β-blockers may provoke oxygen desaturation during submaximal exercise at moderate altitudes in elderly persons

Faulhaber, Martin, Markus Flatz, and Martin Burtscher. beta-blockers may provoke oxygen desaturation during submaximal exercise at moderate altitudes in elderly persons. High Alt. Med. Biol. 4:475-478, 2003. Frequency of therapeutic beta-blocker use in elderly mountaineers is unknown. Therefore, the aim of this field study was to measure the regular beta-blocker intake in elderly persons visiting moderate altitudes. In a subset of mountaineers on beta-blockers, exercise response at two different altitude levels was compared to matched controls. The observed frequency of beta-blocked persons among the interviewed elderly mountaineers (age > 35) was 7%, mainly (65%) due to hypertension. In subjects taking beta-blockers, arterial oxygen saturation (84 +/- 6% vs. 90 +/- 3%, p < 0.05) was decreased and heart rate (120 +/- 17 bpm vs. 112 +/- 14 bpm, p = 0.01), rate pressure product (22,192 +/- 6459 vs. 17,576 +/- 4010, p < 0.05), and ratings of perceived exertion (14 +/- 3 vs. 12 +/- 3, p < 0.05) were increased during a submaximal step test at 2311 In compared to 1480 In. Mountaineers without beta-blocker intake showed no changes. Although the epidemiological data have to be interpreted with caution because of the small sample size and the limitation to a single geographical site, a large number of beta-blocked persons visiting high altitudes was observed. If confirmed in further studies, the increased heart work and exertion could indicate a reduced exercise tolerance of people taking beta-blockers during acute high altitude exposure.