Baseline and maximal exercise performance in extremely preterm and control children
| Baseline | Peak exercise | |||||
| Extremely preterm (EP) | Control | Mean difference (95% CI) (EP–control) | Extremely preterm (EP) | Control | Mean difference (95% CI) (EP–control) | |
| n | 38 | 38 | 38 | 38 | ||
| VO2 (ml/min) | 251 (75) | 256 (47) | −5 (−24 to 34) | 1293 (271) | 1590 (263) | −297 (−419 to −175)*** |
| Heart rate (beats/min) | 93.5 (12.6) | 94.0 (16.0) | −0.5 (−6.7 to 6.5) | 185 (15) | 190 (12) | −5 (−11.3 to 1.2) |
| SpO2 (%)† | 99 (98–99) | 99 (99–100) | −0.3 (−0.9 to 0.2) | 99 (98–100) | 99 (99–100) | −0.2 (−0.6 to 0.6) |
| Respiratory exchange ratio (VCO2/VO2) | 0.87 (0.07) | 0.88 (0.06) | −0.01 (−0.04 to 0.02) | 1.13 (0.06) | 1.12 (0.05) | 0.01 (−0.01 to 0.04) |
| Breathing frequency (breaths/min) | 19.0 (4.9) | 16.7 (4.0) | 2.3 (0.2 to 4.3)* | 57.2 (16) | 50.9 (11.0) | 6.3 (0.1 to 12.6)* |
| Vt/kg (ml/kg) | 11.2 (3.6) | 12.2 (3.7) | 1.0 (−2.7 to 0.64) | 24.2 (8.0) | 28.3 (5.1) | −4.1 (−7.2 to −1.0)** |
| VE/kg (l/min/kg) | 0.2 (0.05) | 0.2 (0.04) | 0.01 (−0.01 to 0.03) | 1.31 (0.36) | 1.42 (0.31) | −0.11 (−0.26 to 0.05) |
| VE/MVV | 0.13 (0.04) | 0.10 (0.02) | 0.03 (0.01 to; 0.05) | 0.83 (0.22) | 0.70 (0.14) | 0.13 (0.04 to 0.21)** |
| Oxygen pulse (ml/beat) | 2.7 (0.8) | 2.7 (0.7) | 0.03 (−0.4 to 0.4) | 7.0 (1.5) | 8.4 (1.5) | −1.4 (−2.1 to −0.7)** |
| PETCO2 (mmHg) | 37.7 (2.4) | 37.3 (2.3) | 0.4 (−0.7 to 1.5) | 35.9 (4.9) | 37.0 (3.8) | −1.1 (−3.1 to 1.0) |
| PETO2 (mmHg) | 106.0 (4.4) | 107.0 (3.9) | −1.0 (−3.0 to 0.8) | 115.4 (4.9) | 114.9 (4.4) | 0.5 (−1.7 to 2.5) |
| EqCO2 | 30.0 (2.4) | 30.5 (2.8) | −0.5 (−1.7 to 0.7) | 32.1 (4.3) | 30.7 (3.1) | 1.4 (−0.30 to 3.10) |
| EqO2 | 34.6 (4.2) | 34.7 (4.1) | −0.1 (−2.0 to 1.8) | 36.3 (5.3) | 34.4 (4.1) | 1.9 (−0.26 to 4.10) |
| Systolic blood pressure (mmHg) | 97.1 (10.7) | 99.0 (8.8) | −1.9 (−8.0 to 4.3) | 127.4 (14.2) | 127.6 (17.6) | −0.2 (−10.0 to 9.6) |
| Diastolic blood pressure (mmHg) | 57.0 (10.6) | 60 (7.5) | −3.0 (−8.5 to 3.0) | 60.5 (10.5) | 63.5 (8.2) | −3.0 (−8.8 to 2.8) |
| Work/kg | – | – | – | 2.70 (0.63) | 3.11 (0.50) | −0.41 (−0.67 to −0.15)** |
| Anaerobic threshold VO2 (ml/min) | 760 (172) | 858 (180) | −98 (−178 to 18) | |||
| Exercise time (min) | – | – | – | 14.4 (1.9) | 15.3 (2.0) | −0.9 (−1.7 to 0.04) |
↵† Data are presented as median (IQR) and log transformed prior to comparisons.
Data are presented as mean (SD),
↵* p<0.05;
↵** p<0.01;
↵*** p<0.001.
All baseline variables are averaged over the final 20 s of rest.
All peak exercise variables are averaged over the final 20 s of maximal completed work, except for anaerobic threshold and time.
EqCO2, ventilatory equivalent for carbon dioxide; EqO2, ventilatory equivalent for oxygen; PETCO2, end-tidal partial pressure of carbon dioxide; PETO2, end-tidal partial pressure of oxygen; SpO2, peripheral oxygen saturation; VE, minute ventilation; VE/MVV, ventilatory reserve; VO2, oxygen consumption; Vt, tidal volume.