Effects of Hypoxia on Heart Rate and Oxygen Saturation

The purpose of this study was to examine heart rate (HR) and peripheral oxygen saturation (SpO2) during rest, balance testing, and aerobic exercise at three different simulated altitudes. METHODS: Seven healthy men were tested three separate times [ambient conditions, 3000 m (9,842 ft.), 5000 m (16,404 ft.)]; at least 24 hours separated each trial. The order of trials was randomized, and participants were blinded to the condition. A hypoxic generator with subjects attached via hose and mask was used to simulate the altitude. Each trial consisted of 20 min of rest, 15 min of balance tests, 5 min of walking (3 mph), 5 min of running (6 mph), and a repeat of the balance tests. Throughout the trial, HR and SpO2 were monitored by finger pulse oximetry. A repeated-measures ANOVA was done to detect mean differences in HR and SpO2 across the three altitudes. RESULTS: There was no significant difference (p \u3e 0.05) in HR between the ambient and 3000 m conditions. However, at 5000 m HR was significantly higher than the other two conditions at rest (79 ± 11 vs. 66 å± 11 and 67 ± 13 bpm), during balance testing (90 ± 14 vs. 81 å±13 and 78 å± 15 bpm), walking (98 å± 8 vs. 90 å± 11 and 88 ±11 bpm), and running (142 ± 10 vs. 120 å± 15 and 135 ± 24 bpm). SpO2 was significantly lower at 5000 m than at 3000 m, and at 3000 m compared to ambient air during each portion of the trial. SpO2 ranged from 96 ± 2% (ambient rest) to 71 ± 5% (5000 m running). CONCLUSIONS: The more severe the hypoxia the greater the decline in SpO2. In response, HR increases to compensate for the lack of oxygen. This was particularly evident at 5000 m