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Keywords:

  • Autonomic nervous system;
  • Beta receptor;
  • Adrenergic receptor blockade;
  • Cardiopulmonary exercise test;
  • Carvedilol;
  • Clinica trial;
  • Hypoxia;
  • Nebivolol

Summary

Aims

Exposure to high altitude (HA) hypoxia decreases exercise performance in healthy subjects. Although β-blockers are known to affect exercise capacity in normoxia, no data are available comparing selective and nonselective β-adrenergic blockade on exercise performance in healthy subjects acutely exposed to HA hypoxia. We compared the impact of nebivolol and carvedilol on exercise capacity in healthy subjects acutely exposed to HA hypobaric hypoxia.

Methods

In this double-blind, placebo-controlled trial, 27 healthy untrained sea-level (SL) residents (15 males, age 38.3 ± 12.8 years) were randomized to placebo (n = 9), carvedilol 25 mg b.i.d. (n = 9), or nebivolol 5 mg o.d. (n = 9). Primary endpoints were measures of exercise performance evaluated by cardiopulmonary exercise testing at sea level without treatment, and after at least 3 weeks of treatment, both at SL and shortly after arrival at HA (4559 m).

Results

HA hypoxia significantly decreased resting and peak oxygen saturation, peak workload, VO2, and heart rate (HR) (P < 0.01). Changes from SL (no treatment) differed among treatments: (1) peak VO2 was better preserved with nebivolol (–22.5%) than with carvedilol (–37.6%) (P < 0.01); (2) peak HR decreased with carvedilol (–43.9 ± 11.9 beats/min) more than with nebivolol (–24.8 ± 13.6 beats/min) (P < 0.05); (3) peak minute ventilation (VE) decreased with carvedilol (–9.3%) and increased with nebivolol (+15.2%) (P= 0.053). Only peak VE changes independently predicted changes in peak VO2 at multivariate analysis (R= 0.62, P < 0.01).

Conclusions

Exercise performance is better preserved with nebivolol than with carvedilol under acute exposure to HA hypoxia in healthy subjects.