Effect on breathing of acute pressure rise in pulmonary artery and right ventricle

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Abstract
The hypothesis that breathing would be regulated in response to right ventricular and pulmonary arterial pressure changes when secondary events are controlled was tested. Dogs were anesthetized, thoracotomies were performed and cardiopulmonary bypass perfusion was established. Lungs were inflated to sustained pressures. The left diaphragmatic lobe was retrogradely cannulated and all other lobar arteries were ligated, forming a pulmonary arterial sac that drained to the oxygenator from the cannula and filled from systemic venous return by the beating right ventricle. Right artrial pressure was adjusted to produce sac flows of .apprx. 400 ml/min. Systemic and pulmonary arterial pressures, sac flow and the integrated diaphragm electromyogram (DEMG) were recorded. Resistive loads were imposed on sac outflow by adjusting a clamp. Loaded mean pulmonary arterial pressures ranged from 27-70 Torr. Loading increased respiratory frequency without affecting peak DEMG amplitude. Responses did not occur after vagotomy. Effects were quantitatively modest: pressurization to .apprx. 50 Torr increased frequency .apprx. 3.4 breaths/min (22%). The magnitude of change was insufficient to explain in intact dogs the ventilatory responses that were attributed to this reflexogenic unit.