Table 2.
A comparison of the mean ± s.e.m. chemoreflex characteristics (all volunteers and all days), measured using hypoxic and hyperoxic rebreathing tests, before and after exposure to 20 min isocapnic (eucapnic) normoxia
| Before exposure | After exposure | |||
|---|---|---|---|---|
| Hypoxic | Hyperoxic | Hypoxic | Hyperoxic | |
| Threshold for CO2 | ||||
| Ventilation (mmHg) | 40±0.5 | 43±0.5 | 40±0.5 | 44±0.5 |
| Tidal volume (mmHg) | 41±0.5 | 43±0.5 | 41±0.5 | 43±0.5 |
| Frequency (mmHg) | 43±0.7 | 46±0.7 | 43±0.7 | 45±0.7 |
| Sensitivities to CO2 | ||||
| Ventilation (l min−1 mmHg−1) | 7.2±0.6 | 7.2±0.9 | 5.7±0.4 | 6.1±0.6 |
| Tidal volume (ml min−1 mmHg−1) | 249±25 | 239±28 | 246±24 | 222±25 |
| Frequency (breaths min−1 mmHg−1) | 4.7±0.7 | 4.1±0.7 | 5.0±0.7 | 4.7±0.8 |
| Basal (subthreshold) | ||||
| Ventilation (l min−1) | 8.5±1.0 | 6.1±0.8 | 8.8±0.8 | 6.6±0.8 |
| Tidal volume (ml) | 588±58 | 462±48 | 565±61 | 456±49 |
| Frequency (breaths min−1) | 10.3±1.0 | 9.8±0.9 | 11.8±0.7 | 6.6±0.8 |