Factors influencing pulmonary gas exchange in patients with acute edematous cor pulmonale due to chronic lung disease

Abstract

The interrelationships between pulmonary ventilation, cardiac output, ventilation-perfusion inequality and arterial blood gas tensions were studied in twelve patients with acute edematous cor pulmonale due to chronic lung disease. Ventilation-perfusion inequality was estimated from measurements of arterial gas tensions, anatomic dead space volume, pulmonary ventilation and blood flow, and was expressed in terms of the relative size of three compartments in a model lung, i.e., an alveolar dead space, a blood shunt and an “effective” compartment. Measurements were obtained during the acute illness and again during the subsequent course. The most striking findings were (1) a positive correlation between cardiac output and alveolar blood shunt, and (2) a negative correlation between cardiac output and alveolar dead space. Among other findings, there was a positive correlation between alveolar blood shunt and arterial carbon dioxide tension, a negative correlation between alveolar dead space and arterial oxygen tension, and a positive correlation between alveolar dead space and minute ventilation. Minute ventilation was only weakly correlated with arterial oxygen and carbon dioxide tensions. It was concluded that, in patients with acute edematous cor pulmonale, the level of cardiac output was a major determinant of the arterial blood gas composition by virtue of its effect on the pattern of ventilation-perfusion inequality, whereas the significance of the level of pulmonary ventilation, in this respect, was comparatively minor.