DE3485891T2 - DRAINAGE DEVICE WITH SUCTION OR FREE DRAIN. - Google Patents

Description

Field of the invention

This invention relates to a drainage device for draining fluid from the body, in particular from the thoracic cavity of the human body.

Background of the invention

The artificial drainage of excess fluids from the body is necessary for the well-being of the patient in a variety of medical treatments, before and after operations, and when the body cannot naturally eliminate such fluids. The fluids to be drained include blood, water and air.

A wide variety of drainage devices have been developed to drain wounds and larger body cavities. These devices generally include a chamber for collecting fluid and an inlet tube for connecting the patient to the chamber. In use, fluids are drained from the patient through the inlet tube into the collection chamber, which is located below the patient to avoid the fluids being returned or sucked back to the patient. Drainage may be effected by gravity, since the chamber is located below the patient, or more effectively by applying suction to an outlet from the collection chamber to suck the fluid into the chamber.

Various surgical procedures on the chest or heart, as well as traumatic wounds such as bullet or stab wounds, cause accumulation of fluids such as blood, water or air in the cavities of the chest or thorax. In the thoracic cavity between the lungs and the surrounding chest wall, such accumulation can impair breathing and cause death by preventing the normal pressure exchange in the thoracic cavity that supports normal lung function. In the thoracic cavity, accumulation of fluid such as blood can prevent healing and recovery of the patient.

In the case of a continuous leak of air into the chest cavity, for example from a ruptured blister - a pustule on the lung - the pressure in the cavity builds up until a tension pneumothorax is caused. Then the affected lung collapses or even both lungs collapse and the patient can suffocate if the air is not released from the chest cavity.

The design of a drainage device for the chest or thoracic cavity presents special problems. To be effective, the drainage device must remove fluids promptly and effectively and prevent their return. It is essential to have unidirectional flow, not only to isolate the patient from the atmosphere to avoid infection, but also to prevent fluid, particularly air, from accumulating in the chest cavity and allowing the lungs to collapse.

The simplest form of such a drainage device comprises a single bottle partially filled with water, which serves as a water-sealing chamber. The bottle has an inlet tube extending from the patient below the water level, and an outlet tube communicating with the air space above the water. This is a rudimentary arrangement, which provides no control or indication of the pressure in the collection chamber. As the withdrawn material gradually fills the bottle, the resistance to drainage increases. To improve this design, a plurality of bottles have been used, connected in series between the patient and a source of suction. Usually three bottles are used: the first, connected to the patient as a drain, collects the fluids; the second, partially filled with water, forms the seal; and the third acts as a pressure regulator, having a tube open to the atmosphere and extending to below the water in the bottle. The depth of this tube below the water level determines the maximum amount of suction that can be through the system because once sufficient suction is achieved to draw air through the tube from the atmosphere and bubble it through the water, increasing the suction level only increases the rate of bubbles and as a result the suction level of the device is limited. However, the arrangement of separate bottles is cumbersome and inconvenient to use and it is very difficult to clean for reuse. This has led to the construction of a variety of one-piece, sterilizable and disposable drainage devices.

US Patent 2,936,757 discloses such a device in the form of a disposable, flexible plastic bag having internal pockets to maintain the water seal and having access tubes extending into these pockets. Unfortunately, the bag contains a vent to the atmosphere which can lead to intoxication of the patient. A flexible material is unsuitable for a drain with a water seal because shock of the device can displace the water and interrupt the use of the drain.

U.S. Patents 3,363,626, 3,363,627, 3,559,647, 3,683,913 and 3,853,128 show the development of a rigid, disposable plastic drainage device which has adapted the three-bottle arrangement into a unitary structure. Each device according to these patents has a fluid collection chamber, a U-shaped water seal compartment and a U-shaped water gauge compartment for suction control. The fluid collection chamber is typically divided into three graduated compartments which fill sequentially during use as the amount of fluid being drained accumulates.

A drainage device incorporating a water seal takes a relatively long time to operate because the device must be supplied with a certain volume of sterile water to create the seal and to fill the U-shaped chamber. This volume of water is relatively large and usually more than one chamber must be filled. Also, the amount of suction that can be applied to a water seal system is limited by the depth of water in the pressure regulating chamber, as mentioned above. The maximum suction that can be applied to commercial water seal containers is about 30 cm of water, since a much longer pressure control chamber is very cumbersome and expensive to manufacture. This is unsatisfactory since suction up to about 60 cm of water is sometimes required.

Furthermore, a drainage device with a water seal is relatively heavy and large, which is a disadvantage both for the hospital staff and for the patient, who often has to hold the device when being moved. Another major disadvantage is the relatively complex instructions required for its use, which can lead to errors and wasted time.

In attempts to overcome these disadvantages, some waterless devices have been developed. US Patent 3,830,328 discloses a simple arrangement which is a single chamber waterless device comprising an inlet tube having a one-way valve to prevent fluid flow back to the patient and a bellows arrangement to roughly measure the pressure in the chest cavity. But this device does not control or allow pressure changes in the chamber.

A newer device without a water seal was manufactured by Davol Inc. under the trademark Thoraklex and includes a chamber for collecting drained fluids fed to the chamber through an inlet having a U-tube within the chamber for holding a small amount of water to indicate an air leak in the system and an outlet to the suction side via a one-way valve. A rubber stopper in the wall of the U-tube provides access for a syringe needle to withdraw fluid from the tube for analysis. The outlet port is connected to atmosphere via a one-way vent to provide a positive pressure relief valve. The outlet is also provided with a negative pressure control consisting of a screw for adjustably closing the outlet passage to regulate the degree of suction. The outlet also includes a float ball gauge calibrated to indicate the suction applied to the patient and connected between the atmosphere and the outlet. This device includes an over-negative pressure relief valve which vents to atmosphere at a preset negative pressure to prevent the vacuum from reaching too high a level. This valve is located in a passageway between the atmosphere and the collection chamber and includes a spring-loaded one-way valve. Since actuation of the valve allows air from the atmosphere to enter the collection chamber which is open to the patient, it is necessary to place a filter in the passageway. This device suffers from the disadvantage that the suction level in the collection chamber can build up rapidly as the valve opens and although the filter is designed to prevent bacteria from entering the chamber the arrangement of the valve opening directly into the chamber further exposes the patient to the risk of infection and also increases the manufacturing costs of this device. A device of this design is also disclosed in British patent application GB 2 082 071 A.

There is therefore a need for a drainage device that avoids the disadvantages of devices with water seals, and yet functions reliably and safely. The device must be capable of applying stable and acceptable suction levels to the patient when operating under vacuum drainage. In its broadest aspect, the present invention aims to provide such a drainage device that also overcomes the aforementioned disadvantages of the prior art.

According to the invention there is provided a device for draining fluid from a cavity in the body of a patient as defined in claim 1.

The means for venting the outlet may comprise a seal across an opening in the outlet to the atmosphere, a spring biasing the seal to close the opening, and a screw which is adjustable to vary the compression of the spring and thereby the biasing force of the spring on the seal and thus to adjust the degree of suction required to overcome the force to open the seal. The force of the spring against the seal may be adjustable by means of a screw acting on the end of the spring opposite the seal. A certain level of suction is sufficient to overcome the force of the spring and the seal then opens to communicate the atmosphere with the outlet and thereby cancel the suction.

To avoid contamination, the means for allowing air to be exhausted from the chamber through the outlet may include a one-way valve that allows air to exit the chamber but not enter it.

The device of the invention may include a gauge for directly indicating the pressure in the collection chamber and for indicating the true suction level applied to the patient regardless of whether there is an air leak from the patient through the device.

The measuring device may comprise a diaphragm which is flexible but impermeable to discharged liquids and air and which is arranged in the chamber wall for communication with both the interior of the chamber and the atmosphere. The diaphragm is connected to a pressure indicating device. Pressure differences between the atmosphere and the pressure within the chamber cause the diaphragm to deform, increasing negative pressure in the chamber causing the diaphragm to deflect inwards towards the interior of the chamber, while increasing positive or decreasing negative pressure causes it to deflect in the opposite direction. This movement of the diaphragm is transmitted to the indicating device to directly indicate the working pressure in the chamber, which is usually less than atmospheric pressure since the device is primarily intended for connection to a suction source. Preferably, the indication is achieved by a worm drive which is rotatably mounted on the diaphragm and projects upwards and acts on a follower element which in turn is coupled to a pointer for indicating the pressure or the suction level on a scale.

In embodiments of the invention, the collection chamber may be provided with features that make setting up, storing and transporting the device more convenient. For example, the collection chamber may be provided with means for suspending and carrying the collection chamber, yet which may be housed flush with the chamber when not in use. Integrated means may also be provided to stabilize the chamber against tipping over when it is resting on a support surface, such as the floor, without the need for time-consuming manipulation of the device or the use of additional devices. For example, the suspension means may be pivotally mounted on the outer surface of the chamber in such a way that they not only allow the chamber to hang, but that they may also be nested and locked on the outer surface for storage to form a carrying handle. In order to stabilize the chamber when it is placed on a support surface, for example the floor or a trolley, a support may be provided on the underside of the chamber which can be rotated from a storage position in a recess in the underside so that it projects outwards and thereby prevents the chamber from being knocked over or tipped over.

The invention will now be described by way of example with reference to the accompanying drawings.

Figure 1 is a perspective view of a drainage device illustrating the invention, showing the means for connection to a patient and a suction source and showing the means for suspending the device or stabilizing it on a support surface;

Fig. 2 is a top view of the device of Fig. 1 with the connections and suspension means removed;

Fig. 3 is a sectional view taken along line 3-3 in Fig. 2 and showing an inlet to the device;

Fig. 4 is a fragmentary sectional front view of an alternative form of inlet for the device of Fig. 1;

Fig. 5 is a fragmentary sectional front view of another form of inlet for the device of Fig. 1;

Fig. 6 is a fragmentary sectional view taken along line 6-6 in Fig. 5;

Fig. 7 is a fragmentary sectional front view of another alternative form of inlet for the device of Fig. 1;

Fig. 8 is a fragmentary sectional view taken along line 8-8 in Fig. 7;

Fig. 9 is a sectional view taken along line 9-9 in Fig. 2;

Fig. 10 is a sectional view taken along line 10-10 in Fig. 2 and showing an outlet for the device of Fig. 1;

Fig. 11 is a perspective view of an alternative outlet for the device of Fig. 1;

Fig. 12 is a fragmentary sectional view of another form of outlet for the device in Fig. 1.

Detailed description

In Fig. 1 there is shown a drainage device suitable for draining fluids from the chest cavity and which comprises a fluid collection chamber 1 defined by side walls 2, a bottom 3, a top 4 and front and rear walls 5 and 6 (Fig. 2). The chamber is preferably made of a lightweight but rigid plastic, such as polystyrene, so that the device can be manufactured relatively inexpensively by known molding techniques. The front wall 5 is transparent to allow the contents of the chamber to be viewed. The other walls 2, 5 and 6, the bottom 3 and the top 4, may be transparent or opaque. Preferably all sides of the chamber except the front walls are opaque so as to shield the contents from the patient's view and to provide a background against which the contents are more easily seen. The chamber is divided internally by partitions 7 between the front and rear walls 5 and 6 into compartments which communicate with each other only across the top of each partition 7. In use the compartments are filled in sequence by the accumulation of drained liquid. In Figure 1 there are shown three partitions 7 connecting the front and rear walls 5 and 6 and which divide the chamber into four compartments, but fewer or more partitions 7 may be used. Graduations 8 are provided on the front wall 5 on each compartment to indicate the volume of accumulated liquid. The chamber 1 shown in the figure preferably has graduations 8 marked up to a total of 2000 ml, although smaller or larger chambers may of course be used. Along the graduations space is provided on the front wall 5 to note the time in which a certain volume is reached. Preferably, as shown in Figure 1, the first compartment 9 is smaller than the other compartments, which are of equal size. This allows more accurate and convenient collection of small or initial amounts of liquid, as may be the case when treating children. For even more accurate collection of very small amounts of liquid, the bottom of the first compartment may be angled upwards, as shown at 10, to reduce the volume at the bottom of the compartment. In accordance with this difference in volume between the compartments, the graduations on the first compartment 9 represent smaller volumes than those on the other compartments. For example, the graduations may be 2 ml up to 10 ml each and then 5 ml up to 250 ml each on the first compartment and then 10 ml up to 2200 ml each on the other compartments.

Above the first compartment 9 there is a switchable inlet 11 on the top 4 of the collection chamber 1 which offers the option of draining fluid through a small reservoir of liquid in the inlet or of avoiding this small amount of liquid. Such an inlet 11 is shown in Figures 1, 2 and 3. The form of inlet shown in these figures is preferred because of its efficiency and ease of use. In this embodiment the inlet 11 on the top 4 of the collection chamber 1 is rotatable in a plane parallel to that of the upper surface 4 and its construction is best seen in Figure 3. There the inlet 11 comprises an inlet chamber 12 formed by an outer surrounding peripheral wall 13 which projects upwards from the top 4 of the collection chamber 1 and which has a substantially flat top 14 above the wall 13. When looking from above at the top surface 4, as in Fig. 2, the wall 13, and consequently the chamber 12 therein, has a flattened circular cross-section with two opposite and parallel sides 15 and 16 to facilitate gripping the inlet 11 for rotation. For this purpose, diametrically opposed projections 17 and 18 may also be provided, as shown in Fig. 2, extending outwardly from the center of the sides 15 and 16 to be grasped by the user's hand. However, if desired, the cross-section of the wall 13 may be a normal circle or an oval. The underside of the wall 13 has an outwardly projecting circular flange 19 (Fig. 3) around its circumference. The flange 19 is surrounded by a circular retaining ring 20 which is secured to the top surface 4 of the collection chamber 1. The ring 20 also has a flange 21 which projects inwardly and over the flange 19 to hold the inlet chamber 12 to the top 4 of the collection chamber 1 and also to allow it to rotate thereon within the retaining ring 20 and its flange 21. To prevent leakage of fluid between the inlet chamber 12 and the collection chamber 1 to the outside of the chambers or non-sterile air from contaminating the chamber, a seal 22 is arranged between the inlet chamber flange 19 and the top 4. The inlet chamber is divided into two compartments 23 and 24 by a partition 25 across the diameter of the chamber 12 and between the sides 15 and 16. The partition 25 extends upwardly from the bottom of the chamber, but does not reach the top 14 of the chamber 12, leaving an air space above the wall 25 which provides the only means of fluid communication between the two compartments 23 and 24, since the bottom of the partition 25 is sealed against the seal 22. Above a compartment 24, an inlet connector 26 and a rubber grommet or test plug 27 extend through the top 14 of the inlet chamber 12. The connector 26 comprises a short rigid tube, the upper end of which is adapted to connect to an inlet tube 28, as shown in Fig. 1. The inlet tube 28 is intended for connection to the patient and is made of a flexible natural rubber or a flexible polyvinyl chloride to prevent the tube 28 from kinking at its junction with the connector 26 and impeding the flow of fluid from the patient. An inner or, as shown in Fig. 1, outer coil of resilient material such as plastic or metal wire 29 may be wound around the inlet tube 28 to provide some rigidity to the tube at the connector 26. The lower end of the connector 26 extends to below the top of the partition 25 in the compartment 24. As fluid is drained from the patient through the inlet tube 28, it is introduced into the compartment 24. As this compartment fills and the liquid level reaches the height of the partition 25, the liquid overflows the wall 25 into the other compartment 23. Since the connector 26 extends below the top of the partition 25, it also extends below the level of the liquid in the compartment 24 and forms with the partition 25 and the inlet chamber wall 13 an inlet channel having a generally U-shaped cross-section as shown in Fig. 3. This U-tube arrangement serves as an indicator of the patient's condition since, when liquid is present in the U-shaped inlet channel, a flow of bubbles in the direction from the connector 26 through the compartment 24 indicates air evacuation from the patient. In addition, movement of the liquid reflects patency, patency and pressure changes in the patient's chest and can indicate whether he is having difficulty breathing. The U-shaped passage is preferably sized to contain 10 to 15 ml of liquid and may be graduated to indicate the volume of liquid therein, for example in divisions of 2 ml up to 10 ml. Instead of having the connector 26 extend so far into the compartment 24, in an alternative embodiment (not shown) the U-tube may be formed by a dividing wall extending downwards from the top of the inlet chamber 12 to below the top of the partition wall 25 and between that wall and the outer wall 13, the inlet connector 26 being between the outer wall and the dividing wall. The spout 27 is made of a rubbery material, for example a natural rubber or a silicone rubber, which allows a hypodermic syringe needle (shown in phantom in Figure 3) to pass through and be withdrawn without exposing the inlet chamber 12 to the atmosphere. A sample of the most recently drained fluid may be taken at any time by means of the syringe by withdrawing some fluid from the compartment 24. When fluid is not being drained and to prepare the device for use, sterile saline solution may be injected through the spout 27 into the compartment 24 in an amount sufficient to fill the bottom of the compartment 24 and such that air drainage can be indicated by the patient by bubbles passing through the fluid as described above.

The inlet 11 is arranged at the top 4 of the collection chamber 1 so that one of the compartments 23 and 24 is above a hole 30 in the top 4 and above a hole 31 in the seal 22. Neither of these compartments has a bottom wall so that the bottom of one of the compartments is open through the holes 30 and 31 while the bottom of the other compartment is closed by the seal 22 and the top 4 of the collection chamber 1. When the compartment 24 fills during drainage as described above and when the drained liquid passes over the partition wall into the compartment 23, the liquid can then fall through the holes 30 and 31 into the collection chamber 1. The hole 30 is arranged so that it is above or nearly above the first collection compartment so that this compartment fills first. To ensure this, a lip 32, shown in Fig. 3, is angled downwards below the hole 30 from the underside of the top 4 to direct the liquid into the first collection compartment 9 (Fig. 1).

A great advantage of the device is that the inlet 11 can contain liquid for sampling or to indicate air discharge from the patient and that liquid can be removed, e.g. by draining it from the inlet into the collection chamber when it is no longer required or to remove a potential blockage of the inlet which may be caused by particles such as lumps or other constituents in the drained liquid. Since the inlet 11 in Fig. 3 is rotatable, the position of the compartments 23 and 24 is reversed when it is rotated through 180 degrees. This places the compartment 24 over the hole 30 and the liquid therein is drained into the collection chamber 1. In this position, the bottom of the other compartment 23 is closed by the seal 22 and fluid from the patient passes directly through the compartment 24 into the collection chamber 1, i.e. without being temporarily held in an inlet channel or passed through fluid there, but the fluid passes directly into the main collection chamber from the inlet tube from the patient. When it is desired to return to the sampling mode or the air bleed indicator mode, or after clearing the inlet of an obstruction, the inlet 11 is again rotated 180 degrees, thereby reversing the positions of the compartments 23 and 24 and rotating them back to the positions shown in Fig. 3. Then bleed fluid enters compartment 24 first and can fill that compartment, or fresh sterile saline solution can be introduced into compartment 24 to fill the "U-tube" inlet channel. The inlet 11 is designed in such a way that the inlet cannot be blocked at any time if the inlet is rotated.

An alternative form of switchable inlet is shown in Figure 4, in an arrangement where the liquid in the inlet channel can be bypassed by the fluid drained from the patient. An inlet chamber 33 is formed by the following parts: a clear front wall (not shown) which is an upward extension of the clear front wall portion 5 of the collection chamber 1; an outer side wall 34 which is a similar extension of the side wall 2 of the collection chamber and which extends upwards from the top 4 of the chamber 1; an inner side wall 35 and a rear wall (not shown) and a substantially flat top surface 36. The side walls 34 and 35 extend slightly less than half the depth of the top surface 4 of the collection chamber 1. An inlet channel of generally U-shaped cross-section, viewed from the front of the device as in Fig. 4, is formed in the inlet chamber 33 by a curved trough 37 which extends between the front and rear walls of the chamber 33 and partially across the chamber from the inner side wall 35, leaving a space 38 between the lip 39 of the trough 37 and the outer side wall 34. A partition wall 40 extends downwardly from the underside of the top surface 36 of the inlet chamber 33 partially into the trough 37 and to below its lip 39 and also extends between the front and rear walls of the chamber 33. Thus, in vertical cross-section, the trough 37, the partition wall 40 and the inner side wall 35 form a generally U-shaped inlet channel. As shown in Fig. 4, two inlets 41 and 42 pass through the top 36 of the inlet chamber 33: a primary inlet 41 above the inlet channel and trough 37 and between the partition 40 and the inner side wall 35, and a secondary inlet 42 above the space 38 between the trough 37 and the outer side wall 34. Attached to the inlets 41 and 42 are sections of flexible tubing 43 and 44 which lead to a common connection in the form of a switching valve 45 to which the main drainage tube from the patient is also attached. The valve 45 can be used to direct drained fluid either through the primary inlet 41 and the U-tube inlet channel or through the secondary inlet 42 and space 38 directly into the collection chamber 1. When using the primary inlet 41, drained fluid passes through liquid in the trough 37 which was previously drained or introduced therein. This liquid seal can serve as an air drain indicator or as an analysis point for drained fluid as described above. Liquid can be drained from the trough 37 or introduced into the trough 37 through a rubber grommet 46 in the top 36 of the inlet chamber 33. The grommet 46 is located between the partition 40 and the secondary inlet 42 and above the outlet arm of the U-tube inlet channel between the partition 40 and the lip 39 of the trough 37. Drained fluid passes through the inlet channel, the space 38 and into the underlying first collection compartment 9. A projection 47 projecting downwardly from the lip 39 of the trough 37 above the compartment 9 helps direct drained fluid into this compartment. If use of the inlet channel is not desired because it is blocked, or if the ability to vent air or take samples is not required, the secondary inlet 42 can be used by rotating the valve 45 to direct the flow of drained fluid to this inlet instead of the primary inlet 41. The fluid then passes directly through the space 38 into the collection compartment 9 without passing through the fluid in the inlet channel.

Another inlet is shown in Figs. 5 and 6 in which the U-tube inlet channel is rotatable in a plane parallel to that of the front wall 5 of the collection chamber 1 so that the inlet channel can be emptied. In a similar manner to the inlet previously described, the inlet chamber 48 is formed by a clear front wall 49 (Fig. 6) which is an upper extension of the front wall (Fig. 1) of the collection chamber 1, with an outer side wall 50 extending upwardly from the side wall 2 (Fig. 1) of the collection chamber 1 and an inner side wall 51 and a rear wall 52 each extending upwardly from the top 4 of the chamber 1. As shown in Fig. 5, the top 53 of the inlet chamber 48 is curved outwardly of the chamber, but a flat top could be used provided sufficient clearance is provided for the rotation of the U-tube inlet channel, as will become apparent hereinafter. The side walls 50 and 51 extend somewhat less than half the depth of the top 4 of the collection chamber 1. The rear wall 52 has a circular hole 54 in which an inlet compartment 55 is rotatably mounted. Viewed from the front, as in Fig. 5, the compartment 55 has a vertical cross-section in the shape of three quarters of the circumference of a circle. When used in the position shown in Fig. 5, the compartment 55 terminates at the 9 o'clock position in a lip 56 over which drained liquid passes into the first collection compartment 9 (Fig. 1) below. At the 12 o'clock position, the compartment 55 has a downwardly projecting partition 57 which extends downwardly to below the level of the lip 56. Between these two o'clock positions, a continuous curved wall 58 forms the outside of the inlet compartment 55, together with front and rear walls 59 and 60. The inlet compartment 55 is thereby closed except for its inlet 61 by the rear wall 60 between the partition 57 and the outer wall 58 and except for its outlet between the wall 57 and the lip 56. Thus, the compartment 55 forms an inlet channel which again has a generally U-shaped vertical cross-section as seen in Fig. 5, so that air evacuation from the patient in the inlet chamber 55 is indicated by bubbles passing through the liquid contained therein, as described above. In order to allow the contents of the inlet channel to be seen, at least the front walls 49 and 59 of the inlet chamber and the inlet compartment are clear. If desired, all walls of the inlet chamber and the inlet compartment can clear, although it is preferable that the rear wall 52 of the inlet chamber be opaque to shield the contents from the patient's view. As can be seen in Fig. 6, the compartment 55 has a circular projection 62 which passes through the rear wall 52 of the inlet chamber 48. The projection 62 is sized to fit snugly into the hole 54 in the rear wall 52 and terminates outside the inlet chamber 48 in a flange 63 which overlaps and abuts the outer surface of the rear wall 52. Since the hole 54 is smaller than the flange 63 and than the rear wall 60 of the compartment 55, the compartment can be twisted within the hole 54 and held there. To facilitate this and to seal the hole 54 from the atmosphere, an annular disk 64 of a suitable resilient material is disposed between the rear wall 60 of the compartment 55 and the rear wall 52 of the inlet chamber 48. The inlet 61 to the compartment 55 passes through the boss 62 as a tubular conduit 65 before bending over a right angle bend 66 to continue upwards and receive a flexible inlet tube 67 from the patient. A rubber grommet 68 or sampling plug is provided in the wall of the bend 66 and faces the inlet 61 to the compartment 55 so that a syringe needle can introduce or withdraw fluid from the compartment 55 as described above. In use, fluid drained from the patient passes down the inlet tube 67, through the conduit 65 into the compartment 55 and through the U-tube inlet channel before passing over the lip 56 into the collection compartments below. When it is desired to remove an obstruction from the compartment 55 or to replace the fluid therein, the compartment 55 can be rotated in an anti-clockwise direction as viewed from the front of the device to a position shown in dashed lines in Figure 5 where the compartment 55 is rotated approximately 90 degrees to empty its contents into the collection chamber 1. Then, when it is desired to minimize obstruction to the passage of drained fluid through the inlet, the compartment 55 can be maintained in this tilted position with no fluid therein, thereby allowing the drained fluid to flow directly into the collection chamber 1.

Another inlet is shown in Figs. 7 and 8 which is similar in construction to that of Fig. 3 except that the inlet slides in a plane parallel to that of the top 4 of the collection chamber 1 rather than rotating to empty the inlet chamber. The inlet chamber 69 is formed by front and rear walls 70 and 71 (Fig. 8) and by side walls 72 and 73 (Fig. 7) with a substantially flat top 74 above these walls. Preferably at least the front wall 70 is clear to make the contents of the inlet chamber 69 visible and the rear wall 71 is opaque to make the contents of from the patient's view and to provide a background which makes the contents more visible. The side walls 72 and 73 may be clear or opaque. As shown in Fig. 8, the front and rear walls 70 and 71 each have outwardly projecting flanges 75 and 76 on their undersides. The flanges 76 and 76 are straight and parallel and lie within parallel guide rails 77 which are attached to the top 4 of the collection chamber 1. Each guide rail has an upwardly projecting projection 78 with a flange 79 which extends inwardly and over the inlet chamber flanges 75 and 76. The inlet chamber 69 is thus supported on the collection chamber 1 but is free to slide between the guide rails 77. The top 4 of the collection chamber 1 has an extension 80 which projects beyond the side wall 2 of the chamber 1. The guide rails 77 continue from the main part of the surface 4 into the overhang 80. The amount of movement of the inlet chamber 69 along the guide rails 77 is determined by stops 81 and 82 at each end of the rails, one stop 81 on the overhang 80 and the other stop 82 on the top surface 4 above the collection compartments. In the preferred form shown in Figures 7 and 8, the flanges 75 and 76 merge with flanges on the side walls of the inlet chamber 69 to form a continuous flange around the bottom of the walls of the chamber 69. Similarly, the stops 81 and 82 have inwardly projecting flanges which together with flanges 79 on the guide rails 77 form a continuous flange which can overlie the continuous flange around the chamber 69. To prevent leakage of fluid between the inlet chamber 69 and the top 4 of the collection chamber 1, a seal 83 is disposed between the flanges 75 and 76 of the inlet chamber and the top surface 4. The inlet chamber 69 is divided into two internal compartments 84 and 85, as shown in Fig. 7, by a partition 86 which extends across the chamber 69 between and substantially perpendicular to the front and rear walls 70 and 71. The partition 86 extends upwardly from the bottom of the chamber 69, but does not reach the top 74 of the chamber, leaving an air space above the wall 86 which provides the only means of fluid communication between the two compartments 84 and 85. The innermost compartment 85 with respect to the top 4 of the collection chamber 1 is divided by a dividing wall 87 into an inlet channel which has a generally U-shaped vertical cross-section when viewed from the front as in Fig. 7, because the dividing wall 87 projects downwardly from the top 74 of the inlet chamber 69 and extends partially downwardly into the compartment 85 to below the top of the dividing wall 86. Between the dividing wall 87 and the inner side wall 73 of the inlet chamber 69, an inlet 88 and a rubber grommet 89 extend through the top 74 of the chamber 69. The inlet 88 serves to attach an inlet tube 90 from the patient and the grommet 89 is used to supply fluid to withdraw fluid from or supply fluid to the inlet channel described above with respect to the other inlets. When the inlet chamber 69 is at the innermost guide rail stop 82, the compartment 84 lies above the holes 91 and 92 through the seal 83 and the top 4 of the collection chamber 1. Since neither of the compartments 84 and 85 has a bottom wall, in this position drained fluid passes from the inlet 88 through the inlet channel in the compartment 85 and then through the compartment 84 and the hole 92 into the collection chamber 1. Drained liquid collects in the compartment 85, the bottom of which is closed off by the seal 83, and when the level reaches the top of the partition 86, it runs into the other compartment 84, through the hole 92 and into the first collection compartment 9 (Fig. 1) below the hole 92. If it is desired to empty the compartment 85, or to pass the drained liquid directly through the inlet chamber 69 without accumulating there, the inlet chamber 69 is displaced between the guide rails 77 until it abuts the outer stop 81. In this position the compartment 84 is moved over the overhang 80 and its bottom is closed by the seal 83 on the overhang 80, while the compartment 85 is moved over the hole 92 and the contents of this compartment are emptied through this hole into the collection chamber 1. Thus, any obstruction in the inlet channel can be cleared in this way and, as above, this inlet offers the option of periodic or continuous collection of drained fluid for sampling or for indicating air discharges from the patient with a supply of fluid in the inlet in one mode of operation, or the option of periodic or continuous passage of drained fluid through the inlet without the use of such a supply of fluid.

The device is designed so that suction can be used to drain the fluids and for this purpose the device shown in Fig. 1 has an outlet 93 for connection to a suction source (not shown). Nevertheless, the device is designed so that it can also operate by gravity drainage if the suction source fails. The outlet 93 comprises a raised housing 94 located on the top 4 and towards the front 5 of the collection chamber above the last compartment thereof. As can be seen more clearly in Fig. 10, the location of the housing 94 places the outlet 93 above a one-way sealing valve 95 in the top of the collection chamber. The valve 95 comprises a resilient cap 96 outside the chamber 1 and has an integral plug which passes through the top of the chamber 1 and terminates within the chamber in an enlarged head 97 to retain the valve 95. The cap 96 covers perforations 98 in the top of the chamber 1 and seals them against backflow of fluid in the direction from the outlet 93 to the chamber 1. The valve 95 is in an internal cavity 99 in the outlet housing 94. The cavity 99 above the valve 95 is in fluid communication with an outlet connector 100 which is adapted to be connected to a flexible outlet tube 101 (Fig. 1) which in turn is adapted to be connected to the suction source. After suction is applied to the outlet 93, the edges of the cap 96 are pulled upward to expose the perforations 98 and since these and the outlet 93 are in communication through the internal cavity 99, suction can be applied to the interior of the collection chamber 1. The valve 95 creates a slight overlap between the compliant cap 96 and the top of the reservoir housing, resulting in a positive pressure of about 1 to 2 cm from the patient, which pressure is commonly referred to as "break-up pressure" when the device is used for gravity drainage. This is the same process as in a water mechanism.

The amount of suction applied to the collection chamber 1 is controllable by an adjustable regulator 102, best seen in Figure 10, which is located in the outlet housing 94. As this figure shows, that part of the housing 94 which contains the regulator 102 is raised above the top of the chamber 1, forming a slot 103 therebetween. The bottom wall of the housing 94 above this slot has a hole 104. The hole 104 opens into an internal channel 105 in the housing 94, is open to the cavity 99 and hence to the outlet connector 100 and to the suction source. The hole 104 in the bottom wall of the housing 94 provides communication between the slot 103 and the channel 105 and is closable by a sealing valve 106 which is biased by a coil spring 107 housed in a channel 108 within a column 109 extending upwardly from the channel 105 and above the valve 106. The channel 108 receives an adjusting screw 110 which is in contact with the end of the spring 107 remote from the valve 106. The screw 110 is adjustable by a nut 111 which is secured to the outside and top of the column 109. Adjustment of screw 110 increases or decreases the pressure of spring 107 against valve 106. Thus, a certain level of vacuum applied to outlet 93 overcomes this pressure and causes seal 106 to open, thereby venting outlet 93 to atmosphere via slot 103 to relieve the suction to a lower level at which the pressure of spring 107 overcomes the suction and closes seal 106. As a result, regulator 102 can be set to open valve 106 at a predetermined vacuum level to ensure that the suction applied to the chamber is not too great. This is a useful measure since many hospitals provide suction throughout the building so that it can be used at certain points in the walls, with no adjustment or control at those end points, or where the suction can only be adjusted from about 80 to 200 cm of water column and is not accurate enough to provide the desired suction levels suitable for chest drainage. Since this available suction, known as "wall suction", is often undesirably high, for example 200 inches (500 cm) of water column or more when 10 to 40 inches (25 to 100 cm) is the range normally used, the adjustability of the device according to the invention is invaluable. Moreover, when the valve 106 opens to relieve the suction, the atmospheric pressure thereby admitted into the outlet 93 is prevented by the valve 95 from entering the collection chamber 1 and poisoning the patient. Wall suction in hospitals is variable and can become dangerous if it becomes too strong. Therefore, a regulator of the type described will open more as the wall suction increases, thereby compensating for this sudden strong suction. To date, regulators of the type described have been found to handle at least half of all increased suction effects. A second one-way sealing valve 112 of the same type as valve 95 is disposed in the top 113 of the inner channel 105. The valve 112 has a resilient cap 114 outside the channel 105 which is exposed to the atmosphere outside the device. The cap 114 has a resilient plug which passes through the top 113 and terminates within the channel 105 in an enlarged head 115 to retain the valve 112. The cap 114 covers perforations 116 in the top 113 of the inner channel 105 and seals them against backflow of the atmosphere into the channel 105. Valve 112 serves as an over-positive relief valve so that if the suction source fails in the closed position, the device can still operate as a gravity drainage system, placing the collection chamber 1 below the patient and not endangering the patient. Under these circumstances, excess pressure in the collection chamber 1 can be vented to atmosphere through valves 95 and 112, but these are one-way valves and prevent air from flowing in the opposite direction and poisoning the patient.

An alternative form of outlet 93 is shown in Fig. 11 and provides accurate measurement of air discharges from the patient. This inlet is of the same construction as that shown in Fig. 10 except that a ball flow meter 117 is located between the outlet housing 94 and the top 4 of the plenum chamber 1. This has in effect expanded the internal cavity 99 of Fig. 10 to form a ball flow meter. Consequently, the valve 95 continues through the top 4 of the plenum chamber 1 at the bottom of the meter 117 and the housing 94 is located at the top of the meter. The meter 117 is a conventional ball flow meter and includes a clear column 118 between the outlet housing 94 and the top 4 of the collection chamber 1. The column 118 has an internal bore containing a ball indicator 119. The bore is open at the top to the internal outlet cavity 99 (Fig. 10) and at the bottom through perforations 98 (Fig. 10) in the top 4 of the collection chamber 1. The bore is conical in shape and is narrower at the bottom than at the top. The outer surface of the column 118 is marked with graduations 120. Air passed through the collection chamber 1 by the patient passes through the column 118 on its way to the outlet. This air flow propels the ball 119 up the column 118, whereupon the height of the ball can be read off the graduation 120 to give a measure of the air flow rate. This rate can provide a valuable indicator to medical personnel to inform them of the severity and extent of air leakage from the patient.

Another form of outlet 93 is shown in Fig. 12 which allows more precise control over the level of suction applied to the chamber 1. This outlet comprises a first housing 121 at the top 4 of the chamber 1 above a one-way valve 95 and forms a compartment 122 above the valve 95. The housing 121 is sealed against air flow from the atmosphere into the compartment 122 and comprises an inner side wall 123, an outer side wall 124, rear and front walls (not shown) and a top 125. Another one-way valve 126, identical in construction to valve 95, is fitted in the outer wall 124 of the housing 121 and covers perforations 127 through this wall. The valve 126 serves the same function as the valve 112 in Fig. 10 and allows excess positive pressure in the chamber 1 to be relieved by opening the valve 95 to the compartment 122 and the valve 126 to the atmosphere outside that compartment, as described above with respect to the valve 112. To protect the valve 126, a circular cap 128 surrounds the valve 126 on the outside of the wall 124. The periphery of the cap 128 is sealed to the wall 124, but a central opening 129 in the cap 128 allows access of the atmosphere to the valve 126. The top 125 carries a second housing 130 which similarly has an inner side wall 131, an outer side wall 132, front and rear walls (not shown) and a top 133 forming a further compartment 134 therein. The compartment 134 is open to the atmosphere via openings 131a and 132a in the side walls 131 and 132. A circular membrane 135 is inserted into the top 125 of the first housing 121 and is exposed on both sides to the compartments 122 and 134. The membrane 135 is flexible and impermeable to fluids and is preferably made of natural or silicone rubber. A stepped retaining ring 136 surrounds the diaphragm 135 which is sealed around its circumference between an inner step in the ring 136 and a flange 137 projecting downwardly from an upper retaining ring 138. The peripheral portions of the rings 136 and 138 are sealed to each other and also to the housings 121 and 131, completing a fluid-tight seal between the compartments 122 and 134. The lower ring 136 has a central opening 139 through which the narrow tip 140 of an outlet tube 141 extends. The tube 141 extends downwards and then bends over a shoulder 142 and passes sealingly through the inner wall 123 of the housing 121. Outside the housing 121, the tube 141 bends upwards over a further shoulder 143 and terminates in a connector 144 for attaching an outlet tube 101 for connection to a suction source (not shown). The upper side of the diaphragm 135 has a central sleeve 145 integral therewith which is accessible through a central opening 146 in the upper retaining ring 138 for a stem 147 which terminates at its lower end in a spherical projection 148 which sits in the sleeve 145. The shaft 147 has a similar spherical projection 149 at its upper end, below which a disk 150 is disposed on the shaft 147 which is prevented from moving along the shaft 147. The disk 150 supports a spring 151 which is wound around the shaft 147 and which extends upwardly through the compartment 134 to be held at its upper end by a similar retaining arrangement attached to the underside of an adjusting screw 152 which extends upwardly through the top 133 of the housing 131. The retaining arrangement on the screw 152 has a shaft 153 extending downwardly therefrom and terminating in a spherical projection 154. Above the projection 154, a disk 155 around the shaft 153, which is prevented from moving along the shaft 153, holds the upper end of the spring 151. The adjustment screw 152 extends through the top 133 and through an internally threaded column 156 inserted into the top 133. The screw 152 is adjustable by a nut 157 secured to the outside and top of the column 156. The spring 151 is in tension between the adjustment screw 152 and the diaphragm 135. When suction is applied through the tube 141, the pressure in the compartment 134 decreases, the valve 95 opens, and suction is applied to the chamber 1 to initiate drainage of fluids from the patient. The diaphragm 135 also tends to be drawn downward against the tip 140 of the tube 141 and it moves against the tension set by the adjusting screw 152 on the spring 151, which tension tends to pull the diaphragm 135 upward and away from the tip 140 of the tube 141. At a certain level of suction set by the adjusting screw 152, the suction overcomes the spring force and the diaphragm 135 is drawn into contact with the tip 140 to cover it and close the tube 141, thereby suction source is cut off from chamber 1 and the level of suction that can be applied to the patient is limited. The suction source will remain closed from chamber 1 until the level of suction in chamber 1 drops due to fluids entering from the patient. When the suction within chamber 1 drops, the force of spring 151 overcomes the suction and draws diaphragm 135 away from tip 140 of tube 141 to re-expose chamber 1 to the suction source. The area of tip 140 should be small relative to the area of diaphragm 135 and the diaphragm should be sufficiently compliant that it does not flex to an undesirable extent and become trapped at tip 140 by excessive suction. This outlet arrangement has the advantage of operating very quickly and completely to limit excessive suction.

For connection for use, the drainage device is usually provided with inlet and outlet tubes 28 and 101 for the collection chamber 1, mounted as shown in Fig. 1. The inlet tube 28 is for connection to the patient and the outlet tube 101 is for connection to the suction source. To avoid any error in correctly connecting the tubes, the tube 28 may be marked with the word "patient" at intervals along its length. Similarly, the outlet tube 101 may be marked with "wall suction" or similar words. Additionally or alternatively, the tubes may be color-coded to conform to instructions accompanying the device. The tubes are preferably made of clear plastic to make their contents visible, but they may also be made of latex or other suitable flexible plastic material. Near their connection points to the device, each of the tubes may be connected internally or externally to a section of coil spring around the tube to prevent kinking of the tubes.

The drainage device includes a pressure gauge for directly measuring the pressure in the collection chamber 1, which provides valuable information to hospital personnel as to what level of suction is actually being applied to the patient. As shown in Figs. 1 and 2, the pressure gauge 158 is arranged on the top 4 of the collection chamber 1 between the inlet 11 and the outlet 93. As shown in Fig. 9, the gauge 158 has a base plate 159 with a central hole 160. Adjacent to the hole 160 and between this hole and the front 5 of the collection chamber 1 is a wall 161 perpendicular to the base plate 159 and parallel to the front 5. A transparent window 162 is arranged inclined downwards between the top of the wall 161 and the front edge of the base plate 159. Triangular side walls 163 (Figs. 2 and 9), which may be clear or opaque may be, together with the wall 161, window 162 and base plate 159 form a housing for indicating the measured pressure on a graduated scale 164 marked in an arc on the front of the wall 161 as best seen in Fig. 1. A shaft 165 pivotally mounted in a hole through the wall 161 at the center of the arc of the scale 164 carries a pointer 166 for indicating the reading of the gauge 158 on the scale 164. The other end of the shaft 165 is pivotally mounted in a hole in an upright support 167 on the base plate 159 on the other side of the central hole 160 opposite the wall 161. The upright support 167 is supported by a strut 168 between its top and the wall 161. The shaft 165 carries a pinion 169 between the wall 161 and the upright support 167 which engages a vertical rack and pinion 170 (as best seen in Fig. 9). The rack and pinion 170 has helical gear teeth in the form of a screw to permit calibration of the meter 158 as described below. The underside of the rack and pinion 170 projects through the central hole 160 in the base plate 159 and has a spherical projection 171 which is rotatably mounted in a sleeve 172 which is integrally mounted at the center of a circular diaphragm 173. The diaphragm 173 is flexible and impermeable to fluids and is preferably made of natural or silicone rubber. A stepped retaining ring 174 surrounds the diaphragm 173 which is sealed around its circumference in an inner step in the ring 174 and between that step and a circular projection 175 projecting downwardly from the base plate 159. The bottom of the ring 174 has a central hole 176 for communication between the interior of the chamber 1 and the diaphragm 175. The outer wall 177 of the retaining ring 174 is sealed in a hole (not shown) in the top 4 of the collection chamber 1 and an outwardly projecting flange 178 at the top of the wall 177 overlaps the outer surface of the top 4 of the collection chamber 1 to better retain and seal the assembly in the hole in the top 4. The bottom wall 179 also prevents the diaphragm 173 from excessively deflecting if a high suction condition from the patient is present at the time. The underside of the base plate 159 is sealed to the upper surface of the flange 178 and, since the membrane 173 is impermeable, the meter 158 is therefore sealed into the top 4 of the collection chamber 1 to seal off the atmosphere from the chamber.

The upper end of the rack gear 170 is rotatably held in a hole in the strut 168. The upper side of the rack gear 170 has a screw fitting 180 formed integrally therewith for calibrating the measuring device 158 by rotating the rack gear 170 in the ball-socket connection 171/172 at its lower end. A such twisting operates the rack and pinion gear 170 as a worm gear so that the position of the pinion 169 can be adjusted for a given position of the diaphragm 173. However, there is sufficient friction between the flexible diaphragm and the gear to maintain the gear position once adjusted. Thus, with the chamber 1 at atmospheric pressure, the screw fitting 180 can be twisted to set the pointer 166 to zero. It has been found that a small amount of stretching in the diaphragm 173 will cause the pointer 166 to return to zero since there is always a small percentage of permanent deformation left in the rubber of the diaphragm 173 as it is deformed up and down. The residual stretching overcomes this and returns the indicator 158 to zero and increases the accuracy over the rest of the scale 164 since the position is relative. Preferably, the diaphragm 173 is sealed in the retaining ring 174 with some radial extension. In operation, the pressure in the chamber acts on the diaphragm, relatively positive pressure bending it upwards and relatively negative pressure bending it downwards. The rack and pinion 170 moves with the diaphragm and this movement is transmitted via the pinion 169 to the pointer 166 to accurately indicate the pressure in the chamber 1 on the scale 164. The scale 164 may be graduated in any suitable range of units. Conveniently, the gauge 158 may be marked to directly read the suction head in cm of water, e.g. from 0 to 60 cm at intervals of 2 cm suction head, as these units of measurement are conventionally used in connection with vacuum sources in hospitals. Graduations may also be provided indicating 1 and 2 cm pressure from the patient when the device is used for gravity drainage, as previously explained.

The drainage device is also provided with features which enable hospital personnel to handle the device more easily and safely. The top 4 of the collection chamber 1 is equipped with hangers 181 and 182, shown in Fig. 1, for hanging the device from, for example, a bed. Each hanger 181 and 182 consists of an elongated part 183 which terminates in an open hook 184 for hanging the collection chamber. The other end of each hanger terminates in a closed hook 185 which engages an eyelet 186 through a hole 187 therein. Each eyelet 186 is located near the rear of the top 4 of the chamber 1 and projects upwardly therefrom, one behind the inlet 11 and the other behind the outlet 93, as can be seen more clearly in Fig. 2. The hangers 181 and 182 are made of a material such as polypropylene which is strong enough to support the collection chamber 1 when it is full of aspirated liquid, yet flexible enough to allow the top of each hanger to come together with the other so that their open hooks 184 engage each other, to interlock with each other and form a carrying handle for the device, as indicated in dashed lines in Fig. 1. Also, the hangers 181 and 182 can be folded down onto the top 4 of the chamber 1 for storage by nesting one on top of the other. It will be understood that the length of the elongated portions 183 of the hangers must be such as to allow this formation of a handle and nesting of the hangers.

The base 3 of the collection chamber is provided with a recess 189 which extends over the depth of the bottom 3 of the chamber 1 and over a major part of its length. The recess 189 accommodates, during storage, a foot 190 which is pivotally mounted at its center on the bottom 3 of the collection chamber. When the chamber is to be placed on a flat surface, such as the floor or other surface, the foot 190 can be rotated out, as indicated in Fig. 1, to a position which is substantially perpendicular to the front and rear walls of the chamber to stabilize the device against tipping over. During transport or when the device is suspended by means of the hangers 181, 182, the foot 190 can be rotated into alignment with the bottom 3 of the chamber 1, fitting into the recess 189 without protruding therefrom. To hold the foot 190 in the recess 189, a hole 191 (Fig. 1) on the longitudinal axis of the foot 190 and on each side of its center engages projections (not shown) provided on the bottom 3 of the chamber 1.

Claims (29)

1. Apparatus for draining fluid from a cavity in the body of a patient, the apparatus comprising: a chamber (1) for receiving the fluid; an inlet (11) to the chamber (1) for connection to the cavity; and an outlet (93) from the chamber (1) for connection to a vacuum source, characterized in that the outlet comprises means (102) in the outlet (93) for venting the outlet (93) to the atmosphere at a predetermined suction level, and valve means (95) which allow air to be drawn from the chamber through the outlet (93) but which prevent air from entering the chamber (1) when the vent means (102) is venting to the atmosphere. 2. Device according to claim 1, in which the venting device (102) comprises a seal (106) over an opening (104) in the outlet (93) to the atmosphere, a spring (107) which biases the seal (106) to close the opening (104), and a screw (110) which is adjustable to change the compression of the spring (107) and thereby the biasing force of the spring (107) on the seal (106) and thus to adjust the degree of suction required to overcome the force to open the seal (106). 3. Apparatus according to claim 1 or 2, wherein the outlet (93) additionally comprises a valve (112) between the environment outside the outlet (93) and the interior of the outlet (93) to relieve excess positive pressure in the interior of the outlet (93). 4. Device according to one of claims 1 to 3, characterized in that the device has an opening which is in fluid communication with the interior of the chamber (1), and in that the device further comprises a measuring instrument (158) having the following features: - a flexible membrane (173) arranged across the opening and sealingly attached to the periphery of the opening, the membrane (173) being impermeable to the fluid and to air and forming a seal for the opening, the membrane (173) bulging in response to pressure differences between the interior of the chamber (1) and the environment; and - an indicator (166) connected to the membrane (173) to move in response to the bulges of the membrane (173) to provide a measurement of the pressure differences. 5. Device according to claim 4, wherein the membrane (173) is stretched across the opening. 6. The apparatus of claim 4 or 5, further comprising a follower (170) connected to the diaphragm (173) for movement in response to the curvature of the diaphragm, the indicator (166) responsive to movement of the follower (170) to provide the measurement of the pressure difference. 7. Device according to claim 6, wherein the follower member (170) comprises a threaded shaft (170) which is rotatably connected to the membrane (173) and is mounted on the membrane (173) for a backward and reciprocating movement therewith, and wherein the indicator has a gear (169) which engages the shaft (170) and is rotatable thereby. 8. Device according to claim 7, in which the shaft (170) ends at its end opposite the diaphragm (173) in a fitting (180) in which a tool for rotating the shaft (170) is accommodated and whereby the measuring instrument (158) is calibrated. 9. Device according to one of the preceding claims, characterized in that the inlet (11) comprises an inlet passage comprising: - means (24, 25) for directing the fluid upwards from the body cavity before the fluid is received in the chamber (1); and - means (19, 20, 21) for selectively removing the upwardly directing means from the path of the fluid in the inlet passage. 10. Apparatus according to claim 9, wherein the inlet passageway comprises a first wall extending downwardly from the top of the passageway, wherein the upwardly conducting means comprises a second wall (25) extending upwardly from the bottom of the passageway, the second wall (25) terminating below the top (14) of the passageway at a height above the bottom of the first wall, and wherein the means for selectively removing comprises means for selectively causing fluid entering the inlet passageway to either (a) flow beneath the first wall and over the second wall, or (b) flow into the chamber without flowing over the second wall. 11. Device according to claim 9 or 10, wherein the inlet passage is movable in relation to the chamber (1). 12. Apparatus according to claim 11, wherein the inlet passage is arranged in an inlet space (12), the second wall (25) extending between opposite sides of the space to form the inlet passage and an overflow passage within the space. 13. Device according to claim 12, in which the space (12) is movable from the one position in which the lower part of the inlet passage is sealed and the lower part of the overflow passage is open to the chamber (1) so that drained fluid passes upwards over the second wall (25) and through the overflow passage to the chamber (1), to another position in which the lower part of the overflow passage is sealed and the lower part of the inlet passage is open to the chamber (1) so that drained fluid passes through the lower part of the inlet passage into the chamber (1) without passing upwards. 14. Device according to claim 13, wherein the inlet chamber (12) is movable from one position to the other position by rotation. 15. Apparatus according to claim 14, wherein the inlet space (12) has an outer peripheral wall (13) extending upwardly from the top of the chamber (1), the wall having an outwardly directed projecting circular rim (19) at its bottom, and the chamber (1) having an opening (30) through the top of the chamber (1), a retaining ring (20) being attached to the top and around the opening, the ring (20) having an outwardly directed projecting rim (21) surrounding and projecting over the rim (19) of the inlet space to retain the space on the top of the chamber, the space (12) being movable by rotation within the retaining ring (20) to locate either the inlet passage or the overflow passage over the opening through the top of the chamber. 16. Device according to claim 12, in which the inlet chamber (69) is movable from one position to the other position by displacement. 17. Apparatus according to claim 16, wherein the inlet space comprises an outer peripheral wall (70, 71, 72, 73) extending upwardly from the top of the chamber (1), the wall having outwardly extending parallel edges (75, 76) on the bottom of at least two opposite sides (70, 71) of the outer wall, the chamber having an opening (92) through the top of the chamber and parallel guide rails (77) attached to the top, the edge projecting beyond one of the edges of the space to retain the space on the top of the chamber so that the space is movable by translation along the rails (77), the apparatus further comprising stops (81, 82) between the rails limiting the extent of movement of the space so that either the inlet passage or the overflow passage is above the opening is arranged. 18. Device according to one of claims 11 to 17, in which the inlet space (12) is movable without cutting off the supply of drained fluid into the chamber (1). 19. The apparatus of claim 10, wherein the first and second walls are portions of a continuous wall extending from the bottom of the first wall and the top of the second wall, and wherein the inlet passage further comprises a pair of side walls sealingly attached to opposite edges of the continuous wall, the inlet passage further comprising an inlet opening in one of the side walls, the means for selectively removing comprising means for rotationally moving the inlet passage to selectively locate the top of the second wall below the bottom of the first wall to pour the contents of the inlet passage into the chamber. 20. Apparatus according to claim 10, wherein the chamber has a first inlet arranged to supply the fluid to the inlet passage and a second inlet arranged to cause the fluid to bypass the inlet passage and flow directly into the chamber, the means for selectively removing comprising means for diverting the flow of the discharged fluid from the first inlet to the second inlet and vice versa. 21. Apparatus according to claim 19 or 20, wherein the means for selective removal operates without cutting off the supply of drained fluid to the chamber. 22. Apparatus according to any preceding claim, additionally comprising a sampling means to permit withdrawal of discharged fluid from the inlet passage. 23. Device according to one of the preceding claims, characterized in that it further comprises the following features: - A device (181) for suspending the chamber (1); - a device (190) for stabilizing the chamber (1) on a support surface, the stabilizing device comprising a support (190) which is attached to the base surface (3) of the chamber and is rotatable between a first position in which the support lies within the boundary lines of the base surface and a second position in which the support extends beyond the boundary lines of the base surface and thereby stabilizes it. 24. Device according to claim 23, wherein the suspension device (181) can be folded in for support against the chamber (1) and folded out to form a carrying handle for the chamber and wherein the support (190) is rotatable and centrally mounted in a recess (189) in the base of the chamber, the support being dimensioned so that it can be completely accommodated within the recess. 25. Apparatus according to claim 24, wherein the suspension means (181) comprises a pair of hangers (181, 182) each having a central elongated portion (183) terminating at one end in an open hook (184) for suspending the chamber (1) and at the other end in a closed hook (185), and wherein the chamber has a pair of eyes (186) attached to the closed hooks (185), the hangers (181, 182) being dimensioned so that they can alternatively (a) be fitted onto one another between the eyes or (b) engage one another by means of the open hooks to form a carrying handle. 26. Apparatus according to any one of claims 1 to 8, wherein the inlet comprises a substantially U-shaped inlet passage through which the fluid passes before being poured into the chamber (1), the passage being arranged to hold a liquid reservoir in the lower part of the passage and means being provided for emptying the liquid reservoir into the chamber (1). 27. Apparatus according to any one of claims 1 to 8, further comprising means for temporarily locating the substantially U-shaped inlet passage in the path of fluid into the chamber so that when the passage is located in the path the fluid passes through a liquid reservoir in the bottom of the passage before being poured out of the passage into the chamber (1), the passage in the path causing an air leak in the cavity to be presented in the form of air bubbles in the liquid reservoir. 28. Apparatus according to claim 26, further comprising means for sampling the reservoir from the liquid immediately previously drained from the cavity. 29. Apparatus according to any preceding claim, comprising: - means for creating a substantially horizontal gas/liquid interface in the inlet in the path of the fluid into the chamber; and - means for removing the interface from the path of the fluid.