Pilot canine investigation of the cardiopulmonary baroreflex control of ventricular contractility.

We performed a pilot investigation of the cardiopulmonary baroreflex control of ventricular contractility in two conscious dogs. We specifically measured spontaneous beat-to-beat hemodynamic variability before and after the administration of propranolol. We then identified the transfer function relating beat-to-beat fluctuations in central venous pressure (CVP) to maximal ventricular elastance (E(max)) to characterize the cardiopulmonary baroreflex control of ventricular contractility, while accounting for the influences of arterial blood pressure fluctuations on E(max) via the arterial baroreflex and heart rate fluctuations on E(max) via the force-frequency relation. Our major finding is that the cardiopulmonary baroreflex responds to an increase (decrease) in CVP by increasing (decreasing) E(max) via the beta-sympathetic nervous system.