To evaluate the effect of O2 administration and O2 removal on renal Na+ excretion, 12 hypoxemic eucapnic patients affected by chronic obstructive pulmonary disease (COPD) and 9 normal subjects were studied. After 1 h in the supine position. O2 was administered for 3 h by a tight-fitting face-mask. Urine and blood samples for renal Na+ excretion evaluation were taken at times 0, 60 and 180 min. After O2 removal both the blood and the urine samples were taken again for a further 3 h. In normal subjects, urinary Na+ excretion did not vary after both O2 administration and removal. On the contrary, in patients affected by COPD renal Na+ excretion significantly increased during O2 administration (from basal values of 0.08±0.01 to 0.17±0.02 mEq/min at 180 min, p <0.05), and returned to baseline levels (0.13±0.03 mEq/min) after 3 h from O2 removal. The basal fractional excretion of filtered Na+ was significant lower in hypoxemic patients than in normal subjects (0.72±0.3% in patients with COPD vs. 0.95±0.7% in normal subjects, p < 0.05), while, at the end of O2 administration. it became higher in patients with COPD than in controls (1.62±0.4% in patients with COPD vs. 0.89±0.5 in control subjects, p <0.001). In conclusion, our findings showed an oxygen-related increase of both the urinary Na+ excretion and the fractional excretion of filtered sodium in patients affected by COPD. © 1993 S. Karger AG, Basel.
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