Effects of venous return on respiratory response.

This study reevaluated the link between the rate of CO2 flow to the pulmonary circulation and changes in cardiac output to the respiratory responses following leg lifting in normal man subjects. Thirty healthy subjects (mean age = 22.2 years) were subjected to the experimental maneuver which increased venous return to the right heart. Cardiac output was significantly increased and with it a significant increase in CO2 output by the lungs was found. These results were associated with a significant increase in expired ventilation. The rapidity of the ventilatory response to the increase in cardiac output suggests the existence of pressoreceptors localized in the pulmonary circulation which, when activated, results in the elicitation of respiratory reflexes. The end result is an adjustment in the respiratory response in accordance with venous return.