Pulmonary mechanics and hemodynamics during changes in ventilation and blood volume

¹ Tufts University School of Medicine, Boston City Hospital, Boston, Massachusetts

Pulmonary hemodynamics and ventilatory mechanics were investigated in anesthetized, closed-chest dogs. Inflation of the lung reversed the fall in compliance associated with spontaneous respiration, but decreased cardiac output. Deepening anesthesia reduced cardiac output, pulmonary artery pressure, minute ventilation and airflow resistance. Pulmonary hemodynamics were not changed by the elevated vascular pressures during diffusion respiration. Carbon dioxide increased pulmonary artery pressure in relation to the ventilatory response. An inspiratory airway resistance lowered functional residual capacity, pulmonary compliance and intrathoracic pressures. The effects of an expiratory resistance were essentially opposite. Both transfusion and hemorrhage produced a fall in compliance despite opposite effects upon the circulation.