This invention relates to microwave monitoring.

There are many situations in which multiple entities, which may include people, and which, more particularly, may include patients in a hospital ward, are monitored. Monitoring is done in different ways. Thus, patients may be examined at regular intervals, for example, daily or hourly, for temperature, blood pressure, heart rate and so forth, by a nurse using a thermometer, a sphygmomanometer and a watch and recoding the measurements on a chart. This is labour-intensive and prone to mistaken readings and/or recordings. The information, entered by hand on paper, for long term storage, needs to be transcribed into electronic form, when more errors can creep in, and which, again, is labour intensive. The chart, moreover, carries only limited information, and for a full history, the clinician needs to access the main file, which will not be on the ward. And it has been known for paper items to get misfiled or simply lost. It is proposed to use electronic recording means, more specifically touch screen tablet computers such as the iPad, personal to each patient, for recording patient condition, as well as providing an appointment diary, a drug schedule and many other important information items, so that all the information a clinician needs is instantly available at any time.

This is clearly highly advantageous, but still requires measurements to be taken and recorded by nurses and is in this regard as prone to error as with paper entries.

The present invention provides methods and apparatus whereby measurements and data can be entered into a record keeping system without risk of human error, and with more frequent if not, when required, continuous monitoring.

The invention comprises wireless monitoring of microwave-responsive sensors integrated into a record keeping system.

The record keeping system may comprise individual electronic data logging devices, such, for example, as patient-specific tablets in a hospital environment.

The microwave-responsive sensors may comprise garments incorporating electrically conductive elements, such as threads, woven or knitted into the garments, perhaps, that give different microwave responses under different conditions. For example, an upper- body garment incorporating knitted conductive threads will give different microwave responses under different conditions of stretch, and this can be an indication of a patient's breathing rate and whether breathing is normal or shallow. Likewise, a wristband sensor may be monitored to indicate pulse rate. Microwave responsive fabrics may be used to monitor temperature and humidity, and may be used to indicate abnormal sweating or bedwetting, as well as abnormally high or low temperature. Microwave interrogation of sensors can be effected by sensing the amplitude of reflected, transmitted or absorbed microwave energy, or a change in frequency, particularly a resonant frequency.

Interrogation can be effected by measuring response to a sweep through a frequency range of a transmitted signal.

Individual sensors can comprise an identification feature whereby a plurality of sensors may be interrogated by a common transmitted signal and responses matched to the sensors. An identification feature might, for example, be a particular resonant frequency. A sweep through a frequency range including all the resonant frequencies would yield reflected signals, say, at or near those resonances, and these would show up as peaks in an amplitude/frequency graph on which the departures from the resonances could be measured to give an indication of the variable involved. Wireless monitoring according to the invention will now be described with reference to the accompanying drawings, in which:

Figure 1 is a view of a fabric with electrically conductive elements; Figure 2 is a close-up of an electrically conductive element of Figure 1 ;

Figure 3 is a view of a garment incorporating microwave-responsive sensors;

Figure 4 is a diagrammatic illustration of a microwave generator/receiver/analyser set-up with multiple tablets; and

Figure 5 is graph of amplitude against frequency showing transmitted and reflected signals. The drawings illustrate methods of gathering information from a subject by measuring at least one property of an electrically conductive textile at a microwave frequency.

Figures 1 and 2 illustrate a fabric 11 incorporating electrically conductive threads 12. The fabric 11 is a knitted fabric, principally of elastomeric threads 13, covered with polyester fibres. The conductive threads 12 are of polyethylene multifilament yarn coated with a nanolayer of silver, copper or other high conductivity metal.

When the fabric 11 stretches, electrical properties of the conductive threads 12 will change. One of the conductive threads 12 is connected to a pressure sensor 14, which has an electrical output, serving as an aerial therefor. Figure 3 illustrates a vest 15, which incorporates patches 16 of fabric such as fabric 11.

Figure 4 illustrates a microwave set-up for making measurements of properties of a textile 11, comprising a microwave generator 41 and a microwave receiver/analyser 42. These are capable of operation over the frequency range 9kHz to 20GHz. The receiver/analyser 42 communicates with tablets 43a, 43b, 43c, 43d.

The generator 41 could, of course, be connected to the textile 11 by a cable 43, typically a coaxial cable with an N-type connector attached to a terminal 17 attached to a conductive thread (Figure 1), and the receiver/analyser 42 may be similarly connected. However, either the generator 41 or the receiver 42 or both may be wirelessly connected, to give a wearer of a garment improved freedom of movement/activity, and this is especially useful when more than one tablet is involved..

Microwave power of the order of lmW can be effective for communication between generator and textile and receiver and textile over distances of the order of a few metres while being at a safe level for subjects and attendant personnel. The arrangement may be used for patient monitoring, as, for example, for ECG monitoring, or blood pressure monitoring, using, for example, stretchable threads in a sleeve, or temperature monitoring, using threads with a high rate of change of resistance with temperature, as taught for example in WO2009001108. The arrangement may also be used for monitoring personnel in hazardous environments to give indication of ambient conditions, and for monitoring athletes and other sportspeople in training or during actual performance.

Provision for cable connection might be used for calibration. Particularly accurate measurement may be made if the measuring frequency is close to a resonant frequency of the textile. At such frequency, the reflected or transmitted radiation may be at a maximum or minimum, changing rapidly as the measurement frequency or the resonant frequency changes. Figure 5 is a graph of amplitude against frequency, showing a transmission signal having four signals Sa, Sb, Sc, Sd at different frequencies and reflected signals S'a, S'b, S'c, S'd, at slightly different frequencies, the frequency shifts in each case being due to the deviation of a measured property from it expected value, but each reflected signal being so close to its transmitted counterpart as to be readily identifiable.