| Group 1 | Group 2 | Group 3 | Group 4 | Group 5 | |
| Age (years)*** | 17 (2.9 ) (14.9 to 19.1) | 18.6 (2.8) (16.4 to 20.7) | 21.6 (4.6) (18.6 to 24.7) | 22.2 (3.3) (19.9 to 24.4) | 29.1 (6.2) (24.5 to 33.8) |
| BMI (kg/m2) | 21.7 (6.5) (13 to 28.2) | 20.7 (6.2) (16 to 25.3) | 20.9 (8.8) (15 to 26.8) | 18.3 (6.8) (13.7 to 22.8) | 18.8 (5.4) (14.8 to 22.8) |
| VC (%)*** | 44.5 (16) (33.1 to 55.9) | 23.3 (5.4) (19.2 to 27.5) | 25.9 (8.4) (20.3 to 31.6) | 14.8 (4.2) (12 to 17.6) | 12.1 (2.4) (10.2 to 14) |
| MVV (l/min)*** | 60.8 (18.1) (47.9 to 73.7) | 34.7 (8.2) (28.4 to 41) | 41.4 (11.7) (33.5 to 49.2) | 26.4 (13.6) (17.2 to 35.4) | 18.2 (4.0) (15.2 to 21.3) |
| VT (ml)** | 425 (188) (291 to 559) | 252 (88) (184 to 320) | 305 (74) (256 to 355) | 274 (84) (218 to 331) | 241 (44) (208 to 275) |
| RR (breath/min)** | 17.5 (5) (13.9 to 21.1) | 22.4 (6.4) (17.6 to 27.3) | 19.3 (4.1) (16.6 to 21.9) | 19.6 (2.5) (17.9 to 21.2) | 24.8 (4.8) (21.1 to 28.5) |
| VE (l/min) | 6.9 (2.2) (5.3 to 8.5) | 5.3 (1.7) (4 to 6.6) | 5.8 (1.4) (4.8 to 6.7) | 5.4 (1.7) (4.2 to 6.6) | 5.9 (1.1) (5.0 to 6.8) |
| Ti/Ttot | 0.46 (0.04) (0.44 to 0.49) | 0.44 (0.08) (0.39 to 0.5) | 0.41 (0.08) (0.36 to 0.46) | 0.44 (0.04) (0.41 to 0.47) | 0.43 (0.05) (0.40 to 0.47) |
| MIP (cm H2O)*** | 46.7 (14.8) (36.1 to 57.2) | 24.1 (8.5) (17.6 to 30.6) | 26.9 (10.1) (20.1 to 33.7) | 14 (5.6) (10.2 to 17.7) | 11.1 (3.2) (8.7 to 13.5) |
| P0.1 | 1.84 (0.78) (1.28 to 2.4) | 1.61 (0.37) (1.32 to 1.9) | 1.42 (0.4) (1.14 to 1.69) | 1.35 (0.5) (1.02 to 1.67) | 1.48 (0.71) (0.93 to 2.02) |
| TT0.1* | 0.019 (0.008) (0.013 to 0.025) | 0.034 (0.022) (0.017 to 0.051) | 0.024 (0.01) (0.017 to 0.031) | 0.046 (0.021) (0.031 to 0.06) | 0.059 (0.026) (0.039 to 0.079) |
| Tlim (s)** | 422 (186) (288 to 555) | 429 (249) (237 to 620) | 256 (195) (125 to 387) | 202 (197) (70 to 334) | 121 (81) (59 to 183) |
Data are presented as mean (SD) with 95% confidence interval.
BMI, body mass index; VC, vital capacity; MVV, maximal voluntary ventilation; VT, tidal volume; RR, respiratory rate; VE, minute ventilation; Ti, inspiratory time; Ttot, total breath time; Ti/Ttot, duty cycle; MIP, maximum inspiratory pressure; P0,1, occlusion pressure; TT0.1, tension-time index; Tlim, muscle endurance time.
Group 1, no assisted ventilation (NIPPV) and 24/24 h normocapnia; group 2, nocturnal hypercapnia prior to start of NIPPV implementation; group 3, nocturnal NIPPV with no breathlessness; group 4, nocturnal NIPPV with breathlessness; group 5, full-time NIPPV.
*p<0.05; **p<0.01; ***p<0.001 (ANOVA).