Medical signal processing using the Software Monitor

The Software Monitor is a portable PC which is capable of processing and analysing in real time the vital physiological signals recorded non-invasively from healthy subjects or unwell hospital patients. Its main advantage is that it offers, in one intelligent monitor, the fusion of multiple sources of information. This makes it possible to track physiological instability (since unexpected combinations of changes are often an indication of deterioration) and to generate reliable alarms (since robustness is increased as a result of using multiple sources of information). In the current version of the Software Monitor, the following vital signs are being recorded: three channels of ECG (electrocardiogram), blood pressure using an inflatable cuff, oxygen saturation using pulse oximetry, respiration using impedance pneumography and skin temperature using a thermistor inside the blood pressure cuff. All of these signals are sampled at different rates (from the ECG which is sampled at 256 Hz to the blood pressure which is only measured two or three times per hour) but the data samples from each channel are given a timestamp which is synchronised with a master clock (Townsend and Tarassenko, 2000). The number of physiological signals could be increased if desired as this simply requires the appropriate sensor, associated electronics and a corresponding software module.