Underwater Drainage Apparatus With Air Flow Meters

Abstract

An underwater drainage apparatus is provided for evacuating fluids from body cavities and comprises an integrally formed collection chamber, underwater seal chamber and a pressure regulating manometer chamber. Air flow meters are provided in the underwater seal chamber and the pressure regulating chamber for measuring the flow of gasses there through. A valve is provided between the underwater seal and the collection chamber to permit high negative pressures to be developed in the pleural cavity when required by the patient.

Parent Case Text

FIELD OF THE INVENTION

This invention relates to underwater drainage apparatus of the type disclosed in our prior U.S. Pat. Nos. 3,363,626 and 3,363,627 and in patent application Ser. No. 734,645 filed June 5, 1968, now U.S. Pat. No. 3,559,647 issued Feb. 2, 1971, the present invention being a continuation-in-part of the aforesaid prior patent application.

Description

BACKGROUND OF THE INVENTION

Prior U.S. Pat. Nos. 3,363,626 and 3,363,627, both issued Jan. 16, 1968 disclose and claim an underwater drainage apparatus which is constructed as a one piece unitary device having a collection chamber, underwater seal chamber and pressure regulating manometer chamber. There is also provided an underwater seal saver which prevents the loss of the underwater seal during conditions of high negativity in the patient's pleural cavity. This device also provides an indicator so that the physician can readily ascertain whether such high negativity conditions occurred.

In prior application Ser. No. 734,645, now U.S. Pat. No. 3,559,647 issued Feb. 2, 1971, there is disclosed an improved underwater drainage apparatus which incorporates all of the advantages of the prior patents hereinbefore referred to and provides a unique construction in the pressure regulator manometer to prevent the loss of water due to bubbling through the manometer chamber. In addition such prior patent provides air flow meters which measure the flow rate of air through the pressure regulator monometer and through the underwater seal.

Problems have arisen in the measurement of air flow through the pressure regulator manometer and through the underwater seal chamber with the air flow meters disclosed in U.S. Pat. 3,559,647 referred to herein above. Such air flow meters are provided with a series of apertures and as air flow through the manometer or underwater seal increases the air passes upwardly through additional apertures. However, it has been found that the air flow cannot always be regulated so that it flows through sequential apertures as the flow increases. That is to say, the air bubbles sometimes tend to pass down the passageway to an aperture intended to measure a substantially greater air flow. Thus, it is difficult at times to accurately measure the air flow with the meters so constructed.

Another 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 patient's breathing efforts. That is to say, if there is a blockage in the patient's bronchial tubes, the patient must make a strong respiratory effort 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.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a new and improved underwater drainage apparatus which overcomes the problems referred to herein in the use of previous underwater drainage apparatus.

According to the present invention there are provided air flow meters in the underwater seal and in the pressure regulator manometer, these meters being of an improved design to provide a more accurate means of measuring air flow through the water seal and through the pressure regulator manometer. This is achieved by an air flow meter of unique design having a passageway which is inclined downwardly from the point where the air enters the meter. Disposed above the downwardly extending passageway is a series of chambers having apertures therein to permit the passage of air upwardly there through. The first chamber and aperture for passage of air through the flow meter is located directly above the point at which air enters the meter. Thus, the first air flow through the meter will always pass through the first chamber and aperture of the air flow meter. As the air flow increases the air bubbles must pass along the downwardly extending passageway and as these bubbles are constantly seeking to rise through the liquid they will pass upwardly through the next chamber and aperture in the sequence of passageways through the air flow meter. Means are provided in the air flow meter for maintaining the bubbles in alignment with the passageways which they pass through so that the number of passageways through which gasses are passing can be readily determined. In this manner the gas flow through the underwater seal and through the pressure regulator manometer may be accurately determined.

In the passageway interconnecting the collection chamber and the underwater seal there is provided a cylinder valve which is normally open to permit the passage of gasses from the pleural cavity through the underwater seal. However, during conditions of high negativity in the pleural cavity the water in the underwater seal rises through this passageway and in so doing raises the cylinder valve to close the passageway thus maintaining the high negativity in the pleural cavity. The cylinder valve is so designed that it will move to the closed position in response to hydraulic pressure but will not be moved from its open position in response to the passage of gasses through the passageway interconnecting the collection chamber and the underwater seal nor will it close due to differences in gas pressures within the passageway.

It is a primary object of the present invention to provide an improved underwater drainage apparatus.

It is a further object of this invention to provide a drainage apparatus in which air flow meters are provided which accurately measure the passage of air through the pressure regulating manometer and through the underwater seal.

It is still another object of the present invention to provide in an underwater drainage apparatus a means for maintaining a high negative pressure within the pleural cavity when such conditions arise.

Other objects and many of the attendant advantages of the present invention will become apparent from the detailed description that follows with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

There follows a detailed description together with accompanying drawings of a preferred embodiment of the invention. However, it is to be understood that the invention in capable of numerous modifications and variations apparent to those skilled in the art within the spirit and scope of the invention.

In the drawings:

FIG. 1 is a sectional view through the center plane of an underwater drainage apparatus constructed according to the present invention.

FIG. 2 is a sectional view along the lines 2--2 of FIG. 1.

FIG. 3 is a perspective view of the valve and the casing for the valve.

FIG. 4 is a sectional view along the lines 4--4 of FIG. 1.

FIG. 5 is a perspective view of the air flow meter.

FIG. 6 is a top plan view of the air flow meter shown in FIG. 5.

FIG. 7 is a sectional view along the lines 7--7 of FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings there is shown an improved drainage apparatus 10 constructed in accordance with the present invention. The apparatus may be formed from two separate sections, one section being molded with all of the chambers and walls formed therein and the other section being a flat sheet which is secured to the first section along all walls. Alternatively, the apparatus could be molded in two separate halves, the mold for each half being identical with the halves joined together along the center plane.

Referring now to FIG. 1 there is shown an improved underwater drainage apparatus and having a collection or trap chamber 11, an underwater seal chamber 12 comprising a first column 12a and a second column 12b. There is also provided a pressure regulator chamber 13 having a first column 13a and a second column formed in two portions 13b and 13c. The apparatus is completely enclosed except for an opening 14 from the collection chamber 11 which opening is adapted to be connected to the pleural cavity of the patient, an opening 15 adapted to be connected to a vacuum source and an opening 16 which is open to atmosphere from the pressure regulator chamber 13.

One feature of the present invention is the provision of a pediatric collection compartment which is formed by a partition 20 in the main collection chamber 11. The angled upper end portion 20a of the partition 20 reflects the liquid entering through opening 14 into the pediatric collection compartment 21. The compartment 21 is of a relatively small cross section so that the amounts of liquid collecting therein can be readily measured in increments of one cubic centimeter. In a preferred embodiment of the invention this compartment will hold 250 cubic centimeters after which additional liquid will flow over the upper end portion 20a of the partition 20 into the adjacent chamber 22 and when chamber 22 is filled the liquid will flow over the upper end of partition 23 into compartment 24. As is more clearly shown in FIG. 2 the partitions 20 and 23 are formed by the walls of that portion of the unit in which the chambers are formed being secured directly to the back face of the flat member 25 forming the other portion of the unit.

The underwater seal chamber 12 is formed with columns 12a and 12b, these columns being separated by a partition element 26 which is formed as shown in FIG. 2 by securing wall portion 26 directly to the flat member 25.

At the upper end of column 12b there is provided an enlarged reservoir 35 which has a recessed lower end portion 36. This structure provides a water seal saver and tell tale as described in our prior U.S. Pat. No. 3,363,627.

There is also provided at the upper end of column 12b a means for preventing the water forming the underwater seal from rising in column 12b. This means comprises a cylindrical check valve 37 the structure of which is more clearly shown in FIG. 3. There is provided a chamber 38 which is offset with respect to column 12b and this chamber has a lower wall 39 and an upper wall 40 having an aperture 41 therein. The edge 42 of the upper wall 40 and the side edges 43 and 44 of chamber 38 are secured directly to the rear face of member 25 so that only entry into chamber 38 is through column 12b and through aperture 41. Within chamber 38 there is provided a cylindrical valve member 45 having a height slightly less than the length of the chamber 38 as shown more clearly in FIG. 1. Normally the valve 45 rests on the bottom 39 of chamber 38. However, during conditions of high negativity within the patient's pleural cavity such that liquid from the water seal rises in column 12b to pass into chamber 38, valve 45 floats and rises within chamber 38 to close off aperture 41, thus preventing the liquid from the water seal from rising into chamber 35. In this manner the high negative pressure which the patient has built up in the pleural cavity which the patient may require in order to fully expand the lung is permitted to be maintained. When the high negative pressure in the pleural cavity is reduced, the water within chamber 38 returns to the water seal at the lower end of column 12b, thus permitting the valve 45 to return to its position on the bottom wall 39 and normal operation of the device is resumed. It has been found that scoring lines (not shown) across the upper surface of valve 45 prevents the valve from sticking in the upper position closing off aperture 41.

At the lower end of column 12a of the underwater seal chamber 12 the cavity is enlarged as shown at 12c and within this enlarged cavity there is provided an air flow meter 46. The air flow meter measures the amount of air passing from the pleural cavity through the opening 14 into the collection chamber 11 and downwardly through column 12b and upwardly through column 12a to the vacuum pump. The air flow meter provides means for accurately measuring the quantity of air passing through the underwater seal and for conveniently determining whether this air flow is increasing or decreasing. This determination would be significant for diagnosing a patient's condition suffering, for example, from a bronchopleural fistula. The details of construction of the air flow meter are shown in greater detail in FIG. 5 to 7 inclusive. The meter is provided with a rear wall 47 and a front wall 48 having a common duct or passageway 49 formed therein. Front wall 48 and rear wall 47 have an integral connecting portion 50 which forms the upper wall of passageway 49. Connecting portion 50 has a series of apertures 51a, 51b...51i and beneath each of these apertures there is formed in portion 50 a separate and independent plenum chamber 52. The lower end of each plenum chamber connects with the common passageway 49. Disposed above and separating each of the apertures 51a, 51b....51i is a partition member 53.

The air flow meter 46 is disposed within the underwater seal chamber at the lower end thereof between the columns 12a and 12b with the duct 49 extending at a slight angle to the horizontal. The lower wall of duct 49 is cut away beneath the aperture 51i and its plenum chamber 52 so that this passageway is disposed in the path of flow and directly above passageway 12e forming the end of the curved end portion of column 12b. Thus gasses passing downwardly along column 12b will flow upwardly through passageway 12e into plenum chamber 52 and its associated aperture 51i. By inclining the passageway 49 as shown greater volumes of gasses will pass through succeeding apertures in sequence. Thus, the air flow meter 46 provides a means for measuring the quantity of gasses passing from the patient's pleural cavity. For example, aperture 51i measures a volume of gas flow of from 0 to 2 liters per minute. Aperture 51h measures a gas flow of from 2 to 4 liters per minute. The last aperture 51a measures a gas flow in excess of 28 liters per minute.

It has been found that the angle at which the air flow meter is disposed within the underwater seal chamber is important for proper operation of the meter. Angles of from 7.degree. to 13.degree. to the horizontal have been found generally satisfactory with best results being obtained where the duct 49 extends at an angle of 10.degree. with respect to the horizontal. It has also been found that the dimensions of the apertures 51a, 51b...51i are critical and these values have been empirically determined to be as follows:

Underwater Seal Air Flow Meter

Aperture Size Volume (Inch) (measured liters per minute) __________________________________________________________________________ 51a .120 28- 51b .120 22-28 51c .120 16-22 51d .120 10-16 51e 0.63 8-10 51f 0.73 6-8 51g .073 4-6 51h .078 2-4 51i .070 0-2 __________________________________________________________________________

The partitions 53 provide a means for separating the bubbles passing through each of the apertures so that the number of passageways through which gas is passing can be readily determined.

The pressure regulator manometer 13 is formed with a first column 13a having its upper end exposed to atmosphere and a second column which comprises portions 13b and 13c. The upper ends of columns 13b and 13c are connected via passageway 54 with the vacuum source through opening 15. The purpose of portions 13b and 13c is to confine the bubbles rising through the chamber to the portion 13b so that liquid rising with the air bubbles will engage the baffle 55 which will serve to deflect the liquid downwardly into portion 13b or 13c after which the gas may continue its upward movement through passageway 54 to the opening 15.

In practice, water will flow clockwise around the partition separating column 13b and 13c forming "racetrack" like path of water. Much of the water engaging the baffle 55 will flow into portion 13c.

It can be seen that with the arrangement shown the portion 13c provides a relatively calm body of liquid as compared with the portion 13b which may be bubbling vigorously. Consequently, the level of liquid in the second column of the pressure regulator chamber 13 can be readily determined by noting the level of liquid in portion 13c.

In the event that some liquid does flow upwardly past the baffle 55 it will be engaged by a second baffle 56.

At the lower end of the column 13b there is provided an air flow meter 57. This air flow meter 57 is identical to the air flow meter 46 previously described except with respect to the size of the apertures therein. The aperture 51i' is located directly above and in the path of flow of the passageway 13e which is the end of the lower upturned end portion of passageway 13a. The common duct in the lower end portion of the air flow meter 57 is disposed at an angle of from 7.degree. to 13.degree. to the horizontal with best results being obtained at an angle of 10.degree.. The hole sizes for the air flow meter are as follows:

Pressure Regulator Air Flow Meter

Aperture Size Volume (Inch) (measured liters per minute) __________________________________________________________________________ 51a' .147 38- 51b' .128 32-38 51c' .128 26-32 51d' .120 20-26 51e' .120 16-20 51f' .093 12-16 51g' .101 8-12 51h' .101 4-8 51i' .116 0-4 __________________________________________________________________________

The basic operation of the apparatus 10 is similar to the basic operation of the apparatus as described in prior U.S. Pat. Nos. 3,363,626 and 3,363,627. The improvements described in the present invention have not changed this basic operation. Rather, they have been designed for the purpose of increasing the efficiency, controllability and applicability of the present type of apparatus. The effect that each of these individual features has on the basic operation is believed to be clear from the preceeding description of these structional elements. However, for purposes of convenience, the operation of the invention will be briefly summarized.

When the apparatus is to be used with a vacuum pump, an amount of liquid is introduced into the pressure regulator chamber 13 through opening 16 which will give the desired vacuum after the pump is turned on. Because of the relative sizes of column 13a on the one hand and 13b and 13c on the other hand, the water may be filled to the level of the desired degree of vacuum as once the vacuum pump is operated and column 13a evacuated, the water level will not change significantly. The desired amount of liquid is introduced through opening 15 into the underwater seal chamber and the opening 15 is then connected to the vacuum pump. Opening 14 is connected to the pleural cavity of the patient and the vacuum pump is started. The liquid is evacuated from column 13a and air bubbles through the pressure regulator chamber 13b to maintain the vacuum within the device at the water level set. Any liquid rising through the pressure regulator chamber with the air bubbles will engage the baffle 55 and fall downwardly into portion 13c. The liquid in the underwater seal chamber will rise in column 12a and any air or gasses within the pleural cavity will pass downwardly through column 12b and through air flow meter 46.

Any fluid (gasses and liquids) coming from the patient's pleural cavity enter the apparatus through opening 14. Liquids fall into the collection chamber 11 and gasses pass through the underwater seal column 12b and 12a. Initially liquids from the pleural cavity fill the compartment 21 and subsequently overflow into compartment 22 and compartment 24.

When the pressures within the pleural cavity reach a very high negativity as, for example, when the patient attempts to expand the lungs but some blockage exists in the bronchial passages, the pressures within the collection chamber 11 may be reduced below the pressure within the column 12a. Consequent1y, the liquid in seal chamber 12 will rise rapidly in column 12b. As described in prior U.S. Pat. No. 3,363,627 the water seal saver chamber 35 prevents this liquid from passing into the collection chamber 11. However, in accordance with a further feature of this invention the valve 37 operates to close off the passageway from collection chamber 11 to column 12b and thus permits the patient to maintain the high negative pressure within his pleural cavity which is necessary to expand the lungs.

When normal breathing is resumed the valve 37 will return to its open position and permit communication between the chamber 11 and column 12b and the water within the water seal saver chamber 35 will pass downwardly into the underwater seal except for a small portion within the depressed part 36 which will remain to indicate to the attending physician that such a condition of high negativity has existed.

The air flow meters 46 and 57 give a clear indication of the degree of gasses passing through the underwater seal and pressure regulator chamber respectively. If gas is passing through all of the apertures in the air flow meter 46 and no air flow is indicated in the meter 57, the physician is aware that the leakage in the patient's pleural cavity is completely overcoming the pump and than an emergency condition exists. The physician can determine improvement in the patient by noting decreased gas flow through meter 46 from day to day and the particular air flow meter provided according to the present invention gives an exceedingly accurate measurement of such gas flow.

If desired, a valve and housing structure similar to valve 37 could be located within column 13a. This valve would normally be open to permit passage of air downwardly through passageway 13a. However, when very high positive pressure develops in the patient's pleural cavity caused, for example, by a coughing spell, the water in the pressure regulator manometer rises in column 13a to close the valve. Otherwise the water in the pressure regulator manometer would pass outwardly through opening 16.

It is possible to use the air flow meters 46 and 57 and/or the valve 37 in connection with conventional one, two or three bottle systems. The air flow meter and a check valve similar to valve 37 may be made as separate units and installed in the tubing connecting conventional bottle systems. For example, in a single bottle system a check valve similar to valve 37 may be inserted between the patient and the collection chamber. This would permit flow of fluid from the patient to the collection chamber but the valve would close upon the development of high negativity in the pleural cavity to prevent the return of fluids to the pleural cavity. In a two bottle system the check valve could be installed between the collection chamber and water seal bottle to prevent loss of the water seal during periods of high negativity. Similarly an air flow meter similar to meter 46 could be mounted in fluid in or adjacent to the water seal to measure gas flow from the pleural cavity.

Although the invention has been described in considerable detail in respect to a preferred embodiment thereof, it should be apparent that the invention is capable of numerous modifications and variations which are readily apparent to those skilled in the art without departing from the spirit or scope of the invention as defined in the appended claims.

Claims

We claim:

1. In a drainage device for draining fluids from a cavity comprising an inlet opening adapted to be placed in communication with the cavity to be drained, a collection chamber in fluid communication with the inlet opening, a seal chamber having first and second columns in fluid communication with each other at the lower ends thereof, the upper end of the first column being in fluid communication with the collection chamber, the upper end of the second column being in fluid communication with a preselected fluid pressure level, said chamber adapted to receive a body of liquid within the first and second columns, and air flow measuring means disposed in said seal chamber, said air flow measuring means including a series of independent gas passageways and a common duct extending beneath said passageways, the gas passageway at one end of said measuring means being disposed immediately above and in the path of fluid flow from the connection of said first column to said second column and said common duct extending angularly downwardly across said second column.

2. In a drainage device according to claim 1 wherein each of said independent gas passageways of said air flow measuring means includes a plenum chamber disposed adjacent said common duct and an aperture of a diameter less than said plenum chamber at the upper end of said plenum chamber providing communication between said plenum chamber and said second column.

3. In a drainage device according to claim 2 wherein the apertures of said independent gas passageways are of varying diameter.

4. In a drainage device according to claim 3 and further including walls extending upwardly between said apertures forming separate passages in said second column for each of said independent gas passageways.

5. In a drainage device according to claim 4 wherein said column duct extends angularly downwardly across said second column at an angle to the horizontal of between 7.degree. and 13.degree..

6. In a drainage device for draining fluids from a cavity comprising an inlet opening adapted to be placed in fluid communication with the cavity to be drained, a vacuum opening adapted to be placed in fluid communication with a vacuum source and with the inlet opening for drawing fluid from the cavity into the device, a manometer for regulating the vacuum, said mano-meter comprising first and second columns in fluid communication with each other, said manometer adapted to receive a body of liquid within the first and second columns, the first column being exposed to atmosphere and the second column being exposed to the vacuum source, and air flow measuring means disposed in said manometer for measuring the air flow from said first column into said second column, said air flow measuring means including a series of independent gas passageways and a common duct extending beneath said passageways, the gas passageway at one end of said measuring means being disposed immediately above and in the path of fluid flow from the connection of said first column to said second column and said common duct extending angularly downwardly across said second column.

7. In a drainage device according to claim 6 wherein each of said independent gas passageways of said air flow measuring means includes a plenum chamber disposed adjacent said common duct and an aperture of a diameter less than said plenum chamber at the upper end of said plenum chamber providing communication between said plenum chamber and said second column.

8. In a drainage device according to claim 7 wherein the apertures of said independent gas passageways are of varying diameters.

9. In a drainage device according to claim 8 and further including walls extending upwardly between said apertures forming separate passages in said second column for each of said independent gas passageways.

10. In a drainage device according to claim 9 wherein said common duct extends angularly downwardly across said second column at an angle to the horizontal of between 7.degree. and 13.degree..

11. In a drainage device for draining fluids from a cavity comprising an inlet opening adapted to be placed in communication with the cavity to be drained, a collection chamber in fluid communication with the inlet opening, a seal chamber having first and second columns in fluid communication with each other at the lower ends thereof, the upper end of the first column being in fluid communication with the collection chamber, the upper end of the second column being in fluid communication with a preselected fluid pressure level, said seal chamber adapted to receive a body of liquid within the first and second columns, and valve means disposed in said first column, said valve means closing the fluid communication between said first column and the collection chamber in response to a predetermined fluid pressure differential between the cavity to be drained and the second column of the seal chamber.

12. In a drainage device for draining fluids from a cavity comprising an inlet opening adapted to be placed in communication with the cavity to be drained, a collection chamber in fluid communication with the inlet opening, a seal chamber having first and second columns in fluid communication with each other at the lower ends thereof, the upper end of the first column being in fluid communication with the collection chamber, the upper end of the second column being in fluid communication with a preselected fluid pressure level, said seal chamber adapted to receive a body of liquid within the first and second columns, and valve means disposed in said first column, said valve means closing the fluid communication between said first column and the collection chamber in response to liquid rising in said first column from the seal chamber to move said valve means upwardly.

13. In a drainage device according to claim 12 wherein said valve means comprises a cylinder within a valve chamber having a restricted aperture at the upper end thereof, said cylinder having a weight sufficient to rest at the lower end of the valve chamber and maintain said aperture open during normal operation of said device and to float upwardly to close said aperture when the pressure differential between the cavity and the second column is sufficient to cause the liquid within the seal chamber to rise into the valve chamber.

14. In a drainage device for draining fluids from a cavity comprising an inlet opening adapted to be placed in communication with the cavity to be drained, a collection chamber in fluid communication with the inlet opening, a seal chamber having first and second seal columns in fluid communication with each other at the lower ends thereof, the upper end of the first seal column being in fluid communication with the collection chamber, the upper end of the second seal column being in fluid communication with a preselected fluid pressure level, said seal chamber adapted to receive a body of liquid within the first and second seal columns, first air flow measuring means disposed in said seal chamber, said air flow measuring means including a series of first independent gas passageways and a first common duct extending beneath said passageways, the gas passageway at one end of said measuring means being disposed immediately above and in the path of fluid flow from the connection of said first seal column to said second seal column and said first common duct extending angularly downwardly across said second seal column, a vacuum opening in said drainage device adapted to be placed in fluid communication with a cacuum source and with the inlet opening for drawing fluid from the cavity into the device, a manometer for regulating the vacuum, said manometer comprising first and second manometer columns in fluid communication with each other, said manometer adapted to receive a body of liquid within the first and second manometer columns, the first manometer column being exposed to atmosphere and the second manometer column being exposed to the vacuum source, and second air flow measuring means disposed in said manometer for measuring the air flow from said first manometer column into said second manometer column, said second air flow measuring means including a series of second independent gas passageways and a second common duct extending beneath said passageways, the gas passageway at one end of said measuring means being disposed immediately above and in the path of fluid flow from the connection of said first manometer column to said second manometer column and said second common duct extending angularly downwardly across said second manometer column.

15. In a drainage device for draining fluids from a cavity comprising an inlet opening adapted to be placed in communication with the cavity to be drained, a collection chamber in fluid communication with the inlet opening, means forming a water seal chamber in communication with said collection chamber, and air flow measuring means for measuring the air flow from the collection chamber through the water seal chamber, said air flow measuring means including a series of independent gas passageways and a common duct extending beneath said passageways, said common duct extending angularly downwardly along the path of the air flow from the collection chamber through the water seal chamber.

16. In a drainage device according to claim 15 wherein each of said independent gas passageways of said air flow measuring means includes a plenum chamber disposed adjacent said common duct and an aperture of a diameter less than said plenum chamber at the upper end of said plenum chamber.

17. In a drainage device for draining fluids from a cavity comprising an inlet opening adapted to be placed in communication with the cavity to be drained, a collection chamber in fluid communication with the inlet opening, means forming a water seal chamber in communication with said collection chamber, a pressure regulator chamber in communication with the water seal chamber, and air flow measuring means for measuring the air flow through the pressure regulator chamber, said air flow measuring means including a series of independent gas passageways and a common duct extending beneath said passageways, said common duct extending angularly downwardly along the path of the air flow through the pressure regulator chamber.

18. In a drainage device according to claim 17 wherein each of said independent gas passageways of said air flow measuring means includes a plenum chamber disposed adjacent said common duct and an aperture of a diameter less than said plenum chamber at the upper end of said plenum chamber.

19. In a drainage device for draining fluids from a cavity comprising an inlet opening adapted to be placed in communication with the cavity to be drained, a collection chamber in fluid communication with the inlet opening, a water seal chamber, a passageway interconnecting the collection chamber and water seal chamber, and valve means disposed in said passageway, said valve means being normally open and closing said passageway when water from said water seal chamber rises in said passageway.

20. In a drainage device for draining fluids from a cavity comprising an inlet opening adapted to be placed in communication with the cavity to be drained, a collection chamber in fluid communication with the inlet opening, a water seal chamber, a pressure regulator chamber, passageways interconnecting the collection chamber and water seal chamber and interconnecting the water seal chamber and pressure regulator chamber, a passageway to atmosphere in the pressure regulator chamber, and valve means in said passageway to atmosphere, said valve means being normally open and closing said passageway in response to water rising in said passageway from the pressure regulator chamber.

21. In a drainage device for draining fluids from a cavity comprising an inlet opening adapted to be placed in communication with the cavity to be drained, a collection chamber, a fluid passageway in fluid communication with the inlet opening and the collection chamber to receive fluids drained from the cavity and means in said fluid passageway for preventing the flow of fluid into the cavity during conditions of high negativity within the cavity, said means comprising a chamber with a restricted aperture at the upper end thereof and a valve within said chamber, liquid seal means disposed in said device on the side of said valve away from said cavity to prevent atmospheric pressure from reaching said cavity, said valve having a weight sufficient to rest at the lower end of the valve chamber and maintain said aperture open during normal operation of said device and to float upwardly to close said aperture when the pressure differential between the collection chamber and the cavity is sufficient to cause liquid fluid to rise within the passageway.