Table 1.
Baseline characteristics of the patients before and after matching
| Unmatched cohort (n=933) | Matched cohort (n=468) | |||||||
| High PEEP, n=259 | Low PEEP, n=674 | SMD | P | High PEEP, n=234 | Low PEEP, n=234 | SMD | P | |
| Age (years) | 64.0 [56.0 to 71.0] | 66.0 [58.0 to 73.0] | 0.201 | 0.018 | 65.0 [59.0 to 71.0] | 64.0 [55.2 to 71.0] | 0.134 | 0.268 |
| Male sex | 192 (74.1) | 483 (71.7) | 0.056 | 0.463 | 175 (74.8) | 176 (75.2) | 0.010 | 0.999 |
| BMI (kg m−2) | 27.8 [25.8 to 31.1] | 27.6 [25.2 to 30.7] | 0.105 | 0.327 | 27.7 [25.4 to 30.4] | 28.1 [25.7 to 31.3] | 0.105 | 0.303 |
| Transferred under invasive ventilation | 29 (11.2) | 59 (8.8) | 0.082 | 0.261 | 23 (9.8) | 22 (9.4) | 0.014 | 0.999 |
| Days between intubation and admission | 0 [0 to 0] | 0 [0 to 0] | 0.047 | 0.514 | 0 [0 to 0] | 0 [0 to 0] | 0.039 | 0.675 |
| Use of noninvasive ventilation | 24/242 (9.9) | 52/630 (8.3) | 0.058 | 0.424 | 23/220 (10.5) | 20 (9.3) | 0.037 | 0.749 |
| Duration of noninvasive ventilation (h) | 8.0 [5.5 to 14.0] | 7.0 [2.0 to 20.0] | 0.036 | 0.976 | 8.0 [4.4 to 14.0] | 5.5 [2.2 to 9.0] | 0.135 | 0.749 |
| Chest CT scan performed | 94/253 (37.1) | 229/660 (34.7) | 0.053 | 0.486 | 83/228 (36.4) | 82/228 (36.0) | 0.009 | 0.999 |
| Lung parenchyma affected | 0.071 | 0.987 | 0.266 | 0.610 | ||||
| 0% | 3/94 (3.2) | 8/229 (3.5) | 1/83 (1.2) | 5/82 (6.1) | ||||
| 25% | 28/94 (29.8) | 75/229 (32.8) | 27/83 (32.5) | 24/82 (29.3) | ||||
| 50% | 29/94 (30.9) | 68/229 (29.7) | 24/83 (28.9) | 23/82 (28.0) | ||||
| 75% | 28/94 (29.8) | 65/229 (28.4) | 26/83 (31.3) | 25/82 (30.5) | ||||
| 100% | 6/94 (6.4) | 13/229 (5.7) | 5/83 (6.0) | 5/82 (6.1) | ||||
| Chest radiograph performed | 142/163 (87.1) | 384/431 (89.1) | 0.054 | 0.567 | 132/148 (89.2) | 133/149 (89.3) | 0.019 | 0.999 |
| Quadrants affected | 0.184 | 0.306 | 0.287 | 0.151 | ||||
| 1 | 13/139 (9.4) | 24/384 (6.2) | 13/130 (10.0) | 5/133 (3.8) | ||||
| 2 | 37/139 (26.6) | 85/384 (22.1) | 35/130 (26.9) | 30/133 (22.6) | ||||
| 3 | 32/139 (23.0) | 110/384 (28.6) | 29/130 (22.3) | 35/133 (26.3) | ||||
| 4 | 57/139 (41.0) | 165/384 (43.0) | 53/130 (40.8) | 63/133 (47.4) | ||||
| Severity of ARDS | 0.447 | <0.001 | 0.158 | 0.246 | ||||
| Mild | 81/256 (31.6) | 103/663 (15.5) | 63 (26.9) | 52 (22.2) | ||||
| Moderate | 161/256 (62.9) | 469/663 (70.7) | 157 (67.1) | 160 (68.4) | ||||
| Severe | 14/256 (5.5) | 91/663 (13.7) | 14 (6.0) | 22 (9.4) | ||||
| Co-existing disorders | ||||||||
| Hypertension | 86 (33.2) | 227 (33.7) | 0.010 | 0.938 | 77 (32.9) | 81 (34.6) | 0.036 | 0.769 |
| Heart failure | 8 (3.1) | 31 (4.6) | 0.079 | 0.364 | 8 (3.4) | 14 (6.0) | 0.121 | 0.275 |
| Diabetes | 56 (21.6) | 154 (22.8) | 0.030 | 0.727 | 54 (23.1) | 51 (21.8) | 0.031 | 0.825 |
| Chronic kidney disease | 14 (5.4) | 28 (4.2) | 0.059 | 0.480 | 11 (4.7) | 10 (4.3) | 0.021 | 0.999 |
| Baseline creatininea (μmol l−1) | 78.0 [65.0 to 98.8] | 77.0 [63.0 to 96.0] | 0.025 | 0.305 | 80.0 [67.0 to 99.0] | 77.0 [66.0 to 94.8] | 0.052 | 0.337 |
| Liver cirrhosis | 1 (0.4) | 2 (0.3) | 0.015 | 0.999 | 1 (0.4) | 1 (0.4) | <0.001 | 0.999 |
| Chronic obstructive pulmonary disease | 13 (5.0) | 63 (9.3) | 0.168 | 0.032 | 12 (5.1) | 23 (9.8) | 0.179 | 0.078 |
| Active haematological neoplasia | 5 (1.9) | 10 (1.5) | 0.034 | 0.574 | 5 (2.1) | 5 (2.1) | <0.001 | 0.999 |
| Active solid neoplasia | 8 (3.1) | 16 (2.4) | 0.044 | 0.498 | 8 (3.4) | 5 (2.1) | 0.078 | 0.576 |
| Neuromuscular disease | 4 (1.5) | 4 (0.6) | 0.093 | 0.228 | 4 (1.7) | 3 (1.3) | 0.035 | 0.999 |
| Immunosuppression | 7 (2.7) | 16 (2.4) | 0.021 | 0.814 | 7 (3.0) | 8 (3.4) | 0.024 | 0.999 |
| Previous medication | ||||||||
| Systemic steroids | 13 (5.0) | 23 (3.4) | 0.080 | 0.258 | 12 (5.1) | 7 (3.0) | 0.108 | 0.349 |
| Inhalation steroids | 22 (8.5) | 88 (13.1) | 0.148 | 0.054 | 18 (7.7) | 38 (16.2) | 0.266 | 0.006 |
| Angiotensin converting enzyme inhibitor | 49 (18.9) | 112 (16.6) | 0.060 | 0.439 | 44 (18.8) | 52 (22.2) | 0.085 | 0.423 |
| Angiotensin II receptor blocker | 26 (10.0) | 78 (11.6) | 0.049 | 0.562 | 25 (10.7) | 19 (8.1) | 0.088 | 0.429 |
| Beta-blockers | 34 (13.1) | 145 (21.5) | 0.223 | 0.004 | 30 (12.8) | 46 (19.7) | 0.186 | 0.060 |
| Insulin | 15 (5.8) | 50 (7.4) | 0.066 | 0.473 | 14 (6.0) | 18 (7.7) | 0.068 | 0.583 |
| Metformin | 44 (17.0) | 105 (15.6) | 0.038 | 0.618 | 42 (17.9) | 35 (15.0) | 0.081 | 0.455 |
| Statins | 67 (25.9) | 217 (32.2) | 0.140 | 0.068 | 61 (26.1) | 81 (34.6) | 0.187 | 0.056 |
| Calcium channel blockers | 50 (19.3) | 118 (17.5) | 0.046 | 0.568 | 47 (20.1) | 40 (17.1) | 0.077 | 0.476 |
| Vital signs | ||||||||
| Heart rate (bpm) | 82.5 [72.0 to 95.5] | 84.5 [75.0 to 98.0] | 0.130 | 0.215 | 83.0 [72.0 to 96.0] | 83.4 [70.5 to 98.6] | 0.025 | 0.820 |
| Mean arterial pressure (mmHg) | 79.5 [73.7 to 86.2] | 81.0 [73.5 to 88.5] | 0.061 | 0.740 | 79.9 [74.2 to 86.1] | 79.9 [73.0 to 87.5] | 0.062 | 0.317 |
| Organ support | ||||||||
| Continuous sedation | 249 (96.1) | 646 (96.1) | <0.001 | 0.457 | 225 (96.2) | 224 (96.1) | 0.001 | 0.544 |
| Inotropic or vasopressor | 206 (79.5) | 526 (78.3) | 0.031 | 0.488 | 189 (80.8) | 188 (80.7) | 0.002 | 0.872 |
| Vasopressor | 206 (79.5) | 525 (78.1) | 0.035 | 0.507 | 189 (80.8) | 187 (80.3) | 0.013 | 0.870 |
| Inotropic | 6 (2.3) | 33 (4.9) | 0.139 | 0.724 | 6 (2.6) | 16 (6.9) | 0.204 | 0.884 |
| Fluid balance (ml) | 584.0 [22.0 to 1227.0] | 648.0 [41.5 to 1492.0] | 0.105 | 0.623 | 605.0 [9.6 to 1298.0] | 635.0 [30.0 to 1428.5] | 0.091 | 0.320 |
| Urine output (ml) | 720.0 [362.5 to 1125.0] | 710.0 [383.8 to 1165.0] | 0.053 | 0.836 | 720.0 [362.5 to 1107.5] | 700.0 [400.0 to 1190.0] | 0.070 | 0.997 |
Data are median [IQR] or number (%). Percentages may not total 100 because of rounding. CT, computed tomography; PEEP, positive end-expiratory pressure; SMD, standardised mean difference.
a
Most recent measurement in 24 h before intubation, or at ICU admission under invasive ventilation.