Inspiratory muscle training, altitude, and arterial oxygen desaturation: a preliminary investigation.

INTRODUCTION Specific inspiratory muscle training (IMT) has been shown to significantly attenuate the fall in arterial oxygen saturation (SpO2) during exhaustive exercise while breathing a hypoxic gas mixture of 14% oxygen. The aim of the current study was to assess the impact of IMT on resting SpO2 over a range of altitudes in healthy individuals. METHODS Resting SpO2 and the Borg Score were examined at altitudes of 0 or 400 m (0-400 m; 0-1312.3 ft), 1400 m, 4880 m, and 5550 m (4593 ft, 16,011 ft, and 18,209 ft) in 14 military personnel who were part of a climbing expedition to the Nepali Himalaya. Volunteer participants were randomly assigned to either a control (N = 7) or IMT (N = 7) group: IMT consisted of 1 set of 30 breaths twice daily at 50% maximal inspiratory mouth pressure (MIP) for 4 wk prior to departure. RESULTS MIP was similar between groups pre-IMT but increased significantly by 15% post-IMT. Baseline maximal expiratory mouth pressure was not different between groups. The Borg Score increased significantly from 1400 m, but was not different between groups at any altitude. Resting SpO2 declined significantly at ascending altitudes in both groups and was similar between groups at altitudes of 0-400 m and 1400 m. However, at altitudes of 4880 m and 5550 m, SpO2 was significantly higher (6%) in the IMT group. CONCLUSION IMT can attenuate the fall in resting SpO2, but only at altitudes of 4880 m and above. Conversely, IMT had no effect on resting levels of dyspnea as measured by the Borg Score.