Table 1 Comparison of baseline characteristics between the traditional and low tidal volume subgroups
Variables | Subgroup with PaO2/FiO2 > 150 | Subgroup with PaO2/FiO2 ≤ 150 | ||||
|---|---|---|---|---|---|---|
Traditional tidal volume (n = 162) | Low tidal volume (n = 183) | p value | Traditional tidal volume (n = 235) | Low tidal volume (n = 256) | p value | |
Age (years) | 50.3 ± 18.5 | 50.8 ± 16.8 | 0.800 | 52.5 ± 17.3 | 50.7 ± 16.6 | 0.233 |
Male [n (%)] | 95 (58.6) | 117 (63.9) | 0.317 | 138 (58.7) | 148 (57.8) | 0.838 |
BMI (kg/m2) | 27.2 ± 7.0 | 27.4 ± 7.6 | 0.803 | 26.8 ± 6.4 | 27.4 ± 6.59 | 0.273 |
Ethnicity (White, %) | 119 (73.4) | 138 (75.4) | 0.678 | 162 (68.9) | 190 (74.2) | 0.194 |
Ethnicity (Black, %) | 31 (19.1) | 28 (15.3) | 0.345 | 42 (17.8) | 41 (16.0) | 0.583 |
Comorbidities | ||||||
Chronic dialysis [n (%)] | 6 (3.7) | 3 (1.6) | 0.226 | 4 (1.7) | 6 (2.3) | 0.620 |
Leukemia [n (%)] | 4 (2.4) | 3 (1.6) | 0.579 | 5 (2.1) | 7 (2.7) | 0.669 |
Immunosuppression [n (%)] | 17 (10.4) | 13 (7.1) | 0.256 | 24 (10.2) | 32 (12.6) | 0.436 |
Diabetes [n (%)] | 22 (13.5) | 25 (13.6) | 0.997 | 33 (14.0) | 36 (14.0) | 0.973 |
Elective surgery [n (%)] | 12 (7.4) | 17 (9.2) | 0.520 | 18 (7.6) | 26 (10.1) | 0.371 |
Radiographic ALI score median (IQR) | 4 (3–4) | 4 (3–4) | 0.671 | 4 (4–4) | 4 (4–4) | 0.650 |
Pneumothoraces [n (%)] | 12 (7.4) | 16 (8.7) | 0.687 | 44 (18.7) | 35 (13.6) | 0.117 |
Chest tube [n (%)] | 42 (25.9) | 38 (20.7) | 0.218 | 57 (24.2) | 71 (27.7) | 0.412 |
Parameters on screen | ||||||
PaO2/FiO2 (mmHg) | 161.5 ± 59.2 | 165.0 ± 65.8 | 0.601 | 103.8 ± 39.1 | 107.2 ± 41.6 | 0.358 |
PaO2 (mmHg) | 103.9 ± 49.2 | 101.7 ± 43.5 | 0.677 | 81.4 ± 32.4 | 79.1 ± 27.8 | 0.400 |
Indexes within 24-h preceding trial | ||||||
Maximum respiratory rate | 31.3 ± 12.4 | 28.9 ± 10.0 | 0.053 | 30.5 ± 10.7 | 30.8 ± 10.7 | 0.748 |
Minimum mean blood pressure (mmHg) | 63.5 ± 14.3 | 63.7 ± 14.2 | 0.862 | 61.1 ± 13.5 | 59.8 ± 11.1 | 0.220 |
Maximum serum creatinine (mg/dL) | 1.76 ± 1.68 | 1.76 ± 1.47 | 0.979 | 1.75 ± 1.61 | 1.54 ± 1.37 | 0.129 |
Minimum platelet count (109/L) | 154.3 ± 108.9 | 145.7 ± 98.7 | 0.439 | 157.9 ± 108.9 | 176.6 ± 135.2 | 0.094 |
Maximum white blood cell (109/L) | 15.6 ± 10.6 | 14.5 ± 8.8 | 0.272 | 14.6 ± 8.9 | 15.2 ± 11.8 | 0.587 |
Parameters on day 0 of the trial | ||||||
Fluid intake (mL) | 5217.7 ± 3782.1 | 5065.2 ± 4070.9 | 0.719 | 4896.0 ± 4045.2 | 5366.1 ± 4293.9 | 0.213 |
Fluid output (mL) | 2374.0 ± 1716.2 | 2473.2 ± 1698.6 | 0.590 | 2375.6 ± 1694.9 | 2396.8 ± 1630.3 | 0.887 |
PaO2/FiO2 (mmHg) | 212.2 ± 65.2 | 210.6 ± 56.0 | 0.817 | 103.2 ± 26.7 | 104.2 ± 26.5 | 0.684 |
PEEP on day 0 (cmH2O) | 7.4 ± 3.8 | 7.4 ± 3.2 | 0.999 | 8.9 ± 3.9 | 9.5 ± 3.9 | 0.109 |
PEEP on day 1 (cmH2O) | 6.5 ± 3.2 (n = 162) | 6.8 ± 2.3 (n = 179) | 0.294 | 9.6 ± 3.3 (n = 233) | 11.1 ± 3.7 (n = 251) | < 0.001 |
Plateau pressures on day 1 (cmH2O) | 28.8 ± 7.6 (n = 125) | 27.3 ± 7.3 (n = 137) | 0.086 | 31.6 ± 8.2 (n = 186) | 31.6 ± 7.6 (n = 211) | 0.975 |
Plateau pressures on day 2 (cmH2O) | 30.6 ± 8.4 (n = 146) | 22.5 ± 5.8 (n = 151) | < 0.001 | 33.7 ± 8.6 (n = 223) | 26.4 ± 6.4 (n = 239) | < 0.001 |
Driving pressure on day 1 (cmH2O) | 21.6 ± 6.9 (n = 125) | 19.7 ± 6.9 (n = 137) | 0.027 | 22.6 ± 7.2 (n = 186) | 21.8 ± 6.7 (n = 211) | 0.276 |
Driving pressure on day 2 (cmH2O) | 23.9 ± 7.2 (n = 146) | 15.4 ± 5.3 (n = 151) | < 0.001 | 23.9 ± 7.3 (n = 223) | 15.3 ± 5.3 (n = 239) | < 0.001 |