| All patients | DMD | SMA | Other NMD | |
| Patients n | 52 | 20 | 10 | 22 |
| Patient characteristics | ||||
| Age yrs | 14.9 (10.1–16.1) | 16.1 (14.9–17.9)* | 11.3 (9.5–15.0) | 12.5 (7.6–15.6) |
| Weight kg | 37.0 (24.7–59.5) | 46.5 (35.5–60.5) | 29.2 (18.0–38.0) | 33.0 (24.0–51.0) |
| Height cm | 151 (125–164) | 168 (159–174) | 138 (126–164) | 145 (124–168) |
| BMI z-score | -0.56 (-2.00–0.90) | -0.45 (-2.00–0.37) | -2.00 (-2.00–0.84) | -0.48 (-2.00–1.36) |
| Lung function parameters | ||||
| FVC % pred | 36.5 (29.0–48.0) | 34.0 (28.0–42.3) | 30.5 (24.5–61.5) | 42.0 (32.5–61.5) |
| FRCHe % pred | 66.5 (52.0–83.0) | 69.0 (61.0–85.0) | 52.0 (44.0–77.0) | 66.0 (52.8–84.0) |
| Daytime blood gases | ||||
| Daytime Pa,O2 mmHg | 92.0 (84.0–97.8) | 89.5 (83.5–97.5) | 92.5 (83.0–100.0) | 92.0 (85.0–95.8) |
| Daytime Pa,CO2 mmHg | 39.0 (37.0–42.0) | 38.5 (36.5–41.5) | 37.5 (34.0–42.0) | 39.0 (38.0–42.0) |
| pH | 7.42 (7.40–7.43) | 7.42 (7.40–7.44) | 7.42 (7.41–7.43) | 7.41 (7.40–7.43) |
| HCO3- mmol·L−1 | 24.18 (22.75–26.30) | 24.23 (22.79–26.22) | 22.70 (21.36–26.33) | 24.31 (23.00–26.31) |
| Respiratory parameters | ||||
| VT mL·kg−1 | 7.0 (5.0–9.1) | 6.5 (5.0–8.7) | 9.7 (7.8–11.2) | 6.9 (4.6–9.0) |
| fR breaths·min−1 | 22.8 (17.6–25.5) | 20.0 (17.5–22.9) | 23.0 (16.0–26.5) | 24.0 (20.9–28.4) |
| V′E L·min−1 | 5.9 (5.2–6.6) | 6.0 (5.3–6.8) | 5.7 (4.9–7.0) | 5.9 (5.2–6.6) |
| fR/VT breaths·min−1·mL−1 | 0.08 (0.06–0.12) | 0.07 (0.05–0.08) | 0.06 (0.05–0.12) | 0.11 (0.06–0.14) |
| ΔPgas/ΔPdi | 0.32 (0.20–0.52) | 0.29 (0.20–0.40) | 0.55 (0.40–0.69)¶ | 0.34 (0.18–0.42) |
| CL,dyn mL·cmH2O−1 | 41 (24–58) | 64 (44–80)* | 29 (15–41) | 32 (24–55) |
| RL,insp cmH2O·L−1·s−1 | 6.6 (3.4–8.1) | 5.2 (3.4–7.2) | 5.9 (3.4–11.0) | 6.7 (3.7–8.4) |
| Respiratory muscle performance | ||||
| SNIP cmH2O | -27.5 (-39.0– -19.5) | -22.0 (-33.5– -12.5) | -27.0 (-38.5– -18.0) | -35.0 (-40.0– -23.5) |
| Sniff Poes cmH2O | -30.5 (-45.0– -25.0) | -25.0 (-35.5– -22.3) | -32.0 (-60.0– -23.3) | -32.0 (-47.0– -26.0) |
| Sniff Pdi cmH2O | 37.4 (25.2–57.0) | 27.0 (19.2–36.7)# | 56.0 (33.0–77.8) | 40.0 (28.0–58.0) |
| Pgas,cough cmH2O | 38.1 (21.0–51.0) | 23.0 (14.5–36.3)* | 37.2 (27.5–47.3) | 50.5 (37.3–68.3) |
| PE,max cmH2O | 33.0 (22.0–43.5) | 28.5 (21.0–34.9) | 20.5 (8.0–33.0) | 42.0 (24.4–64.1) |
| PI,max (cmH2O) | -30.5 (-40.2– -20.2) | -37.4 (-41.3– -21.0) | -30.0 (-30.8– -24.0) | -28.0 (-41.8– -16.1) |
| Respiratory muscle endurance | ||||
| Ttoes | 0.05 (0.02–0.07) | 0.06 (0.04–0.08) | 0.03 (0.02–0.08) | 0.05 (0.02–0.06) |
| Ttdi | 0.15 (0.08–0.26) | 0.25 (0.12–0.40) | 0.11 (0.07–0.19) | 0.17 (0.09–0.21) |
Data are presented as median (interquartile range), unless otherwise stated. DMD: Duchenne muscular dystrophy; SMA: spinal muscular atrophy; NMD: neuromuscular disease; BMI: body mass index; FVC: forced vital capacity; % pred: % predicted; FRCHe: functional residual capacity measured by the helium dilution technique; Pa,O2: arterial oxygen tension; Pa,CO2: arterial carbon dioxide tension; VT: tidal volume; fR: respiratory frequency; V′E: minute ventilation; fR/VT: rapid and shallow breathing index; ΔPgas/ΔPdi: ratio of gastric pressure swing to transdiaphragmatic pressure swing during spontaneous breathing; CL,dyn: dynamic lung compliance; RL,insp: inspiratory lung resistance; SNIP: sniff nasal inspiratory pressure; Poes: oesophageal pressure; Pdi: transdiaphragmatic pressure; Pgas,cough: gastric pressure during a maximal cough manoeuvre; PE,max: maximal static expiratory pressure; PI,max: maximal static inspiratory pressure; Ttoes: tension-time index of the inspiratory muscles; Ttdi: tension-time index of the diaphragm. *: p<0.05 compared with SMA or other NMD; #: p<0.05 compared with SMA; ¶: p<0.05 compared with DMD or other NMD.