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 PaOO2 and of alveolar ventilation based on identification of mean alveolar Pco2 with arterial blood Pco2. Submitted on March 25, 1960