Table 4.
Ventilatory characteristics and adjunctive therapies during the first week after ARDS onset in university and non-university hospitals
| University hospital (n = 87; 592 days of mechanical ventilation) | Non-university hospital (n = 111; 599 days of mechanical ventilation) | p value | |
|---|---|---|---|
| Ventilatory parameters averaged over the first week after ARDS onset, mean (SD); median (IQR) | |||
| Driving pressurea (cmH2O) | 15.7 (5.1); 15 (13–19) | 16.3 (4.7); 16 (13–19) | 0.40 |
| Driving pressure when FiO2 > 0.4 and PEEP ≥ 5 (cmH2O)b | 15.1 (4.4); 16 (12–19) | 17.0 (5.0); 18 (14–20) | 0.02 |
| PEEP (cmH2O) | 10.1 (4.2); 10 (7–13) | 8.4 (3.9); 8 (6–11) | 0.005 |
| PEEP when FiO2 > 0.4 and PEEP ≥ 5 (cmH2O)b | 11.7 (4.7); 10 (8–15) | 9.7 (3.7); 9 (7–12) | 0.005 |
| PEEP categories, n (%) | |||
| ≤5 cmH2O | 11 (12.6) | 24 (21.8) | 0.05 |
| ≤10 cmH2O | 41 (47.1) | 58 (52.7) | |
| ≥11 cmH2O | 35 (40.2) | 28 (25.5) | |
| Tidal volume (ml/kg PBW) | 8.9 (2.0); 8.6 (7.6–10.0) | 8.9 (2.4); 8.7 (7.6–10.0) | 0.99 |
| Plateau pressure (cmH2O) | 26.4 (5.8); 27 (23–31) | 25.3 (5.4); 25 (22–28) | 0.18 |
| Plateau pressure categories, n (%) | |||
| ≤30 cmH2O | 54 (70.1) | 89 (86.4) | 0.007 |
| >30 cmH2O | 23 (29.9) | 14 (13.6) | |
| Compliancec (ml/mbar; ml/mbar/kg PBW) | 42 (32–54); 0.62 (0.49–0.80) | 38 (29–48); 0.59 (0.45–0.73) | 0.06; 0.23 |
| Respiratory frequency (breaths/min) | 20 (16–22) | 18 (13–22) | 0.17 |
| FiO2 | 0.44 (0.40–0.54) | 0.48 (0.41–0.57) | 0.07 |
| PaO2 (mmHg) | 91 (84–105) | 92 (78–107) | 0.64 |
| PaO2/FiO2 (mmHg) | 208 (169–250) | 194 (155–248) | 0.19 |
| PaCO2 (mmHg) | 42 (38–47) | 42 (37–48) | 0.91 |
| pHa | 7.41 (7.36–7.45) | 7.42 (7.36–7.46) | 0.59 |
| Days with ventilatory mode during the first week after ARDS onset, n (% of all days of mechanical ventilation) | <0.001 | ||
| Biphasic intermittent positive airway pressure | 281 (47.5) | 271 (45.2) | 0.44 |
| Pressure controlled ventilation | 69 (11.7) | 111 (18.5) | 0.001 |
| Pressure support ventilation | 105 (17.7) | 75 (12.5) | 0.01 |
| SIMV + pressure support ventilation | 31 (5.2) | 41 (6.8) | 0.24 |
| SIMV | 24 (4.1) | 10 (1.7) | 0.01 |
| Volume-controlled ventilation (assist/control) | 28 (4.7) | 15 (2.5) | 0.04 |
| Non-invasive ventilation | 31 (5.2) | 38 (6.3) | 0.41 |
| Other | 9 (1.5) | 7 (1.2) | 0.60 |
| Not specified | 14 (2.4) | 31 (5.2) | 0.01 |
| Days applying adjunctive therapies, n (% of all days of mechanical ventilation); median (IQR) | |||
| Prone positioning or rotation bed, all days | 44 (7.4) | 22 (3.7) | 0.005 |
| Sedatives all days, duration/patient (days) | 439 (74.2); 12 (7–21) | 411 (56.8); 5 (2–10) | 0.03; <0.001 |
| Neuromuscular blocking agents, all days | 11 (1.9) | 7 (1.2) | 0.33 |
ARDS acute respiratory distress syndrome, FiO 2 fraction of inspired oxygen, PaO 2 partial pressure of arterial oxygen tension, PaO 2 /FiO 2 arterial-to-inspired oxygen ratio, PEEP positive end-expiratory pressure, PBW predicted body weight, SIMV Synchronized intermittent mandatory ventilation, SD standard deviation, IQR interquartile range
aDriving pressure = plateau pressure – PEEP
bAll other ventilatory parameters during therapeutic ventilation did not differ between groups in this sensitivity analysis, including only those ventilation days – during the first week after ARDS onset with FiO2 > 0.4 and PEEP ≥ 5 cmH2O – that represented minimum values as criteria for the start of weaning in the low tidal volume trial of the ARDS Network [12] (261 of 592 days (44.1%) in university hospitals and 299 of 599 days (49.9%) in non-university hospitals)
cCompliance = tidal volume / (plateau pressure – PEEP)