Estimated changes in CPET variables in COVID-19 patients from 3 to 12 months in estimated values from linear mixed models and observed values at 3 and 12 months
| 3 months | 12 months | Change from 3 to 12 months, estimate (95%CI) | p-value | |||
| n | Mean (sd) | n | Mean (sd) | |||
| Performance | ||||||
| V′O2peak, mL·min−1 | 180 | 2306 (797) | 177 | 2451 (776) | 93 (40 to 144) | <0.001 |
| V′O2peak, % predicted | 180 | 87 (19) | 177 | 92(20) | 5.0 (3.1 to 6.9) | <0.001 |
| V′O2peak·kg−1, mL·kg−1·min−1 | 180 | 27 (9) | 177 | 29 (8) | 0.7 (0.1 to 1.3) | 0.03 |
| V′O2peak·kg−1, % predicted | 180 | 82 (19) | 177 | 86(21) | 3.4 (1.6 to 5.1) | <0.001 |
| Perceived dyspnoea Borg CR10 at max load | 175 | 8 (2) | 175 | 9(2) | 0.1 (−0.2 to 0.4) | 0.39 |
| Ventilation | ||||||
| V′E at max. load, L·min−1 | 180 | 82 (30) | 177 | 88 (29) | 2.8 (−0.3 to 6.2) | 0.08 |
| Breathing reserve, % | 180 | 20(20) | 177 | 19(19) | −0.4 (−3.3 to 2.5) | 0.80 |
| Circulation | ||||||
| Heart rate at max.load, beats·min−1 | 180 | 153 (22) | 177 | 155(22) | 0.0 (−2.5 to 2.3) | 0.95 |
| Heart rate at max. load, % predicted | 180 | 90(11) | 177 | 92 (10) | 0.5 (−1.0 to 1.8) | 0.49 |
| Systolic BP at max. load, mmHg | 170 | 191(35) | 164 | 190(32) | −3.8 (−10.7 to 3.2) | 0.31 |
| Diastolic BP at max. load, mmHg | 170 | 84(18) | 164 | 83(18) | −0.5 (−3.7 to 2.8) | 0.78 |
| Oxygen pulse at max. load, mL·stroke−1 | 180 | 15(4) | 177 | 16(4) | 0.6 (0.3 to 0.9) | <0.001 |
| Oxygen pulse at max. load, % predicted | 180 | 98(20) | 176 | 102(22) | 4.6 (2.5 to 6.8) | <0.001 |
| Gas exchange | ||||||
| V′E/V′CO2 slope | 180 | 29(6) | 177 | 29 (5) | −0.1 (−0.8 to 0.7) | 0.88 |
| V′E/V′CO2nadir | 180 | 29 (4) | 177 | 29(4) | −0.1 (−0.5 to 0.4) | 0.77 |
| RER at max. load | 180 | 1.06 (0.10) | 177 | 1.07 (0.10) | −0.01 (−0.03 to 0.01) | 0.28 |
| PETCO2 at AT, kPa | 178 | 4.7(0.6) | 173 | 4.8 (0.5) | 0.03 (−0.04 to 0.11) | 0.39 |
| PCO2 at max. load, kPa | 164 | 4.6 (0.6) | 142 | 4.8 (0.6) | 0.2 (0.1 to 0.3) | <0.001 |
| Anaerobic threshold | ||||||
| V′O2 at AT, mL·min−1 (V-slope) | 174 | 1339 (423) | 170 | 1526 (555) | 53 (8 to 97) | 0.02 |
| V′O2at AT, % predicted V′O2max | 174 | 52(12) | 170 | 58 (18. | 2.9 (1.3 to 4.6) | <0.001 |
| Lactate at max. load, mmol·L−1 | 160 | 8.2 (3.7) | 162 | 9.2 (3.8) | 0.7 (0.2 to 1.2) | 0.003 |
Estimated change from linear mixed models. The results are adjusted for centre, ICU stay, age, sex, BMI, and comorbidity at 3 months. 95% CIs and p-values are found by bootstrapping. The results are given from models with main effects only, as the interaction effects were not significant. V′O2: oxygen uptake; V′E: expired ventilation; BP: blood pressure; O2: oxygen; V′CO2: carbon dioxide output; RER: respiratory exchange ratio; PET: end tidal pressure; PCO2: partial pressure of carbon dioxide; AT: anaerobic threshold