US3512521A - Breath isolator for pulmonary function testing - Google Patents

Description

May 19,1970

Filed Dec. 6, 1965 SPIROMETER 4 w. (LJONES 3,512,521

BREATH ISOLATOR FOR PULMONARY FUNCTION TESTING 2 Sheets-Sheet 1 1 N VEN TOR:

WILLIAM C. JON ES ATT'YS y 19, 1970 w. c. JONES 3,512,521

BREATH I'SOLATOR FOR PULMONARY FUNCTION TESTING Filed Dec. 6, 1965 2 Sheets-Sheet 2 I N VEN TOR:

WILLIAM C. JONES BY United States Patent Office 3,512,521 Patented May 19, 1970 3,512,521 BREATH ISOLATOR FOR PULMONARY FUNCTION TESTING William C. Jones, 16 W. 328 Walnut Lane, Timber Trails, Elmhurst, Ill. 60126 Filed Dec. 6, 1965, Ser. No. 511,721 Int. Cl. A6lb /08 U.S. Cl. 128-2138 8 Claims ABSTRACT OF THE DISCLOSURE A breath isolator adapted to be interposed between a patient and a spirometer during pulmonary function testing. The isolator includes a casing having a chamber which communicates with the spirometer. Within the chamber is a disposable and collapsible breathing bag formed of air-impermeable material and communicating with a tube into which the patient breathes. The bag thereby constitutes an air-impermeable barrier within the chamber, the portion of the chamber outside of the bag constituting a displacement chamber from which air is displaced as a patient breathes into the bag.

This invention relates to a breath isolator for pulmonary function testing, and more specifically, to a device for use in conjunction with conventional pulmonary function testing equipment for isolating a patients breath without at the same time impairing the operation of that equipment.

In my prior Pat. 3,086,515, issued Apr. 23, 1963, I disclose an apparatus for use in measuring a patients breathing, his vital lung capacity, and other pulmonary function characteristics. The apparatus includes a bellows having a breathing tube connected thereto. \As a patient breathes into the tube, the movable wall of the bellows advances and retracts, and a suitable recording device registers the extent of movement on a graph. In function, such an apparatus is similar to a spirometer and, in fact, the term spirometer is commonly used, and shall be used herein, to mean any pulmonary function testing apparatus capable of so recording a patients breathing characteristics, whether such an apparatus utilizes a bellows or a canister partially immersed in a body of liquid.

An important disadvantage in the use of a conventional spirometer arises from the fact that a patient must breathe directly into and from the apparatus. Where the apparatus is to be used in testing successive patients, the dangers of cross-contamination are substantial and may not be completely eliminated even if efforts are made to sterilize the unit between successive tests. In any event, etfective sterilization is a time-consuming operation and therefore, greatly limits the extent of use of such an apparatus in running pulmonary function tests.

Accordingly, it is an object of the present invention to provide a device which eliminates the need for sterilizing a spirometer to protect successive users and to prevent the possibilities of cross-contamination, and which therefore greatly increases the frequency of safe use of such a spirometer. Another object is to provide a device which is intended for use in conjunction with a spirometer and which provides an imperforate barrier between a patients breath and the chamber and operating mechanism of the spirometer.

A further object is to provide a device which provides a positive displacement chamber interposed along the breathing line between a mouthpiece and the expandable chamber of a spirometer. Still another object is to provide means for optionally exerting a positive return pressure on the air in the mouthpiece line, such positive return pressure being desirable or necessary in running inspiraiiry flow rate tests, reciprocable action tests, and the Yet another object is to provide a pulmonary function testing device which isolates a patients breath from a spirometer, and which includes a plastic bag as an imperforate barrier, such bag being intended for disposal after use by a single patient. In this connection, it is a further object to provide a device adapted to accommodate disposable bags of different selected size, depending upon the type of pulmonary function test to be conducted. A still further object is to provide a device which, through its use of disposable bags, greatly reduces the problems of leakage which are otherwise encountered in tests such as helium dilution tests.

Other objects will appear from the specification and drawings in which:

FIG. 1 is a perspective view of a device embodyig the present invention;

FIG. 2 is an exploded perspective view of such a device;

FIG. 3 is a broken side elevational view of the device in one position of use;

FIG. 4 is a side elevational view similar to FIG. 3 but showing the device in a second position of use;

FIG. 5 is an enlarged cross sectional view taken along line 5-5 of FIG. 3;

FIG. 6 is an enlarged sectional view of the detachable fastening means taken along line 66 of FIGURE 5;

FIG. 7 is an enlarged perspective view of the lever means for exerting a positive return pressure on breathing an.

In the embodiment of the invention illustrated in the drawings, the numeral 10 generally designates an elongated canister or easing defining a chamber 11 therein. The side wall 12 of the canister is essentially a tube of generally elliptical or non-circular cross section, the cross section being substantially uniform throughout the entire length of the canister. At opposite ends, the tubular side wall 12 is closed by end walls 13 and 14. A suitable handle 15 may be secured to the side wall to facilitate carrying the unit.

End wall 14 is provided with an opening 16 which communicates with the interior of the canister and which is adapted to receive the end fitting 17 of a hose 18 which conveys air from the device and a conventional spirometer 19. As previously indicated, the spirometer, diagrammatically indicated in FIG. 1, may be of the type disclosed in my prior Pat. 3,086,515, although other types of conventional spirometers may be used.

The end wall 13 at the opposite end of the canister or casing is provided with an enlarged central opening 20 which, in the illustration given, is generally oval or elliptical in shape. The opening'20 is large enough to permit the passage therethrough of a breathing bag 21 as that bag is inserted into or withdrawn from the chamber of the canister. The bag'is substantially identical to the bag disclosed in my co-pending application, now Pat. No. 3,321,976, issued May 30, 1967. It is formed from a polyester film and is completely sealed except for a single reinforced opening 22 in one end thereof. The polyester film, used because of its gas impermeable properties, is relatively hard and non-stretchable. To reinforce opening 22 and to provide an effective means for sealingly connecting the bag within the canister and for sealingly attaching such bag to a mouthpiece tube 23, a patch 24 is laminated on the bags surface. The patch is formed from a resilient and slightly elastic plastic material such as poly-vinyl chloride and is provided with an opening of a diameter slightly smaller than the outside diameter of breathing tube 23. The patch is sealed to the bag by heat sealing or by suitable adhesives in the zone immediately adjacent the periphery of opening 22. As shown in FIGS. 2 and 5, the outermost portions of the patch remain unsealed to the bag.

Insertion of the breathing tube 23 into the bag through opening 22 causes a stretching of the patch about the surface of the tube, and it has been found that such stretching action results in an effective air-tight seal between the bag and the inserted mouthpiece tube.

It is essential in operation of the device that the space within chamber 11 outside of bag 21 be completely sealed except for opening 16 which communicates with the spirometer. Means must therefore be provided for sealing the enlarged opening 20 in end wall 13 against the leakage of air from that portion of the chamber disposed outside of bag 21. In the illustration given, such means comprises a closure assembly 25.

The closure assembly comprises a pair of inner and outer clamping plates 26 and 27 having aligned central openings 28 and 29. Openings 28 and 29 are slightly larger in diameter than the diameter of bag opening 22 and breathing tube 23, but are smaller in diameter than the smallest outer planar dimensions of patch 24. As indicated in FIGURES 2 and plate 27 is larger than plate 26 and, adjacent its outer periphery, is provided with fastening elements 30 which are capable of engaging and tightly clamping the assembly against end wall 13.

In the illustration given, each fastening element comprises a rotatable member 31 which extends through an opening in plate 27 and which is provided at its inner end with laterally projecting lugs 32. A cup-shaped member 33 extends inwardly through the opening in the plate to the extent permitted by an annular flange 34 which bears against the plates outer surface. Lateral slots 35 permit the arms or lugs 32 of the rotatable member to project outwardly from the cup-shaped member, and a retaining ring 36 disposed along the inner surface of the clamping plate holds the members 31 and 33 in operative position. A spring 37 extends between the inner end of the cup-shaped member and the end of rotatable member 31, and urges the rotatable member outwardly in a direction away from chamber 11.

As shown most clearly in FIG. 2, the outer surface of canister end wall 13 is provided with apertured fasteners 38, the apertures having lateral extensions which permit the reception of the inner ends of fastening members 31 when the lugs or arms 32 are in alignment with such extensions. Thus, attachment of the closure assembly to the canister is achieved simply and quickly by aligning the parts and then urging the wing-headed fastener members 31 inwardly against the force of springs 37 until lugs pass inwardly through the extensions of the apertures, and thereafter rotating the fastening members to lock the parts together. Since springs 37 are under compression when the parts are so assembled, considerable force is maintained to prevent leakage between end wall 13 and the closure assembly.

Leakage is further prevented by the provision of a resilient sealing gasket 38 along the inner surface of clamping plate 26. When the parts are assembled, the gasket, which may be formed of sponge rubber or any other suitable material, tightly and sealingly engages the outer surface of end wall 13.

In assemblying the parts, the flexible patch 24 of the bag is first inserted outwardly through the opening 28 in clamping plate 26. The two clamping plates are then brought together to tightly sandwich the patch therebetween, the bag is inserted into the canister through end wall opening 20, and the wing-headed fasteners are adjusted to secure the closure assembly in place. Breathing tube 23 is then fitted through plate opening 29 into opening 22 of the bag. The sealing relationship between the tube and the bag effectively prevents the leakage of air between the breathing bag and a patient, and the closure assembly 25 prevents the escape of air from the chamber (but outside of bag 21) through opening 20.

A lever assembly 39 is disposed within chamber 11 to exert a gentle and substantially uniform collapsing force against bag 21 during those pulmonary function tests (such as inspiratory flow rate tsets, or reciprocable action tests) in which a moderate positive return pressure is necessary or desirable. The assembly comprises a pair of elongated levers 40 and 4.1 which are disposed in sideby-side reversing relation and which have a pair of ends pivotally linked together. Lever 41 is slightly longer than lever 40 and has its opposite end pivotally secured to the inner surface of casing .10 adjacent end plate 13.

When the casing or canister is in the normal position illustrated in FIG. 3, the lever assembly 39 is rendered inoperative. Levers 40 and 41 simply rest on the bottom inside surface of the canister beneath bag 21. Thus, when the canister is in its normal position, no significant back pressure is created. In the normal operation of the device, as in running single forced expiratory tests, a positive back pressure is generally considered unnecessary and undesirable.

In those tests where positive return pressure is desirable, the canister is simply inverted into the position illustrated in FIG. 4. The lever assembly 39 then acts as an automatic bag deflator. The weight of the arms causes them to pivot downwardly about the point of pivotal connection between arm 41 and canister 10, bringing arm 40, adjacent its point of pivotal connection to arm 41, into contact with the distal end of bag 21. In addition, arm 40, which rests upon the bag, pivots about its point of connection with arm 41 to engage substantially the entire length of the bag and expel, under gentle positive pressure, most of the air within the bag. Since the combined weight of both arms is applied primarily to the distal end portion of the bag, there is no danger that the deflating means will tend to close off a portion of the bag adjacent end plate 13 and breathing tube 23 before the more distal portions of the bag are deflated.

In use, the parts are assembled as already described, and a patient breathes into bag 21 through breathing tube 23. As the bag expands, air is displaced from chamber 11 through opening 16 which communicates with the spirometer. The only air which passes to the spirometer is air disposed within chamber 11 outside of bag 21. Therefore, even if the patients breath is contaminated, the interior surfaces of the canister and the surfaces of the spirometer remain protected. There is no danger of cross contamination between successive users of the device because after each use, the parts are disassembled and bag 21 is discarded, a new bag and mouthpiece tube 23 being used for each patient.

It has been found that a bag having a maximum capacity of six liters is sufficiently large for practically all pulmonary function tests. It is believed apparent that for proper operation of the device, such a bag should be elongated to fit easily within chamber 11, having a length which constitutes at least a major portion of the length of that chamber, and that the size of the chamber should be in excess of the maximum size of the bag. An advantage of the present invention lies in the fact that bags of a wide variety of sizes within the range of 1 to 10 liters may be used and, to provide adequate versatility, the size of chamber 1.1 should therefore fall within the range of 11 to 13 liters. Preferably, the size of the chamber should be 1 to 2 liters larger than the bag, to reduce any cushioning effect resulting from excessive volume differential; therefore, if bags of only 6 liter capacity are to be used, the optimum volume of the chamber should be approximately 7-8 liters.

With respect to the use of bags of different sizes, it should be mentioned that while a bag having a capacity of 6 liters is generally suitable for lung volume tests, bags of different sizes are preferable for other types of tests. For example, a smaller bag would be desirable in conducting helium dilution or residual volume tests, because a smaller volume of diluted helium in the bag will result in a more accurate estimate of the residual volume of a patients lungs after an equilibrium of gases within the bag has been achieved. Also, the smaller size of the bag further reduces the possibilities of leakage with a gas such as helium, which has a greater capacity than other gases to pass through films or other membranes. In the past, when helium dilution tests have been run without using the structure of the present invention, an appreciable leakage of helium through the bellows of spirometers has been observed. Since the structure of the present invention in effect isolates breathing air from the air being directly measured by the spirometer, the helium does not pass to the spirometer but is instead confined in bag 21, breathing tube 23, and the patients lungs, with the result that the problems of leakage which have been heretofore encountered are eliminated or substantially reduced.

The bag 21 has been described as being formed of a gas impermeable plastic film. It is to be understood, however, that substantially all plastic films are permeable to gases to a slight extent. Such slight permeability has no appreciable adverse effect on the effectiveness of the structure described herein because of the short duration of the testing period and because of the insignificantly low gas diffusion rate involved. It is important to note, however, that respiratory pathogens such as bacteria, virus, etc., are vastly larger than the gas molecule. Consequently, the plastic film of the bag is an effective barrier against the various respiratory pathogens.

While in the foregoing I have disclosed an embodiment of the invention in considerable detail for purposes of illustration, it will be understood by those skilled in the art that many of these details may be varied without departing from the spirit and scope of the invention.

I claim:

1. A breath isolator for pulmonary function testing having two positions of operation, comprising a casing defining a chamber therein and having a pair of openings in wall portions thereof, means for connecting one of said openings to a breathing tube and for connecting the other of said openings to a tube for conveying air between said chamber and a spirometer, a collapsible breathing bag formed of thin, flexible, air-impermeable and generally inelastic material disposed within said chamber, said bag having an opening therein and being detachably sealed about said bag opening to said one opening of said casing, whereby, said bag comprises an air-impermeable barrier within said chamber between said openings of said casing, and said chamber outside of said bag constitutes a displacement chamber from which air is displaced through said other of said openings as a patient breathes into said bag, and bag deflating means disposed within said casing and comprising a lever assembly mounted for movement under the influence of gravity to engage and exert a deflating force upon said bag when said casing is oriented in a first position with said lever assembly disposed above said bag, said lever assembly being inoperative to exert a deflating force on said bag when said casing is oriented in a second position.

2. The structure of claim 1 in which said lever assembly comprises a pair of levers hingedly connected at their ends and extending one over the other, one of said levers having an opposite end hingedly secured to said casing at a point above said bag when said casing is in said first position.

3. The structure of claim 1 in which said casing chamber and said bag are elongated, said lever assembly comprising an elongated first lever pivotally connected at one end thereof to said casing at a point above said bag when said casing is in said first position, said first lever having its opposite end pivotally connected to an elongated second lever disposed between said first lever and said bag and engaging said bag to exert a deflating force against the same when said casing is in said first position.

4. The structure of claim 3 in which said first elongated lever is pivotally connected to said casing at a point above said bag and adjacent said one opening of said casing, said elongated levers extending generally longitudinally With respect to said elongated bag.

5. A breath isolator for pulmonary function testing, comprising a casing defining a chamber therein and having a pair of openings in Wall portions thereof, means for connecting one of said openings to a breathing tube and for connecting the other of said openings to a tube for conveying air between said chamber and a spirometer, and a collapsible breathing bag formed of thin, flexible, air-impermeable material disposed within said chamber, said bag having an opening therein and being detachably sealed about said bag opening to said one opening of said casing, whereby, said bag comprises an air-impermeable barrier within said chamber between said opening of said casing, and said chamber outside of said bag constitutes a displacement chamber from which air is displaced through said other of said openings as a patient breathes into said bag, said bag being provided with a flexible patch sealed to the bag about the opening thereof and having peripheral portions unsecured to said bag, said casing including a closure assembly detachably secured thereto about said one opening thereof and sealingly engaging the peripheral portions of said patch.

6. The structure of claim 5 in which said closure assembly comprises a pair of clamping plates having aligned apertures therein, said apertures being larger than the opening of said bag but smaller than the dimensions of said patch, said bag extending through one of said plates and having the patch thereof clamping between said plates.

7. The structure of claim 6 in which the clamping plate through which said bag extends is provided with a resilient gasket sealingly engagable with the outer surface of said casing, and fastening means provided by said closure assembly and said casing for detachably securing the parts together.

8. The structure of claim 7 in which means are provided within said chamber for urging said bag into collapsed condition, said means comprises a pair of elongated members arranged in side-by-side relation within said chamber, one of said members being pivotally connected at one end thereof to the inner surface of said casing adjacent said one opening of said casing and being pivotally connected at its other end to the other of said members, said other of said members being adapted to rest upon said bag when said casing is oriented so that said members are positioned above said bag.

References Cited UNITED STATES PATENTS 2,591,120 4/1952 Blease 128-1455 2,904,034 9/1959 Haupt 128-1455 3,037,497 6/1962 Roberson 128-1455 3,158,152 11/1964 Bloom 128-1455 3,304,939 2/1967 Manley 128-145] FOREIGN PATENTS 1,207,372 8/1959 France.

RICHARD A. GAUDET, Primary Examiner K. L. HOWELL, Assistant Examiner

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