Time course of Ptco2 changes over the study period
| Time (min) | Oxygen minus air Ptco2 mean (SD) (mm Hg) | 95% CI | p Value* |
| 0 | 0 (2.3) | −1.1 to 1.1 | 1.0 |
| 5 | 1.6 (3.7) | −0.2 to 3.4 | 0.8 |
| 10 | 2.3 (4.4) | 0.2 to 4.5 | 0.038 |
| 15 | 3.0 (4.4) | 0.8 to 5.2 | 0.01 |
| 20 | 1.2 (2.6) | −0.2 to 2.5 | 0.78 |
| 25 | 2.0 (2.8) | 0.6 to 3.4 | 0.008 |
| 30 | 2.8 (2.7) | 1.5 to 4.2 | <0.001 |
| 35 | 3.1 (3.0) | 1.6 to 4.5 | <0.001 |
| 40 | 1.2 (2.2) | 0.2 to 2.3 | 0.028 |
| 45 | 0.1 (1.8) | −0.8 to 1.0 | 0.8 |
| 50 | −0.1 (2.0) | −1.1 to 0.9 | 0.82 |
↵* Paired t test.
Ptco2, transcutaneous carbon dioxide tension.