Summary
Pettenuzzo et al. conducted a comprehensive systematic review and meta-analysis evaluating the effects of prone positioning during veno-venous extracorporeal membrane oxygenation (V-V ECMO) in patients with acute hypoxemic respiratory failure. Analyzing data from 22 studies (3,465 patients), the review concluded that prone positioning is associated with significantly improved 28-day and hospital mortality rates despite longer ECMO duration and fewer ventilator-free days, highlighting the complexity of interpreting these outcomes.
Key Points:
- Study Scope and Methodology: The meta-analysis included 22 studies (2 randomized controlled trials [RCTs] and 20 non-RCTs), evaluating 3,465 patients undergoing V-V ECMO, focusing on the impact of prone positioning on various clinical outcomes, primarily 28-day mortality.
- Primary Outcome – 28-day Mortality: Prone positioning significantly reduced 28-day mortality (OR 0.64, 95% CI 0.42–0.98, p=0.040), with a low certainty of evidence due to heterogeneity and potential biases.
- Hospital Mortality Improvement: Patients who underwent prone positioning also experienced significantly lower hospital mortality (OR 0.67, 95% CI 0.54–0.83, p<0.001).
- Increased ECMO Duration and Reduced Ventilator-free Days: Despite mortality benefits, prone positioning was associated with fewer 28-day ventilator-free days and prolonged ECMO duration, suggesting the beneficial effects of prone positioning might require extended periods to manifest fully.
- Subgroup Analysis Findings: Greater mortality benefit from prone positioning was associated with younger age, higher SOFA scores, non-Covid-19 related acute hypoxemic respiratory failure, and lower rates of prone positioning before ECMO cannulation.
- Lack of Benefit in Prior Proning: Patients previously proned before ECMO cannulation did not demonstrate additional benefits from subsequent prone positioning during ECMO, indicating a potential ceiling effect or prior maximal benefit.
- Quality of Evidence Concerns: The overall quality of evidence was rated as low or very low due to risk of bias, inconsistency, and publication biases, emphasizing the need for cautious interpretation and further high-quality research.
- Adverse Events: No significant differences in ECMO-related adverse events were observed between the prone positioning and control groups.
- Clinical Implications: The findings support cautious use of prone positioning during V-V ECMO, particularly in specific patient subgroups identified as most likely to benefit.
- Future Research Directions: Further randomized trials are required to establish causation clearly, refine patient selection criteria, and optimize timing and duration of prone positioning during ECMO.
Conclusion
This systematic review and meta-analysis suggest that prone positioning during V-V ECMO for acute hypoxemic respiratory failure can improve short-term survival outcomes, particularly 28-day and hospital mortality, despite prolonged ECMO support and reduced ventilator-free days. Continued investigation through randomized studies is critical to define clearer clinical guidelines.
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