Initial ventilatory parameters after ICU admission by weight among the subgroup of 1045 patients who were intubated on mechanical ventilation but did not fulfil the criteria for ARDS on ICU admission
| Ventilatory parameter on ICU admission | Underweight (n = 35) | Normal (n = 349) | Overweight (n = 374) | Obese (n = 218) | Severely obese (n = 69) | p Value |
| Tidal volume* (ml) mean (SD) | 480 (135) | 595 (168) | 625 (159) | 628 (312) | 614 (168) | 0.003 |
| Tidal volume/IBW (ml/kg IBW) mean (SD) | 8.1 (2.4) | 9.3 (2.5) | 9.4 (2.4) | 10.1 (6.2) | 9.7 (2.7) | 0.004 |
| Number of patients (%) ventilated with tidal volumes: | ||||||
| ⩽8 ml/kg IBW | 17 (49%) | 121 (35%) | 115 (31%) | 53 (24%) | 27 (39%) | 0.01 |
| 8.1–10 ml/kg IBW | 12 (34%) | 103 (30%) | 119 (32%) | 77 (35%) | 10 (14%) | 0.02 |
| 10.1–12 ml/kg IBW | 4 (6%) | 65 (30%) | 84 (22%) | 46 (21%) | 15 (22%) | 0.5 |
| >12 ml/kg IBW | 2 (6%) | 50 (14%) | 47 (13%) | 37 (17%) | 15 (22%) | 0.1 |
| Peak pressure† (cm H2O) mean (SD) | 22 (7.5) | 22 (6.3) | 22 (6.9) | 24 (7.7) | 28 (8.0) | <0.0001 |
| Static total respiratory system compliance‡ (ml/cm H2O) mean (SD) | 28 (6.7) | 34 (12) | 38 (23) | 34 (13) | 36 (22) | 0.5 |
| PEEP§ (cm H2O) mean (SD) | 5.6 (1.6) | 6.4 (2.6) | 6.6 (2.5) | 6.7 (2.8) | 8.5 (4.1) | <0.0001 |
| Number of patients (%) ventilated with PEEP: | ||||||
| ⩽5 cm H2O | 29 (83%) | 238 (68%) | 229 (61%) | 137 (63%) | 27 (39%) | <0.0001 |
| 5.1–7.5 cm H2O | 3 (9%) | 28 (8%) | 32 (9%) | 19 (9%) | 8 (12%) | 0.9 |
| 7.6–10 cm H2O | 2 (6%) | 62 (18%) | 89 (24%) | 42 (19%) | 23 (33%) | 0.004 |
| >10 cm H2O | 1 (3%) | 16 (5%) | 21 (6%) | 18 (8%) | 11 (16%) | 0.006 |
*Tidal volumes missing in 10 normal, 9 overweight, 5 obese and 2 severely obese patients.
†Peak pressure not available in 15 underweight, 112 normal, 117 overweight, 78 obese and 20 severely obese patients.
‡Compliance (tidal volume/(static plateau pressure – PEEP)) not available in 21 underweight, 171 normal, 170 overweight, 78 obese and 32 severely obese patients.
§Not available in 5 normal, 3 overweight and 2 obese patients.
ARDS, acute respiratory distress syndrome; IBW, ideal body weight; ICU, intensive care unit; PEEP, positive end expiratory pressure.