| Obese group | Non-obese group | p Value | |
| Age (years) | 48.3 (11.6) | 36.0 (19.0) | 0.004 |
| Sex (M:F) | 21:9 | 20:10 | 0.999 |
| Hip circumference (cm) | 126.7 (16.5) | 98.7 (10.7) | <0.001 |
| Waist circumference (cm) | 130.5 (18.9) | 84.2 (15.2) | <0.001 |
| Waist-hip ratio | 1.03 (0.10) | 0.85 (0.10) | <0.001 |
| Height (m) | 1.70 (0.08) | 1.71 (0.09) | 0.697 |
| Weight (kg) | 123.4 (25.8) | 69.5 (15.6) | <0.001 |
| BMI (kg/m2) | 42.8 (8.6) | 23.6 (3.7) | <0.001 |
| Neck circumference (cm) | 44.5 (4.0) | 35.7 (4.5) | <0.001 |
| Smoking status (S/E/N) | 3/10/18 | 1/5/24 | 0.173 |
| Epworth Sleepiness Score* | 8.5 (6.0, 12.0) | 3.0 (2.0, 5.0) | <0.001 |
| MRC Dyspnoea Score* | 2.0 (1.0, 3.0) | 1.0 (1.0, 1.0) | <0.001 |
| HADS-A* | 4.0 (3.0, 9.0) | 0.0 (0.0, 2.0) | <0.001 |
| HADS-D* | 4.0 (2.0, 7.0) | 1.0 (0.0, 1.0) | <0.001 |
| Pimax (cm H2O) | 92.5 (33.9) | 92.4 (36.3) | 0.994 |
| Sniff Pnasal (cm H2O) | 87.7 (25.4) | 95.0 (32.7) | 0.337 |
| Sniff Poes (cm H2O) | 107.3 (22.1) | 99.0 (28.1) | 0.229 |
| Sniff Pdi (cm H2O) | 133.6 (23.7) | 125.6 (39.1) | 0.362 |
| Pemax (cm H2O) | 134.4 (33.0) | 105.4 (34.1) | 0.001 |
| Cough Pgas (cm H2O) | 236.8 (55.6) | 182.5 (60.6) | 0.001 |
| Cdyn (sitting, l/cm H2O) | 0.117 (0.047) | 0.182 (0.065) | <0.001 |
| Cdyn (lying, l/cm H2O) | 0.087 (0.043) | 0.134 (0.051) | 0.001 |
| FEV1 (l) | 2.6 (0.9) | 3.4 (1.0) | 0.003 |
| FEV1 (% predicted) | 80.1 (21.9) | 94.4 (18.6) | 0.008 |
| VC sitting (l) | 3.4 (1.0) | 4.1 (1.1) | 0.006 |
| VC (% predicted) | 84.4 (18.7) | 96.7 (17.9) | 0.012 |
| VC supine (l) | 3.1 (1.1) | 3.9 (1.1) | 0.004 |
| FEV1/FVC (%) | 77.7 (12.5) | 81.4 (10.1) | 0.211 |
| Pao2 (kPa) | 10.2 (0.8) | 11.9 (1.4) | <0.001 |
| Paco2 (kPa) | 5.3 (0.5) | 4.9 (0.3) | 0.001 |
| Bicarbonate (mmol/l) | 25.3 (1.9) | 24.2 (0.8) | 0.006 |
| pH | 7.42 (0.03) | 7.42 (0.02) | 0.407 |
BMI, body mass index; Cdyn, dynamic compliance; FEV1, forced expiratory volume in 1 s; FVC, forced vital capacity; Paco2, Pao2, arterial carbon dioxide and oxygen tensions; HADS, Hospital Anxiety and Depression Score (A, anxiety; D, depression); Pdi, transdiagraphmatic pressure; Pemax, Pimax, maximum expiratory and inspiratory pressures; Pgas, gastric pressure; Poes, oesophageal pressure; Pnasal, nasal pressure; S/E/N, smoker/ex-smoker/non-smoker; VC, vital capacity.
*Non-parametric data are given as median (25th, 75th percentiles using Tukey’s Hinges).