Dexamethasone Improves Maximal Exercise Capacity of Individuals Susceptible to High Altitude Pulmonary Edema at 4559 m

Abstract

Abstract

Siebenmann, Christoph, Bloch, Konrad E., Lundby, Carsten, Yvonne Nussbaumer-Ochsner, Michèle Schoeb, and Marco Maggiorini. Dexamethasone improves maximal excercise capacity of individuals susceptible to high altitude pulmonary edema at 4559 m. High Alt. Med. Biol. 12:169–177, 2011.—We have previously demonstrated that prophylactic intake of dexamethasone improves maximal oxygen uptake (Vo₂max) in high altitude pulmonary edema (HAPE) susceptible subjects 4 to 6 h after a 2-day climb to 4559 m. However, since with this ascent protocol HAPE usually develops after the first night at 4559 m or later, we hypothesized that a continued dexamethasone prophylaxis would result in an even more pronounced improvement of Vo₂max after an additional night at high altitude.

Vo₂max of 24 HAPE susceptibles was evaluated on a bicycle ergometer at an altitude of 490 m and at 24 h after rapid ascent to 4559 m. Subjects were divided into two groups: The control group (n = 14) performed both tests without dexamethasone, whereas the dexamethasone group (n = 10) received dexamethasone 8 mg twice a day (b.i.d), starting 24 h prior to ascent.

At 4559 m, Vo₂max was 61% ± 6% of the baseline value in the control group and 70% ± 9% in the dexamethasone group (p = 0.025). Similarly, O₂ pulse (Vo₂/heart rate) was 68% ± 7% and 77% ± 11% of baseline, respectively (p = 0.043). Arterial O₂ saturation at maximal exercise did not differ between groups, whereas at rest it was 83% ± 10% in the control group and 91% ± 4% in the dexamethasone group (p = 0.009).

Dexamethasone prophylaxis increased Vo₂max of HAPE-susceptible individuals after the first night at 4559 m without affecting arterial O₂ saturation at maximal exercise. This might be explained by a sustained effect of dexamethasone on maximal cardiac output and pulmonary O₂ diffusion, both resulting in enhanced convectional O₂ transport to the locomotor muscles.