WO2004073577A1

WO2004073577A1 - Pad

Info

Publication number: WO2004073577A1
Application number: PCT/GB2004/000658
Authority: WO
Inventors: Christopher Rowe
Original assignee: Huntleigh Technology Plc
Priority date: 2003-02-24
Filing date: 2004-02-19
Publication date: 2004-09-02

Abstract

A pad (1) to be placed under a mattress or cushion or directly under a patient includes channels (5) with air at atmospheric pressure. The channels' geometry designed to maximise atmospheric pressure fluctuations caused by patient movements. The channels (5) have connectors (2) at their ends leading to a housing (3) accommodating a pressure sensor, associated controls, The pressure sensor recordings are fed into a micro-controller, analysed and various types of movement distinguished, including large and small body movements, patient occupancy, patient location, patient entry/exit, and patient movements related to physiological processes for example, respiration, heartbeat or pulse and the desired parameter or parameters provided as an output.

Description

PAD

The present invention relates to an air filled pad for patient monitoring, in particular a stand alone pad that is capable of monitoring all, a combination of or any one of patient occupancy, patient exit and entry, patient body movement and patient physiological processes, such as respiration, pulse or heartbeat.

It is known that there is a link between the rate of spontaneous body movements and the risk of developing pressure sores (Exton-Smith et al, 1961) . A cheap and reliable method of recording patient movement would be a significant aid to patient assessment and monitoring, particularly with a device which could be used on a wide range of beds and other furniture in both a clinical and domestic/residential setting.

There have been several systems developed to measure body movement, body position and bed exit using fluctuations in air pressure in the supporting cells of air mattresses and in sealed inflatable bodies inserted between a patient and supporting surface.

However, all these systems have cells at a pressure greater than atmosphere, requiring air pressure pumps and associated controls for their operation. The aim of this invention is to seek improvements.

Accordingly, the invention provides, a pad for monitoring patient movement, the pad to be located under a patient and comprising at least one chamber at atmospheric pressure, detection means to detect air-pressure fluctuations at substantially atmospheric pressure within the pad as a result of patient movement, and control means to collect the data and analyse the data to provide an output related to movement of a patient on the pad. Advantageously, the pad is not inflated and therefore has no requirement for a pump making the whole system simpler, more portable, easier to operate and cheaper. The mechanical properties of the pad are such that patient movement creates pressure waveforms centred on atmospheric pressure that are clearly distinguishable. Preferably, the detection means and control means are located within the pad. Preferably, the pad can be placed under a support, for example a mattress or cushion, or more preferably, directly under the patient.

Preferably, the pad chamber comprises at least one channel open at one end and leading to the detection means, for example, a pressure sensor, at the other end. Preferably, the one or more channels can include foam inserts to filter out certain pressure fluctuations.

Preferably, more than one pad can be located under different parts of a patient to detect patient movement at these different locations, or alternatively, the pad when located under a support comprises channels that extend to different areas of a support to detect patient movement at these different areas on the support .

Preferably, the control means collects the pressure sensor recordings which are analysed and distinguished between the different types of movement detected, between voluntary large and small body movements, for example, patient entry/exit and patient location, involuntary body movements and body movements due to respiration, heartbeat, and pulse and all, a combination of or any one of the desired movements is provided as an output. Therefore, the pad is capable of providing information relating to the voluntary body movements, involuntary body movements and the body movements indicating respiration, pulse or heartbeat and all or some or only one of the movements can be chosen to be provided as an output .

In one preferred embodiment, the output is adapted to provide information relating to patient occupancy. Similarly, patient entry/exit can be monitored by the detection of sudden large changes in the air pressure within the pad. In another preferred embodiment, the output is adapted to provide information relating to the involuntary body movements of a patient on the pad. Involuntary body movement monitoring provides an indication of whether a patient is sitting or sleeping normally. These involuntary body movements of a patient and can be monitored in combination with the body movements associated with any one or combination of respiration, heartbeat and pulse to be provided as an output if required. In a further embodiment, the output is tailored to provide purely physiological monitoring of a patient by the detection and analysis of body movements relating to any one or a combination of respiration, heartbeat or pulse. Therefore, the pad enables the recording of long-term non-invasive physiological monitoring of a patient .

Preferably, the output can be displayed on a panel, stored on a media for later retrieval, transferred via direct or remote link to another location or used to activate an alarm.

The present invention is described by way of examples below, with reference to the accompanying drawings in which: Figure 1 is a schematic diagram of a one embodiment of the invention;

Figure 2 shows the signal processing technique; Figure 3 shows the output of the pad relating to patient occupancy; Figure 4 shows the output of the pad related to respiration and body movement; and

Figure 5 shows the output of the pad related to respiration and pulse of the patient. Referring to Figure 1, a pad 1 includes channels 5 for air flow, the location and configuration of the channels 5 designed to maximise pressure fluctuations to be measures either as a result of voluntary body movements, involuntary body movements or body movements during any respiration, heartbeat or pulse. The pressure in the pad 1 varies around atmosphere and even below atmosphere depending upon the type of body movements . The number of channels 5 can vary from a single channel to a more complex design comprising an array of channels covering the whole of a patient body or patient support. The pad 1 is made by RF welding two sheets of PU along the sides and channel edges, the channels 5 having one or more open ends with connectors 2 at some of their ends . For some applications, foam inserts are included within the pad 1 to filter out some movements.

In use, the air flows through the pad 1 via the connectors 2 to a housing 3 containing a pressure sensor and associated controls. The other end of the pad 1 can also be open to atmosphere. The pad 1 can be located directly under a patient or under a support such as a mattress or seat. The pad 1, if required can be held in position by suitable restraining means (not shown) . The pad 1 design and the location of the pressure sensor in the circuit can be varied depending on the desired output .

The control housing 3 accommodates the pressure sensor, associated circuitry for signal analysis and data output and the power supply. All of the pressure sensor and control components can be incorporated into the sensor pad itself. The processing of the pressure signal can be performed by analogue circuitry or digitally by a micro-controller. In the preferred embodiment, the pressure sensor recordings are input into a micro- controller. The micro-controller analyses the various types of movement detected and distinguishes the movements relating to voluntary large and small body movements, such as patient entry/exit, involuntary movements during patient occupancy/patient location and the body movements relating to respiration, heartbeat or pulse and provides an output with the required parameter or parameters .

The output can take many forms including LEDs , visual displays, sound, vibration or a switch to trigger alarms. The data can be stored on a media for later retrieval or transferred via direct or remote link to another location. Therefore, the pad system works by accurately measuring the very small pressure changes in the pad caused by body movements, respiration, heartbeat and pulse whilst a patient is sitting or lying on the pad and processing the signal to calculate and extract the desired parameter.

Figure 3 shows the output when monitoring patient occupancy, showing the pressure signals when a patient is simply sitting on the pad 1. The need to detect patient occupancy is important for domestic, clinical and safety reasons and is measured by calculating the variance level of the pressure signal which increases significantly when the pad 1 is occupied. The variance is calculated and if it is higher than a set value (calibrated experimentally) the micro-controller 13 will send an output as required to a display, alarm, telemetry system or similar to indicate that the pad 1 is occupied or not occupied. In some systems the pad 1 is used to detect the location of a patient on a chair or on a bed and transmit the information to a remote display.

In more general use, it is important to know if a patient has got out of bed or a seat when they shouldn't and in this case the pad 1 raises an alarm when this occurs. When monitoring a patient, data is collected not only when a patient gets out of the seat or bed but also to show how long they have occupied it . For patient entry and exit the micro-controller stores the previous variance level and detects if the level moves from empty to occupied for bed entry and vice versa for bed exit .

The need to assess patient movement is very important in clinical settings as it is known that patients who have limited movement are much more susceptible to the development of pressure ulcers. Movement rates can also give important information on other states such as Parkinson's disease, and the pad 1 can therefore be used in applications where movement monitoring is required. The movement can be calculated from the same variance method used to measure occupancy, with a significant movement giving a variance level very much higher than for simply occupied. The movement information can be sent to a display, alarm, telemetry system or similar to give data on movement rate, time since last movement or any similar information.

An important part of treatment for some patients is that they are rolled on a regular basis to make sure they are not lying in the same position for extended periods of time. The pad 1 is also used to detect patient movement as a result of involuntary body movements as distinct from carer assisted log rolling.

The patient occupancy, movement and entry/exit outputs are determined by calculating the variance level of the complete signal from the pressure sensor. To separate respiration, heart beat and pulse from the patient body movements, digital signal processing including filtering is used as shown in Figure 3. The outputs relating to respiration, and pulse are shown in Figures 4 and 5. Figure 4 shows normal breathing followed by small movement and rapid breathing; whereas Figure 5 show the monitoring of respiration and pulse.

The outputs relating to the respiration, heartbeat or pulse can be sent to a display, alarm, telemetry system or similar as required.

Moreover, the pad 1 can mechanically filter some pressure waveforms within the pad 1 before they are recorded by the pressure sensor. Foam inserts with their added firmness dampen the higher frequency components of pulse to leave a clearer respiration waveform. The pad 1 can be made of differing materials to give different mechanical properties, the foam can be of differing types, the number of channels 5 used and their geometry can be varied as well as the size of the pad 1 to suit the parameter to be provided. The pad 1 can be incorporated within a larger pad comprising a plurality of similar smaller pads sited at predetermined sites over a patient support to detect patient movement and for physiological monitoring of the patient over different areas of the support. Equally the pad 1 can comprise an array of channels 5 configured to span over the whole of a patient support to detect patient movement and physiological monitoring at different areas of the support .

Claims

1. A pad for monitoring patient movement, the pad adapted to be located under a patient, the pad comprising at least one chamber at atmospheric pressure, and detection means to detect air-pressure fluctuations at substantially atmospheric pressure within the pad as a result of patient movement, control means to collect the data and analyse the data to provide an output related to movements of a patient on the pad.

2. A pad as claimed in claim 1 wherein the detection means and control means are located within the pad.

3. A pad as claimed in claims 1 or 2 wherein the control means collects the pressure sensor recordings which are analysed and distinguished between the different types of movement detected, between voluntary large and small body movements, for example, patient entry/exit and patient location, involuntary body movements and body movements due to respiration, heartbeat, and pulse and all, a combination of or any one of the desired movements is provided as an output.

4. A pad as claimed in claims 1, 2, or 3 wherein the pad can be placed under a support for supporting a patient .

5. A pad as claimed in claims 1, 2 or 3 wherein the pad can be placed directly under the patient .

6. A pad as claimed in claim 1 wherein the pad chamber comprises at least one channel open at one end and leading to the detection means at the other end.

7. A pad as claimed in claim 5 wherein the one or more channels include foam.

8. A pad as claimed in any preceding claim wherein the pad extends under different parts of a patient to detect patient body movements at these different parts.

9. A pad as claimed in claims 1 to 3 wherein the output is adapted to provide information relating to patient occupancy.

10. A pad as claimed in claims 1 to 3 wherein the output is adapted to provide information relating to patient entry and patient exit from the pad.

11. A pad as claimed in claims 1 to 3 wherein the output is adapted to provide monitoring of patient body movements .

12. A pad as claimed in claims 1 to 3 wherein the output is tailored to provide physiological monitoring of a patient relating to any one or combination of respiration, heartbeat or pulse.

13. A pad as claimed in any one of the preceding claims wherein the output is displayed on a panel .

14. A pad as claimed in any one of the preceding claims wherein the output is stored on a media for later retrieval or transferred via direct or remote link to another location.

15. A pad as claimed in any one the preceding claims wherein the output comprises an alarm.