Fig. 1From: Volume and its relationship to cardiac output and venous returnThe importance of a compliant region in the circulation. a A bellows trying to pump fluid around a system with stiff pipes and no compliance. Flow is not possible because pressing on the bellows instantly raises the pressure everywhere and there is no pressure gradient for flow. b An open compliant region which allows changes in volume for changes in pressure. Flow can occur and there are pulsations throughout. c The compliant region is much large than in (b). The pulsations are markedly dampened and only produce ripples on the surface of the compliant regionBack to article page