Effect of age on the regional perfusion and washouts of injected xenon in normal men.

The aim of this work was to localize the alveoli with low ventilation-perfusion ratio which are responsible for the age related increase of the ideal alveolar-arterial O2 partial pressure difference. For this purpose, we measured: (1) the washouts of perfused 133 Xenon (Xe) in the whole lung and in 6 horizontal slices of the right lung, and (2) the topographical distribution of perfusion (Qi) in 27 healthy, non-smoking seated men, between 18 and 65 years. The distribution of Qi is unaffected by age. The global and regional washouts slowed with age, the trends being the same in the 6 investigated regions. This data was interpreted as indicating that in our subjects the low VA/Q units are not situated predominantly at the base, but are scattered throughout the lung.