Consideration of an activity sensor suitable for rate responsive pacing

A three axis accelerometer and an acoustic sensor were monitored during simulated unconditioned physical activities. True RMS values of the outputs were compared with the activity, ECG rate and an impedance derived estimate of minute ventilation. Each axis of the three axis accelerometer was capable of indicating a limited range of specific activities with a quick response. For moderate activity, the acoustic sensor provided the best rejection of non-metabolic activity.