PHYSIOLOGICAL MOVEMENT MONITORING

Abstract: A method and apparatus for monitoring a living body (9), for example a baby, involving transmitting radiation towards the body, receiving the radiation transmitted after modification by the body and processing the received radiation to determine the position and/or the state of the body, for example to determine if the body is breathing or its heart beating.

Description: PHYSIOLOGICAL MOVEMENT MONITORING This invention relates to the monitoring of physiological movement including breathing, heart beat, local limb and general body movement. Monitoring the breathing of a human subject is currently possible using methods involving the attachment of sensors to the subject via supporting belts wrapped around the body typically in the thoracic or abdominal regions. Such sensors may exploit the hall effect which is an electromagnetic phenomenon involving a change in electric field across a semi-conductor in response to movement of the latter which in this application may result from breathing induced chest or abdominal movement. Other types of attached sensors exploit the piezo electric effect in which breathing movement generates electric signals corresponding to the resultant compression of a sensor. Still further attached sensor methods exploit breathing induced changes of sensor capacitance or electric resistance this latter using a strain gauge. In most cases the sensors are mounted in a support and held against the body by means of a light weight supporting belt or in the case of a method exploiting electric resistance changes of a strain gauge a plurality of such gauges are incorporated in a garment. In addition to the above attached sensor methods there exist methods in which a sensor is located under a mattress on which lies the subject to be monitored. Breathing action will generate corresponding reaction forces in the contacting regions of the mattress which can be transmitted through the mattress to a sensor contacting the underside albeit with significant attenuation. Such methods can only be used on sufficiently thin mattresses of a type capable of transmitting such forces and in practice are not suitable for sprung mattresses. Because of the inevitable high level of attenuation of induced forces resulting from breathing movement transmitted through a suitable mattress, signal to noise ratios will be small and sensitivity to other - non breathing movements - relatively high. If this method is used to detect apnoea - cessation of breathing - then false indications of breathing can result and genuine apnoea fail to be detected. Regarding the methods described involving sensors attached to the body using belts or incorporated in garments such methods can cause discomfort or even trauma in subjects under test particularly in the case of very young subjects or babies. Further, breathing signals can be corrupted or distorted by movement of the subject. All the above attached sensors employ signal and power leads to enable breathing movement signals to be processed by remote control units and such leads can impede subject mobility and thus create inconvenience and possible discomfort. None of the methods described can detect local limb or generally body movement. According to one aspect of the present invention there is provided a method of monitoring a living body including the steps of transmitting radiation towards the body, receiving radiation transmitted after modification by the body and processing the radiation so received to give an indication of changes of position and/or state of the body. Preferably, a non-contacting method for locally or remotely monitoring and distinguishing between different modes of physiological movements of a supine non-cooperative body including those due to breathing, heart beat, limb movement and general body repositioning, comprises a radiation field preferably, though not essentially, optical, generated by one or more radiation emitters which may have associated components to extend the effective size and uniformity of the field and one or more radiation detectors which may have associated components to increase their effective area of sensitivity, the emitter and detector system forming a radiation field of sensitivity by means of which different physiological positional and movement modes of a body, within this field, irrespective of the body's position, may be mcnitored by detecting emitted radiant power levels temporally and or spatially modified by the size, geometry, position and movements of the body, different movement modes and positional changes being distinguishable by electronically processing detector signal outputs. If the body is stationary in all respects i.e. with no breathing, no heart beat and immobile no change in detected radiant power will result yielding constant output signal levels from each photodetector. Breathing action will create periodic movement of the chest and abdomen which will generate corresponding changes in transmitted radiant power passing over the thoracic and abdominal regions hence corresponding modulated outputs from the associated photodetectors. Heart beat will generate periodic, transient signals which may be distinguished from breathing signals using electronic filtration methods. Local limb movement will generally produce a non-periodic relatively infrequent transient signal usually of amplitude significant . y higher than breathing and hear beat signals and a likely change in average signal level/s from the associated detector or detectors output/s arising from a 5 permanent positional change of a limb. Rotational body position changes i.e. turning over or turning onto the side will generate non-periodic high amplitude transient signals from the associated photodetectors and generally changes in individual detector 0 steady output levels characteristic of the new body position. Significant translational changes in body position corresponding for example to a baby moving across or down its cot will create a new transmitted field characteristic producing in some photodetactors significant reductions in mean output signal levels from a previous high level (un- intercepted) condition and significant increases in other photodetector mean output levels resulting from the removal of the bodily obstruction impeding direct radiant transmission to a detector. Knowledge of limb movement, bodily rotational or translational movement can provide valuable information regarding the well being or medical condition of the subject in particular the quality of sleep or extent of restlessness in e_ther a sleeping or waking condition. In situations where the subject is covered by blankets or quilts over heating can arise if the head becomes covered and for very young babies such over heating can be life threatening. Measurement of breathing and other non-periodic movements described above can still be made as indicated and complete covering deduced from the transmitted field characteristic. Unlike inanimate bodies or structures where mean position is generally predictable animate bodies such as humans tend to have unpredictable mobility characteristics whilst sleeping or reclining in the supine position and particularly for babies co- operation in monitoring breathing or heart beat will be non - existent. By creating a sufficiently extensive radiant field of sensitivity from a distributed set of emitters and comprehensive photodetection facilities from corresponding detectors a body within a defined region e.g. a cot or bed can be detected and located irrespective of its position or orientation within this region. Breathing, heartbeat and other physiological movements including shivering for example can thus be monitored and the detection of extended apnoea periods carried out with the subject at any position or location within the field in the absence of any attached sensors or associated, possibly inhibiting, signal and power leads. Extended apnoea attacks are of particular concern for young babies and facilities may be incorporated into an optical detection and processing facility to generate appropriate visual or audible alarms when pre-selected apnoea period thresholds are exceeded. Breathing and other physiological movement data may be recorded and processed locally or transmitted via modulated mains, radio, telephone, or fibre optics communication links to a remote signal processing and recording facility this having particular relevance to applications in hospitals. Alternatively physiological data may be processed locally and transmitted via communication links to remote locations in the processed form where it may be displayed, recorded or made to trigger alarms. For application to very young babies including premature babies unable to either rotate their bodies or move around a cot a full field capability as described above may prove unnecessary and in this case limited field coverage may be deployed to " cover the region occupied by the baby. This procedure would reduce overall system costs. After several months a baby will be able to move around its cot and a full field movement detection facility would be advantageous in this case. This may be provided using a single system as described or a combination of connectable modular systems to increase sensitive field size. Instead of generating a constant local or extended radiant 0 field from the appropriate set of distributed radiant emitters, which would occur if all the emitters were energised simultaneously, emitters may be energised sequentially using energising current pulses with periods significantly shorter than the minimum time constants of the physiological movements being monitored. In this case the associated photodetectors would generate corresponding output pulses which may be processed to provide the appropriate movement behaviour. By this means significantly less emitter energising power would be necessary which would extend battery life if a system were required to be portable. Furthermore sequential emitter energisation may enhance the capability for a system to be more spatially selective than if all emitters were energised simultaneously which will enable differential movement to be detected more easily. This could have particular importance in the area of apnoea monitoring. One form of apnoea - obstructive apnoea - results from an obstruction of the airway which can lead to suffocation. The effect on breathing movement is to induce a condition called paradoxical breathing in which abdominal and thoracic movements are in antiphase. The detection of such antiphase breathing movement provides a highly effective means for detecting this very serious condition of obstructive apnoea. According to another aspect of the present invention there is provided apparatus for monitoring a body including transmitter means for transmitting radiation towards a body to be monitored, receiver means for receiving the transmitted radiation after modification by the body and processor means for processing the modified radiation to give an indication of changes of position and/or state of the body. This invention provides a means of remotely detecting human physiological movement using relatively robust and durable solid state opto - electronics in the form of light emitting diodes and semi-conductor photodetectors though more conventional light sources including incandescent and fluorescent types may also be employed using detectors of corresponding spectral response. However these latter would not be very suitable when sequential pulsing was appropriate due to their relatively long switching time constants. Such conventional light sources could be used however for continuous - non pulsing - applications. Conventional light emitting diodes (L.E.D.,s), are relatively small in area and to increase their effective area and also that of small area photodetectors optical diffusers may be employed with or without associated reflectors. By this means a system may be made to tolerate sufficient variations in body height above a bed or mattress and maintain a high sensitivity to low amplitude breathing and/or heart beat induced movements. A similar costly, but nevertheless otherwise practical alternative to diffusing optics to extend the vertical measurement range is to employ several vertically orientated columns of adjacent emitters and/or detectors. Such an arrangement may operate under either a continuous or sequential pulsing mode (in this latter case photodetectors and /or emitters having short time constants) for battery economy and spatial selectivity. A second alternative is to employ long vertically orientated single detectors, charge coupled diode arrays or position sensitive diodes. However detection of transmitted light using any one of the last three options would significantly increase the cost of a monitoring system. Instead of, or as well as, using optical diffusers certain transparent patterned plastics may be used in front of a detector to increase i_ 3 effective area of sensitivity. Such patterned transparent plastics typically of acrylic are available with regular parallel rows of ripple patterns formed into their surface which may act as elongate sets of narrow cylindrical lenses capable of refracting incident light to an off axis detector thus increasing its effective area of sensitivity. Such regular patterned transparent plastics may be used to 0 increase the effective area of an emitter particularly if used with associated reflecting optics. If use in combination with optical diffuser systems such patterned plastics may also be employed to enhance light diffusion efficiency. Another method for increasing the effective sensitive area of a photodetector is to position a short focal length large spherical or cylindrical convex lens possibly of transparent plastics in front of the detector such that rays intercepted by the lens are refracted to the detector. Such a procedure could be applied effectively instead of using a diffuser though would probably yield a more expensive and less compact system than would be possible with a diffuser. Optical heads fitted with concave spherical or cylindrical mirror type reflectors with emitters and detectors facing their support head would also provide a means for increasing the effective area of these emitters and detectors and hence the operational vertical measurement range. If conventional light sources are employed these may be chosen with elongate configurations long enough to accommodate a large range in subject vertical height above the mattress when vertically orientated. Instead of employing individual sets of emitters existing as either point sources or linear sources or arrays a single uniform rectangular elongate source extending the length of the field of sensitivity may be employed. In this case the radiant energisation and control requirement would be simplified but radiant power levels would need to be chosen to avoid saturation of the opposing photodetectors. In order to avoid any visual disturbance to the subject and to minimise the influence of any ambient illumination spectrally matched infra-red solid state emitters and detectors may be used the latter possessing visible daylight cut off filters. 0 Infra-red sources using associated detector filters to attenuate visible radiation i.e. daylight cut off filters, will reduce the effects of extraneous optical radiation from for example incandescent lights or daylight which if excessive could create unaccεptably high noise signals in the photodetectors. An alternative procedure would be to modulate the light source whether infra-red or visible at a frequency significantly higher than movement transient frequencies and any pulsing frequencies and detect and process transmitted signals using photodetectors and narrow band filters tuned to the radiation source modulation frequency. In practice solid state radiant emitters may be pulsed with significantly higher energisation currents than if continuously energised thus providing a further means for increasing signal to noise ratios. Alternatively to reduce the effects of extraneous optical signals corresponding emitters and photodetectors may be synchronised using for example electronic gating logic to allow detection only for the duration of the emitter energisation pulse. Apart from sequential pulsing of emitters to enhance spatial selectivity which is beneficial when detecting body position simultaneous pulsing of all emitters may be carried out which would simplify emitter control circuitry and would provide battery economy and enhance breathing signal to noise ratios due to the combined contribution from several emitters simultaneously. In application to monitoring babies in cots facilities may be provided to allow the drop side of a cot to be used when a breathing and position monitor is fitted. One arrangement employs a V clamp secured roughly mid way along the emitter unit or optical head to provide balance and one on the 0 opposing photodetector optical head. These clamps may be removably secured onto vertical cot bars typically mid way along the cot side and may be slid up and down and will rely on friction to remain in the chosen position though for additional security a wing nut associated with each clamp may be adjusted to increase the clamping contact pressure. In circumstances where the drop side is required to be lowered to attend to a baby for example the appropriate sensor unit on the drop side (emitter or detector) is slid to the uppermost position and will remain out of contact with the cot bedding when the side is lowered to its lowest position. If required the baby may be monitored with the cot side down because any movement of the baby towards the unprotected side would be detected and appropriate action taken to prevent the baby falling out of its cot. In order to provide the optimum vertical position for opposing emitter and photodetector heads to ensure maximum movement detection sensitivity an audio or visual bleeper may be employed which would be energised under optimum adjustment conditions. In practice the optical head on the non- adjustable cot side would remain in position, typically at the lowest position, and the opposite optical head adjusted to its optimum position when the drop side had been returned to its uppermost position. Ihe optical field interception method described is applicable not only to babies but children and adults using conventional beds. In the case of low base divan beds - the most popular type - sprung bracket supports may be employed which will slide under opposite sides of the bed at a position roughly corresponding to the abdominal or chest area. The brackets typically of plastics may consist of a lower foot slim enough to pass under the beds lower base edge and removably secured into position using for example a sprung plastics plate forced against the underside edge of the base. The inner ends of the feet may be connected by a rigid member to increase stability. The vertical limb of the support may lie against the side of the bed and protrude beyond the level of the bedding. The optical head may be slidably secured to the support at this upper region. To- provide additional stability to an optical head support member a rectangular U bracket may be employed with an upper limb secured under a mattress and the lower limb against the underside edge. Alternatively the lower limb may be replaced by a sprung foot as described. To accommodate different divan base depths and also enhance stability the central vertically orientated limb may be formed from two slidably connectable L shaped members to facilitate length adjustment for the appropriate divan base depth and to ensure adequate contact pressure on the upper or underside base surfaces in order to provide stability for the appropriate optical head. An optical head may be secured onto the divan base support bracket using a horizontal hinge arrangement located at an adjustable vertical position below the upper surface of the mattress such that when not in use or when the bed is unoccupied for example it may be repositioned in its lowest vertical position. In operation it would be rotated upwards about the hinge axes into a vertical position where it would be rigidly locked using for example a magnetic or ball catch mechanism. Instead of employing a rectangular U shaped optical head support member, support may be provided by a rigid panel trapped between a mattress and upper bed base and extending transversely across the full width of the bed with suitable connecting facilities at each emergent end. As an alternative to the above hinge support, vertical position adjustment of the optical heads may be provided by incorporating into the divan bracket a vertical bar onto which a clamp attached to an optical head may be slidably secured. The divan bracket may possess a central vertical limb of circular cross sectional geometry but with facilities to allow vertical adjustment of the optical head but prevent horizontal axial rotation of the head which could result in misalignment between emitter and detector. A second alternative optical head support facility may employ a vertically orientated elongate member connected to the optical head with a vertical slot of length sufficient to accommodate the required vertical adjustment range and connected to a vertical member on the divan bracket with a trap bolt passing through the slot and screwed into the bracket, facilities being provided to prevent rotation of the Optical head connecting member about the axis of the bolt using for example a guide peg secured to the divan bracket and passing through the slot. Alternatively the trap bolt may be firmly secured into the divan bracket and possess vertically orientated flats on its threads to prevent rotation of the slotted member and wing nuts screwed onto the bolt to secure adjustments. For non-divan type beds such as iron frame beds, pine beds, bunk beds, tubular hospital beds and hospital transfer trolleys and hospital incubators the above rectangular angle support bracket may not be suitable to support radial emitter and detector optical head units. In these cases the heads may be secured to side frames, or tubular or angle members, or to the sides of incubators as appropriate using either an adjustable height hinge support or slidable supports clamped onto the appropriate support members using suitably shaped clamps. In the case of incubators clamping to an upper side edge may prove to be the most suitable 0 support position. The physiological movement sensing system described may be used alone or in combination with one or more of the following sensors or sensor systems : a) Thermal radiation temperature sensors to monitor the temperature of exhaled breath or exposed regions of the breathing subject. b) Humidity sensors to monitor the humidity of exhaled breath. c). Gas sensors to monitor the concentration of important exhaled gases including CO^ and 0^. d) Flow rate sensors to monitor flow rate of exhaled gases. e) Acoustic sensors to monitor acoustic signals from breathing and other physiologically induced acoustic sources including the voice e.g. crying or moaning. Although suitable for human applications the non-contacting movement monitoring system may be applied to sleeping animals to -monitor movement, breathing and/or heart rate typically after surgery and in recovery areas as well as for general veterinary investigations of breathing and movement behaviour. Further the movement sensor may have application in monitoring behavioural movement of lower life forms including amphibians, reptiles, fish, birds and insects all in appropriately contained environments. Further the method may have horticultural applications in monitoring plant or tree growth and/or movement over short or long periods and may also have application in monitoring dimensional changes and/or movement of inanimate objects or systems on earth or elsewhere. As well as employing optical radiation emitters and detectors to monitor position and movement - specifically in the area of human physiology alternative radiation types may be employed using suitable radiation emitter and detector systems and subject to compatability of the monitored subject and environment. Such radiation types may be electromagnetic including ultra-violet, microwave, X rays and J rays, or particulate radiation including electrons, nutrons, protons and other sub nuclear particles or radiations. Alternatively ultrasonic radiations may be employed. In all cases the environments involved must be capable of transmitting the appropriate type of radiation and the monitored subject capable of absorbing sufficient of the incident radiation irrespective of the type employed such that detectable radiation shadows or intensity contrasts are formed in the plane of the appropriate radiation detector or detection system. This invention may be performed in various ways and some specific embodiments with possible modifications will now be described by way of example with reference to the accompanying drawings . Fig. 1 Shows a perspective of a child's cot fitted with opposing localised optical movement sensor heads. Fig. 2 Shows a section through a cot and its occupant intercepting a fraction of emitted radiation. Fig. 3 Shows a perspective of a cot fitted with opposing large field optical movement sensors. Fig. Shows a section through a cot with a photodetector fitted with an optical diffuser. Fig. 5 Shows a section through a cot with a photo-emitter fitted with an optical diffuser. Fig. 6 Shows a section through a cot with optical diffusers fitted to both photodetectors and photo-emitters. Fig. 7 Shows a section through a cot with a plurality of photodetectors . Fig. 8 Shows a section through a cot with a plurality of photo-emitters. Fig. 9 Shows a section through a cot with a plurality of photodetectors and photo-emitters. Fig.10 Shows a perspective of a cot fitted with an elongate photo-emitter and a single photodetector. Fig.11 Shows a plan view of a cot fitted with a single photo-emitter and a plurality of photodetectors. Fig.12 Shows a plan- view of a cot with a plurality of opposing photo-emitters and detectors providing a means for position determination. Fig.13 Shows a perspective of a cot fitted with a horizontal elongate light source and an associated optical diffuser. Fig.14a and 14b Show an elongate light source produced by end mounted individual sources. Fig.15 Shows adjacent photo-emitters and detectors with an opposing diffuse reflector- Fig.16 Shows adjacent photo-emitters and detectors with an opposing specular reflector. Fig.17 Shows diffuse reflections from a common mount for a photodetector and photo-emitter. Fi .13 Show . s optical emitter and detector heads fitted with fibre optic cables. Fig.19 Shows a schematic arrangement of an optical movement monitoring system with associated signal processing and display facilities. Fig.20a - 20c Show a side view, a plan view and a perspective view 5 respectively of a single point optical head mounting arrangement on a vertical cot bar. Fig. 1 Shows a perspective of a divan bed with a limited field optical head supported by the bed base. Figs. 2a and b Show an end view of a divan bed fitted with opposing optical heads slidably mounted on supports secured under the bed base and an enlarged view of a support foot. Fig.23 Shows a view of a single support arrangement in Fig.22 with additional stabilising members supported under the mattress Fig.24 Shows an end view of a divan bed fitted with an optical head support arrangement involving an elongate rigid support member extending the full width of the bed and trapped between mattress and bed base. Fig.25 Shows a U shaped support clamp to accomodate bedding drape. Fig.26 Shows an arrangement in Fig.25 with lockable hinge supports for optical heads. Figs. 27a, b and c Show optical head supports suitable for frame beds. Many of the explanatory figures to follow show schematic representations of optical radiation emitters and opposing photodetectors between which lie a radiation absorbing intercepting body. A point emitter source will produce a sharp shadow of an intercepting body but an extended source will produce a somewhat more diffuse or indistinct shadow behind the intercepting body due to radiation contributions from different areas of the source. The combined transmitted radiation power in the plane of a detector will decrease in proportion to the amount of emitted radiation intercepted as for a point source but for reasons of illustrative clarity schematic figures involving intercepted radiation will generally show sharp shadows or illumination contrasts irrespective of the size of the emitter source. Fig.l shows a perspective view of an unoccupied cot 1 with drop side 2 adjusted to its uppermost position level with the opposing fixed side 3. Located on opposite sides 2 and 3 of the cot are opposing localised optical emitter and detector heads 5 and 6 respectively the positions of those being interchangeable. The illustration of Fig.l shows an optical radiation emitter head 5 supporting an emitter 7 and an opposing detector head 6 supporting a photodetector 8. A fraction of the radiation from the emitter 7 will be intercepted by the photodetector 8 generating either a current or voltage output signal level proportional to the intercepted radiant power level. This output signal level will be a maximum and constant for constant emitted radiation levels in the absence of an intercepting optically absorbing body. If an optically absorbing body is placed between the emitter and detector such that it intercepts a fraction of the emitted radiant power a proportional reduction in detected output will result this falling to a minimum for complete interception of emitted radiation. If the detected radiation from the emitter were partially intercepted by a human body 9 Fig.2 say a baby laying in the cot 1 with its abdominal or thoracic regions at the same longitudinal position as the optical heads 5 and 6 then low amplitude vertical movement say due to breathing, or indeed heart beat would generate corresponding changes in detected radiant power levels hence proportional output signals from the photodetector 8. An opposing emitter 7 detector 8 pair will define a zone of sensitivity _A bounded by upper and lower lines 10 Fig. 2. (The vertical closely spaced lines represent radiation flux) . The narrower the zone the more critical the location of an intercepting body in order for its vertical movement to be detectable. This zone width will increase with the vertical dimensions of emitter 7 and detector 8 sensitive areas. If sensitivity to movement is required over the entire cot mattress area then instead of employing localised optical heads 5 and 6 which will only provide a limited field of sensitivity but would be adequate for a very young or premature baby unable to mobilise itself a full field movement sensitivity capability could be produced by employing an optical emitter head 12 and detector head 13 Fig.3 each extending the full length of the mattress 11. The emitter head 12 will contain a horizontal row of individual eπ_i__ar3 7 directing radiation towards a corresponding set of photodetectors 8 supported in the detection head 13. A living human subject lying between the emitter and detector optical heads will now generate changes in detected radiant signal levels generally in several photodetectors proportional to the amplitude of movement irrespective of the subjects location in the cot. Further from a knowledge of the bodily intercepted and un- intεrcepted detected optical radiation levels the position of the body within the area of the cot can be deduced. In order to increase vertical measurement range to allow for variations in vertical height between different sized babies when lying down or to allow for large vertical height variations arising, for example from rotational positional changes the effective sensitive area of a detector may be significantly increased by the use of diffusers. Fig. 4 shows a section through a cot 1 and subject 9 lying between an emitter 7 and detector 8. Located in front of and close to the detector 8 is an optical diffuser 14 supported by and running the full length of the detector head 13. This diffuser in combination with a high reflectivity detector support head 13 will scatter .light intercepted by it to the detector thus increasing the effective movement sensitivity zone from &A (Fig.2) to A shown in reduced scale in Fig. . and defined by the zone bounding lines 10. A is typically very much greater than 6A. Instead of using a diffuser 14 to increase the effective sensitive area of a detector 8 it may be applied to an emitter optical head 12 Fig. 5 significantly increasing its effective emission area and hence that of the movement sensitivity zone to A defined by the zone bounding lines 10 where A f is typically much greater than _A (Fig. 2). An inspection of Fig. 4 will, indicate that the zone height on the emitter side is smaller than ...at on the deteccor side and increases progressively as the detector is approached. The effect of this is to produce a high sensitivity and small measurement range on the emitter side, the left hand side in Fig.4, and a progressively decreasing sensitivity but increasing measurement range as the detector 0 side is approached. In the case of an emitter with an associated diffuser the converse is true with maximum measurement range and minimum movement sensitivity close to the emitter hence diffuser and minimum range but maximum sensitivity on the detector side with intermediate ranges and sensitivities in between these outer limits. In order to create more uniform conditions with sensitivity and range remaining significantly more constant for all positions between emitter and detector diffusers may be used with both emitter and detector head Fig.6. In this figure the sensitive zone is more rectangular as shown by the vertical cross hatched region. In practice diffusers will generally not be perfect and internal optical reflectors may be employed to create more uniform illumination conditions between diffuser and associated optical head. Further the photodetector may be orientated and located on its support such that its light sensitive area does not necessarily face a corresponding emitter. It may for example face vertically down or up or even away from the opposing emitter facing a highly diffused reflective support member in order to improve uniformity of response to subject vertical movement over a prescribed vertical range. Instead of using diffusers to increase the effective areas of either o "both pho o-emit ers and detectors n order to increase the range over which vertical movement may be measured a vertical set of two or more individual detectors may be used 15 Fig. 7. mounted on a support head 16 and facing a single emitter 7. Alternatively a vertical set of two or more photo-emitters may be used 17 mounted in a support head 18 Fig.8 together with a single opposing photodetector 8. The set of photo-emitters would approximate to a linear radiation source but if emitter separation were large compared to their individual active areas measurement dead spots may result and similarly for multiple detection. In either case this limitation may be significantly reduced using optical diffusers 14 Fig. 7 and Fig. 8 shown in broken line. If opposing multiple detectors 15 and emitters 17 are used together Fig. 9 then both range and uniformity of movement sensitivity across the cot or bed width will be increased particularly if diffusers 14 are used shown in broken line in Fig. 9. LED emitters whether infrared or visible have in general a significantly narrower spectral band width than conventional incandescent light sources and this may be exploited in reducing the effects of extraneous light sources by- employing matching narrow band pass optical filters in front of the detectors. In practice the lenses of infrared detectors frequently have associated filters to reject or attenuate visible light thus improving signal to noise ratios. Alternatively, or in addition LED emitters may be modulated and the resultant modulated detected signal filtered using a narrow band pass electronic filter centred on the modulation frequency. All optical frequencies lying outside this pass band will be rejected or attenuated. If this method is chosen to attenuate extraneous light effects then modulation frequencies must be chosen to be non- synchronous with unwanted extraneous frequencies. For U.K. 5 applications AC mains frequencies of 50 Hz will yield a 100 Hz optical modulation of typical incandescent or fluorescent light. Thus for U.K. applications LED modulation and photodetector electronic filter pass band frequencies should differ from and be non-synchronous with 100Hz. 30 In circumstances where LED emitters are pulsed then corresponding detectors may be electronically gated open for the duration of a pulse ensuring insensitivity to any light outside such pulse periods hence yielding high signal to noise ratios. If photo-emitters are not operated in a pulsed radiation mode but energised continuously to generate constant radiant power levels then visible conventional incandescent sources may be used instead of LEDs. The latter would in general generate a much greater spectral range of radiation with significantly higher radiant power levels. If such emitters are under run by only a few per cent their life will be increased many fold. Also such emitters are readily available or can be configured, to provide relatively large radiant emission areas compared with typical LEDs and would thus limit the number of emitters necessary to accommodate a large vertical movement measurement range. For example a single elongate typically tubular incandescent emission source 19 Fig.10 will provide adequate vertical measurement range with a single detector 8. If a large field photodetector head 13 is employed consisting of several detectors 8 shown in plan Fig.11 then the field of sensitivity will be increased significantly. Fluorescent sources tend to have cylindrical geometries and may be used in place of the above incandescent sources. In all cases involving visible light sources there may result visual disturbance of the bed or cot occupant. However in the case of babies or young children such sources would provide a child's night light function thus providing dual benefits - movement and breathing detection and night time reassurance and security. Low amplitude vertical movement associated with breathing or 0 heart beat will generally produce a corresponding low amplitude periodic modulation in transmitted light levels and corresponding low amplitude periodic modulated output signal levels from effected photodetectors. In these circumstances output signals will generally include a direct current dc component together with the above significantly lower level movement modulated signals. The dc component may be readily removed using electronic filtration methods possibly preceeded by amplification this latter to improve overall signal to noise ratios and facilitate subsequent electronic data handling or processing. The dc component provides an effective means for detecting and quantifying any rotational or transitional positional changes of the subject since these will provide significant changes in output levels from effected photodetectors. For example a rotational change such as a baby turning over from lying on its back to its side will create a signal reduction in dc output level from effected photodetectors. Alternatively if a baby moves down its cot its position may be determined from those photodetectors for which transmitted radiation has not been intercepted Fig.12. By employing unfocussed and uncollimated LEDs significant emitted radiated beam angular divergences or beam spreads can result typically — 30° about an LEDs axial position 20 Fig. 12 such that radiation from a particular photo-emitter will pass to several adjacent photodetectors so long as the emitter - detector lines of 3ight, for example 20, 21 and 22 remain un-intercepted. In practice emissions will possess more divergent components than indicated but only two are shown in Fig.12 for clarity these being symmetrically disposed about the LEDs axis 20. It can be seen therefore that a single emitter can generata signals in several neighbouring detectors and each 0 photodetector may thus receive signals from different emitters. By energising the set of emitters sequentially rather than simultaneously emissions from different emitters to a particular detector may be distinguished. From a knowledge of un-intercepted axial and divergent beams the longitudinal and lateral positions of a subject e.g. a baby over the area of a cot can be deduced. If accurate location of body position within a sensitive area is not important or if non accurate positioning information is acceptable then the set of individual emitters on the emitter optical head may be replaced by a single uniform continuous emitter. This may be produced by employing one or more elongate fluorescent tubes 23 Fig. 13 - shown in broken line - preferably low voltage for safety, running the full length of the emitter optical head 12. To extend the vertical movement range the fluorescent tube may be positioned behind a diffuser 14 mounted on the optical head 12. Instead of employing fluorescent tubes to provide a uniform extended light source other sources could be used including incandescent or high powered LEDs. In this case optical radiation either visible or infrared would be beamed along an emitter support head 24 Fig. 14 - preferably highly diffusely reflecting - by mounting an emitter 7 at one or both ends of the head. To enhance radiant emission uniformity an optical diffuser 14 Fig. 14b, mounted in front of the reflecting head 24 and supported by this head, may be employed. By using one or a small number of such radiant sources together with reflection and diffusion optics emitter energisation and control requirements will be significantly reduced and the overall cost and complexity of a movement sensing system reduced. 0 An alternative to employing opposing emitter and photodetectors supported on optical heads disposed on either side of the subject to be monitored would be to support emitters 7 and detectors 8 on a single support head 25 preferably but not essentially with emitters located vertically above detectors forming emitter/ detector pairs Fig.15. Opposite such a pair would be supported a high reflectivity head 26 of horizontal length preferably equal to that of the emitter / detector support head ' . Radiant emission not intercepted by a body would pass to the reflector head which would in effect form an extended secondary emission source. If the reflector head produced diffuse reflections then a fraction of incident light would be scattered back to the photodetector having been intercepted by the intervening body producing a detected signal output dependant upon body movement and position. To avoid, direct reflections from the body from emitted radiation which would yield a dependence upon the emissivity characteristics of the body an optical stop (not shown) could be provided close to the emitter to prevent direct radiation passing to the body in which case only radiation reflected from the opposing reflector head would be utilised. A diffusely reflecting head would not require critical vertical orientation adjustments of the reflecting surface since small angular deviations of this surface about the vertical would be tolerable. If higher reflected signal power levels were required to enhance for example detector signal to noise ratios then specular reflectors could be employed instead of a diffuse ones. Such a specular reflector may consist of a plane vertically orientated mirror 27 Fig. 16 typically of plastics, which would provide a cost effective reflector facility but would require more precise vertical orientation than that for a diffuse reflector though if detectors were used in conjunction with a diffuser 28 tolerances in reflector orientation positions would be significantly increased. Alternatively tolerances in reflector orientation would also be increased by employing a highly diffused reflecting emitter 7 - detector 8 support head 29 Fig. 17 with the detector orientated such that it was sensitive to diffuse reflections 30 from the support head 29 derived from specular reflections 31 from the opposing reflecting head 27 Fig. 16. If a convex mirror was used instead of a plane one 27 Fig. 16 then this would also make mirror orientation adjustments in a vertical plane less critical. If reflecting surfaces with high diffuse reflectivity, including those with retroreflective properties, are used then higher radiant power levels than would be produced with conventional diffusely reflecting surfaces can be generated yielding higher detector signal to noise ratios but avoiding the requirements for critical setting up which can exist for mirror type reflectors. An alternative to locating photo-emitters 7 and detectors 8 on optical support heads mounted directly onto the sides of a cot or bed as appropriate would be to replace each emitter 7 and/or detector 8 by respective fibre optics cables 32 ami 33 Fig. 13 with corresponding active ends 34 and 35 on support heads 36 and 37 respectively and emitters and detectors (not shown) located at the other ends of their corresponding fibre optics cable 32 and 33 respectively and secured in a control unit 38 Fig.18. The geometrical arrangements on the optical support heads 36 and 37 of the active ends 34 and 35 of said fibre optics cables may be similar to that involved with corresponding directly mounted emitters 7 and detectors 8. Emitter fibre optics cables 32 may be energised sequentially or simultaneously as for directly mounted emitters 7. For simultaneous energisation a single high powered source may be used if all optical fibre input ends are brought together. Radiation wavelengths may be in the visible or infra red and radiant emissions modulated if required for enhanced signal to noise ratios. Photodetection procedures applicable to direct mounted detector configurations to provide for example extraneous light source rejection and spatial selectivity may also be applied to detectors employing fibre optics. The output signals from the various photodetectors will provide information relating to movements corresponding to breattϊing and heart beat for example both of which will be relatively low amplitude. High amplitude transient output signals will result from local limb movements or general bodily positional movements and near steady state signal levels will indicate the geometrical position of a baby within the sensitive field. Fig. 19 shows a schematic arrangement of an electronic control and display system including detector signal processing equipment 40 radiant emitter drive circuitry 41 and display and interfacing electronics 42 all preferably in the same containment. Facilities are included to minimise the effects of extraneous optical signals typically from incandescent or daylight sources using for example 5 electronic filtration and / or modulation methods. To distinguish between the different transient signals of the various modes of physiological movement, narrow band electronic filters or equivalent may be used. Facilities 42 may be provided to generate appropriate output data for 0 visual displays and audio indications to enable monitoring of each of these physiological variables directly and present information in a clear and unambiguous form either locally to the subject or remotely via radio, fibre optics, telephone or mains transmission links. Facilities may also be provided to interface 42 the processing control unit output signals to a computer 43 for further processing and recording as appropriate. When certain physiological parameters e.g. breathing rate or apnoea periods fall outside preset safe limits local or remote visual and or audible alarms will be activated to allow remedial action to be taken. Similarly if a baby is restless during sleep or indeed when awake this may be a matter for concern since the baby may be unwell e.g. feverish or become cold due to kicking off the bed clothes and this condition can be deduced by detecting high amplitude transients from local or general body movements as well as positional changes. The position of a baby within the sensitive area of a cot 1 which for full length emitter and detector heads 12 and 13 Fig. 12 respectively represents the area of the cot mattress, may be deduced from the set of the photodetector 8 output levels. High level mean outputs indicating un- intercepted transmitted light from emitters 7 and low level mean outputs indicating intercepted emissions. Detector output information may be fed directly to an oscilloscope (not shown) for visual display and possible processing or to a computer 43 or microprocessor using a suitable analogue to digital converter and a seriel e.g. RS232 or parallel IEEE data transfer link 44 and a graphic illustration of a body and its position displayed on a visual display unit 45. Periodic modulations from 0 breathing or heart beat and local limb movements yielding non periodic infrequent transients may be represented graphically by for example intensity modulations of the corresponding physiological regions on a display schematic or alternatively by modulated colour changes at these regions. Heart beat and breathing motion may be distinguished by programming different colours onto the appropriate region of a graphics image or schematic on a VDU 45. In this section frequent use is made of the terms - light emitting diode and liquid crystal dot matrix elements. For reasons of convenience, light emitting diode will be abbreviated by 'LED' as previously and liquid crystals by 'L.C. As an alternative or in addition to using a computer 43 to generate a visual indication of body position, breathing and heart beat as well as local limb movement an LED or L.C. two dimensional dot matrix display may be employed 46 Fig. 19. In this case the general position of a body may be displayed schematically using for example illuminated LED or contrasting L.C. dot matrix elements 47 corresponding to radiant emissions intercepted by the body. Fig. 19 shows a 4 X 4 dot matrix array for illustrative purposes but in practice to achieve higher spatial resolution dot matrix arrays with significantly larger numbers of elements may be used. A visual indication of breathing may be given by breathing induced intensity modulation of the corresponding LED or L.C. dot matrix elements. Similarly local limb movement and or general movement or restlessness can be made to generate corresponding transient changes in effected LED or L.C. dot matrix elements. Heart beat may be displayed by 0 intensity modulations of the corresponding illuminated LED or L.C. dot matrix elements within the array or on a separate dedicated LED or L.C. dot matrix element 48. To distinguish heart beat from breathing this latter may be displayed on a second dedicated LED or L.C. dot matrix element 49 intensity modulated by breathing action. Other local limb or general body movement transients may be displayed on a third LED or L.C. dot matrix element 50 again intensity modulated by such transients. As an alternative to intensity modulation of dedicated LED's or liquid crystals to provide visual indications of the various physiological movement modes bar graph type displays may be used , one for each mode or a single display employed with, a facility to switch between modes as required. Instead of employing dot matrix arrays consisting of relatively large LEDs or L.C.s, high resolution graphics display units may be used in order to provide better image and display quality where appropriate. As an alternative to producing local visual image intensity or colour modulation of the appropriate physiological movement characteristics a more quantitative procedure may be employed by generating corresponding graphics traces using an amplitude vs time display mode. This is particularly applicable to computer and graphics display systems as well as to analogue and digital oscilloscope units. By using computers or microprocessors important mathematical functions of the more periodic type of signal modulations i.e. those from breathing and heart beat can be calculated. Such functions would include frequency, frequency deviation or standard deviation, apnoea delays ( for breathing ) and 0 apnoea repetition rates as well as mean amplitude and amplitude deviation or standard deviation. Furthermore random physiological movement transients from limb or general body movement may be quantified using computer or microprocessing methods and visual and or audio indications or alarms produced when appropriate movement threshold limits, which may be preset by the equipment user, are exceeded. In the case of application to monitoring young babies for example extended apnoea periods beyond 15 seconds may prove to be a matter of concern and in this case an apnoea threshold limit of 15 seconds would be set with longer delays triggering alarms. Signal processing methods described so far involve time domain analysis. By using electronic frequency analytical techniques for example Fourier transform analysis periodic and transient frequency spectra may be generated from the appropriate real time movement data and may provide an alternative and powerful way of characterising such movements though such a procedure would generally involve significantly more expensive processing instrumentation. If required audio indications of heart beat, breathing and local limb or general body movement may be generated with audio output modulated transducers 51, 52 and 53 Fig. 19 respectively. Breathing and heart beat repetition rates will in general fall below audio frequencies of approximately 30Hz thus to hear them audio signal frequencies typically of several hundred Hertz can be employed and modulated by the appropriate movement signals. Repetition rates of breathing and heart beat are unlikely to be equal and coherent thus simultaneous audio indication of both variables are possible but to distinguish them from 0 each other it is preferable to employ separate individually switchable audio indicators as shown one for breathing 52 and one for heart beat 51. An audio indication of the general position of a baby in a cot may be produced by for example generating a low frequency signal when the baby is at one end of the cot and a progressively higher frequency signal for positions towards the other end. Audio alarm signals may be generated when a baby assumes an undesirable location within a cot. All visual and audio indication signals may be generated locally or remotely using for example radio, fibre optics, mains or telephone communication links and recorded using either analogue or digital methods for example a computer disc storage system. Fig.20a shows a side view of a baby's cot 1 with a large field optical head 54 supported by a single vertical cot bar 55 using a clamp 56 see also Fig. 20c. A supporting bar 55 is typically centrally positioned along the appropriate cot side and the optical head clamp 56 - shown with a V configuration 61 in Fig. 20b - is secured in position along the length of a bar 55 such that it remains stable through frictional forces which may be increased by increasing clamping pressure using a bolt and wing nut arrangement 62 Fig. 20b. Under low friction conditions - i.e. with the wing nut released the optical head 54 may be slid up and down the bar 55. This optical head support clamp arrangement 56 may be used for both the fixed cot side 3 and the vertically adjustable - drop side 2. Operational conditions will correspond with opposing optical support heads adjusted along the appropriate support rail 55 to a lower position shown in short broken line 57 on the drop side 2 Fig. 20a and 20c and continuous line 58 on the opposite fixed side 3 in Fig. 20c. When the drop side 2 is required to be lowered because of attention to a baby the optical head 54 may be raised to its uppermost position 59 shown in long dash broken line in Fig. 20a and 20c to avoid interference resulting from lowering the cot side. The fixed cot side optical head may remain in its lower position 58 unless bedding or mattress changes are required. Support clamps 56 may be of various types but the 'V configuration 61 Fig.20b may be used with a range of cot bar cross sectional geometries. For applications employing short field optical heads e.g. for immobile premature babies, support for these heads may be similar to that for relatively long large field optical heads. Monitoring systems described for cot applications show optical heads located on the insides of opposing cot sides. In these circumstances in order to avoid possible discomfort or even injury to a baby in a cot optical heads and associated fittings would have smooth surfaces and no sharp edges or corners. Optical heads may also be located on the outside of each opposing cot side but in this case to avoid small measurement dead spots due to optical beam interference by cot bars emitters or detectors must not be located directly behind cot bars though if diffusers are employed this interference effect would be negligible and in this case location of emitters or detectors in an optical head becomes non critical. 5 For older children or adults involving low base divan beds 63 Fig. 21 an alternative means for supporting optical heads is necessary . In all cases a support needs to be mechanically stable and provision made to allow vertical adjustment of opposing optical heads 64 (where one of these may be a reflecting head). Fig.22a shows one such arrangement indicating an end view of opposing optical heads 64 slidably mounted on stable vertical stiffened lower support members 66 see also Fig. 23. To facilitate vertical adjustment each upper support member 65 may possess a long slot 67 - shown cross hatched in member 65 - through which passes a bolt 68 firmly secured into the member 66 and preferably with vertically orientated machined flats on the threads to prevent rotation of the member 65 away from the vertical. An adjacent guide peg (not shown) may be used as an alternative to machined flats on a bolt. The slotted member 65 may slide freely over the bolt 68 and the required vertical position secured by tightening a wing nut or equivalent 69 on the bolt 68. Each lower support member 66 may possess sprung feet 70 to create adequate contact pressure with the floor when inserted under the lower edge 71 of the divan base 72 Figs. 22 and 23. To enhance mechanical stability of optical head supports and facilitate accurate re-positioning if optical heads are required to be moved away from a bed a rigid elongate panel member 73 shown in broken line in Fig. 22a and b passing under the bed base 72 may be employed with end securing facilities 77 to the feet 70 of support vertical side members 66. With or without the connecting member 73 additional support may be provided using upper side members 74 Fig.23 on each vertical support member 66 slidably adjustable along the length of the appropriate member 66 to accommodate different divan base 72 heights and enhancing support by entrapment between mattress underside 79 and upper surface 76 of the bed base 72. As an alternative to under bed support feet 70 with or without connecting member 73 optical head 64 support may be provided by a rigid elongate panel member 78 Fig.24 extending transversely across the bed 63 and trapped between the underside 79 of the mattress 75 and bed base upper surface 76 and with emergent end provision to rigidly secure optical head 64 short vertical support members 65. To allow bedding to drape sufficiently over the side edges of a bed the side member 65 may be shaped to form a deep 'U' geometry 80 with an inner slotted limb 81 being connectable to the under mattress support panel 78 Fig.24. Such a U shaped geometry 80 may be used with other optical head support members . Under non-operational conditions such as when a bed is unoccupied, when an occupant requires to get out of bed, or for very sick occupants when bedding is required to be changed whilst the bed is occupied optical heads supports may be hinged 82 at heights typically corresponding to the mattress upper surface 83 Fig.26 and lowered into a non operational position 84 shown in broken line in Fig. 26. 5 This hinge arrangement may be used with other optical support members. Vertical adjustment and securement of optical heads 64 for an under the mattress support member 78 Fig. 24 - 26 may be essentially the same as that described for those methods 0 involving a lower support member 66 and under the bed foot 70 see Figs. 21 - 23. As for the latter application optical heads have upper support members 65 containing slots slidably secured to the- under mattress support member 78 by bolts with machined flats 68 firmly screwed into the memDβrs 2578 adjustments being secured and stabilised with wing nuts or equivalent 69. In applications involving frame beds which include pine beds, bunk beds, hospital beds, hospital transfer trolleys and other iron frame bed types, horizontal side frames are 30 generally suitable for mounting optical heads using clamps with geometries to suit the frame cross sectional geometry. Vertical adjustments and securement of optical heads for frame bed applications are again similar to the ones described for divan beds but with the slotted 67 upper support member 65 slidably secured to the appropriate frame clamp using again bolts 68 and wing nut or equivalent 69 to stabilise and secure optical head vertical adjustments Figs. 27a - c. For rectangular side frame cross sectional geometries 85 Fig.27a typical of pine beds a rectangular G section geometry clamp 86 may be used with a clamp bolt 87 screwed through a threaded hole 88 in the clamp 86 with a cushioned or freely rotatable end plate (not shown) to avoid damage to the bed frame 85 when clamped. For frame beds with tubular cross sectional geometry side members 89 Fig.27b a similar arrangement for supporting an optical head support member 65 to that shown in Fig.27a can be used but conveniently with the 'G' section geometry support block 86 in Fig.27a replaced by a support block 90 with an upper inverted V section geometry 91 Fig.27b with a clamp bolt 92 screwed into the lower arm such that on tightening the clamp bolt 92 the clamp 90 will be secured to the frame 89 by a three point pressure contact. For beds with metallic angle side support frames 93 Fig.27c a rectangular 'G' section clamp 94 may be employed to support the member 65 using a clamp bolt 87 to secure the clamp 94 to the angle frame 93. 5 Applications of optical heads discussed so far have involved support members being secured in some way to a bed, cot or incubator for example all of which would generally be stationary during monitoring operations. In such cases mechanically stable free standing optical head supports may 0 be employed with facilities to locate each opposing optical head in the appropriate operational position. Such supports may stand on the floor on either side of the bed, cot or incubator. Alternatively a common single free standing optical head support stand may be employed with one optical head secured to the stand side and an opposing optical head to the other side by a transverse overhanging support arm secured to the main stand. Similar optical head free standing support methods may be applied to any stationary monitoring situation including patient monitoring on stationary hospital transfer trolleys or stationary wheel chairs with appropriate orientation and location facilities for optical heads. In circumstances where a vehicle is moving e.g. a moving transfer trolley or wheel chair or even an ambulance optical heads are more appropriately secured directly to the vehicle and any mechanically induced noise in detector signal outputs, due to optical head vibrations, may be removed by electronic filters or equivalent in the electronic signal processing system. The above embodiments are given by way of example only, many variations are possible without departing from the invention. For example, collimators may be used to reduce the influence of unwanted radiations and thus improve the optical signal to noise ratios.

Claims: LAIMS 1. A method of monitoring a living body including the steps of transmitting radiation towards the body, receiving radiation transmitted after modification by the body and processing the radiation so received to give an indication of changes of position and/or state of the body. 2. A method according to claim 1 including the step of producing an alarm signal when the position and/or state of the body meets certain predetermined criteria. 3. A method according to any preceding claim, wherein the radiation employed is optical. 4. A method according to claim 1 or 2, wherein the radiation employed is infra red. 5. A method according to claim 1 or 2, wherein the radiation employed is ultrasonic. 6. A method according to any preceding claim, wherein radiation is transmitted intermittently towards the body. 7. A method according to any preceding claim including the step of filtering the radiation so received before the processing of the radiation to give an indication of changes of position and/or state of the body. 8. A method according to any claim 7, where the filtration of the radiation is achieved by using a physical filter. 9. A method according to claim 7, where the filtration of the radiation is achieved by using an electronic filter. 10. A method according to any one of claims 7 to 9 including the step of modulating the transmitted radiation and matching the filter to that modulation. 11. A * method according to any preceding claim including the step of transmitting the radiation through a collimator. 12. A method according to any preceding claim including the step of allowing the radiation modified by the body to pass through a collimator before it is received. 13. A method according to any of claims 1 to 4 or 6 to 12, where the steps of transmitting and/or receiving radiation includes the use of fibre optics. 14. A method according to any preceding claim including the step of providing a visual display to give an indication of the position and/or state of the body. 15. A method according to any preceding claim, wherein the radiation received is processed in order to detect and characterise breathing of the body. 16. A method according to any preceding claim, wherein the radiation received is processed in order to detect and characterise heart beat of the body. 17. A method according to any preceding claim, in which the radiation is reflected prior to being received. 18. Apparatus for monitoring a body including transmitter means for transmitting radiation towards a body to be monitored, receiver means for receiving the transmitted radiation after modification by the body and processor means for processing the modified radiation to give an indication of changes of position and/or state of the body. 19. Apparatus according to claim 18, wherein the processor means is arranged to produce an alarm signal when the position and or state of the body meets certain predetermined criteria. 20. Apparatus according to claims 18 or 19, wherein the transmitter means comprises one or more optical light emitting diodes. 21. Apparatus according to claims 18 or 19, wherein the transmitter means comprises one or more infra red light emitting diodes. 22. Apparatus according to claims 18 or 19, wherein the transmitter means comprises ultrasonic emitting means. 23. Apparatus according to any one of claims 18 to 21, wherein the receiver means comprises one or more semiconductor photodetectors. 24. Apparatus according to any one of claims 18 to 23, wherein the processor means comprises an electronic processor. 25. Apparatus according to any one of claims 18 to 23, wherein the processor means comprises a computer. 26. Apparatus according to any of claims 18 to 25 including filtering means for filtering the received radiation before it is processed. 27. Apparatus according to claim 26 where said filtering means comprises a physical filter. 28. Apparatus according to claim 26 where said filtering means comprises an electronic filter. 29. Apparatus according to any one of claims 26 to 28 where the transmitting means transmits modulated radiation and the filter matches that radiation. 30. Apparatus according to any one of claims 18 to 29 including a collimating means through which the radiation is transmitted before it is modified by the body. 31. Apparatus according to any one of claims 18 to 30 including a collimating means through which the radiation is transmitted after modification by the body, but before it is received. 32. Apparatus according to any one of claims 18 to 31, wherein the transmitting and/or receiving means include fibre optics. 33. Apparatus according to any one of claims 18 to 32 including a visual display means for displaying information including that relating to the position and/or state of the body. 34. Apparatus according to any one of claims 18 to 33, wherein the processor means is arranged to detect and characterise breathing of the body. 35. Apparatus according to any one of claims 18 to 34, wherein the processor means is arranged to detect and characterise heart beat of the body. 36. Apparatus according to any one of claims 18 to 35, in which reflecting means are provided for reflecting radiation prior to receipt by the receiving means.

Inventors: FOTHERGILL IAN ROBERT, FOTHERGILL, IAN, ROBERT
Applicants: FOTHERGILL IAN ROBERT, FOTHERGILL, IAN, ROBERT
Application year: 1997
Main classification: A61B5
IPC codes: A61B5