title: Dexamethasone improves maximal exercise capacity of individuals susceptible to high altitude pulmonary edema at 4559 m.
abstract: We have previously demonstrated that prophylactic intake of dexamethasone improves maximal oxygen uptake (Vo(2)max) 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 Vo(2)max after an additional night at high altitude. Vo(2)max 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, Vo(2)max was 61% ± 6% of the baseline value in the control group and 70% ± 9% in the dexamethasone group (p=0.025). Similarly, O(2) pulse (Vo(2)/heart rate) was 68% ± 7% and 77% ± 11% of baseline, respectively (p=0.043). Arterial O(2) 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 Vo(2)max of HAPE-susceptible individuals after the first night at 4559 m without affecting arterial O(2) saturation at maximal exercise. This might be explained by a sustained effect of dexamethasone on maximal cardiac output and pulmonary O(2) diffusion, both resulting in enhanced convectional O(2) transport to the locomotor muscles.
authors: Institute of Physiology, Y23 J64, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland. christoph.siebenmann@access.uzh.ch
authors: Christoph
authors: C
authors: Siebenmann
authors: Konrad E
authors: KE
authors: Bloch
authors: Carsten
authors: C
authors: Lundby
authors: Yvonne
authors: Y
authors: Nussbamer-Ochsner
authors: Michèle
authors: M
authors: Schoeb
authors: Marco
authors: M
authors: Maggiorini
mesh_terms: D000328:Adult; D000532:Altitude Sickness / Q000097:blood / Q000517:prevention & control*; D001784:Blood Gas Analysis; D003907:Dexamethasone / Q000494:pharmacology / Q000627:therapeutic use*; D004311:Double-Blind Method; D004334:Drug Administration Schedule; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D005938:Glucocorticoids / Q000494:pharmacology / Q000627:therapeutic use*; D006801:Humans; D006976:Hypertension, Pulmonary / Q000097:blood / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000187:drug effects*; D012129:Respiratory Function Tests; D013997:Time Factors
chemical_list: D005938:Glucocorticoids; D003907:Dexamethasone