Table 2.
Ventilatory variables and rescue therapy at start of ventilation 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 ∗ | |
| Ventilation support | ||||||||
| Assisted ventilation | 84/257 (32.7) | 185/671 (27.6) | 0.112 | 0.092 | 77/232 (33.2) | 61/233 (26.2) | 0.154 | 0.265 |
| Tidal volume (ml kg−1 PBW) | 6.4 [5.9 to 7.1] | 6.5 [5.9 to 7.0] | 0.043 | 0.296 | 6.4 [5.9 to 7.1] | 6.4 [5.9 to 7.0] | 0.028 | 0.642 |
| PEEP (cmH2O) | 14.2 [13.0 to 16.0] | 12.0 [10.0 to 14.0] | 0.911 | <0.001 | 14.3 [13.0 to 16.0] | 12.0 [10.1 to 14.0] | 0.927 | <0.001 |
| Peak pressure (cmH2O) | 28.0 [25.5 to 30.5] | 26.0 [23.0 to 29.3] | 0.391 | <0.001 | 28.0 [25.5 to 30.5] | 26.3 [23.0 to 29.5] | 0.346 | 0.007 |
| Driving pressure (cmH2O) | 13.8 [12.0 to 15.7] | 14.0 [11.9 to 16.2] | 0.130 | 0.180 | 13.7 [11.8 to 15.5] | 14.0 [11.5 to 16.7] | 0.158 | 0.425 |
| Mechanical power (J min−1) | 19.4 [16.4 to 23.8] | 18.0 [14.8 to 21.5] | 0.294 | 0.009 | 19.4 [16.4 to 23.9] | 18.2 [15.0 to 21.4] | 0.267 | 0.061 |
| Compliance (ml cmH2O−1) | 33.5 [27.5 to 39.5] | 33.1 [26.5 to 41.1] | 0.037 | 0.807 | 33.7 [28.5 to 40.1] | 33.8 [26.1 to 42.2] | 0.007 | 0.924 |
| Total respiratory rate (min−1) | 21.7 [19.7 to 24.0] | 21.5 [19.1 to 24.0] | 0.027 | 0.835 | 21.7 [19.8 to 24.0] | 21.5 [19.0 to 24.0] | 0.087 | 0.480 |
| FiO2 | 0.52 [0.45 to 0.63] | 0.60 [0.50 to 0.70] | 0.385 | <0.001 | 0.53 [0.45 to 0.65] | 0.57 [0.48 to 0.68] | 0.163 | 0.079 |
| etCO2 (kPa) | 4.9 [4.4 to 5.6] | 4.9 [4.3 to 5.5] | 0.086 | 0.799 | 4.9 [4.4 to 5.6] | 4.9 [4.3 to 5.5] | 0.067 | 0.662 |
| Fractional dead space, Enghoff | 0.14 [0.07 to 0.23] | 0.19 [0.10 to 0.29] | 0.424 | <0.001 | 0.15 [0.08 to 0.24] | 0.18 [0.09 to 0.26] | 0.225 | 0.063 |
| Laboratory tests | ||||||||
| pH | 7.37 [7.32 to 7.41] | 7.36 [7.30 to 7.40] | 0.195 | 0.046 | 7.37 [7.32 to 7.40] | 7.37 [7.32 to 7.41] | 0.084 | 0.115 |
| PaO2 (kPa) | 11.5 [10.0 to 13.5] | 10.7 [9.6 to 12.5] | 0.267 | <0.001 | 11.4 [9.9 to 13.1] | 11.0 [9.7 to 13.1] | 0.035 | 0.311 |
| PaO2/FiO2 | 19.0 [14.2 to 25.7] | 16.9 [12.7 to 22.3] | 0.193 | <0.001 | 17.9 [14.0 to 23.9] | 18.2 [14.2 to 24.8] | 0.083 | 0.587 |
| PaCO2 (kPa) | 5.7 [4.9 to 6.3] | 6.0 [5.3 to 6.7] | 0.319 | 0.004 | 5.8 [5.1 to 6.4] | 5.8 [5.2 to 6.4] | 0.060 | 0.730 |
| Lactate (mmol l−1) | 1.1 [0.9 to 1.4] | 1.2 [0.9 to 1.5] | 0.151 | 0.073 | 1.1 [0.9 to 1.4] | 1.2 [1.0 to 1.4] | 0.150 | 0.132 |
| Creatinine (μmol l−1) | 74.0 [62.8 to 93.5] | 74.0 [61.0 to 97.0] | 0.013 | 0.961 | 76.0 [64.0 to 96.2] | 74.0 [63.0 to 95.2] | 0.070 | 0.658 |
| Rescue therapy | ||||||||
| Prone positioning | 58 (22.9) | 231 (34.8) | 0.265 | 0.048 | 55 (24.0) | 75 (32.8) | 0.195 | 0.175 |
| Duration (ha) | 8.0 [5.0 to 12.0] | 8.0 [4.0 to 14.0] | 0.169 | 0.739 | 8.0 [6.0 to 12.0] | 9.0 [4.0 to 14.0] | 0.143 | 0.651 |
| Recruitment manoeuvre | 5 (2.6) | 15 (2.7) | 0.007 | 0.964 | 5 (2.9) | 5 (2.6) | 0.018 | 0.903 |
| ECMO | 0 (0.0) | 0 (0.0) | <0.001 | 0.999 | 0 (0.0) | 0 (0.0) | <0.001 | 0.999 |
| Use of NMBA | 77 (30.0) | 175 (26.0) | 0.088 | 0.111 | 75 (32.2) | 59 (25.2) | 0.155 | 0.052 |
| Hours of usea | 0.0 [0.0 to 8.0] | 0.0 [0.0 to 8.0] | 0.046 | 0.241 | 0.0 [0.0 to 8.0] | 0.0 [0.0 to 6.0] | 0.085 | 0.101 |
Data are median [IQR] or number (%). Percentages may not total 100 because of rounding. ECMO, extracorporeal membrane oxygenation; NMBA, neuromuscular blocking agent; PBW, predicted body weight; PEEP, positive end-expiratory pressure; SMD, standardised mean difference.
a
In patients who received it.
∗
Calculated using pairwise contrasts in a mixed-effect generalised linear model with day, group and an interaction day group as fixed effect, and with patients and centre as random effect. A binomial distribution was used for binary variables and a Gaussian distribution for continuous.