Table 1.
—Demographic Characteristics and Unadjusted Outcomes of Patients in 5 BMI Groups
| Characteristics | Underweight (BMI < 18.5) (n = 61) | Normal Weight (18.5 ≤ BMI < 25) (n = 542) | Overweight (25 ≤ BMI < 30) (n = 417) | Obese (30 ≤ BMI < 40) (n = 315) | Morbidly Obese (BMI > 40) (n = 74) | P Value Including All BMI Groups | P Value Excluding Underweight Group |
| Age,a y | 50.2 ± 16.8 | 51.6 ± 17.9 | 52.1 ± 18.3 | 51.0 ± 15.5 | 49.3 ± 13.1 | .76b | .51b |
| Gender, % women | 41.0 | 41.7 | 36.0 | 45.7 | 68.9 | < .001c | < .001c |
| Pao2/Fio2d | 131.0 ± 60.3 | 125.3 ± 55.3 | 129.1 ± 58.5 | 129.5 ± 59.1 | 148.1 ± 65.3 | .065 | .031 |
| APACHE III scorea | 97.2 ± 35.2 | 89.9 ± 29.8 | 87.2 ± 30.1 | 83.7 ± 30.5 | 81.5 ± 28.6 | < .001b | .001b |
| Prerandomization tidal volume per kilogram predicted body weight | 8.5 ± 2.1 | 9.1 ± 2.0 | 9.5 ± 2.2 | 9.5 ± 2.4 | 10.2 ± 2.6 | .001 | .008 |
| Diabetes, % | 13.1 | 11.8 | 13.2 | 17.5 | 35.1 | < .001c | < .001c |
| ALI risk factor | |||||||
| Trauma, % | 3.2 | 6.7 | 11.3 | 11.7 | 9.5 | .004c | .006c |
| Sepsis, % | 25.0 | 21.7 | 25.4 | 28.9 | 31.1 | .03c | .03c |
| Pneumonia, % | 44.2 | 37.8 | 33.8 | 32.4 | 35.1 | .004c | .004c |
| 90-d mortality, % | 45.9 | 33.4 | 30.2 | 27.6 | 32.4 | .03e | .17e |
| VFDsf | 2 (0-20) | 15 (0-23) | 14 (0-23) | 17 (0-24) | 15 (0-22) | .23b | .85b |
| OFDsf | 9 (0-19) | 16 (0-25) | 20 (1-26) | 17 (0-25) | 23 (8-27) | .005b | .07b |
ALI = acute lung injury; APACHE = Acute Physiologic and Chronic Health Evaluation; ODFs = organ-failure-free days; VFDs = ventilator-free days.
a
mean ± SD.
b
Wilcoxon rank sum test for trend.
c
χ2 test.
d
ratio of partial pressure of arterial to fraction of inspired oxygen.
e
Cochrane-Armitage test for trend.
f
median (intraquartile range).