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Influence of sildenafil on lung diffusion during exposure to acute hypoxia at rest and during exercise in healthy humans.

Snyder EM, Olson TP, Johnson BD, Frantz RP

Department of Pharmacy Practice and Science, University of Arizona, 1703 E. Mabel, Tucson, AZ, 85721, USA, snyder@pharmacy.arizona.edu.

We sought to determine the influence of sildenafil on the diffusing capacity of the lungs for carbon monoxide (DL(CO)) and the components of DL(CO) (pulmonary capillary blood volume V (c), and alveolar-capillary membrane conductance D (M)) at rest and following exercise with normoxia and hypoxia. This double-blind placebo-controlled, cross-over study included 14 healthy subjects (age = 33 +/- 11 years, ht = 181 +/- 8 cm, weight = 85 +/- 14 kg, BMI = 26 +/- 3 kg/m(2), peak normoxic VO(2) = 36 +/- 6 ml/kg, mean +/- SD). Subjects were randomized to placebo or 100 mg sildenafil 1 h prior to entering a hypoxic tent with an FiO(2) of 12.5% for 90 min. DLCO, V (c), and D (M) were assessed at rest, every 3 min during exercise, at peak exercise, and 10 and 30 min post exercise. Sildenafil attenuated the elevation in PAP at rest and during recovery with exposure to hypoxia, but pulmonary arterial pressure immediately post exercise was not different between sildenafil and placebo. Systemic O(2) saturation and VO(2peak) did not differ between the two conditions. DL(CO) was not different between groups at any time point. V (C) was higher with exercise in the placebo group, and the difference in D (M) between sildenafil and placebo was significant only when corrected for changes in V (c) (D (M)/V (c) = 0.57 +/- 0.29 vs. 0.41 +/- 0.16, P = 0.04). These results suggest no effect of sildenafil on DLCO, but an improvement in D (M) when corrected for changes in V (c) during short-term hypoxic exposure with exercise.

Published 28 March 2008 in Eur J Appl Physiol.
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