GB2176595A

GB2176595A - Pressure sensing device

Info

Publication number: GB2176595A
Application number: GB08514132A
Authority: GB
Inventors: Robert Scott Mcminn
Original assignee: Warner Lambert Co LLC
Current assignee: Warner Lambert Co LLC
Priority date: 1985-06-05
Filing date: 1985-06-05
Publication date: 1986-12-31
Also published as: AU5966286A; GB8514132D0; WO1986007266A1; JPS62503079A

Abstract

A pressure sensitive member (15) having first and second configurations, the member being movable from said first to said second configuration by application of an increased differential pressure on said member, the member having no stable configurations intermediate said first and second configurations whereby rapid movement from said first to said second configuration is achieved.

Description

SPECIFICATION Pressure sensing device This invention relates to pressure sensing devices and more particularly concerns pressure sensing devices which are adapted for use in medical applications, especially administration sets for administering fluids to the body of a patient.

Medical fluids are introduced into a body of a patient by means of an intravenous administration set which includes a source of medical fluid, a fluid flow control device and tubing which extends between the fluid flow control device and the patient. The fluid flow control device supplies fluid to the tubing at the desired rate and in the desired volume but any fault between the fluid flow control device and the patient will prevent the desired administration of the fluid being achieved.

Problems which can occur in the use of the intravenous administration set include an obstruction in the tubing, for example because of pinching or kinking and errors in location relative to the patient, e.g. where an administration needle is inserted into tissue instead of a vein. Such situations can be very dangerous as the patient may not receive the desired amount of medical fluid as delivered by the fluid flow control device or the fluid may be dispersed in tissue which can cause serious medical problems.

It is known to monitor pressure in the intravenous administration set (IV administration set) downstream of the fluid flow control device and to provide an output signal when the pressure exceeds a predetermined maximum.

Such a device is described, for example, in U.S. Patent Specification No. 4,394,862 which incorporates a pressure transducer operatively engaged with the IV administration set tubing downstream of the fluid flow control device.

This transducer produces continuously an output signal which is monitored by a pressure monitor circuit to produce a warning signal when the pressure exceeds a certain predetermined maximum. The warning signal may be used to terminate fluid flow and/or to sound a warning alarm.

Pressure sensitive devices have also been proposed for detecting increases in pressure of portions of the body of a patient. U.S.

Patent Specification No. 3,704,708 describes a device for observing and measuring arterial blood pressure which comprises a housing having a cavity sealed at one end by a flexible membrane and at the other end by a pressure responsive transducer. The device is positioned over an arterial duct of the patient and the output from the transducer is displayed by suitable display means.

U.S. Patent Specification No. 4,421,124 describes a pressure detection arrangement which is adapted to be embedded between the skin of a portion of the body of a patient and means to surround that portion to support or immobilise it such as a cast. The pressure detection arrangement is a bifurcated capsule comprising a reservoir cavity and an indicator cavity separated by a frangible disc or by an extendable bladder. A coloured fluid is contained within the reservoir cavity and excess pressure between the skin and the cast, for example due to swelling, causes the coloured fluid to enter the indicator cavity by breaking the frangible disc or extending the bladder.

The indicator cavity has a transparent or translucent wall to permit visual inspection of the coloured fluid therein.

U.S. Patent No. 4,316,466 discloses a fluid pressure sensor means having a variable volume chamber defined by a wall having a high coefficient of flexibility. The wall expands with increase in fluid pressure therein. When the wall expands to a certain predetermined extent, representing a predetermined fluid pressure, it operates an associated switch means in an electrical circuit which can be used to cut-off the power to the fluid supply means to prevent a further build-up of pressure.

U.S. Patent Specification No. 4,146,028 utilises an expansible chamber or accumulator tube in the IV administration set for collecting and storing medical fluid in the event of a temporary blockage or restriction. The object of this arrangement is to hold the medical fluid until the blockage or restriction is removed so that the desired amount of fluid is eventually delivered to the patient without the intervention of an attendant.

It is an object of the present invention to provide a simple warning device for use with IV administration sets which is reliable and easy to use. It is a further object to provide a warning device which is relatively easy to sterilise and in which the components thereof contacting the IV administration set are disposable.

Another object is to provide a warning device which reacts quickly and positively as soon as a predetermined pressure is reached.

A further object is to provide a device which is in direct contact with the fluid in the IV administration set to avoid errors due to mechanical factors.

According to the present invention we provide a pressure sensitive member having first and second configurations, the member being movable from said first to said second configuration by application of an increased differential pressure on said member, the member having no stable configurations intermediate said first and second configurations whereby rapid movement from said first to said second configuration is achieved.

Preferably the member is a flexible membrane which advantageously comprises a tubular portion having a closed end and a peripheral radial extension at its other end.

The invention also includes a pressure sensitive device incorporating a pressure sensitive member in which the pressure sensitive member is disposed at the end of a tubular arm communicating with a fluid conduit for connecting in the tubing of an IV administration set.

The device may comprise a T- or a Y-joint and the ends of the joint may be provided with luer-type connections.

The pressure sensitive device may be provided with a sensor for detecting the configuration of the pressure sensitive member.

The sensor may be an optical sensor.

Referring to the accompanying drawings: Figure 1 is a cross-section of a device according to the present invention shown in an unoperated condition; and Figure 2 is a cross-section as in Fig. 1 shown in an operated condition.

The device shown in the drawings comprises a T-shaped component 10 which is adapted to be incorporated in the tubing of an IV administration set downstream of a fluid flow control device. The device comprises a male luer-type connection 11 for attachment to tubing connected to the fluid flow control device and a female luer-type connection 12 for attachment to tubing connected to the body of a patient. Thus, in operation, the device does not interfere with the flow of fluid to the patient.

A side tube 13 is provided with a luer-type connection 14 which carries a preformed membrane 15 which comprises a tubular portion 16 closed at one end 17 and having a peripheral radially outwardly extending flange portion 18. The membrane 15 may be made from a flexible liquid impervious material such as a plastics or rubber material. Preferably the material employed is a rubber latex.

In the embodiment shown the device is connected to the body 19 of an optical sensor including a light source 20 and light detector 21. The optical sensor is connected to an electronic control unit 23 connected to an audible alarm generator 24. The body 19 is provided with a luer-type connection to receive the connection 14 and the flange portion 18 of the membrane is retained by engagement with the shoulder 25.

When excessive pressure occurs in the fluid passing through the device the fluid pressure in arm 13 increases at a certain predetermined critical pressure the membrane 15 will "snap" over to the position shown in Fig. 2. There are no intermediate stable positions for the membrane 15 between the positions shown in Figs. 1 and 2.

In the position shown in Fig. 2 the light beam of the optical sensor is interrupted and this is detected by the control unit 23 which causes alarm 24 to be sounded.

The pressure at which the membrane "snaps" over can be predetermined by selecting appropriate values for a number of factors including the nature (e.g. elasticity) and thickness of the material of the membrane, the size of the membrane and the cross-sectional area of the arm 13. If desired, a number of devices having differing pressure triggering values can be provided so that a user can select an appropriate device for the particular application.

Generally, the triggering pressure value will be about 300 mm. Hg. since research has shown that this is the maximum pressure likely to be encountered in the normal operation of an IV administration set.

It will be apparent that the device, excluding the sensing device, can be made as a disposable unit and that is is relatively easy to produce in a sterile condition.

A number of modifications to the particular embodiment described above are possible within the scope of the invention. The shape of the membrane may be modified provided that the "snap" action feature is retained.

The sensor can be of any type but is preferably an electronic beam device connected to an appropriate control unit. The control unit can provide an output signal which is used to sound an audible alarm as described above and/or a visual alarm such as a warning light.

In addition or alternatively the signal from the control unit can be used to prevent further build-up of pressure by removing power to the fluid flow control device and/or by releasing the pressure in the IV administration tubing.

Claims

1. A pressure sensitive member having first and second configurations, the member being movable from said first to said second configuration by application of an increased differential pressure on said member, the member having no stable configurations intermediate said first and second configurations whereby rapid movement from said first to said second configuration is achieved.

2. A member according to Claim 1 in which the member is a flexible membrane.

3. A member according to Claim 1 in which the member comprising a tubular portion having a closed end and a peripheral radial extension at its other end.

4. A pressure sensitive device incorporating a pressure sensitive member as claimed in any of Claims 1 to 3, in which the pressure sensitive member is disposed at the end of a tubular arm communicating with a fluid conduit for connecting in the tubing of an IV administration set.

5. A pressure sensitive device according to Claim 4, in which the device comprises a T-or a Joint.

6. A pressure sensitive device according to Claim 4 or 5, in which the device is provided with luer-type connections.

7. A pressure sensitive device according to any of Claims 4 to 6 having a sensor for detecting the configuration of the pressure sensitive member.

8. A pressure sensitive device according to Claim 8 in which the sensor is an optical sensor.