Optical non-contact measurement of abdominal volume change during anaesthesia

A low cost optic method for chest wall measurement is described. The equipment operates in real time and allows changes in breathing patterns to be tracked. A low power Helium Neon laser beam is used to generate a plane of light that can be positioned rapidly (1 ms) by means of a galvanometer mounted mirror to illuminate the chest wall at a selected position. At each illumination position, a frame of information from a video camera is processed by special purpose electronics, to extract shape information from the illuminated contour and thus reduce the amount of data that requires to be processed. The plane is sequenced through a number of positions to derive 3-D information for the complete chest surface. Information from the hardware is passed to a Personal Computer to process and display the results. Alternate forms of data can be presented to the operator within three minutes of measuring a 108 second breathing episode