Table 2.
Mechanical ventilation variables by adherence to lung protection and mortality status at two years.* Values are median (interquartile range) unless stated otherwise
| Ventilation variables | Ventilator settings† | P value‡ | Mortality status | P value‡ | |||
|---|---|---|---|---|---|---|---|
| All eligible (n=6240) | Non-adherent (n=3692) | Adherent (n=2548) | Alive (n=2083) | Dead (n=4157) | |||
| Positive end expiratory pressure (cm H2O) | 10 (8-10) | 10 (5-10) | 10 (8-10) | 0.070 | 10 (8-10) | 10 (7-10) | 0.971 |
| PaO2:FiO2 | 172 (114-215) | 180 (114-234) | 165 (113-199) | <0.001 | 188 (128-234) | 163 (107-208) | <0.001 |
| No (%) with arterial pH <7.25§ | 634 (10) | 379 (10) | 255 (10) | 0.216 | 126 (6) | 508 (12) | <0.001 |
| Static compliance of respiratory system (mL/cm H2O) | 31 (23-42) | 32 (23-44) | 30 (24-39) | <0.001 | 31 (23-42) | 31 (24-42) | 0.177 |
| Plateau pressure¶ (cm H2O) | 23 (20-27) | 24 (20-28) | 23 (20-26) | <0.001 | 23 (20-27) | 23 (20-27) | 0.943 |
| Respiratory rate (breaths/min) | 27 (20-35) | 24 (19-32) | 30 (24-35) | <0.001 | 26 (20-35) | 28 (20-35) | 0.018 |
| Tidal volume (mL/kg predicted body weight) | 6.6 (5.9-7.8) | 7.5 (6.8-8.6) | 5.9 (5.6-6.1) | <0.001 | 6.6 (6.0-7.9) | 6.6 (5.8-7.8) | 0.014 |
PaO2=partial pressure of arterial oxygen; FiO2=fraction of inspired oxygen.
*All variables are for eligible mechanical ventilator settings.
†Defined as eligible for lung protective ventilation if mechanical ventilation was delivered through an endotracheal or tracheostomy tube with FiO2 ≥0.50 or positive end expiratory pressure >5 cm of water. Ventilator modes for which tidal volume is not routinely measured (high frequency oscillation or airway pressure release) were considered not eligible for analysis of lung protective ventilation.
‡P values are adjusted for within patient correlation using robust variance estimate.
§From arterial blood gas measurements abstracted from medical records twice daily, when available.
¶Plateau pressures represent average value over five imputed datasets for patients with missing values.