Respiratory training, hypoxic ventilatory response and acute mountain sickness.

A low hypoxic ventilatory response (HVR) has been observed in endurance athletes and has also been associated with low exercise ventilation and a high susceptibility to acute mountain sickness (AMS). In other studies, respiratory training was found to improve cycling endurance and decrease exercise ventilation. We therefore hypothesized that respiratory training alone may reduce HVR and increase AMS susceptibility. In 16 healthy subjects, we measured HVR (delta VE vs. delta SaO2) and the susceptibility to AMS (Lake Louise Score). Eight subjects then underwent respiratory training (30 min isocapnic hyperpnea, 4-5 times weekly, 4-5 weeks), thereby increasing breathing endurance (the time to exhaustion while breathing at 60-75% of MVV) from 455 +/- 193 sec to 2049 +/- 476 sec (p < 0.05). Eight subjects served as controls. No significant change of HVR (0.67 +/- 0.36 vs. 0.55 +/- 0.22) or of AMS score (3.5 +/- 2.1 vs. 3.9 +/- 2.2) was observed after training, and there was no significant difference from controls. We conclude that respiratory training neither depresses HVR nor increases the risk of AMS.