Propranolol does not impair exercise oxygen uptake in normal men at high altitude.

摘要: Decreased maximal O2 uptake (VO2max) and stimulation of the sympathetic nervous system have been previously shown to occur at high altitude. We hypothesized that tachycardia mediated by beta-adrenergic acted defend VO2max Propranolol treatment beginning before high-altitude (4,300 m) ascent reduced heart rate during submaximal exercise in six healthy men treated with propranolol (80 mg three times daily) compared five subjects receiving placebo (lactose). Compared sea-level values, fell on day 2 altitude, but magnitude fall was similar groups (26 +/- 6 vs. 32 5%, P = NS) remained altitude both once discontinued. During 30 min (80% VO2max) exercise, propranolol-treated maintained levels were as large those subjects. The maintenance or 4,300 m could not be attributed increased minute ventilation, arterial saturation, hemoglobin concentration. Rather, it appeared transporting a greater proportion each heartbeat. Thus, contrary our hypothesis, blockade did impair due perhaps compensatory mechanisms acting maintain stroke volume cardiac output.