[Features of external respiration and pulmonary hyperemia in man during immersion]

Reactions of external respiration on catheterization of main blood vessels were studied in healthy subjects following 12 hr and 5-6 day immersion. The purpose of the investigation was to detect respiratory signs of hyperemia in pulmonary circulation under these conditions. Results of the investigation were compared with the data of great vessel catheterization in patients of a cardiological clinic afflicted with cardiac diseases with lung hyperemia and lung tissue hyperhydration. The results obtained failed to confirm suppositions about elevated blood filling of the lung and a possible increase of lung tissue hydration during water immersion. Catheterization of great vessels in patients and healthy subjects in most cases leads to an increase of respiratory minute volume. In patients with cardiac diseases the respiratory minute volume grew with an adequate rise in breathing rate, respiratory volume and gas exchange parameters unaltered; this suggested excessive blood filling of the lung and resulting higher respiratory resistance. After immersion the healthy subjects displayed an utterly different pattern, i.e. the growth of their respiratory minute volume was provided exclusively by the growth of respiratory volume while breathing rate did not change and gas exchange increased. These observations were considered an evidence of hyperemia and hyperhydration of pulmonary tissue.