Table 1.
Pulmonary ventilation (
), respiratory rate (f), end tidal O2 (PET, O 2) and CO2 (PET, CO 2) pressure, heart rate (HR), cardiac index (CI) and arterial oxygen saturation (S aO 2) of subjects breathing air and at different times (from 1 min to 4 h) in normobaric hypoxia (12.5% O2)
| Air | 1 min | 5 min | 10 min | 15 min | 0.5 h | 1 h | 2 h | 3 h | 4 h | |
|---|---|---|---|---|---|---|---|---|---|---|
 (l min−1) |
11.3 ± 2.0 | 16.2 ± 3.7* | 14.3 ± 2.5* | 12.8 ± 3.2 | 13.5 ± 2.7 | 13.4 ± 2.7* | 13.4 ± 2.1 | 13.4 ± 3.0 | 14.1 ± 4.1 | 14.1 ± 3.3* |
| f (breaths min−1) | 14.3 ± 2.4 | 14.9 ± 2.8 | 15.4 ± 1.9 | 13.5 ± 2.7 | 13.9 ± 2.8 | 14.9 ± 1.9 | 14.8 ± 2.4 | 14.4 ± 2.2 | 17.1 ± 2.0 | 17.5 ± 3.7 |
| PET, O 2 (mmHg) | 103.1 ± 9.9 | 64.7 ± 6.9* | 54.9 ± 3.3* | 53.2 ± 6.6* | 52.3 ± 5.0* | 51.8 ± 5.9* | 52.4 ± 4.2* | 54.6 ± 5.5* | 57.2 ± 7.7* | 54.8 ± 5.5* |
| PET, CO 2 (mmHg) | 39.2 ± 5.2 | 37.0 ± 3.0 | 36.2 ± 2.9 | 36.6 ± 4.4 | 36.6 ± 3.3 | 36.5 ± 4.4 | 36.0 ± 4.4 | 34.4 ± 5.6* | 32.4 ± 5.7* | 33.6 ± 3.7* |
| HR (beats min−1) | 69.8 ± 6.6 | 73.0 ± 5.7* | 77.3 ± 7.3* | 74.7 ± 9.6 | 73.5 ± 9.1 | 73.7 ± 9.9 | 72.8 ± 11.1 | 68.8 ± 9.7 | 68.2 ± 11.6 | 66.8 ± 11.0 |
| CI (l min−1m−2) | 3.75 ± 0.64 | 3.95 ± 0.66* | 4.27 ± 0.82* | 4.11 ± 0.88 | 4.06 ± 0.85 | 4.12 ± 0.67 | 4.17 ± 0.60* | 3.17 ± 0.68 | 3.58 ± 0.66 | 3.60 ± 0.96 |
| S aO 2 (%) | 99.4 ± 0.7 | 96.1 ± 2.5* | 91.9 ± 2.3* | 90.1 ± 2.0* | 90.7 ± 1.2* | 87.7 ± 2.1* | 88.9 ± 1.8* | 87.7 ± 3.8* | 90.0 ± 1.1* | 90.3 ± 3.2* |
Values are mean ± SD obtained from 6 subjects. *P < 0.05 compared with pre-hypoxia, as assessed by Wilcoxon matched-pairs signed-ranks test.