Power capability of skeletal muscle to pump blood.

This article describes the various ways in which an electrically stimulated, muscle-wrapped pouch can be used to pump blood. The fundamental equations that allow calculation of the output and input power are developed. The output power in watts is 23.5 X 10(-4) (Pm - PDP)F, where Pm is mean arterial pressure and PDP is pouch diastolic pressure (mmHg); F is the pouch output flow (liters/min). The input power in watts is the oxygen consumed by the muscle in milliliters per second multiplied by 20.1. The oxygen consumed is equal to the product of muscle capillary flow and the A-VO2 difference across the muscle. The ratio of output power to input power is the efficiency; typical values range from 7 to 15%. At rest the typical 350 gm heart produces an output power of about 3.5 milliwatts/gram. Skeletal muscle can produce 10-15 milliwatts per gram; however, it is not known how long conditioned or unconditioned muscle can sustain this power level. In addition, it is not known what power level an electrically stimulated skeletal muscle can sustain for a prolonged period; this represents a gap in our knowledge of cardiac assistance using skeletal muscle.