Table 4.
Multivariable model assessing predictors of 28-day mortality and ventilator-free days at day 28
|
28-day mortality |
Ventilator-free days at day 28 |
|||
|---|---|---|---|---|
| Odds ratio (95% CI) | p value | Mean difference (95% CI) | p value | |
| Ventilatory variables on day 0* | ||||
| Positive end-expiratory pressure, cm H2O | 1·08 (0·85 to 1·39) | 0·51 | −0·73 (−1·52 to 0·06) | 0·069 |
| Tidal volume, mL/kg predicted bodyweight | 1·28 (1·00 to 1·64) | 0·049 | −0·35 (−1·15 to 0·45) | 0·39 |
| Respiratory system compliance, mL/cm H2O | 0·75 (0·57 to 0·98) | 0·037 | 0·60 (−1·27 to 2·47)† | 0·016 |
| Oxygenation variables on day 0* | ||||
| PaO2/FiO2 | 0·77 (0·43 to 1·38)† | 0·11 | 1·00 (0·27 to 1·72) | 0·0073 |
| Laboratory tests on day 0* | ||||
| pH | 0·71 (0·55 to 0·93) | 0·012 | 1·78 (−0·11 to 3·68)† | 0·42 |
| Lactate, mmol/L | 1·12 (0·88 to 1·43) | 0·37 | −2·68 (−4·44 to −0·90)† | 0·87 |
| Creatinine, μmol/L | 1·04 (0·82 to 1·32) | 0·76 | −1·09 (−2·99 to 0·82)† | 0·59 |
| Vital signs on day 0* | ||||
| Heart rate, beats per min | 1·02 (1·00 to 1·03) | 0·013 | −0·62 (−1·36 to 0·11) | 0·10 |
| Mean arterial pressure, mm Hg | 0·99 (0·96 to 1·02) | 0·46 | 1·22 (−0·59 to 3·03)† | 0·97 |
| Organ support on day 0 | ||||
| Use of vasopressor | 2·07 (0·76 to 5·66) | 0·16 | 0·80 (−1·80 to 3·40) | 0·54 |
| Fluid balance, mL | 1·07 (0·85 to 1·36) | 0·55 | −0·24 (−1·01 to 0·53) | 0·55 |
| Demographic characteristics | ||||
| Age, years | 2·19 (1·65 to 2·90) | <0·0001 | −2·13 (−2·90 to −1·35) | <0·0001 |
| Male gender | 2·16 (1·24 to 3·78) | 0·0069 | −2·38 (−4·24 to −0·52) | 0·013 |
| Body-mass index, kg/m2 | 0·85 (0·66 to 1·09) | 0·19 | 0·51 (−0·24 to 1·26) | 0·18 |
| Hypertension | 1·16 (0·72 to 1·88) | 0·54 | −0·01 (−1·58 to 1·57) | 0·99 |
| Heart failure | 0·73 (0·26 to 2·08) | 0·56 | 1·22 (−2·03 to 4·46) | 0·46 |
| Diabetes | 1·58 (0·93 to 2·67) | 0·087 | −1·12 (−2·88 to 0·64) | 0·21 |
| Chronic kidney disease | 0·89 (0·30 to 2·61) | 0·83 | −0·53 (−4·17 to 3·10) | 0·77 |
| Chronic obstructive pulmonary disease | 1·70 (0·86 to 3·36) | 0·13 | −0·71 (−3·00 to 1·58) | 0·54 |
| Use of angiotensin-converting enzyme inhibitor | 0·85 (0·47 to 1·53) | 0·59 | 2·75 (0·86 to 4·63) | 0·0044 |
| Use of angiotensin II receptor blocker | 0·60 (0·30 to 1·21) | 0·15 | 0·24 (−2·05 to 2·53) | 0·84 |
All models are mixed-effects models with centres as a random effect and considering a binomial distribution (28-day mortality) or a Gaussian distribution (ventilator-free days at day 28). All continuous variables were entered after standardisation to improve convergence of the model, and odds ratios show the increase in one SD of the variable. C statistic (area under the curve) is 0·797 (95% CI 0·757 to 0·836) and Brier score is 0·170 for the 28-day mortality model. Conditional R2 is 0·301 for the ventilator-free days at day 28 model. PaO2/FiO2=ratio of partial pressure of arterial oxygen to fractional concentration of oxygen in inspired air.
Median value from a maximum of six assessments during the first 24 h (day 0).
Variables included as restricted cubic splines; odds ratio or mean difference are determined over the IQR observed for the variable (estimated effect of an IQR increase in the predictor variable); reported p value is for the first spline (appendix pp 25–26).