US3809085A - Surgical drainage system - Google Patents

Abstract

A surgical drainage system including a container for collecting fluid drained from a cavity, such as a pleural cavity, and a drainage tube for placing the container in fluid communication with a cavity to be drained, is provided with a check valve in the drainage tube. The check valve permits the flow of fluid from the cavity to the container and prevents the flow of fluid in the opposite direction thus permitting the development of a high negative pressure in the cavity. The check valve comprises an elongate tapered tube which can be positioned inside the drainage tube with its wide end towards the cavity. The tapered tube is provided with an elongate slot lengthwise of the tube to form a liquid flow passage, the edges defined by the slot being sufficiently flexible to permit fluid to pass outwardly therethrough and to close on being subjected to a negative pressure within said tapered tube to permit the development of a high negative pressure therein.

Description

United States Patent [191 Bidwell et al.

[111 3,809,085 [451 May7, 1974 [22] Filed:

[ SURGICAL DRAINAGE SYSTEM [73] Assignee: Deknatel, Inc., Queens Village,

Long Island, N.Y.

May 23, 1972 21 Appl. No.: 256,158

[52] U.S. Cl. 128/275, 128/276 [51] Int. Cl.A6lf 5/44, A61In 1/00 [58] Field of Search 128/274-278, 128/D1G. 24, 348-350; 137/525.1

[56] References Cited UNITED STATES PATENTS 614,968 11/1898 Mohs 137/525.l 1,326,966 1/1920 Reeves.... 137/525.1 3,020,913 2/1962 Heyer 128/350 V 3,463,159 8/1969 Heimlich 128/275 3,559,647 2/1971 Bidwell et a1. 128/276 3,583,401 6/1971 Harris et a1. 128/275 3,589,392 6/1971 Meyer l37/525.1

Primary Examiner- Charles F. Rosenbaum Attorney, Agent, or Firm-Larson, Taylor and Hinds [57] ABSTRACT A' surgical drainage system including a container for collecting fluid drained from a cavity, such as a pleural cavity, and a drainage tube for placing the container in fluid communication with a cavity to be drained, is provided with a check valve in the drainage tubeJThe check valve permits the flow of fluid from the cavity to the container and prevents the flow of fluid in the opposite direction thus permitting the development of a high negative pressure in the cavity. The check valve comprises an elongate tapered tube which can be positioned inside the drainage tube with itswide end towards the cavity. The tapered tube is provided with an elongate slot lengthwise of the tube to form a liquid flow passage, the edges defined by the slot-being sufficiently flexible to permit fluid to pass outwardly therethrough and to close on being subjected to a negative pressure within said tapered tube to permit the development of a high negative pressure therein.

16 Claims, 21Drawing Figures SHEEI 2 0F 2 PATENTEDIAY 7 1914 FIG. 12A FIG {28 BACKGROUND OF THE INVENTION This invention relates to surgical drainage apparatus. More particularly, the invention relates to such apparatus including a collection chamber and a drainage tube for placing the container in fluid communication with a cavity to be drained. Still more particularly, the invention relates to such apparatus wherein the collection chamber is maintained under a negative pressure to assist drainage of said cavity. In one aspect the invention relates to a check valve for such apparatus and, in another aspect, to such drainage apparatus including the check valve.

Surgical drainage devices are utilized to drain a cavity, such as a pleural cavity. A known device is illustrated in US. Pat. No. 3,559,647 issued Feb. 2, 1971 and incorporated herein by reference. The device therein disclosed includes a collection chamber, an underwater seal chamber, and a pressure regulating chamber.

A problem which has arisen in connection with the use of underwater drainage apparatus is in providing means which will permit the patient to develop high negativity in the pleural cavity when such condition is necessary for the patients breathing efforts. 'That is to say, if there is a blockage in the patients bronchial tubes, the patient must make a strong respiratory efiort in order ,to expand the lungs and permit air to flow around this blockage into the lung cavity. In doing this the rib cage is expanded so as to produce a very high negativity in the pleural cavity. However, prior types of underwater drainage apparatus will defeat such respiratory efforts by permitting the air to be drawn back into the pleural cavity from the drainage apparatus. Thus, it has been found desirable to provide some means to prevent the back flow of gasses from the underwater drainage apparatus to the pleural cavity during such conditions of high negativity so as to permit the negative pressures to develop in the pleural cavity necessary for an inspiratory effort.

It is an object of the present invention to provide a new and improved drainage apparatus which overcomesthe problem referred to herein in the use of previous underwater drainage apparatus.

It is a further object of the present inventionto provide a new and improved check valve for use in such drainage apparatus. 7

SUMMARY OF THE INVENTION The foregoing and other objects which will be apparent to those having ordinary skill in the art are achieved according to the present invention by providing a surgical drainage system comprising a collection chamber, a drainage tube adapted to place the chamber in fluid communication with a cavity to be drained, and a check valve located in said drainage tube to permit the passage of fluid from said cavity to said collection chamber and to prevent the passage of fluid from said collection chamber to said cavity to permit the development of high negative pressure in said cavity, said check valve being positioned within said drainage tube and comprising an elongate tapered tube the wide portion of said tapered tube being positioned in saiddrainage tube towards said cavity, the narrow portion of said tapered tube being positioned towards said collection chamber, said tapered tube including an elongatedslot lengthwise of the tube to form a liquid flow passage, the length of said slot being at least twice the width of said tapered tube at its widest part, the edges defined by said slot being sufficiently flexible to permit fluid drained from said cavity to pass therethrough and to close on being subjected to low pressure inside said tapered tube to permit development of a high negative pressure in said cavity. I I

BRIEF DESCRIPTION OF THE DRAWINGS There follows a detailed description of a preferred embodiment of the invention, together with accompanying drawings. However, it is to be understood that the detailed description and accompanying drawings are provided solely for the purpose of illustrating a preferred embodiment and that the invention is capable of numerous modifications and variations apparent to those skilled in the art without departing from the spirit and scope of the invention. v

FIG. 1 is a cross sectional view of an underwater drainage apparatus of the type shown in U.S. Pat. No. 3,559,647;

FIG. 2 is a sectional front elevation of a check valve according to the present invention and shown positioned in a drainage tube;

FIG. 3 is a right side elevation of the check valve of FIG. 2; I

FIGS. 4A-D are sectional views taken along lines AA, BB, CC, and DD, respectively, of FIG. 3;

FIG. 5 is a schematic front elevation of an alternative valve according to the invention;

FIG. 6 is a schematic left side view of the valve of FIG. 5; t

FIGS. 7A, B and C are schematic sectional views along the lines AA, BB, CC and DD, respectively, of FIG. 6; i

FIGS. 8A and 8B are schematic sectionalviews of the valve of FIGS. 5 taken approximately along the lineBB and showing the valve in,respectively, closed and open position; v

FIG. 9 is a schematic front elevation of an alternative valve according to' the invention;

FIG. 10 is a schematic left side view of the valve of FIG. 9; r I

FIGS. 11 A, B and C are schematic sectional views along the lines AA, BB, CC and DD, respectively, of FIG. 9; and

FIGS. 12A and B are schematic sectional views of the valve of FIG. 9 taken approximately along the line BB and showing the valve in, respectively, closed and open positions.

Referring now to FIG. 1 there is shown anunderwater drainage apparatus 10 having a "trap chamber 11, anunderwater seal chamber 12 comprising afirst column 12a and asecond column 12b, and apressure regulator chamber 13 having afirst column 13a and a second column formed in two portions, namely 13b and 13c. The apparatus is completely enclosed except for anopening 14 adapted to be connected to the pleural cavity of the patient by means of tube 14a anopening 15 adapted to be connected to a vacuum source by means oftube 15a and anopening 16 to atmosphere.

One feature of the illustrated device is a pediatric uid into thepediatric collection compartment 21. The main feature ofcompartment 21 is that it is of a small enough cross section so that the amount of liquid collecting therein can be readily determined in increments of 1 cubic centimeter. In a typical embodiment this compartment will hold 250 cubic centimeters of liquid after which additional liquid will simply flow over theupper portion 20a and into the main portion of the trap chamber 1 l which would normally be designed to hold approximately 3,000 centimeters.

Trap chamber 11 is also provided with a solid crossrib designed to strengthen the trap chamber to prevent implosion. Thisrib 24 separates the bottom of the trap chamber into twoparts 23a and 23b. 23a would fill up first after which further liquid would flow over 24 to 23b.

Theunderwater seal chamber 12 is formed bypartitions 30, 31 and 32 which form first andsecond columns 12a and 12b communicating through passage 33 at their lower ends.

At the upper end ofcolumn 12a there is provided an enlarged reservoir 35 with a recessed bottom 36. These elements serve the same purpose as the enlarged reservoir and recess shown in previous US. Pat. No. 3,363,627.

The device includes agas flow meter 45 for determining the flow rate of gas passing through the underwater seal chamber- Obviously, for gas to flow upwardly incolumn 12b, the level of liquid in 12a must be at the bottom thereof. The flow meter comprises a series of openings formed in theweb partition member 47;

Thecolumn 12b includes an enlarged reservoir area 120 to hold the water in the underwater seal in the event of violent bubbling of air throughcolumn 12b, as might occur in the case of a very large bronchlpleural fistula.

The portion of the apparatus to the left of partitionv 32 (as shown in FIG. 1) represents thepressure regulator chamber 13 having afirst column 13a with its upper end exposed to atmosphere and a second column which comprises twoportions 13b and 13c, each of which is exposed at its upper end to the pressure atvacuum opening 15. Thus, the upper ends ofportions 13b and 13c, together with the upper portion ofcolumn 12b form a common space exposed to the pressure atvacuum opening 15.

An important feature of the device also includes a meter which clearly and visually shows the rate of airflow upwardly through the second column of the pressure regulator chamber. This flow meter comprises a web partition member extending across the flow meter and having formed therein a plurality of airflow holes 51a, 51b, 51c, and 51d.

The upper end ofcolumn 13a includes a funnel shapedopening 52 to facilitate placing water into the pressure regulator chamber. There is also formed arelief opening 53 to assure continued communication betweencolumn 13a and the atmosphere in the event that theopening 16 becomes obstructed.

The basic operation of the apparatus is similar to the basic operation of the apparatus as described in previous US. Pat. Nos. 3,363,626 and 3,363,627. When the apparatus is to be used as a three-bottle apparatus, an amount of liquid is introduced into thepressure regulator chamber 13 throughopening 16 which will give the desired vacuum after the pump is turned on, and a desired amount of liquid is introduced into theunderwater seal chamber 12 throughopening 15.Opening 14 is then connected to the pleural cavity of the patient andopening 15 is connected to a vacuum pump. The pump is then turned on gradually as the liquid rises in the second column of the pressure regulator chamber (portions 13b and 13c). As the capacity of the vacuum pump increases, the liquid rises inportions 13b and 13c until all of the liquid is contained in these portions. A further increase in the capacity of the pump will cause air bubbles to be drawn through opening 51a into theportion 13b and hence through theopening 15 to the vacuum pump. Any liquid rising with the bubbles will engage a baffle and fall downwardly. Meanwhile the liquid in the underwater seal chamber may rise incolumn 12b in which case bubbles will flow upwardly through an opening inmember 47 to theopening 15 and hence to the vacuum pump.

The fluids (gases and liquids) coming from the patient enter theapparatus 10 atopening 14. Liquids fall into thecompartment 21 as gases pass through the opening 34 and hence to the underwater seal chamber. Once thechamber 21 has been filled, additional liquid entering theopening 14 flows over theupper portion 20a of thepartition 20 into the firstmain portion 23a of trap chamber 11. When this fills, further liquid will flow over 24 into 23b.

If compliance occurs within the pleural cavity of the patient, the absolute pressure in the trap chamber 11 couldbe reduced far below the absolute pressure in the vicinity ofopening 15. Consequently, the liquid inseal chamber 12 will rise rapidly incolumn 12a. As described in previous US. Pat. No. 3,363,627, the compliance chamber 35 prevents much of this liquid from passing to the opening 34. However, the spray of liquid carried upwardly by the bubbles will engage separation chamber 39 where it will lose its momentum and fall downwardly back to thecolumn 12a or to the area 35.

When the patient is breathing normally, the liquid levels in the two legs of the underwater seal chamber will fluctuate in response to pressure fluctuations in the pleural cavity associated with normal breathing assuming of course, that there is a sufficient amount of water in the underwater seal chamber so that bubbling does not commence when the pressure in the pleural cavity reaches its maximum value. With this in mind, it can be seen that these fluctuations serve as a diagnostic tool to indicate the presence of conditions such as emphysema and asthma which require that the patient work harder (create a greater negative pressure in the pleural cavity) in order to cause expansion of the lung. These conditions will be indicated by a larger than normal' rise of the liquid inthe leg of the underwater seal chamber in communication with the trap chamber during inspiration.

The normal or steady state operation of the apparatus has been described above. Assume, now, however, that the negative pressure, or the compliance, within the pleural cavity of the patient increases drastically. This causes the. pressure in chamber 11 to be reduced drastically thus pulling the water inseal chamber 12 upwards incolumn 12a. This may cause a loss of water seal in which event chamber 11 is placed in direct communication withchamber 13. The patient is working to create a negativity in the pleural cavity which is higher than that prevalent inchamber 13. Thus, when the .water seal is lost, the patients ability to create a high negativity in the pleural cavity is impaired. While this is a problem in the device described, it is more severe in a device not operating with vacuum. In this type of device,column 12b ofwater seal chamber 12 is open to atmospheric pressure. If the water seal is lost due to high negativity,'the pleural cavity will be exposed to atmospheric pressure and the patients lung might collapse.

In order to preventthis occurrance, it has been proposed to provide a check valve between the water seal chamber and the collection chamber such that when a condition of high negativity exists in the pleural cavity, the check valve will close and prevent the loss of a water seal. Where thereis no high negativity in the pleural cavity, the check valve remains open thus permitting normal operation of the water seal. It will be recognized that in this arrangement, during a condition of high negativity, the pleural cavity is in communication with the collection chamber and connecting tubing. The patient must work against this large dead space to create high negativity in the pleural cavity.

- According to the present invention, a check valve is provided in a drainage tube between the cavity to be drained and the collection chamber. The check valve is preferably located close to the cavity to reduce the dead space. In addition to minimizing the dead space, a check valve according to the present invention has several additional inherent advantages. For example, the valve opening through which the drained fluids pass is large relative to the size of the drainage tube in which it is placed thus presenting a minimum resistance to fluid flow. Further, the tendency of the valve members to adhere after prolonged use is reduced. This is a particularly severe problemdue to the adhesive nature of the fluids being drained.

I In accordance with thepresent invention, theopening 64 for the passage'of liquids is large relative to the size of the device and relative to the size of the drainage tube. This is accomplished by providingelongate slot 64 along taperedtube 61 in the manner shown.Slot 64 extends diagonally across the tube in which it is positioned. Preferably,slot 64 extends diagonally across the tube from a point nearthe widest portion of the tapered tube adjacent a wall of the: tube to a point near the narrowest portion of the tube adjacent the tube wall. With reference to FIG. 2, it will be seen that liquid being drained will causeflexible edges 65, 66 to part along the length ofslot 64. Therefore, the opening which edges 65, 66 may assume is potentially huge relative to the size of the device and of the drainage tube. It will therefore be seen that by providing theslot 64 in a tapered tube in this manner, it is possible to provide a check valve with reduced resistance to flow.

Resistance to flow is further reduced in this embodiment'by providing a recessed portion 16' indrainage tube 16 to accommodatecheck'valve 60. The inside dimensions of thewide portion 62 of taperedtube 61 is A check valve according to the present invention is shown in FIG. 2 positioned in adrainage tube 16 connected to collection container10 of FIG. 1. While, in this embodiment, the collection container includes a water seal chamber and operates under suction, it will be apparent that thedevice can be operated without suction, in which case'column 27 ofwater seal chamber 12 isopento atmosphere. Similarly, the device may be operated without a water seal in which case collection chamber 11 isopen to atmosphere or to a regulated pressure. In any event, the surgical drainage system includes collection chamber 11 placed in fluid communication with a cavity to be drained by adrainage tube 16 such as a thoracotomy tube used for draining a pleural cavity.Che'ckvalve 60 comprises an elongate taperedtube 61positionedin drainage tube 16 with itswide portion 62 towards said pleural cavity and itsnarrow portion 63 towards collection chamber 11.Tapered tube 61 includes anelongate slot 64 lengthwise of the tube to form a liquid flow passage, the length of the slot being at least twice the width of thewidest portion 62 of taperedtube 61. Theedges 65, 66 defined byslot 64 are sufficiently flexible to permit fluid drained from the pleural cavity to pass therethrough and to close on being subjected to low pressure within the tube to permit development of a high negative pressure in the pleural cavity. Theedges 65, 66 of taperedtube 61 and the tube wall adjoining those edges are fabricated from conventional elastorn'er rubber, or other flexible material such as silicone rubber. Preferably, theelongate tube 61 is fabricated from such flexible material.

chosen to be at least as large as the inside dimensions ofdrainage tube 16 and the tube portion 16' is sized to accommodate the outer dimensions ofcheck valve 60. In this'case, the upper portion ofcheck valve 60 is cylindrical and has the same inside diameter and wall thickness asdrainage tube 16. Tube portion 16' is thus cylindrical and has an inside diameter slightly larger than that of the wide portion ofcheck valve 61 and larger than the outside diameter ofdrainage tube 16. Checkvalve 60 is conveniently positioned intube 16 by means of adhesive 68 located around the upper cylindrical portion ofcheck valve 60. Tube 16' is conveniently secured totube 16 by means of adhesive 69 or I by rubber connectors of the like.

In order to further minimize resistance to fluid flow, the taper oftube portion 61 is offset with respect to a longitudinal axis passing through thewide portion 62 of the tube. This is most easily seen with reference to F IG, 2. There the tube is viewed normal to a plane passing throughslot 64 and a line lengthwise of the tube at 71 on thetube wall oppos'ite'slot 64. When viewed in that direction, the left side wall is not tapered and the right side wall is tapered diagonally across the inside oftube 16.Slot 64 thus extends diagonally across the inside of the drainage tube. In this embodiment,slot 64 is a straight line. However, the slot can be curved such as by providingtube 61 with a non-linear taper. In either event, however, it is preferred that the valve slot ex,- tends along the tapered portion of the check valve from a point near the widest point oftapered tube 61 to a point near the narrowest point thereof.Tapered tube 61 is sized to accommodate aslot 64 having a length at least twice thewidest portion 62 of the tapered tube. Still more preferably,slot 64 is at least three times as long and is conveniently up to six or more times as long.

longed use. While the contact meant the valve of FIG.

2 is small relative to other check valves, it is reduced still further according to the invention in the embodiments depicted in FIGS. -12.

In FIG. 5, taperedtube 72 is similar to taperedtube 61 except that the tube is circular in cross section along its length (see FIGS. 7A, B and C) and alongitudinal sealing member 73 is located just inside theslot 74 formed byedges 75, 76 (FIG. 8B) of the tube wall. Sealing member 73 (shown schematically in FIG. 5) is conveniently a cylindrical rod of a rigid material such as plastic, glass; or the like, fixed in position intube 72 just behindslot 74 in any convenient way such as by being inserted into pockets provided for the purpose intube 72, by being molded into the tube, or by adhesives or the like. When liquid drains through the valve, edges 75, 76 easily extend to the position shown in FIG. 8B thus providing an opening which is large relative to the tube diameter. When the tube is subjected to reduce pressure, the edges are brought together in essentially edge to edge contact thus reducing the contact area to a minimum. The walls which are preferably very pliant to permit fluid flow and to close on a reduction in pressure, are prevented from inward collapse bymember 73.

In the embodiment shown in FIGS. 9-l2,tube 80 is tapered similarly as in the embodiments of FIGS. 2 and 5 such that aslot 81 extends diagonally across the inside of a tube in which the valve is located. However,slot 81 is fabricated from a tapered tube generally circular in section, the slot being formed by slitting the tube lengthwise and positioning edges 82, 83 thus formed adjacent the inner surface of the tube wall at apoint 84 generally opposite the lengthwise slit as shown in FIG. 12A. When liquid flows intotube 80 from the cavity being drained, the tube walls uncurl to the position shown in FIG. 128, thus separatingedges 82, 83 from the inner wall of the tube to form a slot for the passage of liquid.

As shown in the drawings, the tapered tube portion of the check valve according to the invention may take several forms in section such as oval, circular, or U- shaped as shown and others that will be apparent to those having ordinary skill in the art. Where the section is oval, as in the embodiment of FIG. 2, the slot is preferably located at an apogee thereof. i

What is claimed is:

1. A surgical drainage system comprising a collection chamber, a drainage tube adapted to place the chamber in fluid communication with a cavity to be drained, and a check valve located in said drainage tube to permit the passage of fluid from said cavity to said collection chamber and to prevent the passage of fluid from said collection chamber to said cavity to permit the development of high negative pressure in said cavity, said check valve being positioned within said drainage tube and comprising an elongate tapered tube having a wide portion and a narrow portion, the wide portion of said tapered tube being positioned in said drainage tube towards said cavity, the narrow portion of said tapered tube being positioned towards said collection chamber, said tapered tube including an elongate slot lengthwise of the tube between said wide portion and said narrow portion to form a liquid flow passage, the length of said slot being at least twice the width of said tapered tube at its widest part, the edges defined by said slot being sufficiently flexible to permit fluid drained from said cavity to pass therethrough and to close on being subjected to low pressure inside said'tapered tube to permit development of a high negative pressure in said cavity. v

2. A surgical drainage system according to claim 1 wherein said elongate tube comprises a flexible material.

3. A surgical drainage system according to claim 1 wherein said elongate tube is generally oval in section, said slot being located .at an apogee thereof.

4. A surgical drainage system according to claim 1 wherein said tube comprises an elongate member fixed inside said tube adjacent said slot.

5. A surgical drainage system according toclaim 4 wherein said. tube is generally circular in section.

6. A surgical drainage system according to claim 1 wherein said tube is fabricated from a tapered tube generally circular in section, said slot being formed by slitting the tube lengthwise and positioning the edges thus formed adjacent the inner surface of the tube wall at a point generally opposite the lengthwise slit.

7. A surgical drainage system according to claim 1 wherein said drainage tube includes a compartment having an inside diameter larger than the inside diameter of said drainage tube, said tapered tube being positioned within said compartment, the inside diameter of the wide portion of said tapered tube being at least as large as the inside diameter of said drainage tube.

8. A drainage system according to claim .1 wherein said device includes means for maintaining a reduced pressure in said chamber. v

9. A surgical drainage system according to claim 1 wherein said tapered tube is tapered such that when the tube is viewed from a direction normal to a plane passing through said slot and a line lengthwise of the tube on the tube wall opposite said slot, the tube wall at said slot tapers inwardly and the tube wall opposite said slot is not tapered whereby said slot extends diagonally across the inside of a drainage tube in which it is placed.

10. A check valve for a surgical drainage system comprising an elongate tapered tube having a length at least twice the wide portion of said tube, said tapered tube having a wide portion and a narrow portion, said tapered tube including an elongate slot lengthwise of the tube between said wide portion'and said narrow portion to form a liquid flow passage through said check valve in a direction from the inside of said tube to the outside thereof, the length of said slot being at least twice the width of said tube at its widest part, the edges defined by said slot being sufficiently flexible to permit fluid to pass outwardly therethrough and to close on being subjected to a low pressure within said tapered tube to permit the development of a high negative pressure therein.

1 1. A check valve according to claim 10 wherein said elongate tube comprises a flexible material.

12. A check valve according to claim 10 wherein said elongate tube is generally oval in section, said slot being located at an apogee thereof.

13. A check valve according to claim 10 wherein said tube comprises an elongate member fixed inside said tube adjacent said slot.

14. A check valve according to claim 10 wherein said tube is generally circular in section. I

15. A check valve according to claim 10 wherein said tube is fabricated from a tapered tube generally circular in section, saidslot being formed by slitting the tube lengthwise and positioning the edges thus formed adjapoint generthe tube wall opposite said slot, the tube wall at said slot tapers inwardly and the tube wall opposite said slot is not tapered whereby said slot extends diagonally across the inside of a drainage tube in which it is placed.

Claims (16)

1. A surgical drainage system comprising a collection chamber, a drainage tube adapted to place the chamber in fluid communication with a cavity to be drained, and a check valve located in said drainage tube to permit the passage of fluid from said cavity to said collection chamber and to prevent the passage of fluid from said collection chamber to said cavity to permit the development of high negative pressure in said cavity, said check valve being positioned within said drainage tube and comprising an elongate tapered tube having a wide portion and a narrow portion, the wide portion of said tapered tube being positioned in said drainage tube towards said cavity, the narrow portion of said tapered tube being positioned towards said collection chamber, said tapered tube including an elongate slot lengthwise of the tube between said wide portion and said narrow portion to form a liquid flow passage, the length of said slot being at least twice the width of said tapered tube at its widest part, the edges defined by said slot being sufficiently flexible to permit fluid drained from said cavity to pass therethrough and to close on being subjected to low pressure inside said tapered tube to permit development of a high negative pressure in said cavity.

2. A surgical drainage system according to claim 1 wherein said elongate tube comprises a flexible material.

3. A surgical drainage system according to claim 1 wherein said elongate tube is generally oval in section, said slot being located at an apogee thereof.

4. A surgical drainage system according to claim 1 wherein said tube comprises an elongate member fixed inside said tube adjacent said slot.

5. A surgical drainage system according to claim 4 wherein said tube is generally circular in section.

6. A surgical drainage system according to claim 1 wherein said tube is fabricated from a tapered tube generally circular in section, said slot being formed by slitting the tube lengthwise and positioning the edges thus formed adjacent the inner surface of the tube wall at a point generally opposite the lengthwise slit.

7. A surgical drainage system according to claim 1 wherein said drainage tube includes a compartment having an inside diameter larger than the inside diameter of said drainage tube, said tapered tube being positioned within said compartment, the inside diameter of the wide portion of said tapered tube being at least as large as the inside diameter of said drainage tube.

8. A drainage system according to claim 1 wherein said device includes means for maintaining a reduced pressure in said chamber.

9. A surgical drainage system according to claim 1 wherein said tapered tube is tapered such that when the tube is viewed from a direction normal to a plane passing through said slot and a line lengthwise of the tube on the tube wall opposite said slot, the tube wall at said slot tapers inwardly and the tube wall opposite said slot is not tapered whereby said slot extends diagonally across the inside of a drainage tube in which it is placed.

10. A check valve for a surgical drainage system comprising an elongate tapered tube having a length at least twice the wide portion of said tube, said tapered tube having a wide portion and a narrow portion, said tapered tube including an elongate slot lengthwise of the tuBe between said wide portion and said narrow portion to form a liquid flow passage through said check valve in a direction from the inside of said tube to the outside thereof, the length of said slot being at least twice the width of said tube at its widest part, the edges defined by said slot being sufficiently flexible to permit fluid to pass outwardly therethrough and to close on being subjected to a low pressure within said tapered tube to permit the development of a high negative pressure therein.

11. A check valve according to claim 10 wherein said elongate tube comprises a flexible material.

12. A check valve according to claim 10 wherein said elongate tube is generally oval in section, said slot being located at an apogee thereof.

13. A check valve according to claim 10 wherein said tube comprises an elongate member fixed inside said tube adjacent said slot.

14. A check valve according to claim 10 wherein said tube is generally circular in section.

15. A check valve according to claim 10 wherein said tube is fabricated from a tapered tube generally circular in section, said slot being formed by slitting the tube lengthwise and positioning the edges thus formed adjacent the inner surface of the tube wall at a point generally opposite the lengthwise slit.

16. A check valve according to claim 10 wherein said tapered tube is tapered such that when the tube is viewed from a direction normal to a plane passing through said slot and a line lengthwise of the tube on the tube wall opposite said slot, the tube wall at said slot tapers inwardly and the tube wall opposite said slot is not tapered whereby said slot extends diagonally across the inside of a drainage tube in which it is placed.

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