Clinical question / background:
- In patients with ARDS, does ventilation with lower tidal volumes versus traditional higher tidal volumes reduce death and ventilator-free days?
Design:
- Randomized, single-blinded, controlled trial
- 861 participants in 10 U.S. centers
- Inclusion: mechanically ventilated patients with ARDS
- ARDS: Bilateral opacities on CXR/CT present within 1 week of known clinical insult not explainable by cardiogenic edema, lung effusions/nodules/collapse WITH impairment in oxygenation defined by ratio PaO2/FiO2 < 300 (FiO2 as decimal e.g. 0.21 instead of 21%)
- Exclusion: pregnancy, chronic lung disease, severe burns (>30% TBSA), patients with neuromuscular disease, < 18 y/o
Intervention:
- Low tidal volume ventilation – 6 ml/kg/breath (ideal body weight)
- Plateau pressure < 30 cm water
Control:
- Traditional tidal volume ventilation – 12ml/kg/breath (ideal body weight)
- Plateau pressure < 50 cm water
Results:
- Lower tidal volume ventilation associated with reduced mortality
- 31.0% vs 39.8% (p=0.007)
- Lower tidal volumes associated with increased ventilator-free days
- 12+/-11 days vs 10 +/-11 days (p=0.007)
- Lower tidal volumes associated with fewer days without non-pulmonary organ failure (circulatory, renal, liver, coagulative)
Take-home:
- Adult patients with acute respiratory distress syndrome should be ventilated with tidal volumes of 6 ml/kg, limiting plateau pressures to 30 cm water
Strengths:
- Well-designed, strong power to detect difference in clinical outcomes
Weaknesses / Critiques
- Single-blinded, so physicians aware of allocation, potentially biased in care provided
- Protocol allowed for varying PEEP levels to control for acidemia, may have favored intervention group + confounded
- Auto-PEEP in intervention group (due to high respiratory rate) possibly contributed to favorable oxygenation
- Addressed in post-hoc analysis and proven to be non-factor as was permissive hypercapnia in intervention group
Follow-up / Real World Application
- Foundation of tidal volume strategy in mechanical ventilation on ICU patients with ARDS
- Cited in Cochrane review — Petrucci N, Iacovelli W. Lung protective ventilation strategy for the acute respiratory distress syndrome. Cochrane Database Syst Rev. 2007 Jul 18;(3)
- ARR 10%, 28-day mortality benefit with NNT of 10
