Table 2.
Pao2 and Paco2 before and during apnoea. Figures shown are mean (standard deviation) arterial oxygen and carbon dioxide tensions (kPa). TA, onset of apnoea; TA+x, apnoea duration where x denotes min after TA. Figures before apnoea (at baseline breathing air, and at the end of preoxygenation) include data from all participants in the high flow nasal oxygen (HFNO; where data are available, n=39) and facemask oxygen (FM, n=39) groups. During apnoea, figures include data only from the 60 participants who completed 18 min of apnoea (HFNO, n=36; FM, n=24). Comparisons were made using the independent t-test.
| Baseline | After preoxygenation | TA | TA+2 | TA+4 | TA+6 | TA+9 | TA+12 | TA+15 | TA+18 | ||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Pao2 | HFNO | 12.8 (2.4) | 59.9 (8.1) | 55.7 (7.2) | 40.4 (8.1) | 30.4 (8.1) | 28.2 (8.2) | 26.7 (7.3) | 26.0 (7.2) | 24.5 (6.7) | 23.6 (6.7) |
| FM | 12.7 (2.3) | 60.2 (9.4) | 50.7 (9.9) | 35.5 (11.6) | 30.5 (11.1) | 28.7 (10.2) | 27.1 (9.9) | 25.2 (9.4) | 23.8 (9.1) | 22.2 (8.3) | |
| P | 0.978 | 0.978 | 0.249 | 0.422 | 1.000 | 0.999 | 0.999 | 0.999 | 0.999 | 0.987 | |
| Paco2 | HFNO | 5.3 (0.5) | 4.5 (0.9) | 6.5 (0.9) | 7.1 (0.8) | 7.7 (0.8) | 8.2 (0.8) | 9.0 (0.9) | 9.6 (0.9) | 10.1 (1.0) | 10.7 (1.1) |
| FM | 5.3 (0.5) | 5.0 (0.7) | 6.6 (0.8) | 7.1 (0.7) | 7.8 (0.7) | 8.3 (0.8) | 8.9 (0.8) | 9.5 (0.9) | 10.0 (1.0) | 10.6 (1.1) | |
| P | 0.660 | 0.009 | 0.996 | 0.999 | 0.999 | 0.999 | 0.999 | 0.999 | 0.996 | 0.999 |