A system for non-invasively measuring blood pressure on a treadmill

Measurement of signal to artifact ratio yielded optimal frequencies for a Korotkoff-based automatic system for measuring blood pressure on a treadmill. Maximal Korotkoff sounds occurred just above the crease of the elbow over the brachial artery. Output of a piezoelectric microphone and charge amplifier was measured during treadmill exercise for frequency bands from 8 to 57 Hz. An automatic system filtered output from 40 to 45 Hz, rectified it, then compared it to a threshold that had fixed and exponentially decaying components. For five subjects, the system decisions of systolic and diastolic pressures compared well with those of two observers using stethoscopes. The system shows promise for improved measurements of blood pressure during treadmill exercise.