Continuous recording of the oscillometric mean arterial pressure by the differential servo system with two photoplethysmographic sensors

A differential servo system with two photoplethysmographic sensors is described for beat-to-beat recording of the finger mean arterial pressure (MAP). The mean arterial pressure for every cardiac cycle is a more reliable parameter than the highest and lowest levels of the pressure signal (i.e. systolic and diastolic pressures). In the case of MAP measurement a better accuracy is achieved and the applied servo-system is cost-effective and robust. Frequency requirements to the proposed system are about 2 orders lower than those for a volume-clamp monitor to record the full arterial pressure waveform. At the same time, the beat-to-beat MAP entirely characterizes circulatory dynamics. Comparison between the proposed differential servo-oscillometric and conventional volume-clamp devices revealed a good agreement in MAP during hand elevation, orthostatic maneuver and light physical exercise.