US3362404A - Respiration apparatus for administering intermittent positive pressure breathing therapy - Google Patents

Description

3,362,404 MITTENT Jan. 9, 1968 N. F. BEASLEY j RESPIHATION APPARATUS FOR ADMINISTERING INTER POSITIVE PRESSURE BREATHING THERAPY Filei Nov. le, 1964 I N VEN TOR.

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3W Ny United States Patent O ABSTRACT F THE DISCLOSURE Respiration apparatus for use in administering intermittent positive pressure breathing (IPPB) therapy. The apparatus includes a main valve which is cycled between inspiration and expiration positions to control the flow of pressurized gas through a main conduit from a highpressure source through a pressure regulator to the patient. A flow responsive valve in the main conduit upstream of the main valve and pressure regulator controls operation of the main valve in accord with the rate of tlow therethrough. The inspiration phase of the breathing cycle is terminated when flow through the flow responsive valve drops to a terminal level. Optionally, a nebulizer coupled to the :dow response valve is operated by the high-pressure gas from the source only during the inspiration phase. For purpose of initiating actuation of the main valve to its inspiration position, triggering means coupled to the tlow responsive valve and responsive to a predetermined negative pressure in the main conduit produced by the patient when he makes a slight inspiratory effort, as in normal breathing, is provided. Adjustment means are provided on the apparatus for adjusting the pressure of the gas delivered to the patient, the patient-effort required to initiate inspiration, the terminal flow and the maximum flow capacity of the apparatus, each of these adjustments being made completely independently of one another.

This invention relates t-o respiration apparatus and more particularly to improved apparatus of this type for use in administering intermittent positive pressure breathing therapy.

Intermittent positive pressure breathing, commonly known as IPPB, is a type of induced or assisted breathing for patients who are breathing spontaneously at a selfcontrolled rate and rhythm. IPPB has widespread acceptance as an effective means of relieving and treating a variety o-f respiratory disorders.

In such therapy the patient makes a slight inspiratory effort, preferably no -greater than in normal breathing, to initiate an inspiration phase of the breathing cycle. Gas under a mild control pressure is then supplied to the lungs 'to inflate them. For optimum results, and in particular,

even ventilation of the alveoli, the inspiration phase continues until the ilow requirement is extremely low. The flow taking place just at the end of the inspiratory phase is called the terminal ow. A low terminal flow is desirous because of the nature of thev lungs. They comprise a network of small passages of varying resistance leading to the alveoli. With a low terminal flow, pressure is maintained on the various passages for sufcient time period to insure that the desired even ventilation is achieved.

The gas supplied during the inspiration phase normally comprises air, which in some cases is enriched with oxygen. It is frequently desirable to admix vaporized or nebulized medication with the gas.

Following the inspiration phase is a passive expiration phase in which the pressure is rapidly released, preferably to ambient pressure, and the lungs are vented to the atmosphere. Expiration immediately takes place,

as in normal breathing, because of the elasticity of the lung-thorax system, to complete a single breathing cycle.

In order for apparatus to be effective in administering IPPB therapy, it must satisfy many operational requirements. It is important under many conditions that it have high sensitivity so that a slight inspiratory effort be sufficient to initiate inspiration, and that the terminal ilow be very low. In addition, the maximum flow capacity of the apparatus should 'be sucient to satisfy the peak flow requirement of the patient. During inspiration, an average patient has a peak ow requirement of up to liters per minute. This peak exists near the start of inspiration and thereafter decreases, dropping off quite rapidly near the end of inspiration. Accordingly, it will be -appreciated that effective apparatus must also have a peak ow capacity of approximately 100 liters per minute.

To afford flexibility of use, it is highly desirable that system pressure, sensitivity, terminal flow and peak ow capacity all be adjustable. Situations are often encountered where such adjustment is highly desirable, if not essential. By way of example, different system pressures are required in order to administer optimum therapy to different patients. Sensitivity adjustment may be advantageous to decrease the patient elfort required to initiate inspiration so as to enable a weak patient to activate the apparatus, or, conversely, to increase the patient effort required so as to exercise the lung-thorax system. Increasing the terminal flow is essential where the patients respiratory system or delivery means has a substantial leak. Without such adjustment, the apparatus would not `automatically cycle from inspiration to expiration phases of operation. Moreover, the utility of the apparatus is greatly increased where each of these adjustments may be made completely independently of one another.

A disadvantage inherent in most units currently in use is that terminal iiow cannot be rnade suciently low. The effect is that as soon -as the pressure in the delivery means approaches the control pressure, the unit cycles into its expiration phase. This occurs even though appreciable flow is Still taking place in inflating the lungs, with the result that thorough and uniform ventilation is not achieved. Moreover, where the patients respiratory system is greatly obstructed, units of this general type are totally ineffective and cannot be used.

In certain types of IPPB units, adjustment means make it possible to obtain a low terminal How. However, such adjustment adversely affects the peak flow capacity of these units. In the same connection, terminal ow is often interrelated with sensitivity and system pressure in which case adjustment of one alters the others, and the desired flexibility of use is not attained.

Another problem typically Vencountered with present IPPB units is in conjunction with nebulizer operation. Nebulizers are often arranged to operate continuously during both inspiration and expiration. Thus, the high pressure gas used to operate the nebulizer and the medication supplied during the expiration phase are wasted.

It is, therefore, a primary object of this invention to provide improved respiration apparatus for effective use in administering ideal IPPB thearpy. t

Another object is to provide improved respiration apparatus which is highly sensitive to the patient effort required to initiate inspiration, and has a low terminal ow so as to insure optimum ventilation and a high peak flow capacity.

A further object is to provide apparatus of the type described, further characterized in Vthat system pressure, sensitivity, terminal ow and peak flow capacity may all be adjusted, and that such adjustments :may be made completely independently from one another.

Still another object is to provide respiration apparatus of the type described in which the nebulizer may be operated only during the inspiration phase of the breathing cycle.

It is still another object to provide improved respiration apparatus which is extremely durable and highly reliable and trouble-free in operation.

A still further object is to provide improved respiration apparatus capable of accomplishing all of the foregoing objects, yet which is adapted to be manufactured at a relatively low cost.

These and other objects, features and advantages of the invention will be better understood by referring to the following detailed description taken in conjunction with the accompanying drawing in which:

FIGURE 1 is a semi-schematic view of an illustrative embodiment of the invention with the various elements being shown in the positions occupied during the expiration phase of the breathing cycle;

FIGURE 2 is a view of the triggering valve illustrated in the left-hand side of FIGURE 1 in the condition it occupies as the inspiration phase is being initiated;

FIGURE 3 is a view of the main valve in its open condition during the inspiration phase of the breathing cycle; and

FIGURE 4 illustrates the ow responsive valve in its open condition, as during the inspiration phase.

Referring to the drawing and in particular to FIGURE 1, the apparatus of the invention is arranged to control the ow of pressurized gas from a source to delivery means 12 through conduit means 14. It includes, in general, a main valve 16 operable between inspiration and expiration positions to permit and block flow, respectively, through the conduit means; a flow-responsive valve 18 for actuating the main valve 16 and a triggering valve 20 for initiating actuation of the main valve to its inspiration phase of operation. Also included in the illustrative apparatus, in series in the conduit means 14, are a suitable inlet lter 22 adjacent the source 10 and an adjustable pressure regulator 24 between the flow responsive valve 18 and main valve 16. A nebulizer 26 controlled by a valve 28 is arranged optionally to admix nebulized medication with the gas being supplied to the patient.

The source 18 may, by way of example, comprise a tank of compressed air or oxygen or a pump for compressing ambient air, or combination of the two. The delivery means 12, on the other hand, will be understood to include any of the numerous means adapted for connection to the patients respiratory system, such as a face mask, mouth piece, or tracheal tube.

The gas supplied from the source 10 is generally at a considerably higher pressure than that to be delivered to the patient. Moreover, in order to attord the desired flexibility in administering eiective IPPB therapy to a variety of different patients, it is desirable that means be provided for adjusting the pressure of the gas delivered to the patient. For these reasons, the adjustable pressure regulator 24 is provided. Experience has shown that virtually all operational situations can be accommodated and safe operation is assured when the pressure is adapted to be preset within the range of l0 to 60 cm. of water.

The main valve 16 for valving gas ow to the patient includes an elongated housing 30 separated by a transverse plate 32 into inlet and outlet compartments 34 and 36. Located centrally of the plate 32 is an aperture 38 that provides communication between the two compartments. Connection of the valve in the conduit means 14 on its upstream side is by a passage 40 in the wall of the inlet compartment 34 and on its downstream side by a passage 42 in the wall of the outlet compartment 36, preferably having a one-way check valve 43. Flow of gas takes place into the inlet compartment 34 through the passage 40, then to the outlet compartment 36 through the aperture 38 and iinally out through the passage 42.

Valving is achieved by means of a poppet 44 movable into and out of sealing relationship with a seat 46 formed on the plate 32 around the periphery of the aperture 3S. The poppet 44 is disposed in the outlet compartment 36 and is carried by an elongated, cylindrical spool 48 to which it is atlixed. The spool 48, in turn, is supported by a transverse guide plate 50 in the housing 30, and is free for longitudinal sliding movement. The poppet moves between a seated or expiration position and an open or inspiration position, illustrated in FGURES 1 and 3, respectively. A compression spring 52 disposed around the spool 48 and abutting the poppet 44 and plate 5t) at its opposite ends serves to bias the poppet toward its expiration position of FIGURE 1.

In the inspiration position of the poppet 44, it cooperates with the seat 46 to restrict the main flow path to the patient. The extent of the restriction is adjustably established by an adjustment screw 54 threadedly engaged in a bore S6 in the end of the housing 30. Movement of the poppet 44 away from the seat 46 is limited by the spool abutting the screw 54, as illustrated in FIGURE 3. In this manner, the peak flow capacity of the apparatus for a given setting of the pressure regulator Z4 is established.

Movement of the poppet 44 to its inspiration position is accomplished by a resilient, ilexible diaphragm 58 affixed to the spool 48. The diaphragm 58 is arranged transversely in the inlet compartment 34 at a location spaced toward the adjacent end of the housing from the inlet passage 40, so as not to interfere with the flow path through the valve 16. The end of the housing together with a diaphragm deiine a pressure-sensing chamber 60. When a pressure signal is received in the chamber 60, the diaphragm 58 moves away from the end of the housing, causing the spool to move the poppet to its inspiration position of` FIGURE 3. Conversely, when the pressure signal is subsequently removed, the poppet 44 moves back to its inspiration position shown in FIG- URE 1 under the influence of the spring S2.

The pressure signal for effecting such operation of the main valve 16 is supplied by the flow-responsive valve 18. This latter valve is constructed and arranged in accordance with the teachings in my copending application Ser. No. 383,610, now Patent No. 3,311,125 entitled Flow Responsive Valve for Supplying Pressure Signal, led July 20, 1964. For present purposes, it is briefly noted that the valve 18 includes a body 62 formed with a chamber including a main section 64 and relatively enlarged pressure-sensing section 66. A plurality of passages communicate with the main section 64 at spaced locations. These include an inlet passage 68 and an outlet passage 70 in constant communication with one another through the main section 64 to establish a primary iiow path and a signal passage 72.

Slidably mounted in the upper portion of the main section 64 is a piston 74 with its upper end projecting upwardly into the pressure-sensing section 66 and its lower end disposed proximate the port 70a at the junction of the outlet passage 70 with the main section. In this position, the lower end of thepiston 74 is arranged to cooperate with the Wall of the chamber to afford a variable orifice at the port 70a in the primary ow path to the valve. It may be seen that as the piston 74 is moved longitudinally in the main section, the effective opening of the port 70a is varied, With the size being a minimum in the limit position illustrated in FIGURE l.

A positioning element 76 is provided in the lower end of the main section 64 for establishing the limit position of the piston 74 and, hence, the minimum size of the variable orice. To enable longitudinal adjustment of the element 76, it is externally threaded at its lower end and engaged in a correspondingly threaded portion of the main section. At its upper end the element 76 is. necked down in diameter, so as not to interfere with the aforementioned primary flow path through the valve 18.

For the purpose of intermittently providing communication between the inlet passage 68 and the signal pas,-

sage 72, so that the valve may supply a pressure signal, an auxiliary signal passage 78 is provided through the positioning element 72. This passage 78 includes, in series, an axial bore, a transverse bore and a circumferential groove. As may be seen, the groove is of suflicient width as to remain in communication with the port opening to the signal passage 72 upon full range of longitudinal adjustment of the element 76. In the limit position of the piston 74 of FIGURE 1, it will be seen that the piston functions as valve means to block the opening to the auxiliary signal passage 78 in the element 76. On the other hand, when the piston 74 moves upwardly toward the position of FIGURE 4 to increase the size of the variable orifice, such -blocking is removed and a pressure signal is delivered.

Movement of the piston 74 from its limit position of FIGURE 1 to supply a pressure signal and to increase the size of the va-riable -orifice is achieved by means of a resilient, flexible diaphragm 84 connected to the piston. The diaphragm 84 extends transversely across the pressure-sensing section 66, separating it into an upstream compartment adjacent the main section 64 of the chamber and the downstream compartment adjacent the upper or terminal end of the chamber. These compartments are, in turn, connected to the inlet and outlet passages 68 and 70, in the valve body 62. Besides the resiliency of the diaphragm 84, a relatively light compression spring 86 urges the piston 74 downwardly toward its limit position.

Accordingly, the lower or upstream side of the diaphragm 84 senses pressure on the inlet side of the variable orifice at the port 70a, while the upper or downstream side of the diaphragm senses pressure on the downstream side of the orifice. As is known in the art, the pressure differential across an orifice of a given size varies in accordance with the rate of flow. Increases in the rate of tiow bring about a corresponding increase in the pressure differential. Conversely, for a given rate of liow, as the size of the orice increases, the pressure differential thereacross proportionately decreases. Therefore, when flow through the primary liow path reaches a threshold level at which the pressure differential across the oriiice in its minimum size is sufiicient to overcome the forces urging the piston to its limit position, upward movement of the piston 74, as, for example to the position of FIGURE 4, takes place. The effect is to unblock the opening to the auxiliary signal passage in the element 76 to enable a pressure signal to be delivered. When the primary flow subsequently decreases to a terminal liow level, which for present purposes may be assumed to be substantially equal to the threshold liow, the piston 74 moves back to its seated position of FIGURE 1.

It is advantageous from an operational standpoint to provide for adjustment for the terminal flow within the range of one-half to twenty liters per minute. That is, the positioning element 76 is movable to vary the initial size of the variable orifice, so that a pressure signal is supplied so long as the primary flow exceeds the adjusted rate within the specified range.

An important feature of the valve 18 is that as the primary flow increases and the pressure differential across the variable orifice increases, the diaphragm 84 responds to move the piston 74 further away from the positioning element 76. This in turn, results in the oriiice increasing in size and obstruction or restriction to flow thereacross when the flow requirement is high is greatly reduced as compared to a situation in which the orifice were lixed in size. As a consequence, the terminal iiow may be made extremely low, eg., one half liter per minute, yet the peak flow capacity of the apparatus may be made sufiiciently high to satisfy the patients peak requirement.`

The pressure signal from the flow-responsive valve 18 is delivered to the pressure-sensing chamber 60 of the main valve 16 through the signal conduit 88. It is noted that the effective area of the diaphragm 58 in the pressure sensing chamber 60 is somewhat larger in the expiration position of the main valve 16 than the area on the opposite side thereof. Moreover, the pressure signal supplied to the chamber 60 for actuating the diaphragm 58 is from the upstream side of the regulator 24, whereas the pressure existing on the opposite side of the diaphragm has been reduced by the regulator. Accordingly, diaphragm movement to actuate the valve is assured upon the pressure signal being supplied. To enable the diaphragm 58 to move back to its initial position of FIGURE 1, when the signal is terminated, a bleed passage with a restricted orifice is provided in the signal conduit 88.

Triggering or initiation of actuation of the main valve 16 to itsinspiration position is achieved by the triggering valve 20. This valve functions to cause the primary flow through the flow-responsive valve 18 and in corresponding portion of the main conduit means 14 to exceed momentarily the threshold or terminal fiow. As a result, a pressure signal is supplied to the chamber 60 and the main valve 16 is actuated t-o its inspiration position.

The triggering valve 20 comprises 'a housing 92 separated by a diaphragm 94 into upper and lower compartments 96 and 98. The lower compartment 9S is connected to the main conduit means 14 adjacent the delivery means 12 by a conduit 100. As a result, the `diaphragm 94 is sensitive to a slight inspiratory effort by the patient, which produces a negative pressure in the lower compartment 98.

The upper compartment 96 is connected to the main conduit means 14 by a triggering conduit 102 at 4a location between the variable orifice in the flow-responsive valve 18 and the main vlave 16. In the illustrative case, such connection is upstream of the regulator 24. Preferably the conduit 102 is restricted by an orifice 104 sized to limit flow to the upper compartment 96 to a rate just slightly greater than the maximum possible terminal flow. It will be recalled that the how-responsive valve 18 is adapted to be adjusted to establish a terminal fiow within the range yof one-half to twenty liters per minute, and accordingly, the orifice 104 is sized to limit iiow to just slightly more than twenty liters per minute. Extending from the upper compartment 96 is a bleed passage 106 for bleeding the gas supplied to that compartment through the conduit 102. For the purpose of assuring positive action of the triggering valve 18, the bleed passage 106 preferably is restricted by an orifice 108 sized in relation to the orifice 104, so that a slight positive pressure on the order of five cm. of water will be maintained in the compartment 96 when fiow thereto is taking place.

Flow of pressurized gas through the triggering conduit 102 to the upper compartment 96 is alternately permitted and blocked by a valve assembly including a rocker arm 110, a closure element 112 and a support rod 114. The arm 110 is pivotally mounted in the housing 92 and mounts the closure element 112 for movement into and out of sealing relationship within the end of the conduit 102. Movement of the arm 110 in this manner is achieved by the rod 114 which in turn is afixed to the upper side ofthe diaphragm 94.

Downward movement of the diaphragm 94 toward the position of FIGURE 2 to move the closure element 112 out of such sealing relationship with the conduit 102 is resisted by a light compression spring 116. In order to adjustably establish the patient effort required to so move the diaphragm 94, an -adjustment screw 118 is provided. The screw 118 is threadedly engaged in the lower end of the housing 92, and is formed with a shoulder for abutting the lower end of the spring 116.

It will be appreciated that when 'a patient effort is exerted to move. the diaphragm to the position of FIG- URE 2, flow of gas takes place from the source to the upper compartment 96 of the triggering valve 20 through an alternate primary flow path including conduit means 14, flow responsive valve 18 and conduit 102. Since such ow is at a rate at least just slightly greater than the adjusted terminal flow of the flow-responsive valve 1S, a pressure signal is supplied to actuate the main valve 16 to its inspiration position. Primary ow then, of course, takes place through the conduit means to the patient. Commencement of such primary tlow causes a positive pressure to be exerted by the lower side of the diaphragm 94 of the triggering valve 20 by virtue of the connection of the conduit 161). As a result, the triggering valve 20 is quickly reset to its initial position of FIGURE 1, to condition it for subsequent operation. It is to be noted, however, that inspiratory ilow to the patient continues, so long as flow through the main valve to the patient exceeds the adjusted terminal flow of the how-responsive valve 18.

In many IPPB therapy situations, it is desirable to utilize a nebulizer to admix nebulized medication with the gas delivered to the patient. For this purpose, the nebulizer 26 is provided. It is connected to the conduit means 14 adjacent the delivery means 12 by a manifold `assembly 120. The details of the construction and arrangement of the nebulizer forms no part of the present invention. For this reason, it is not described in detail. It is sufficient for present purposes to note that it includes .an inlet nozzle 122 through which high pressure gas is `delivered to a container 124 containing liquid medication. 'The medication is nebulized `by virtue of the action of the capillary tube 126 and the gas impinging upon the :surface of the liquid. The admixture of gas and nebulized medication is delivered to the conduit means 14 through an outlet passage 128.

Pressurized gas for operating the nebulizer 26 is supplied through a conduit 132 connected to the signal conduit 38. Thus, the nebulizer operates only when the ow responsive valve is supplying a pressure signal. As previously noted, when the pressure signal is supplied, the main valve 14 is actuated to its inspiration position. Thus, nebulizer operation is correlated with actuation of the main valve. This is highly advantageous in that nebulizer operation is desired only during the inspiration phase of operation. Control of the nebulizer operation is achieved by means of a conventional needle valve 28 installed in the conduit 132.

Expiration by the patient to the atmosphere is through a passage 134 in the manifold assembly 120. The passage 134 is closed during the inspiration phase of operation by a diaphragm-type exhalation valve 136. The lower end of the valve 136 is positioned in close proximity to the portion of the manifold assembly deiining the end of the passage 134. Accordingly, upon a slight inspiratory effort by the patient, the valve 136 is drawn down to a seated position to close the passage 134. The passage 134 is maintained closed during the entire inspiration phase by positive pressure in the valve 136 supplied from the outlet compartment 36 of the main valve 16 through the conduit 138. Bleeding of pressurized gas from the valve 136 to open the passage 134 during the expiration phase is provided or by an axial bleed passage 140 in the adjustment screw 54. Expiration iiow from the patient back to the main valve 16 is blocked by the check valve 43. In the expiration position of the main valve 16 illustrated in FIG- URE 1, the bleed passage 140 is open to the atmosphere, so that the exhalation valve 136 is depressurized. However, upon the main valve 16 being actuated to its inspiration position f FIGURE 3, the bleed passage 14() is blocked.

Operation It is assumed initially that the apparatus of the invention is appropriately adjusted to achieve the desired system pressure, sensitivity terminal flow, peak ow capacity and nebulizer output. The apparatus is normally conditioned for the expiration phase of the breathing cycle with the various elements in the relative positions shown in full lines in FIGURE 1. The -main valve 14 is in its expiration position with the poppet 44 seated to block primary ow to the patient. Likewise, the flow-responsive valve 18 has its piston 74 in its limit position, wherein the variable orice is of minimum size and the auxiliary signal passage is blocked to prevent a pressure signal from being delivered, and the triggering valve 20 has its closure element 112 blocking flow through the conduit 102. The exhalation valve 136 on the other hand, is depressurized to enable the patient to expire to the atmosphere through the passage 134;.

A slight inspiratory eitort by the patient, as is exerted in commencing the inspiration phase of normal breathing, draws a slight negative pressure in the adjacent portion of the conduit means 14. Such pressure acts through the conduit 10) and lower compartment 98 of the triggering valve 2t) to draw the diaphragm 94 downwardly. This causes the rocker arm to pivot and the closure element 112 to move down away from sealing relationship with the end of the conduit 102. As soon as the closure element 112 is cracked off its seat, primary ow of high pressure gas takes place from the source 10 to the upper compartment 96 through the tlow path including conduit means 14, the flow responsive valve 18 and the triggering conduit 102. Because of the relative sizes of the orices 104 and 10S in the ow path to and from the compartment 96, a positive pressure of approximately tive cm. of water acts on the upper side of the diaphragm 94 to insure positive opening of the valve 20 to the condition illustrated in FIGURE 2.

With the triggering valve 20 open, ow through the aforementioned path to this valve takes place at a rate at least slightly greater than the adjusted threshold (terminal) ow of the flow-responsive valve 18. Thus, the pressure differential across the variable orifice at the port 70a, sensed by the diaphragm 84, exceeds the forces biasing the piston 74 toward its lower limit position of FIG- URE 1. The piston 74 is therefore moved upwardly away from the positioning element 76 to open the auxiliary signal passage and cause a pressure signal to be issued. Simultaneously, the size of the variable orice is increased so as to reduce the restriction to primary flow, and thereby insure that the peak demand of the patient can be met.

The pressure signal from the flow-responsive valve 18 is transmitted to the main valve 16 by the conduit 88, where it serves to actuate and maintain the latter valve in its inspiration position illustrated in FIGURE 3. In so, functioning, the pressurized gas moves the diaphragm 58 away from the end of the housing 30, carrying with it the spool-poppet assembly 48, 44 against the biasing force of the spring 52. This results in opening of the primary flow path through the aperture 38, and inspiratory flow takes place to the patient. The extent of poppet movement away from its seat 46 is limited by the spool 48 abutting the adjustment screw 54. In this manner, the primary ow is throttled or restricted, to the desired extent so as to establish the peak flow capacity of the apparatus.

Upon movement of the main valve 16 to its inspiration position of FIGURE 3, pressurized gas is delivered through the conduit 138 to pressurize the exhalation valve 136. Such pressurization of this valve causes it to seat and block the exhalation passage 134 during the entire inspiration phase. The associated bleed passage 140 in the adjustment screw 56 is blocked by the spool 48.

Pressurized gas downstream of the main valve 416 acts through the conduit 100 and the lower compartment 98 of the triggering valve 20 to reset the latter lfor subsequent operation. The pressure in the conduit means 14 downstream of the main valve builds up quite rapidly to a level above that (tive cm. of water) existing in the upper compartment 96 of the valve 20. Accordingly, the diaphragm 94 is urged back to its initial position of FIG- URE l to close the triggering valve 2t)` early in the inspiration phase, thus minimizing gas loss. Notwithstanding such closing of the valve 2t), inspiration continues, since the primary flow, now taking place to the patient, exceeds the terminal ow level of the flow-responsive valve A18.

Assuming that nebulizer operation is desired, the control valve 28 is open to the desired extent and nebulized medication is admixed at the manifold assembly 120 with the gas being delivered to the patient. The pressure signal supplied lby the flow-responsive valve 18 through conduits 88 and 132 operates the nebulizer.

As long as the primary gas tiow to the patient exceeds the .adjusted terminal flow of the How-responsive valve 18, the inspiration phase continues with the various elements of the apparatus remaining in the conditions just described. Near the start of inspiration, the tlow requirement of the patient is relatively high, as for example, up to 100 liters per minute. Therefore, the piston 74 is moved a correspondingly large distance away from the positioning element 76 to increase the size of the variable orice at the port 70a to a maximum. As the patient requirement subsequently decreases, as is the case during the latter part of inspiration, the piston commences movement back toward the positioning element 76 to reduce the size of the orifice. During such operation, the pressure of the gas delivered to the patient may be read on a suitable gauge, such as the gauge 142.

When full ventilation has been achieved and the gas flow to the patient drops below the adjusted terminal tiow of the flow-responsive valve 18, the piston 74 seats on the positioning element 76 to terminate the pressure signal. Pressurized gas in the pressure-sensing compartment of the main valve is then bled through the restricted oriiice 90 in the signal conduit 88 to remove the force maintaining the main valve 16 in its inspiration position. Therefore, the compression spring 52 urges the valve back to its expiration position, illustrated in FIGURE 1, with the poppet 44 seated so as to block primary flow to the patient.

Nebulizer operation ceases when the pressure signal terminates and, hence, coincidentally with actuation of the main valve 16 to its expiration position. This repres-ents an important feature of the present apparatus from the standpoint of conserving gas and medication.

The bleed passage 140 through the adjustment screw 54- is opened to the atmosphere upon the main valve 16 being actuated to its expiration position, causingthe exhalation valve 136 to be depressurized. The patient now expires to the atmosphere through the outlet passage 134 in the manifold assembly 120 to complete one breathing cycle. When the patient subsequently exerts another inspiratory effort, a second cycle commences in the same manner as described above.

The apparatus of the invention may be conveniently used in administering highly effective IPPB therapy. Not only is it characterized by high sensitivity to the patient effort required to initiate inspiration, a low terminal flow and a high peak flow capacity, but these parameters, along with system pressure, may all be conveniently adjusted. To adjust sensitivity, it is simply necessary to rotate the adjustment screw 118 of the triggering valve 20 to vary the force of the -compression spring 116 urging the diaphragm 94 to its position in 'FIGURE 1. Similarly, terminal ilow is conveniently adjusted by rotating the positioning element 76 to `alter the minimum size of the variable orifice `at the port 70a. Peak ow capacity is adjustably established by rotating the adjustment screw 54 on the main valve 16 to vary the spacing of the poppet 44.- from its seat 46 in the inspiration position of this valve. System pressure is preset at the desired level by adjusting regulator 24 with `aid of gauge 142. Moreover, the desired tiexibility of operation is obtained by virtue ot the fact that each of these adjustments may be made independently of one another.

While one embodiment of the invention has been illustrated and described in considerable detail, it will be understood that this is only by way of illustration, and that numerous changes in the construction and yarrangement of the various elements may be made without departing from the spirit and scope of the inventlon.

I claim:

1. In respiration apparatus including a source of pressurized gas, delivers means and conduit means connecting the source and the delivery means, the combination of:

a main valve in said conduit means having an inspiration position wherein primary flow of gas takes place from said source to said delivery means through said conduit means and an expiration position wherein such ow is blocked, said main valve normally being in its expiration position and being actuatable between said positions;

a flow-responsive valve in said conduit means between said main valve and said source and operatively associated with said main valve, said How-responsive valve having means responsive to primary iiow therethrough at a rate greater than a predetermined minimum to urge said main valve toward its inspiration position;

pressure regulator means in said conduit means between said ow responsive valve and said main valve; and

triggering means connected to said conduit means adjacent said delivery means and operatively associated with said main valve, said triggering means being operable independently of said How-responsive valve and having means responsive to a slight predetermined negative pressure in said conduit means adjacent said delivery means to initiate actuation of said main valve to its inspiration position.

2. In respiration apparatus including a source of pressurized gas, delivery means and main conduit means connecting the source and the delivery means, the cornbination of:

a main valve in said main conduit means having an inspiration position wherein ow of gas takes place from said source to said delivery means through said main conduit means and an expiration position wherein such ow is blocked, said valve being biased toward its expiration position and being actuated by a pressure Signal to move to its inspiration position;

a How-responsive valve in said main conduit means between said main valve and said source, said flowresponsive valve having means responsive to flow therethrough at a rate greater than a predetermined minimum for supplying a pressure signal; signal conduit means connecting said iiow responsive valve to said main valve for transmitting said pressure signal to said main valve to so actuate the latter; and

triggering means connected to said main conduit means adjacent said delivery means and connected to said now-responsive valve to provide an alternate primary ilow path from said dow-responsive valve for permitting flow through said last mentioned valve at a rate greater than said predetermined minimum, said triggering means having means normally blocking said alternate flow path and being responsive to a predetermined negative pressure in said conduit means adjacent said delivery means to open said alternate flow path.

3. The sub-ject matter of claim 2 including a pressure regulator in said conduit means between said flow responsive valve and said main valve.

4. In respiration apparatus including a source of pressurized gas, delivery means and main conduit means connecting the source and the delivery means, the combination of:

a main valve in said main conduit means having an inspiration position wherein iiow of gas takes place from said source to said delivery means through said main conduit means and an expiration position wherein such flow is blocked, said main valve normally being in its expiration position and being actuated by a pressure signal to move to its inspiration position;

a flow-responsive valve -having an inlet port and an outlet port coupled by said main conduit means to said source and to said main valve, respectively, and a signal port, said How-responsive valve being responsive to flow between said inlet port and said outlet port at a rate greater than a predetermined minimum to supply a pressure signal a signal conduit means connecting said signal port to said main valve for transmitting said pressure signal to said main valve to so actuate the latter;

a pressure regulator in said main conduit means between said flow-responsive valve and said main valve;

a nebulizer connected to said signal port of said owresponsive valve and to said delivery means, said nebulizer being operated by such pressure signal; and

triggering means connected to said conduit means adjacent said delivery means and operatively connected to said ow-responsive valve, said triggering means being responsive to a slight predetermined negative pressure in said main conduit means adjacent said delivery means to cause said flow-responsive valve to supply such pressure signal.

5. In respiration apparatus including a source of pressurized gas, delivery means and conduit means connecting the source and the delivery means, the combination of:

a main valve in said conduit means having an inspiration position wherein flow of gas takes place from said source to said delivery means through said conduit means and an expiration position wherein such ow is blocked, said valve being biased toward its expiration position and being actuated by a pressure signal to move its inspiration position;

How-responsive means coupled to said conduit means between said main valve and said source and coupled to said main valve, said flow-responsive means including a variable orifice which is normally of a minimum size, means responsive to a ilow across said oriiice at a rate greater than a predetermined minimum to increase the size of said orice, and means 4for supplying a pressure signal to actuate said main valve to its inspiration position only when the ow across said orifice exceeds said predetermined minimum; and

triggering means connected to said flow-responsive means and to said conduit means adjacent said delivery means, said triggering means having means responsive to a predetermined negative pressure in said conduit means adjacent said delivery means to initiate flow across said orifice at a rate greater than said predetermined minimum, whereby a pressure signal is supplied by said flow-responsive means to actuate said main valve to its inspiration position.

6. The subject matter of claim '5 including rst adjustment means associated with said flow-responsive means for adjustably establishing said predetermined minimum flow rate and second adjustment means associated with said triggering means independent of said rst adjustment means for adjustably establishing said predetermined negative pressure.

7. The subject matter of claim 6 wherein said main valve includes a restricted oriiice in said conduit means, and third adjustment means independent of each of said tirst and second adjustment means for varying the extent of the restriction.

8. In respiration apparatus including a source of pressurized gas, delivery means and conduit means connecting the source and the delivery means, the combination of:

a main valve in said conduit means having an inspiration position wherein low of Igas takes place from said source to said delivery means through said conduit means and an expiration position wherein such flow is blocked, said main valve normally being in its expiration position and being responsive to a signal to move its inspiration position;

ow-responsive means in said conduit means between said main valve and said source and responsive to tiow therethrough at a rate greater than a predetermined minimum to supply a signal to move said main valve to its inspiration position;

pressure regulator means in said conduit means between said ow responsive valve and Said main valve; and

triggering means connected to said conduit means adjacent said delivery means and including means providing an 1alternate primary ow path from said dow-responsive means sized to permit flow through said How-responsive means at a rate greater than said predetermined minimum, valve means normally Iblocking said alternate primary flow path, and pressure-sensitive means for operating said valve means, said pressure-sensitive means being responsive to a slight predetermined negative pressure in said conduit means adjacent said delivery means to move said valve means to open said alternate primary ow path.

9. The subject matter of claim 8 wherein said triggering means includes means responsive to actuation of said main valve to its inspiration position to move said valve means into such blocking relationship.

References Cited UNTED STATES PATENTS 2,121,311 6/1938 Anderson et al. 128-29 2,391,877 1/1946` Cahan 12S-29 2,535,844 12/1950 Emerson l37-l02 3,138,152 6/1964 Wilson 12S-29 RCHARD A. GAUDET, Primary Examiner.

K. L. HOWELL, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OE CORRECTION Patent No. 3,362,404 January 9, 1968 Noel F. Beasley It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column ll, line 7, after "a pressure signal" insert at said signal port;

Signed and sealed this 15th day of April 1969.

(SEAL) Attest:

EDWARD J. BRENNER Commissioner of Patents Edward M. Fletcher, Jr.

Attesting Officer

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