Table 1.
Patient characteristics at the start of mechanical ventilation (ie, day 0) and outcomes in the derivation cohort
| All (n=1007) |
Time-dependent subphenotypes* |
p value | ||||
|---|---|---|---|---|---|---|
| 1 (n=671) | 2 (n=336) | |||||
| Age, years | 63·7 (10·8) | 63·9 (11·0) | 63·2 (10·2) | 0·35 | ||
| Sex | <0·001 | |||||
| Female | 279 (28%) | 226 (34%) | 53 (16%) | |||
| Male | 728 (73%) | 445 (66%) | 283 (84%) | |||
| BMI, kg/m2 | 28·6 (5·6) | 28·3 (4·5) | 29·1 (7·4) | 0·054 | ||
| Comorbidities | ||||||
| Arterial hypertension | 342 (34%) | 229 (34%) | 113 (34%) | 0·930 | ||
| Heart failure | 42 (4%) | 28 (4%) | 14 (4%) | 1·000 | ||
| Diabetes | 225 (22%) | 163 (24%) | 62 (18%) | 0·044 | ||
| Chronic kidney disease | 45 (4%) | 163 (24%) | 62 (18%) | 0·015 | ||
| Chronic obstructive pulmonary disease | 83 (8%) | 59 (9%) | 23 (7%) | 0·350 | ||
| Immunosuppression | 24 (2%) | 15 (2%) | 9 (3%) | 0·830 | ||
| Day of admission† | ||||||
| Tidal volume per kg predicted bodyweight, mL/kg | 6·46 (1·55) | 6·42 (1·28) | 6·54 (2·00) | 0·24 | ||
| Respiratory rate, breaths/min | 21·00 (4·60) | 20·95 (4·54) | 21·96 (4·84) | 0·001 | ||
| Minute ventilation, L/min | 9·40 (2·70) | 8·97 (2·40) | 10·25 (3·12) | <0·001 | ||
| Positive end-expiratory pressure, cmH2O | 12·6 (2·9) | 12·4 (2·8) | 13·2 (2·9) | <0·001 | ||
| High positive end-expiratory pressure strategy | 269 (27%) | 167 (25%) | 102 (30%) | 0·130 | ||
| Plateau pressure, cmH2O | 27·3 (5·2) | 26·9 (5·1) | 28·0 (5·3) | 0·003 | ||
| Driving pressure, cmH2O | 14·9 (4·4) | 14·8 (4·3) | 15·2 (4·5) | 0·200 | ||
| Compliance respiratory system, mL/cmH2O | 32·3 (12·0) | 31·8 (11·5) | 33·3 (13·0) | 0·082 | ||
| PaO2, mm Hg | 93 (43) | 91 (43) | 98 (43) | 0·026 | ||
| PaO2/FiO2, mm Hg | 148 (75) | 143 (77) | 153 (71) | 0·182 | ||
| Mild | 262 (26%) | 162 (24%) | 100 (30%) | 0·110 | ||
| Moderate | 520 (52%) | 350 (52%) | 170 (51%) | .. | ||
| Severe | 225 (22%) | 159 (24%) | 66 (20%) | .. | ||
| Mechanical power, J/min | 18·4 (6·7) | 17·3 (6·1) | 20·6 (7·3) | <0·001 | ||
| PaCO2, mm Hg | 45·2 (11·8) | 43·5 (10·7) | 48·8 (13·1) | <0·001 | ||
| Ventilatory ratio | 1·64 (0·68) | 1·52 (0·49) | 1·89 (0·91) | <0·001 | ||
| Difference between arterial and end-tidal CO2 | 7·72 (11·14) | 6·71 (10·40) | 9·79 (12·31) | <0·001 | ||
| pH‡ | 7·36 (0·10) | 7·36 (0·09) | 7·34 (0·10) | <0·001 | ||
| Creatinine, μmol/L‡ | 74 (61–96) | 73 (58–93) | 77 (65–97) | 0·015 | ||
| Urine output, mL/day | 705 (370–1148) | 670 (350–1125) | 725 (415–1202) | 0·071 | ||
| Fluid balance, mL/day | 608 (29–1418) | 539 (13–1268) | 712 (71–1587) | 0·048 | ||
| Prone position during first ICU day | 300 (30%) | 199 (30%) | 101 (30%) | 0·520 | ||
| Vasopressor in first ICU day | 792 (79%) | 520 (77%) | 271 (81%) | 0·340 | ||
| Outcomes | ||||||
| Acute kidney injury§ | 447 (44%) | 270 (40%) | 177 (53%) | 0·001 | ||
| Renal replacement§ | 180 (18%) | 109 (16%) | 70 (21%) | 0·088 | ||
| Venous thrombotic event§ | 285 (28%) | 176 (26%) | 109 (32%) | 0·048 | ||
| ICU length of stay, days | 15 (9–27) | 15 (9–25) | 16 (9–30) | 0·36 | ||
| Duration of invasive mechanical ventilation, days | 13 (8–23) | 13 (8–23) | 14 (8–24) | 0·41 | ||
| Ventilator-free days and alive at day 28, days | 2 (0–16) | 5 (0–17] | 0 (0–15) | 0·016 | ||
| Day 7 mortality | 112 (11%) | 72 (11%) | 40 (12%) | 0·83 | ||
| Day 28 mortality | 294 (29%) | 185 (28%) | 109 (32%) | 0·10 | ||
| Day 90 mortality | 349 (35%) | 223 (33%) | 123 (37%) | 0·24 | ||
Data are mean (SD), n (%), or median (IQR). Mild, moderate, and severe PaO2/FiO2 were graded according to Berlin definition. ICU=intensive care unit.
*
Latent class analysis using 8-hourly data from the first 4 days of invasive ventilation was used to identify time-dependent subphenotypes that emerged during the first 96 h of ICU admission.
†
Date of ICU admission was the same as the day of start of mechanical ventilation in this cohort.
‡
In blood samples.
§
During ICU stay.