This invention relates to aspirators, and in particular, but without limitation, to aspirators suitable for use in aspirating body fluids from cavities, such as from the stomach.

When a patient needs to be fed via an enteral feeding tube, it is necessary to insert an orogastric ("OG") or nasogastric ("NG") feeding tube into the patient's stomach. This is achieved by feeding a thin tube into the mouth or nose (respectively) of the patient, down the throat and into the stomach. The tip of the feeding tube needs to be positioned within the stomach so that the patient can be fed with a liquid feed, via the tube. However, there is a serious risk, when feeding enterally, that the tube may be fed into the patient's lung, as opposed to the stomach - due to the bifurcation of the patient's throat.

If the feeding tube is positioned within the patient's lung and feeding commences, this can lead to serious medical complications. It is therefore necessary, before feeding commences, to ensure that the feeding tube tip is correctly positioned within the patient's stomach.

Various methods have been developed in recent years for checking the correct positioning of a feeding tube tip. The primary diagnostic technique is to take chest x-rays of the patient with the feeding tube in-situ. Chest x-rays are generally contraindicated because the patient is necessarily exposed to x-rays during the procedure and whilst occasional chest x-rays are acceptable in many cases, high-dependency or intensive care patients, who are being fed nasogastrically for extended periods, would require multiple chest x-rays over an extended period of time.

Nevertheless, even a chest x-ray is not a completely reliable diagnostic tool because of the proximity an/or overlap of the lung and the stomach of the patient. Chest x-rays therefore require a great deal of expert interpretation because it is possible for an x-ray to appear to indicate correct placement of an NG tube, whereas, in fact, it is located in a different position within the patient's body. Other, secondary tests have been devised to test for the correct placement of an NG tube and these include, prior to feeding, aspirating a sample of liquid through the NG tube. The rationale behind this is that if an acidic aspirate can be obtained, then this typically indicates the placement of the NG tube tip in the patient's stomach, which contains stomach acid. Various aspirators have been developed recently, which improve the usability and effectiveness of aspiration techniques. Examples of these aspirators are described in, for example: WO2015128637 [Aspirate N Go Ltd, 2 Sep 2015], WO2015128638 [Aspirate N Go Ltd, 3 Sep 2015], WO2017134462 [Aspirate N Go Ltd, 10 Aug 2017] and WO2018029492 [Aspirate N Go Ltd, 15 Feb 2018]

The above examples of known aspirators comprises a pH test paper located in-line between the NG tube and a vacuum source, such as a syringe or vacuum pump. Upon applying a vacuum, a sample of liquid can be aspirated up the NG or OG tube, where it eventually comes into contact a pH test strip or piece of litmus paper, which indicates the acidity/alkalinity of the aspirate sample. More sophisticated versions of this device, such as WO2018029492, also include a C02 tester, which tests for the presence, or otherwise, of carbon dioxide, which is only present in exhaled air. Aspirators comprising both pH and C02 testers can help to reduce the number of "false positive" indications as will be readily apparent to the skilled reader.

Despite the above advances, there still exists a particular problem, and that is how to detect a failed aspiration procedure, or a "nil" result. When an aspirator is used to aspirate a sample, but no liquid is aspirated, there is no way for the practitioner to know whether this is because the stomach is empty and hence there is no liquid to aspirate; or whether the NG or OG tube tip is located in the patient's lung, where there would usually be no liquid anyway. As such, a pH test would be inconclusive and so the practitioner would then look to another test, say C02 testing, for a second- stage verification. If the C02 test does not indicate the presence of carbon dioxide, then this could lead the practitioner to conclude that the NG or OG tube tip is not located within the patient's lung and, therefore, that it is "safe" to feed. However, there is still a possibility of a third scenario and that is to say that the NG or OG tube tip has become obstructed or occluded, meaning that no aspirate sample (gas or liquid) has been aspirated at all. In these situations, the NG or OG tube tip could be located in either the stomach or the lung, but neither the pH test nor the C02 test, would indicate anything with any reliability: a nil result on the pH test could mean placement of the tip in the lung, or an obstructed tip; and a nil result on the C02 test could indicate C02 not present (tip in the stomach) or an obstructed tip. With existing aspirators, there is no way for the practitioner to know whether any aspirate has been obtained at all - be that gas or liquid.

A need therefore exists for a solution to this problem and/or for an improved and/or alternative type of aspirator.

Aspects of the invention are set forth in the appended independent claims. Preferred and/or optional features of the invention are set forth in the appended dependent claims.

According to an aspect of the invention, there is provided an aspirator suitable for use in conjunction with an NG or an OG tube, the aspirator comprising a main body with an inlet connectable, in use, to an NG or OG tube; an outlet connectable, in use, to a vacuum source; a colorimetric test strip interposed between the inlet and the outlet; and the aspirator being characterised by means for flow indication interposed between the inlet and the outlet.

By providing means for flow indication between the inlet and the outlet, the practitioner, when using the device, is able to determine whether or not any aspirate (liquid or gas) has been obtained during the application of a vacuum. This gives rise to several possibilities:

If the means for flow indication indicates that there has been a flow of gas/liquid upon application of the vacuum, but the colorimetric test is inconclusive, then the practitioner may be able to use this, differentially, to determine the correct placement, or otherwise of the NG or OG tube tip.

However, if the means for flow indication does not indicate the flow of a liquid or gas during the application of a vacuum, then the practitioner will be able to determine, more readily, that the entire test is a "nil" result and that no conclusions can be safely drawn from the status of the colorimetric tester.

In one embodiment of the invention, the colorimetric tester comprises a pH indicator, such as a pH tester or litmus paper. Additionally or alternatively, the colorimetric tester comprises a C02- sensitive test strip, namely a colorimetric capnometer. In a preferred embodiment of the invention, both a pH and a C02 test strips are provided between the inlet and the outlet of the device.

Preferably, where both pH and C02 colorimetric testers are provided, the pH tester is located upstream of the C02 tester. The reason for this is that during a typical aspiration procedure, gas is aspirated before liquids. By placing the pH (wet) tester upstream of the C02 (dry) tester, it is possible for the gasses to pass by or through the pH tester before reaching the C02 tester. If the opposite were true, then the C02 tester may be spoiled by liquid before liquids can reach the pH tester. Preferably, the flow indication means is located downstream of the first in-line colorimetric test strip, and more preferably, between the two colorimetric testers - where two colorimetric testers are provided.

A liquid-stop device is suitably incorporated into the invention. The liquid-stop device can be located at any point between the inlet and the outlet. A liquid-stop device is a device which permits the passage of dry fluids (e.g. gases) but which self-closes in the presence of wet fluids (e.g. liquids).

The liquid-stop device suitably comprises a porous or perforated hydrophobic membrane with the inlet located on one side thereof, and the outlet located on an opposite side thereof. A perforated hydrophobic membrane may permit the passage of gases through the pores or perforations, but those pores or perforations may be occluded or blocked by liquids, which become preferentially positioned over the pores/perforations due to the hydrophobicity of the membrane's surface.

Most preferably, where both pH and C02 colorimetric testers are provided, the liquid-stop device is interposed between an upstream pH tester and a downstream C02 tester. By placing the liquid-stop device downstream of the pH tester, but upstream of the C02 tester, it is possible to keep the C02 tester dry because dry fluids are typically aspirated before wet ones. The flow indication means can be of any suitable type, but in a preferred embodiment of the invention, it comprises an impeller mounted for rotation within the main body. Suitably, the impeller is rotatably mounted within a stator, which stator has a stator inlet operatively interconnected to the inlet of the device, and a stator outlet, operatively interconnected to the outlet of the device. Thus, upon application of a vacuum at the outlet of the aspirator, fluids are drawn into the main body through the inlet, over and/or around the colorimetric tester, through the flow indication means, and out through the outlet towards the vacuum source.

If there is a flow of fluid, then the impeller would typically rotate due to the passage of fluid over and/or through and/or around it, and this could be observed by a practitioner using the aspirator.

In a preferred embodiment of the invention, the main body and/or the stator is manufactured from a transparent material such that the impeller can be seen from the outside of the aspirator. Thus, upon application of a vacuum, if a fluid flow is present, then the impeller could be seen to be rotating within its stator. This could indicate the presence of a fluid flow.

Additionally or alternatively, the impeller is mounted to rotate within the stator, but is configured so as to vibrate and thereby either provide a tactile feedback (in the form of vibration of the main body), or an audible feedback signal (a whirring sound or clicking noise) when there is a fluid flow through the device. Vibration may be accomplished by offsetting the centre of gravity of the impeller from its rotational axis.

The impeller may be a cross-flow impeller, as this suitably has a lower drag on the flow of fluids through the device.

Additionally or alternatively, the means for flow indication may comprise a body which is displaced in the presence of a fluid flow. This may be, for example, a vane or ball located in a conduit of the device, which is displaced by a flow of fluid. Again, the vane or ball is suitably viewable from without the device, for example, by mounting it behind a transparent viewing window of the main body. Embodiments of the invention shall now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is a schematic plan view of an aspirator in accordance with the invention;

Figure 2 is an internal view of the aspirator shown in Figure 1;

Figure 3 is a schematic cross section of Figure 2 on Ill-Ill;

Figure 4 is an exploded view of the aspirator of Figure 2 on Ill-Ill; and

Figure 5 is a schematic plan view of an alternative embodiment of an aspirator in accordance with the invention.

Referring to Figures 1 to 4 of the drawings, an aspirator 10 in accordance with the invention comprises a main body 12 manufactured from two plastics pieces 12, 12A, which fit together as shall be described hereinbelow.

The main body has an inlet 14, which is connectable to an NG or an OG tube 16 via a Luer or other similar connector 18. An outlet 20 of the aspirator 10 is operatively connectable, in use, to a vacuum source - in the illustrated embodiment, a syringe 22. Application of a vacuum at the outlet 20 draws fluid up through the NG tube 16 and into the main body 12 of the device 10.

The main body 12 is manufactured from transparent plastics material and a decal 24 is applied to its front surface. The decal 24 carries operating instructions and other information (not shown), which may be useful to the practitioner, in use. A first viewing window 26 comprises an aperture in the decal 24 through which a first colorimetric test disc/strip 28 is visible; and a second viewing window 30, also formed as an aperture in the decal 24, is provided through which a second colorimetric test disc/strip 32 is visible. A third viewing window 34 is likewise provided in the decal 24, through which a flow indication means 36 is visible from the outside of the device 10.

As such, when the vacuum source 22 is actuated, fluids are drawn up through the NG tube 16 and into the inlet 14. The fluids pass through/over the first colorimetric tester 28, before flowing through the flow indication means 36, and then through/over the second colorimetric tester 32 and out through the outlet 20. The user can monitor the progress of the aspiration procedure by viewing changes in the colorimetric testers 28, 32 and by comparing their colours to colour charts or coloured comparison areas 38, 40, 42, 44 formed as part of the decal 24.

In one embodiment of the invention, the first colorimetric tester 28 comprises a pH test disc made from litmus paper, which changes colour in the presence of acid/alkalis. The colour chart regions 38, 40 are colour-coded to correspond to acid/alkali colours of the pH tester 28.

The second colorimetric tester 32 is a capnometer, that it is to say a disc of material, which is coated or impregnated with a C02-sensitive substance, which changes colour in the presence, or otherwise of C02. The corresponding colour chart portions 42, 44 are likewise designed to permit comparison with the colour of the second test strip 32 to indicate the presence, or otherwise of C02 in the aspirated fluid sample.

The flow indication means 36 is formed as a cross-flow impeller 46, which is mounted for rotation on an axle 48 and which is located within a stator 50 formed in the main body 12. The stator 50 has a stator inlet 52, which connects to an inlet tube 54, within which is mounted a liquid-stop membrane 56.

The liquid-stop membrane is manufactured from a piece of porous or perforated hydrophobic plastic, which permits gases to pass through the pores or perforations thereof when dry, but which when wetted with a liquid, its pores become blocked or occluded by the liquid - thereby inhibiting and/or preventing the flow of liquids through the membrane 56.

Upstream of the liquid-stop membrane 56 is a further tube portion 58, which provides a fluid pathway into a chamber 60, which houses the pH test disc 28. An inlet conduit 62 is in fluid communication with the chamber 60 and the inlet 14.

Downstream of the stator 50, there is a stator outlet port 64, which leads to a first outlet tube portion 66 which is in fluid communication with a second chamber 68 that houses the C02 test disc 32. Fluids are thus able to enter the second chamber 68 via the first outlet tube portion 66 and to pass through/over the C02 tester 32 before exiting the device via an outlet tube 70, which is in fluid communication with the outlet 20. When a practitioner uses the device 10, they connect its inlet 14 to an NG tube 16 via a Luer- type connector 18; and a vacuum source, such as a syringe 22 or a vacuum pump, is connected to the outlet 20. Upon application of a vacuum, a fluid sample is aspirated through the NG tube and into the device 10.

If the NG tube is correctly positioned within the patient's stomach, it is likely that an acidic aspirate liquid sample will be drawn up. Before this happens, however, the air within the NG tube is first aspirated, and this passes over/through the pH test strip and through the liquid-stop membrane 56. Because the gas is "dry" it is able to pass through the liquid-stop membrane 56 and interact with the flow indicator 46, which will spin as the fluid passes through/around it. The gas sample is then tested by the C02 tester, which, if the NG tube tip is correctly positioned within the patient's stomach, will not indicate the presence of C02. Eventually, liquid aspirate may be aspirated, in which case, the pH tester 28 will change colour when it comes into contact with the aspirated liquid, and this will be visible to the practitioner. When the liquid aspirate contacts the liquid-stop membrane 56, the membrane 56 will wet out and prevent further fluid flow. This will provide a force-feedback to the practitioner, who will then know that the test is complete.

If the NG tube is correctly positioned within the patient's stomach, but the stomach is empty, then it may be possible to aspirate gas, but not liquid in the manner previously described. This will result in the pH tester 28 not undergoing a colour change, and the impeller 46 rotating.

If, however, the NG tube is not located in the patient's stomach, but rather in the lung, then no liquid sample would typically be aspirated, and so the only test that would work would be the flow indication, as indicated by rotation of the impeller 46 and a colour change in the C02 tester 32, which would change colour in the presence of C02. The practitioner would therefore be able to determine that the NG tube tip is incorrectly placed - otherwise a C02 sample would not have been obtained.

In another scenario, where the NG tube is inserted into the body but its tip is obstructed, upon the application of vacuum at the outlet 20, there would be no fluid flow because the NG tube tip would be blocked so no gas or air, in this case, could be aspirated. This would result in the flow indicator impeller 46 not rotating, which would indicate to the practitioner, a "nil" result.

It will be appreciated by the skilled reader that the inclusion of a flow indication means is particularly beneficial when trying to carry out a differential determination, or logic table, such as below:

As can be seen from Figures 3 and 4 of the drawings in particular, the aspirator 10 is conveniently made from two interlocking main body parts 12, 12a with the pH test disc/strip 28, the C02 test disc/strip 32, the impeller 46, and the liquid-stop membrane 56 being "sandwiched" therebetween.

An alternative embodiment of the invention is shown, by way of example only, in Figure 5, in which, in this example, there is only one colorimetric tester 28, 32, which may be either a pH tester or a C02 tester as is required by the clinical circumstances. In this embodiment, the flow indication means 36 takes the form of a lightweight ball 70, which is free to roll around within a "racetrack" 72 type enclosure formed by inner and outer stator walls 50. In this embodiment of the invention, when there is flow through the device 10, the ball 70 will roll around within the racetrack 72 enclosure, thus indicating the presence of a fluid flow.

The invention is not restricted to the details of the foregoing embodiments, which are merely exemplary of the invention.