient breaths air through the delivery means 121 and thesensor 113, the flow of air deflects thejet 117 toward thereceiver 119, increasing the pressure linearly in this receiver, relative to the pressure in thereceiver 120, as the flow rate inconduit 118 increases. The pressure change is applied to anactuator 122, throughsignal conduits 123 and 124, to operate acontrol valve 125 that may be the same as thevalve 19 in FIGS. 1 and 6.

In this case, theactuator 122 is responsive to a preselected pressure differential, including an increase in the pressure at thereceiver tube 119 produced by a given degree of deflection of thejet 117 toward the delivery means 121. The change in the pressure differential is proportional to the deflection of the jet and therefore the cross-flow, and theactuator 122 can be set to operate thevalve 125 at a selected level. For background information regarding a fluid jet deflection device of this general type, reference is made to a report of J. W. Tanney, An Anemometer for Very Low Velocities, File M49-7-82, February, 1967, Low Speed Aerodynamics Section, National Aeronautical Establishment, National Research Council of Canada.

As before, theactuator 122 has twoinflatable actuating members 127 and 128 that are pressurized through theconduits 123 and 124, a lever 129 between these members, an orifice 130 positioned to be blocked and unblocked by the lever,anda spring 131 for assisting themember 128 in urging the lever toward the blocking position. An adjustingscrew 132 is provided to vary the spring force, thereby to set the actuator for operation at a selected output pressure level of the signal produced by thesensor 113.

When the orifice 130 is blocked, a back-pressure signal is applied through aconduit 133 to thecontrol valve 125 to maintain it in the closed condition, as described in connection with FIG. 6, thereby preventing any flow of primary gas through the main flow conduits of the system. In this embodiment, amain flow conduit 134 connects a pressure-regulated source 135 to thevalve 125, which is connected through anothermain conduit 137 to a flow-rate regulating valve 138, from which gas flows to thesensor 113 and the patient through aconduit 139, theconduit 118 of the sensor being a section of this conduit. Aconduit 136 connects the source to thejet tube 115.

In this instance, thesource 135 supplies oxygen, which may be diluted in the regulating valve 138. For this purpose, the valve 138 is a diluter/regulator of the type sold by Bennett Respiration Products as No. 0666, previously mentioned.

When the patient starts to withdraw air from theapparatus 112, theflow control valve 125 is opened in response to the increased pressure in thereceiver tube 119, resulting in the unblocking of the orifice 130. Then oxygen flows through the valve from theconduit 134 to theconduit 137, and thus to the diluter/regulator. Initially, the flow enters acontrol chamber 140, from which it flows through aconduit 141 through a venturi device 142 where outside air is drawn in through afilter 143. Then the mixture is delivered through aconduit 144 to apressure chamber 145 in the diluter/regulator, and passes out through theconduit 139 leading to thesensor 113 and the delivery means In thepressure chamber 145, the back pressure in the system is sensed by a diaphragm 147 that is backed by aspring 148 adjusted by a screw 1.49 to set the pressure range of the device. As the back pressure increases during the inspiration phase, the diaphragm bulges upwardly, and acts through alinkage 150 to shift a flowrestricting plunger 151 towards anorifice 152 forming the inlet to thecontrol chamber 140. The plunger is moved progressively closer to the: orifice, thereby pro gressively reducing the flow rate as the back pressure increases.

As the flow drops to a selected low flow rate, thejet 117 of thesensor 113 returns toward its normal position between the tworeceivers 119 and 120, and the pressure differential declines to the threshold level, whereupon the lever 129 is returned to its blocking positionto close thevalve 125 and terminate inspiration. The expiration phase then occurs in. the same manner as in the apparatus of FIG. 1, the exhalation valve being formed by a port 154 adjacent the delivery means 121, and aninflatable closure 155 pressurized during inspiration through aconduit 157 that communicates with themain flow conduit 137 through arestrictor 158. A restrictedbleed passage 159 relieves pressure in theclosure 155 when the inspiration flow in theconduit 137 is terminated, so the patient can exhale through the port 154.

From the foregoing, it will be evident that the present invention provides an improved respiration apparatus that is truly flow responsive, being operable in response to a flow on the order of l to 4 liters per minute that can be drawn through an open system of conduits, without need for a positively operated check valve for isolating the patient from the air supply openings in therelief valve 21 or the diluter/regulator 138. The result in an apparatus that can be much more comfortable in use, since the resistance of the apparatus to the initial breath is almost imperceptible, and the opening of thecontrol valve 19, 125 supplies gas for pressure breathing as a smooth continuation of the patients first slight effort.

Sensitivity is high, particularly in the apparatus 10, and is easily varied, and low pressure, low quantity jet flows can be used, again particularly the form 10, in which the flow sensor can be made as relatively inexpensive, easy-to-clean, molded plastic part.

It also will be evident that, while two specific embodiments have been illustrated and described, various modifications and changes may be made without departing from the spirit and scope of the invention.

I claim:

1. Flow responsive respiration apparatus for administen'ng intermittent positive pressure breathing therapy to a patient from a source of gas under pressure and through delivery means into which the patient breaths to initiate an inspiration phase of a respiration cycle, said apparatus having, in combination: a

conduit means connectible between said source and said delivery means for carrying gas intermittently therebetween; a flow control valve in said conduit means having an inlet port connected to said source by said conduit means, an outlet port connected to said delivery means by said conduit means, a closure member movable between a first position establishing communication between said ports and a second position disconnecting said ports, and pressureresponsive means for moving said closure member to said first positive in response to a first pressure signal, and to said second position in response to a second pressure signal; a flow sensor in said conduit means adjacent said delivery means comprising means for directing a jet of gas across said conduit means, and a receiver spaced from said jet-directing means to be pressurized thereby in accordance with the condition of said jet, to a first pressure level when there is no cross-flow in said conduit means and to a second pressure level when there is a cross-flow resulting from breathing by the patient; actuator means connected to said flow control valve and to said flow sensor and operable to produce said first pressure signal when said first pressure level exists in said receiver, and to produce said second pressure signal when said second pressure level exists in said receiver, thereby to open said flow control valve and initiate the inspiration phase in response to breathing by the patient through said flow sensor; and means for reducing the rate of flow of gas through said apparatus to the patient in response to increasing back pressure therein as the lungs of the patient are inflated, and thereby to reduce the flow rate through said flow sensor during said inspiration phase until said first pressure level is restored, to close said flow control valve and terminate the inspiration phase. 2. Flow responsive respiration apparatus for administering intermittent positive pressure breathing therapy to a patient from a source of gas under pressure and through delivery means into which the patient breaths to imitate an inspiration phase of a respiration cycle, said apparatus having, in combination:

conduit means connectible between said source and said delivery means for carrying gas intermittently therebetween; a flow control valve in said conduit means having an inlet port connected to said source by said conduit means, an outlet port connected to said delivery and means for reducing the rate of flow of gas through said apparatus to the patient in response to increasing back pressure therein as the lungs of the patient are inflated, and thereby to reduce the flow rate through said flow sensor during said inspiration phase until said first pressure level is restored, to close said flow control valve and terminate the inspiration phase; and wherein said flow sensor has a said jet,

said jet directing means maintains laminar flow in said jet at said first receiver only until said crossflow disturbs the jet,

and the resulting change to turbulent flow produces a marked pressure drop in said first receiver, said sensor also having a second receiver spaced from said first receiver to establish a reference pressure level with respect to which said first and second pressure levels are detectable in said actuator means.

3. Flow responsive respiration apparatus for administering intermittent positive pressure breathing thereapy first receiver aligned with to a patient from a source of gas under pressure and through delivery means into which the patient breathes to initiate an inspiration phase of a respiration cycle, said apparatus having, in combination:

conduit means connectible between said source and said delivery means for carrying gas intermittently therebetween;

a flow control valve in said conduit means having an inlet port connected to said source by said conduit means, an outlet port connected to said delivery means by said conduit means, a closure member movable between a first position establishing communication between said ports and a second position disconnecting said ports, and pressureresponsive means for moving said closure member to said first position in response to a first pressure signal, and to said second position in response to a second pressure signal;

a flow sensor in said conduit means adjacent said delivery means comprising means for directing a jet of gas across said conduit means, and a receiver spaced from said jet-directing means to be pressurized thereby in accordance with the condition of said jet, to a first pressure level when there is no cross-flow in said conduit means and to a second pressure level when there is a cross-flow resulting from breathing by the patient;

actuator means connected to said flow control valve and to said flow sensor and operable to produce said first pressure signal when said first pressure level exists in said receiver, and to produce said second pressure signal when said second pressure level exists in said receiver, thereby to open said flow control valve and initiate the inspiration phase in response to breathing by the patient through said flow sensor;

and means for reducing the rate of flow of gas through said apparatus to the patient in response to increasing back pressure therein as the lungs of the patient are inflated, and thereby to reduce the flow rate through said flow sensor during said inspiration phase until said first pressure level is restored, to close said flow control valve and terminate the inspiration phase;

and wherein said flow sensor has two receivers connected to said actuator means and longitudinally spaced apart on opposite sides of the path of said jet, to be equally pressurized by the jet while there is no cross-flow through said sensor, and to be pressurized unequally when the jet is deflected toward one of said receivers by a cross-flow.

4. Respiration apparatus for administering intermittent positive pressure breathing therapy to a patient from a source of gas under pressure and through delivery means into which the patient breathes to initiate a respiration cycle, said apparatus having, in combination;

conduit means connectible to said source for carrying gas therefrom intermittently to said delivery means;

a flow control valve in said conduit means operable to close the latter in a first condition of the valve and to open the same in a second condition;

a pressure-responsive flow regulator for reducing the flow rate through said conduit means to said delivery means as back pressure builds up in said conduit means during inflation of a patients lungs;

and a flow sensor in said conduit means for actuating said flow control valve between the open and closed conditions in response to breathingin by said patient through said conduit means, said flow sensor including means for directing a' jet across said conduit means, first and second receivers opening into said conduit means, said first receiver being positioned across said conduit means from said jebdirecting means to be pressurized by said jet, thereby to produce a first pressure relationship between said receivers when there is no flow through said conduit means and a second and different pressure relationship when there is a disturbance of said jet by a flow through said conduit means resulting from breathing by the patient;

and actuator means responsive to the change from said first pressure relationship to the second and operable to produce an amplified pressure signal and thereby to actuate said flow control valve and initiate an inspiration phase of said apparatus in response to said flow.

5. In a respiration apparatus for administering intermittent positive pressure breathing therapy to a patient from a source of gas under pressure through delivery means into which the patient breaths to initiate a respiratory cycle, the combination of:

conduit means connectible to said source for carrying gas therefrom to said delivery means;

, a flow control valve for opening and closing said conduit means;

flow sensing means including means for directing a jet of gas across said conduit means, and receiver means positioned across said conduit means to receive gas from said jet-directing means and produce a pressure signal having one value when there is no flow transversely of said jet resulting from breathing of the patient through said conduit means;

and actuator means responsive to changes in said signal, for producing an amplified pressure signal to open and close said valve.

6. In a respiration apparatus for administering intermittent positive pressure breathing therapy to a patient, and including a source of gas under pressure, delivery means for administering the gas to the patient, conduit means connecting said source to the patient to carry the gas to the delivery means, and a selectively operable flow control valve for opening and closing said conduit means between said source and said delivery means, the combination of:

means for directing a jet of gas under pressure across a portion of said conduit means through which the patient breathes in drawing a breath through said delivery means;

receiver means positioned across said portion of said conduit to be pressurized by said jet to a first level when said jet is undisturbed, and to a second level I when said jet isdisturbed by cross-flow in said portion of said conduit means resulting from breathing by the patient;

and actuator means responsive to the change in the pressure in said receiver means from said first level to said second level for producing an amplified pressure signal to open said control valve.

7. A respiration apparatus as defined in claim 6, in which said receiver means include a first receiver positioned across said portion of said conduit means in alignment with said jet, and in which said jet-directing means produces a jet which remains laminar at said first receiver as long as the jet is undisturbed, and changes to turbulent at said first receiver when disturbed by a cross-flow.

8. A respiration apparatus as defined in claim 7 further including a second receiver in said conduit means spaced from said first receiver to establish a reference pressure with respect to which said first and second levels are detectable in said means for opening said control valve.

9. A respiration apparatus as defined in claim 7 further including a disturbance amplifier in said portion of said conduit means, having an edge alongside the path of said jet, adjacent said first receiver.

10. A respiration apparatus as defined in claim 9 further including a plurality of flow-straightening vanes in said portion of said conduit means for directing the cross-flow perpendicular to said jet.

11. A respiration apparatus as defined in claim 6 in which said portion of said conduit is a first restricted conduit communicating with said delivery means, and further including a second, larger conduit also communicating with said delivery means around said first conduit, and having check means therein for directing said cross-flow through said first conduit and passing the flow of gas from said source to said delivery means.

12. A respiration apparatus as defined in claim 6 in which said receiver means comprise two receivers spaced apart on opposite sides of the path of said jet to be pressurized equally thereby when there is no crossflow in said portion of said conduit means, one of said receivers being positioned to be pressurized to a higher level as said jet is deflected by said cross-flow.

13. A respiration apparatus as defined inclaim 12 in which said portion of said conduit means is a tube adjacent said delivery means through which the patient breathes and through which all of the gas is supplied to the patient.

33 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. I 3,817,246 Dated June 18, 1974 I Inventor(s) JAMES WEIGL It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below;

Column 10,line 38, "in" should be ---is-.

Column 11, line 4, "positive" should be --position.

Column 11,line 44, after "delivery" insert -means by said 'conduit means, a closure member movable between a first position establishing communication I between saidports anda second position disconnecting said ports, and pressure-responsive means for moving said closure member to said first position in response "to a first pressure signal, and to said second position I in response to a second pressure signal;

a flow sensor in said conduit means adjacent said delivery meanscomprising means for directing a jet of gas across said conduit means, and a receiver spaced from said jet-directing means to be pressurized thereby in accordance with the condition of said jet, to a first pressure level'when there is no cross-flow in said conduitmeans and to'a second pressure level when there is a cross-flow resulting from breathing by the patient;

actuator means connected to said flow control valve and tosaid flowsensor and operable to produce said first pressure signalwhen said first pressure level exists in said receiver, and to produce said second pressure signal when said second pressure "14050 I I UNITED STATES PATENT "OFFICE I CERTIFICATE 0E CORRECTION I Patent No. 3,817,246 Dated June 1a, 1974 Inventor)JAMES WEIGL Page 2 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

level exists in said receiver, thereby to open said flow control valve and initiate the inspiration phase in response to breathing by the patient through said flow sensor;- i

Column 12,line 57, delete "111011;" and insert therefor -n-tion:--.'

Signed and sealed this 29th day of October 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents

Claims (13)

1. Flow responsive respiration apparatus for administering intermittent positive pressure breathing therapy to a patient from a source of gas under pressure and through delivery means into which the patient breaths to initiate an inspiration phase of a respiration cycle, said apparatus having, in combination: conduit means connectible between said source and said delivery means for carrying gas intermittently therebetween; a flow control valve in said conduit means having an inlet port connected to said source by said conduit means, an outlet port connected to said delivery means by said conduit means, a closure member movable between a first position establishing communication between said ports and a second position disconnecting said ports, and pressure-responsive means for moving said closure member to said first positive in response to a first pressure signal, and to said second position in response to a second pressure signal; a flow sensor in said conduit means adjacent said delivery means comprising means for directing a jet of gas across said conduit means, and a receiver spaced from said jet-directing means to be pressurized thereby in accordance with the condition of said jet, to a first pressure level when there is no cross-flow in said conduit means and to a second pressure level when there is a cross-flow resulting from breathing by the patient; actuator means connected to said flow control valve and to said flow sensor and operable to produce said first pressure signal when said first pressure level exists in said receiver, and to produce said second pressure signal when said second pressure level exists in said receiver, thereby to open said flow control valve and initiate the inspiration phase in response to breathing by the patient through said flow sensor; and means for reducing the rate of flow of gas through said apparatus to the patient in response to increasing back pressure therein as the lungs of the patient are inflated, and thereby to reduce the flow rate through said flow sensor during said inspiration phase until said first pressure level is restored, to close said flow control valve and terminate the inspiration phase.

2. Flow responsive respiration apparatus for administering intermittent positive pressure breathing therapy to a patient from a source of gas under pressure and through delivery means into which the patient breaths to initate an inspiration phase of a respiration cycle, said apparatus having, in combination: conduit means connectible between said source and said delivery means for carrying gas intermittently therebetween; a flow control valve in said conduit means having an inlet port connected to said source by said conduit means, an outlet port connected to said delivery and means for reducing the rate of flow of gas through said apparatus to the patient in response to increasing back pressure therein as the lungs of the patient are inflated, and thereby to reduce the flow rate through said flow sensor during said inspiration phase until said first pressure level is restored, to close said flow control valve and terminate the inspiration phase; and wherein said flow sensor has a first receiver aligned with said jet, said jet-directing means maintains laminar flow in said jet at said first receiver only until said cross-flow disturbs the jet, and the resulting change to turbulent flow produces a marked pressure drop in said first receiver, said sensor also having a second receiver spaced from said first receiver to establish a reference pressure level with respect to which said first and second pressure levels are detectable in said actuator means.

3. Flow responsive respiration apparatus for administering intermittent positive pressure breathing thereApy to a patient from a source of gas under pressure and through delivery means into which the patient breathes to initiate an inspiration phase of a respiration cycle, said apparatus having, in combination: conduit means connectible between said source and said delivery means for carrying gas intermittently therebetween; a flow control valve in said conduit means having an inlet port connected to said source by said conduit means, an outlet port connected to said delivery means by said conduit means, a closure member movable between a first position establishing communication between said ports and a second position disconnecting said ports, and pressure-responsive means for moving said closure member to said first position in response to a first pressure signal, and to said second position in response to a second pressure signal; a flow sensor in said conduit means adjacent said delivery means comprising means for directing a jet of gas across said conduit means, and a receiver spaced from said jet-directing means to be pressurized thereby in accordance with the condition of said jet, to a first pressure level when there is no cross-flow in said conduit means and to a second pressure level when there is a cross-flow resulting from breathing by the patient; actuator means connected to said flow control valve and to said flow sensor and operable to produce said first pressure signal when said first pressure level exists in said receiver, and to produce said second pressure signal when said second pressure level exists in said receiver, thereby to open said flow control valve and initiate the inspiration phase in response to breathing by the patient through said flow sensor; and means for reducing the rate of flow of gas through said apparatus to the patient in response to increasing back pressure therein as the lungs of the patient are inflated, and thereby to reduce the flow rate through said flow sensor during said inspiration phase until said first pressure level is restored, to close said flow control valve and terminate the inspiration phase; and wherein said flow sensor has two receivers connected to said actuator means and longitudinally spaced apart on opposite sides of the path of said jet, to be equally pressurized by the jet while there is no cross-flow through said sensor, and to be pressurized unequally when the jet is deflected toward one of said receivers by a cross-flow.

4. Respiration apparatus for administering intermittent positive pressure breathing therapy to a patient from a source of gas under pressure and through delivery means into which the patient breathes to initiate a respiration cycle, said apparatus having, in combination; conduit means connectible to said source for carrying gas therefrom intermittently to said delivery means; a flow control valve in said conduit means operable to close the latter in a first condition of the valve and to open the same in a second condition; a pressure-responsive flow regulator for reducing the flow rate through said conduit means to said delivery means as back pressure builds up in said conduit means during inflation of a patient''s lungs; and a flow sensor in said conduit means for actuating said flow control valve between the open and closed conditions in response to breathing-in by said patient through said conduit means, said flow sensor including means for directing a jet across said conduit means, first and second receivers opening into said conduit means, said first receiver being positioned across said conduit means from said jet-directing means to be pressurized by said jet, thereby to produce a first pressure relationship between said receivers when there is no flow through said conduit means and a second and different pressure relationship when there is a disturbance of said jet by a flow through said conduit means resulting from breathing by the patient; and actuator means responsive to the change from said first pressure relationship to thE second and operable to produce an amplified pressure signal and thereby to actuate said flow control valve and initiate an inspiration phase of said apparatus in response to said flow.

5. In a respiration apparatus for administering intermittent positive pressure breathing therapy to a patient from a source of gas under pressure through delivery means into which the patient breaths to initiate a respiratory cycle, the combination of: conduit means connectible to said source for carrying gas therefrom to said delivery means; a flow control valve for opening and closing said conduit means; flow sensing means including means for directing a jet of gas across said conduit means, and receiver means positioned across said conduit means to receive gas from said jet-directing means and produce a pressure signal having one value when there is no flow transversely of said jet resulting from breathing of the patient through said conduit means; and actuator means responsive to changes in said signal, for producing an amplified pressure signal to open and close said valve.

6. In a respiration apparatus for administering intermittent positive pressure breathing therapy to a patient, and including a source of gas under pressure, delivery means for administering the gas to the patient, conduit means connecting said source to the patient to carry the gas to the delivery means, and a selectively operable flow control valve for opening and closing said conduit means between said source and said delivery means, the combination of: means for directing a jet of gas under pressure across a portion of said conduit means through which the patient breathes in drawing a breath through said delivery means; receiver means positioned across said portion of said conduit to be pressurized by said jet to a first level when said jet is undisturbed, and to a second level when said jet is disturbed by cross-flow in said portion of said conduit means resulting from breathing by the patient; and actuator means responsive to the change in the pressure in said receiver means from said first level to said second level for producing an amplified pressure signal to open said control valve.

7. A respiration apparatus as defined in claim 6, in which said receiver means include a first receiver positioned across said portion of said conduit means in alignment with said jet, and in which said jet-directing means produces a jet which remains laminar at said first receiver as long as the jet is undisturbed, and changes to turbulent at said first receiver when disturbed by a cross-flow.

8. A respiration apparatus as defined in claim 7 further including a second receiver in said conduit means spaced from said first receiver to establish a reference pressure with respect to which said first and second levels are detectable in said means for opening said control valve.

9. A respiration apparatus as defined in claim 7 further including a disturbance amplifier in said portion of said conduit means, having an edge alongside the path of said jet, adjacent said first receiver.

10. A respiration apparatus as defined in claim 9 further including a plurality of flow-straightening vanes in said portion of said conduit means for directing the cross-flow perpendicular to said jet.

11. A respiration apparatus as defined in claim 6 in which said portion of said conduit is a first restricted conduit communicating with said delivery means, and further including a second, larger conduit also communicating with said delivery means around said first conduit, and having check means therein for directing said cross-flow through said first conduit and passing the flow of gas from said source to said delivery means.

12. A respiration apparatus as defined in claim 6 in which said receiver means comprise two receivers spaced apart on opposite sides of the path of said jet to be pressurized equally thereby when there is no cross-flow in said portion of said conduit means, one of said receiveRs being positioned to be pressurized to a higher level as said jet is deflected by said cross-flow.

13. A respiration apparatus as defined in claim 12 in which said portion of said conduit means is a tube adjacent said delivery means through which the patient breathes and through which all of the gas is supplied to the patient.

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