Table 2.
Main outcomes.
| Low-flow oxygen therapy, LFOT | High-flow oxygen therapy, HFOT | ||||||
|---|---|---|---|---|---|---|---|
| Rest | End- exercise | Difference end-exercise minus rest | Rest | End-exercise | Difference end-exercise minus rest | Difference HFOT minus LFOT at end- exercise | |
| Endurance time, intention-to-treat analysis, s | NA | 688 ± 463 | NA | 773 ± 471 | 85 (7 to 164)* | ||
| Endurance time, per-protocol analysis, s | NA | 612 ± 452 | NA | 713 ± 452 | 101 (27 to 175)* | ||
| Breath rate, 1/min | 16.9 ± 6.4 | 33.4 ± 6.4 | 16.5 (14.9 to 18.1)* | 15.8 ± 6.4 | 32 ± 6.4 | 16.3 (14.7 to 17.8)* | −1.4 (−2.9 to 0.2) |
| Heart rate, 1/min | 79 ± 16 | 137 ± 16 | 59 (55 to 63)* | 78 ± 16 | 135 ± 16 | 57 (54 to 61)* | −2 (−6 to 2) |
| Heart rate reserve, 1/min | 84 ± 16 | 25 ± 16 | −59 (−63 to −55)* | 85 ± 16 | 27 ± 16 | −57 (−61 to −54)* | 2 (−2 to 6) |
| SpO2, % | 97 ± 0 | 96 ± 0 | −1 (−1 to 0)* | 98 ± 0 | 98 ± 0 | −1 (−1 to 0)* | 2 (2 to 2)* |
| Arterial pH† | NA | 7.33 ± 0.00 | −0.07 (−0.08 to −0.06)* | NA | 7.34 ± 0.1 | −0.06 (−0.07 to −0.05)* | 0.01 (−0.01 to 0.02) |
| PaCO2, kPa† | NA | 4.9 ± 0.8 | −0.5 (−0.6 to −0.4)* | NA | 4.8 ± 0.8 | −0.7 (−0.8 to −0.5)* | −0.1 (−0.3 to 0.03) |
| PaO2, kPa† | NA | 14.4 ± 3.2 | 5.0 (4.0 to 5.9)* | NA | 21.6 ± 3.2 | 12.1 (11.1 to 13.1)* | 7.1 (5.8 to 8.5)* |
| Arterial , mmol/l † | NA | 19.3 ± 2.4 | −5.6 (−6.2 to −5.0)* | NA | 19.2 ± 2.4 | −5.7 (−6.3 to −5.1)* | −0.1 (−0.9 to 0.7) |
| SaO2, %† | NA | 97 ± 2 | 4 (3 to 4)* | NA | 99 ± 2 | 5 (5 to 5)* | 1 (1 to 2)* |
| Lactate, mmol/l† | NA | 6.7 ± 2.1 | 5.7 (5.0 to 6.3)* | NA | 6.4 ± 2.2 | 5.4 (4. 8 to 6.1)* | −0.2 (−1.1 to 0.7) |
| Borg dyspnea | 0.3 ± 1.6 | 4.0 ± 1.6 | 3.7 (3.2 to 4.1)* | 0.2 ± 1.6 | 3.3 ± 1.6 | 3 (2.6 to 3.5)* | −0.8 (−1.2 to −0.3)* |
| Borg leg fatigue | 0.4 ± 1.6 | 5.3 ± 1.6 | 4.9 (4.5 to 5.4)* | 0.4 ± 1.6 | 5.4 ± 1.6 | 5 (4.5 to 5.4)* | 0 (−0.4 to 0.5) |
| Treatment comfort, mm VAS | NA | 58 ± 17 | NA | 58 ± 20 | 0 (−6 to 6) | ||
Means ± SD, mean differences (95% confidence intervals). For the primary outcome, endurance time, results are presented for intention-to-treat (n = 79) and per-protocol analyses (n = 68). For all other outcomes, results obtained with the corresponding treatment are presented for the per protocol analysis.
SpO2, pulse oximetry. NA, not applicable.
†
Resting arterial blood gas analyses were obtained once per patient while breathing ambient air, results are listed in Table 1. All other outcomes were obtained while patients were breathing the corresponding treatment. Treatment comfort was rated on a visual analog scale (VAS, 100 mm in length).
*
Difference P < 0.05.