Table 2.
Baseline demographics of four groups of patients specified in our multivariable regression model
| Characteristic | Low P/F and LTVV | High P/F and LTVV | Low P/F and HTVV | High P/F and HTVV | Overall p value |
|---|---|---|---|---|---|
| n | 107 | 115 | 113 | 111 | – |
| Age, years | 51.4 ± 14.3 | 48.8 ± 16.1 | 51.0 ± 16.8 | 51.4 ± 16.9 | 0.56 |
| Female | 50 (47%) | 41 (36%) | 51 (45%) | 42 (38%) | 0.26 |
| APACHE III | 88.3 ± 29.5 | 76.8 ± 28.0 | 87.3 ± 28.2 | 80.9 ± 26.6 | 0.006 |
| Initial P/F ratio | 84.5 ± 20.8 | 183.9 ± 46.5 | 84.0 ± 19.9 | 175.3 ± 47.5 | < 0.001 |
| Initial driving pressure | 14.9 ± 5.3 | 22.9 ± 7.0 | 16.9 ± 5.4 | 24.6 ± 6.6 | < 0.001 |
| Mean PaO2 (mmHg) | 74.1 ± 18.2 | 83.5 ± 21.3 | 75.4 ± 11.7 | 83.0 ± 15.7 | < 0.001 |
| Mean FiO2 (%) | 62.1 ± 15.3 | 49.0 ± 12.2 | 58.2 ± 14.0 | 47.6 ± 11.8 | < 0.001 |
| Mean PEEP (cm H20) | 9.9 ± 2.8 | 7.7 ± 2.6 | 9.1 ± 3.2 | 7.2 ± 2.3 | < 0.001 |
| Lowest systolic blood pressure | 87.6 ± 19.4 | 92.3 ± 19.3 | 87.7 ± 18.1 | 92.3 ± 17.4 | 0.07 |
| Highest temperature | 38.6 ± 0.9 | 38.5 ± 0.8 | 38.5 ± 1.1 | 38.4 ± 0.83 | 0.33 |
| Mean pH | 7.32 ± 0.53 | 7.24 ± 0.90 | 7.29 ± 0.79 | 7.30 ± 0.70 | 0.88 |
| Platelet count | 161.0 ± 115.1 | 149.7 ± 115.5 | 162.8 ± 94.5 | 144.1 ± 100.7 | 0.51 |
| Pneumonia | 49 (45.8%) | 29 (25.2%) | 53 (46.9%) | 39 (35.1%) | 0.002 |
| Sepsis | 28 (26.1%) | 36 (31.3%) | 23 (20.3%) | 27 (24.3%) | 0.29 |
| Aspiration | 15 (14.0%) | 17 (14.8%) | 17 (15.0%) | 14 (12.6%) | 0.95 |
| Multiple transfusions | 4 (3.7%) | 1 (0.8%) | 3 (2.7%) | 9 (8.1%) | 0.03 |
| Trauma | 3 (2.8%) | 23 (20.0%) | 4 (3.5%) | 14 (12.6%) | < 0.001 |
| Other | 7 (6.5%) | 9 (7.8%) | 13 (8.8%) | 8 (7.2%) | 0.54 |
| Days of NMB, median (25–75 IQR) | 0 (0–1) | 0 (0–0) | 0 (0–1) | 0 (0–1) | 0.62a |
Values are shown as either mean ± SD or n (%), unless otherwise indicated
P value < 0.003 significant after Bonferroni correction for multiple comparisons
APACHE Acute Physiology and Chronic Health Evaluation, FiO2 fractional inspired oxygen, LTVV low tidal volume ventilation, IQR interquartile range, LTVV low tidal volume ventilation, NMB neuromuscular blockade, PEEP positive end-expiratory pressure, PaO2 arterial oxygen tension, P/F PaO2/FiO2
aTested by Wilcoxon Rank Sum