Effect of intrapleural pressure on pulmonary shunt through atelectatic dog lung

Abstract

During spontaneous breathing of oxygen, the pulmonary shunt through the left lung, made atelectatic by occlusion of its airway, was calculated from the O₂ and CO₂ tension of the arterial and mixed venous blood. At intrapleural pressure swings of -3 to -12 cm H₂O, the relative blood flow through the atelectatic lung was reduced to 21.6% of the pulmonary blood flow (normal 45%). With wider swings of intrapleural pressure, average -7.5 to -24 cm H₂O, the relative blood flow through the atelectatic lung increased to 45% of the pulmonary blood flow, probably because resistance to blood flow increased in the overdistended right lung. The pulmonary shunt through atelectatic lung varied directly with the increased negativity of the intrapleural pressure.