Unconstrained and noninvasive measurement of heartbeat and respiration using an acoustic sensor enclosed in an air pillow

The authors previously developed an unconstrained and noninvasive measurement system of heartbeat and respiration using an acoustic sensor enclosed in an air pillow (or an air mat). Although the continuous trends of the instantaneous heartbeat and respiration periods were accurately measured with the system, these periods originally should be discretely obtained. The paper improves the pre-proposed measurement system such that the heartbeat and respiration periods are discretely outputted, like the conventional sensors as the electrocardiograph and the thermistor type respiration pick-up.