Lung volume, alveolar ventilation and perfusion interrelationships in chronic pulmonary emphysema

Abstract

In 10 patients with chronic pulmonary emphysema the distribution of ventilation within the lungs was assessed by a nitrogen washout and washin technique. Alveolar ventilation per minute per unit lung volume had a mean value of 5.0 in well ventilated alveoli and 0.19, or 1/26 as much, in poorly ventilated alveoli. Distribution of blood perfusion was estimated by a new method from these data and from O2 consumption and arterial O₂ saturation. On the average, poorly ventilated alveoli which constituted 66% of lung volume were perfused by not more than 52% of the cardiac output. Thus poorly ventilated alveoli were underperfused by blood. Ventilation/perfusion ratios averaged 2.24 in well ventilated alveoli and 0.23 in poorly ventilated alveoli. Oxygen saturation averaged 85% in arterial blood and 97frac12% and 76%, respectively, in end-capillary blood leaving well and poorly ventilated alveoli. Inhomogeneity of this degree within the lung invalidates calculations of diffusing capacity based on any single mean PaO_O2 and of alveolar ventilation based on identification of mean alveolar Pco₂ with arterial blood Pco₂. Submitted on March 25, 1960