The FLARE Four
- In the treatment of acute respiratory distress syndrome (ARDS), large multicenter trials have shown no benefit from routine alveolar recruitment maneuvers, and some have shown evidence of harm
- Full recruitment for patients with ARDS associated with COVID-19 is often easily achieved with low to moderate positive end-expiratory pressure (PEEP)
- A variety of ways of setting PEEP have been reported, none clearly superior to any other; using the ARDSnet low PEEP/high FiO2 table is a reasonable initial strategy
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Alveolar recruitment maneuvers are an appealing intervention for acute respiratory distress syndrome (ARDS) because they generally improve short-term oxygenation. In a fast literature update posted on April 2, 2020, Jehan Alladina, MD, physician in the Division of Pulmonary and Critical Care Medicine, Charles Corey Hardin, MD, PhD, physician in the Division of Pulmonary and Critical Care Medicine, Kathryn Hibbert, MD, physician in the Division of Pulmonary and Critical Care Medicine, and Jenna McNeill, MD, research fellow, of Massachusetts General Hospital provide guidance about recruitment maneuvers and positive end-expiratory pressure (PEEP) in patients who have ARDS associated with COVID-19.
A recruitment maneuver is a sustained increase in mean airway pressure with the goal of opening collapsed alveoli, followed by PEEP to keep alveoli inflated.
Opening alveoli decreases shunt (perfusion without ventilation), improves oxygenation and can simultaneously improve pulmonary mechanics. However, overdistension of lung units that are already open can result in decreased compliance and barotrauma.
Trials of Recruitment and PEEP in ARDS
The "open lung approach"—recruitment using high PEEP, followed by decremental PEEP titration to assess the best tidal compliance—showed no mortality benefit in early clinical trials.
In the Alveolar Recruitment for ARDS Trial (n=1,010), the open lung approach was associated with significantly reduced all-cause mortality compared with low PEEP. However, some patients experienced cardiac arrest or hemodynamic instability on high PEEP, and critics have noted a lack of evidence that recruitment actually occurred.
Furthermore, there is great potential for harm from frequent recruitment and aggressive PEEP titration in unselected patients with ARDS.
PEEP must be titrated to balance the benefit of opening alveoli against the risk of over-distending unaffected regions of the lung. A previous fast literature update concludes that in ARDS, no PEEP strategy is clearly superior to any other.
In patients with ARDS associated with COVID-19, full recruitment is often easily achieved with low to moderate PEEP. A reasonable initial strategy is simply to adopt the ARDSnet low PEEP/high FiO2 table. A select group of patients may benefit from individualized PEEP titration.
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