Evidence for increased intrathoracic fluid volume in man at high altitude

To determine if subclinical pulmonary edema occurs commonly at high altitude, 25 soldiers participated in two consecutive 72-h field exercises, the first at low altitude (200–875 m) and the second at high altitude (3,000–4,300 m). Various aspects of ventilatory function and pulmonary mechanics were measured at 0, 36, and 72 h of each exercise. Based on physical examination and chest radiographs there was no evidence of pulmonary edema at high altitude. There was, however, an immediate and sustained decrease in vital capacity and transthoracic electrical impedance as well as a clockwise rotation of the transpulmonary pressure-volume curve. In contrast, closing capacity and residual volume did not change immediately upon arrival at high altitude but did increase later during the exposure. These observations are consistent with an abrupt increase in thoracic intravascular fluid volume upon arrival at high altitude followed by a more gradual increase in extravascular fluid volume in the peribronchial spaces of dependent lung regions.

Influence of Variations in Body-Fluid Volumes on Sodium Metabolism in Man

A review has been given of recent papers on the influence of acute changes in extracellular, extravascular fluid volume and in plasma volume on the salt metabolism. The influence of intravascular pressure, pitressin, adrenal steroids, etc., has been mentioned. Some work from the author's laboratory has been reported. It was found in this laboratory that a large intravenous infusion-25 ml./min. during 1-2 hours-of iso-oncotic glucose has no influence on sodium excretion in normal man, but that it gives rise to a very high increase of the sodium output in cases of arterial hypertension. Later on it was found that patients with cardiac failure behave as the hypertensive do in this respect. On the other hand, an intravenous infusion of a corresponding amount of iso-oncotic dextran solution gives a considerable decrease of sodium excretion in healthy subjects as well as in patients with the above-mentioned diseases. The correlation between these results and the changes of the kidney function and the renal hemodynamic have been discussed.