Chemoreflex responsiveness to arterial CO2 tension in apnoeic and nonapnoeic groups during isoxic hypoxia and hyperoxia
| Apnoeic | Nonapnoeic | |||
| Evening | Morning | Evening | Morning | |
| Hypoxia | ||||
| rrCO2 mmHg·s-1# | 0.08±0.01 | 0.07±0.01 | 0.08±0.02 | 0.07±0.01 |
| VEb L·min-1 | 13.0±4.7 | 13.4±6.8 | 12.5±9.1 | 11.1±6.6 |
| T mmHg¶ | 41.3±3.3 | 40.0±3.0 | 41.1±3.5 | 40.3±3.6 |
| S L·min-1·mmHg-1+ | 6.0±3.9 | 7.3±3.5 | 3.3±3.4 | 3.5±1.5 |
| Hyperoxia | ||||
| rrCO2 mmHg·s-1# | 0.07±0.01 | 0.07±0.01 | 0.07±0.01 | 0.07±0.01 |
| VEb L·min-1 | 12.6±5.1 | 12.0±4.2 | 9.0±8.0 | 9.3±6.6 |
| T mmHg¶ | 46.7±2.5 | 45.8±3.3 | 46.3±3.5 | 45.3±3.3 |
| S L·min-1·mmHg-1+ | 2.7±1.1 | 3.2±1.3 | 1.4±0.5 | 1.7±0.8 |
| Hypo-hyperoxia | ||||
| S L·min-1·mmHg-1§ | 3.3±3.4 | 4.1±2.9 | 1.8±1.2 | 1.8±3.4 |
Data are presented as mean±sd. rrCO2: rate of rise of carbon dioxide during the modified Read rebreathing test; VEb: basal ventilation; T: ventilatory threshold; S: ventilatory sensitivity. #: evening versus morning, p<0.001; ¶: evening versus morning, p = 0.006; +: apnoeic versus nonapnoeic, p<0.001; §: apnoeic versus nonapnoeic, p = 0.030. 1 mmHg = 0.133 kPa.