Barriers to providing lung-protective ventilation to patients with ALI/ARDS

Introduction

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are associated with significant morbidity and mortality. Mechanical ventilation is the cornerstone of supportive therapy. However, the optimal strategy of ventilation and adjunctive therapies are still evolving. There is evidence to support the use of volume-limited and pressure-limited lung-protective ventilation but practice variability in the clinical management is still a concern mainly in sicker patients. The purpose of this study was to examine the ventilatory prescriptions of clinicians caring for patients with ALI/ARDS.

Methods

We prospectively examined demographic characteristics, APACHE II score and choice of ventilatory settings at the day of diagnosis of ALI/ARDS (AECC criteria) of 84 mechanically ventilated patients from May 2007 through October 2009 in a mixed medical-surgical critical care unit.

Results

ALI/ARDS occurred in 7.1% of admissions and 16.1% of all mechanically ventilated patients. Sepsis was the main cause. All patients were ventilated with pressure control mode. Median tidal volume/predicted body weight was 6.1 (3.5 to 9.9) ml/kg, plateau pressure was 26 (15 to 55) cmH₂O and mean PEEP was 12 (5 to 25) cmH₂O. Univariate analysis showed sepsis-related ALI/ARDS (P = 0.026) and APACHE II score >18 (P < 0.001) were barriers to initiate lung-protective ventilation. In multivariate analysis, APACHE score >18 was an independent predictor. Ventilatory settings were significantly different in this subset of patients (n = 26). The tidal volume/predicted body weight (6.2 (3.5 to 9.9) vs 5.1 (4.3 to 8.5) ml/kg), PEEP (15 (10 to 25) vs 7 (6 to 12) cmH₂O) and plateau pressure (38 (32 to 55) vs 22 (15 to 30) cmH₂O) were higher in the group with APACHE II score >18 (P < 0.001). PaO₂/FiO₂ pH and paCO₂ did not differ between groups. As expected, mortality was higher in this group, 60% vs 22% (P < 0.001).

Conclusions

Protective mechanical ventilation is not completely feasible in the subset of ALI/ARDS patients with higher risk of mortality (APACHE II >18).