POSITIVE PRESSURE BREATHING CIRCUIT

1

POSITIVE PRESSURE BREATHING CIRCUIT BACKGROUND OF THE INVENTION

The concept of respiratory therapy is well known in the art field, and a wide variety of respiratory diseases are treated by use of a positive pressure respiratory system. The positive pressure incident to such systems is generated by devices commonly referrred to as ventilators, respirators or other such positive pressure machines. Generally, the concept is to provide a breathable gas mixture under pressure to the patient to facilitate the respiratory cycle of the patient.

Usually, such breathable gases consist of a composition of air and oxygen which is delivered to the patient under controlled conditions of pressure, temperature, water content and gas composition.

In the typical system, the gas is conducted from the ventilator to the patient by means of a tubing conduit, generally consisting of an inhalation tube and exhaled gases exhausted through an exhalation tube. Furthermore, it is generally accepted that in such systems, the inhalation and exhalation tubes respectively, are separate tubes separately interconnecting the ventilator with the patient face mask in order to complete the circuit as between the ventilator and the patient. The differences existing between the variety of systems available generally involve mainly materials of construction rather than in the make-up of the system. The tubing conduit is usually formed of a flexible material, which is chemically inert and fabricated into a cylindrical configuration, whether corrugated or otherwise, and reinforced in order to prevent kinking and collapse. The tubes or conduits are interconnected to the ventilator and to the patient by any suitable devices, although usually slip-type friction fittings are employed especially for connection of the ventilator to the valving mechanism which is external to the patient. In addition, many of the current respiratory breathing circuits also incorporate a gas powered nebulizer, usually mounted to the housing of the valving mechanism, the nebulizer functioning to create a mist of a variety of liquid medications, which are then administered in conjunction with the positive gas pressure introduced through the inhalation tube.

Another feature of a respiratory circuit and system includes the provision of a heated humidifier which is interposed in the circuit between the ventilator and the inhalation tube. The purpose of the heated humidifier is to raise the temperature of the gas as well as to humidify the same prior to inhalation by the patient. In the usual system, the heater raises the liquid temperature of approximately 120°F. - 140°F. which results in a gas temperature of approximately 110°F. - 130°F. upon exit from the nebulizer or humidifier.

Insofar as the presently existing systems are concerned, a variety of problems have been encountered and it is the purpose of the present invention to overcome these difficulties which are inherent in the present systems. For example, the valving mechanism incident to systems presently available are generally extraneous to the system and the circuit, and hence, a great deal of dead space is usually present in the system. The dead space results in the patient generally breathing in previously exhaled gases during the inhalation cycle since any gas existing in the dead space will tend to be drawn back into the patient during the inhalation cycle. In the event that any bacterial growth develops in the

dead space, it is obvious that the patient is exposed to the danger of inhaling contaminated gas.

In addition, CQ2 is a respiratory stimulant and can cause hyper-ventilation with attendant unfavorable 5 complications. Hence, it is deemed desirable not only to have the valving mechanism associated with circuit per se, but also to position the valving mechanism closely adjacent to the patient to minimize the dead space.

10 Insofar as humidification and heating is concerned, it has been found that since the humidifier is generally positioned in the circuit in a position removed from the patient, that even though the gas may be heated and humidified, the gas will give off both heat and humidity

15 as it travels through the tubing to the patient. For example, when the heat-saturated gas leaves the humidifier through the tubing circuit, it will release heat by contact with the thin wall of the tubing conduit, which in turn is exposed to room air temperature, i.e.,

20 70°-75°F. Hence, it is frequently found that the inlet gas temperature just prior to entering the patient is approximately 85°F. thereby accounting for a temperature drop of approximately 25°F or more. As a result of the heat given up by the gas, condensation will occur

25 in the tubing circuit resulting in a pool of liquid collecting in the tubing. It is apparent that the pooling of liquid in the tubing circuit is not desirable since such pooling actually reduces the lumen opening of the tubing at the point of pooling, which in turn may cause prema

30 ture cycling of a pressure-cycled ventilator, since the reduced lumen presents a pressure gradient which the ventilator senses as a pressure increase. If the pressure equals the shut-off pressure of the ventilator, the ventilator will cycle off and the patient will not have re

35 ceived the proper pressure from the ventilator system. In a volume-cycled ventilator, the reduction in lumen at the point of pooling reduces the volume of gas delivered to the patient since the gas between the ventilator and the pool is compressed and hence, the patient does

40 not receive the proper volume of gas. Furthermore, the compression of the gas is reflected in tubing compliance, or the distention of the tubing as a result of internal pressure and is an important factor in determining the setting of volume-cycled ventilators and is generally compensated for in making the initial settings of the ventilators. The change in volume produced by pooling, however, is not predictable and consequently, cannot be compensated for in the ventilator setting. In presently existing systems, this situation is compensated for by draining the tubing at frequent intervals in order to relieve the pooling problems. It is hence deemed desirable to reduce the amount of condensation in the tubing and one of the purposes of the pres

55 ent invention is to greatly reduce this problem.

Another problem incident to the heat loss of the gases as they travel through the tubing conduit from the humidifier to the patient is that if the temperature of the inhaled gas is below body temperature, there is a

6q tendency of the body of the patient to give up heat to the gas. The heat given up by the patient is energy released as a result of the work by the patient's metabolic system and the continued demand for heat release requires a metabolic system to work harder and this work

65 can become a significant factor in treating a critically ill patient. Additionally, as the temperature of the inhaled gas is raised, through heat loss by the patient, its relative humidity decreases. A humidity deficit in the

6

tube, while at the same time avoiding the possibility of interfering with the sterile condition of the nebulizer or its contents.

Still another feature of the present invention is the provision of an improved humidifier which is provided 5 with an outer jacket surrounding the water chamber and constructed to be in fluid communication with the exhaled gases at the terminal end of the exhalation tube, such that the heat from the exhaled gases may be used to maintain the temperature of the water within 10 the humidifier hence permitting the utilization of the gases within the system, thereby to permit the greatest amount of energy conservation.

Further features of the invention pertain to the particular arrangement of the elements and parts whereby 15 the above outlined and additional operating features thereof are attained.

The invention both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to 20 the following specification, taken in connection with the accompanying drawings in which:

FIG. 1 is a side elevational cross sectional view of the positive pressure breathing system, showing the double tubular concentric orientation of the inhalation and ex- 25 halation lines and the valving system for the circuit, including the inflatable occlusion means and the novel nebulizer means for the invention;

FIG. 2 is a side elevational view, partly in cross section, showing the operation of the inflatable occlusion 30 means incident to the present invention;

FIG. 3 is a side elevational view, partly in cross section, showing the capillary tube system of the nebulizer incident to the present invention;

FIG. 4 is a perspective exploded view showing the pa- 35 tient receiving terminal end of the tubing circuit and the positioning of the nebulizer cartridge with respect to the exhalation tube thereof;

FIG. S is a bottom view showing the shuttering system formed as part of the outer wall of the exhalation 40 tube and showing the shutter in the open position;

FIG. 6 is a bottom view of the tubing circuit, and specifically the outer wall of the exhalation tube, showing the slide mounting means for the nebulizer with the shutter in the closed position occluding the port in fluid communication with the inhalation tube;

FIG. 7 is a top view of the nebulizer cartridge showing the shutter in the open position;

FIG. 8 is a top view of the nebulizer cartridge showing the shutter in the closed position;

FIG. 9 is a side elevational cross-sectional view showing the exhalation tube with the nebulizer cartridge positioned therein in disengageably mounted relationship;

FIG. 10 is a side elevational cross-sectional view showing the gas source end of the circuit and the interconnection thereof with the humidifier for the system;

FIG. 11 is a side elevational cross-sectional view showing one embodiment of the tubing useful in the present invention; 60

FIG. 12 is a side elevational cross-sectional view showing a smooth walled tubing configuration useful within the purview of the present invention, wherein the interior tube includes a helical wire wound thereabout; 6j

FIG. 13 is a side elevational cross-sectional view showing an embodiment of the invention wherein smooth walled tubing is utilized; and

55

FIG. 14 is a perspective view of the system employing the circuit of the present invention and the interconnection thereof with a patient face mask at the patient receiving terminal end and connected to the humidifier at the opposing end of the circuit.

With specific reference to FIG. 1 of the drawings, the details of construction of the double tubular concentrically oriented positive pressure breathing circuit of the present invention is illustrated. The circuit, which is generally referred to by the numeral 10 is shown to consist of an outer exhalation tube 12 and an inner inhalation tube 14. The outer tube 12 is shown to be of smooth walled construction, both along the exterior surface as well as the interior surface, and as illustrated in the preferred embodiment shown in FIG. 1 of the drawings, it is provided with an atomizing channel 16, formed by an outer peripheral wall 17, which together with a portion of the interior wall of the outer tube 12, forms the atomizing channel 16. The outer exhalation tube 12 terminates at a patient terminal end 18 which slip-fits over the exhalation housing member 20. The exhalation housing member 20 is shown to be formed by an outer tube member 21 and an inner tube member 22, the outer exhalation tube 12 slip-fitting over the terminal end of the outer tube member 21, as shown in FIG. 1 of the drawings. Where it is contemplated that the circuit of the present invention is to be formulated for disposable use, the fitting between the outer exhalation tube 12 and the outer tube member 21 of the housing member 20 may be bonded by any suitable means. Where the circuit is intended for reuseable use, the fitting between these two elements may be by way of a friction slip-fit or the like. The atomizing channel 16 extends the entire length of the outer exhalation tube 12 and interconnects with a source of pressurized fluid at the opposed end thereof, the source of pressurized fluid being either extraneous to the system, or forming a separate port in the ventilator.

The inner inhalation tube 14 is similarly shown to be of smooth walled construction and is also shown to have an inflation channel 24 formed by an outer peripheral wall 25, which together with a portion of the interior surface of the wall of the inner inhalation tube 14 forms the inflation channel 24. The inner inhalation tube 14 terminates at a patient terminal end 26 and seals with the inner tube member 22 of the housing member 20. Once again, the inflation channel 24 extends throughout the entire length of the inner inhalation tube 14, and connects at its opposed end with a separate port in the ventilator for providing a source of pressurized fluid for a purpose to be more fully defined hereinafter.

With respect to the exhalation housing member 20, as previously indicated, the member 20 is formed by the outer tube member 21 and the inner tube member 22. The outer tube member 21 also incorporates an housing atomizing channel 28 formed integrally therewith and constructed to matingly engage the atomizing channel 16 of the outer exhalation tube 12 again as depicted in FIG. 1 of the drawings. The housing atomizing channel 28 extends for a distance along the length of the housing member 20 and is turned 90° terminating in an outer peripheral neck 29 to accommodate a tube fitting thereabout. The housing member 20 is shown to be open at its inner end 30 and at the opposed end 31 it is closed by an end wall 32. Finally, the construction of the outer tube member 21 is completed by a circum7

ferential groove 33 accommodating a circumferential shoulder 34 which forms a valve seat as will be more fully explained hereinafter.

The inner tube member 22 is shown to be provided with a housing inflation channel 36, which is constructed to mate with the inflation channel 24 of the inner inhalation tube 14. The housing inflation channel 36 is formed integrally with the inner tube member 22 and terminates in a port 37 which, in turn, establishes fluid communication with an inflation cuff 38, mounted circumferentially about the inner tube member 22. The outer peripheral ends of the cuff 38 are fixedly secured to the outer wall of the inner tube member 22, forming a fluid tight seal such that fluid cannot leak through the seal formed by the outer peripheral ends of the cuff 38. It is apparent that once the circuit is interconnected such that the housing inflation channel 36 is mated with the inflation channel 24 of the inner inhalation tube 14, a fluid flow path is established therethrough, through port 37, such that the inflatable cuff 38 may be inflated by the introduction therein of a fluid under pressure. The inner end 40 of the inner tube member 22 is shown to be open such that open fluid communication is established with the inner inhalation tube 14 when interconnected, and the outer opposed end 41 is shown to extend through an aperture provided in the end wall 32 of the housing 20 and provides a circumferential neck 42 for connection to a patient's face mask or mouthpiece M, as more clearly shown in FIG. 14 of the drawings.

It will also be observed that the inner tube member 22 is provided with a plurality of apertures 44 functioning for a purpose to be more fully described hereinafter. It will further be observed that the inner tube member 22 includes a downwardly depending neck 46 terminating in an atomizing port 47. The lower end of the neck 46 is fixedly secured to the inner surface of the outer tube member 21 in the same manner that the inner tube 22 is fixedly secured through the aperture provided in the end wall 32. Hence, it will be appreciated that the housing member 20 is formed as an integral unit, having the inner tube 22 fixedly secured within the outer tube member 21.

It will further be observed that a portion of the outer tube member 21 is provided with a U-shaped channel 48 (more precisely shown in FIGS. 5 and 6 of the drawings) which functions as the mounting means for mounting the nebulizer onto the outer tube member 21.

Insofar as the valving mechanisms are concerned it will be observed that the inner tube member 22 is provided with a flexible membrane 50 positioned thereabout, the membrane 50 being circumferentially positioned about the inner tube member 22. The membrane 50 forms a valve which seats against the circumferential shoulder 34 such that during the inhalation cycle by the patient negative pressure is created, forcing the membrane 50 against the shoulder 34 in fluid tight relationship. When posiive pressure is exerted against the membrane 50, the membrane 50 will move away from the shoulder 34 and unseat, thereby permitting exhaled gases to flow therethrough.

Insofar as the inner tube member 22 is concerned, an inhalation valve 52 is provided formed by a circumferential ring 53 supporting a frusto-conical central rib member 54 centrally therein. The rib member 54 supports the flexible membrane 55, which is constructed

8

to seat against the inner edges of the ring 53. Hence, when the flexible membrane 55 is seated against the inner edges of the ring 53, the valve member 52 is in the closed position. When gas is passed through the 5 inner inhalation tube 14 and through the inner tube member 22 in the direction of the arrows 56, the flexible membrane 55 unseats from the peripheral edges of the ring 53, thereby permitting the gases to flow through the valve member 52, and on through the inner 10 tube member 22, through the patient face mask M and hence to the patient.

It will be clear from the above description that the valve member 52 and the flexible membrane 50 function as an inhalation valve and an exhalation valve re15 spectively. In other words, as gas is passed through the inner inhalation tube 14, in the direction of the arrows 56, the inhalation valve member 52 opens to permit the inhaled gases through to the patient. Simultaneously, negative pressure is created between the inner tube 20 member 22 and the outer tube member 21, such that the flexible membrane 50 seats against the circumferential shoulder 34, in effect closing the exhalation valve while the inhalation valve member 52 is open. During the exhalation cycle, gases will pass initially into the 25 inner tube member 22, but as the exhaled gases strike against the surface of the flexible membrane 55, the flexible membrane 55 will seat against the outer edges of the ring 53, closing the inhalation valve member 52. As the gases back up, they will flow through the aper30 tures 44 and create positive pressure against the flexible membrane 50. This will then cause the flexible membrane 50 to open, thereby permitting gases to flow through the spacing between the inner tube member 22 and the outer tube member 21. In this manner, unidirectional valve members are established for both the inhalation tube 144 and the exhalation tube 12.

It should be noted that substantially the same effect produced by valve member 52 and membrane 50 may be achieved by location at any point along the exhaled 40 gas path, such as port 107 in FIG. 10, and that the location of valve member 52 and membrane 50 as shown in FIG. 2 is only a preferred location for creating unidirectional flow in the exhalation tube portion of the cir

45 Cuit'

With regard to the inflatable cuff 38, as has been previously described, the inner tube member 22, is provided with the housing inflation channel 36 while the inner inhalation tube 14 is provided with the inflation channel 24. This channel 24 is in turn in fluid communication with a source of pressurized fluid, such as the ventilator provides and during the inhalation cycle when the ventilator cycles on, gases are introduced into the inhalation tube 14, and hence simultaneously down

55 the inflation channel 24. The positive pressure created by the gas through the inflation channel 24 will inflate the cuff 38, thereby assuming the posture shown in FIG. 2 of the drawings. When fully inflated, the cuff will occlude the space between the inner tube 22 and

60 the outer tube 21, and prevent the flow of gas in either direction. Hence, during the inhalation cycle, once the ventilator cycles on and the gas is simultaneously forced down the inhalation tube 14, gas also is forced down the inflation channel 24 to inflate the cuff 38.

6S During this cycle, as previously described, the inflation valve member is open to permit incoming gas to flow to the patient, while the flexible membrane 50 is seated against the shoulder 34, closing the exhalation valve. It