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The effect of age on the distribution of ventilation and perfusion in the lung.

The regional distribution of ventilation and perfusion was studied with xenon-133 in 26 healthy, ambulatory, and mainly nonsmoking men 63 to 77 years of age. The results were compared with 21 young, normal subjects and 11 patients with chronic obstructive pulmonary disease. When the distribution of ventilation from lung apex to base was assessed during breath-holding at total lung capacity after a single continuous inhalation of 133Xe, ventilation in both the young and old normal subjects favored the lower lung regions. When the distribution of ventilation was assessed by wash-out of 133Xe during quiet breathing, ventilation was no longer preferential to the lung base but shifted toward the upper lung zones in both young and old normal subjects. Perfusion increased from lung apex to base in all 3 subject groups. Distribution of ventilation within a lung zone was uniform and identical in both young and old subjects. Distribution of perfusion within a lung zone was also identical in both young and old norma...