High versus low PEEP in non-recruitable collapsed lung tissue: possible implications for patients with COVID-19

Intensivists and intensive care nurses are struggling to provide the best care for patients with proven or suspected coronavirus disease (COVID-19) who are invasively ventilated. Approaches for care vary widely between countries and regions, and new insights are acquired rapidly. These insights include the way in which invasive ventilation is applied.

In COVID-19, the chest CT scan shows bilateral, multilobar ground-glass opacification, which can become very extensive with disease progression, and multifocal consolidative opacities with surrounding spared tissue. Although the affected areas appear to be non-focal, these areas might behave like non-recruitable collapsed lung tissue. This finding might have implications for the way these patients are ventilated.

In 2019, Constantin and colleagues¹ reported a study that compared ventilation with positive end-expiratory pressure (PEEP) according to a low PEEP and FiO₂ table (ie, control group), with a personalised approach based on lung morphology (ie, personalised group). Within the personalised group, patients with focal acute respiratory distress syndrome (ARDS) received low PEEP with prone positioning, and patients with non-focal ARDS received recruitment manoeuvres and high PEEP. There was no difference between the control group and the personalised group in 90-day mortality, the primary endpoint of the study. However, misclassification of patients as having focal or non-focal ARDS was observed in as many as 85 (21%) of 400 patients. In subgroup analyses, an alarmingly higher mortality was found in patients who were misclassified with focal ARDS than in patients who were correctly classified with focal ARDS.

The researchers' rationale behind the personalised approach was that recruitment manoeuvres and high PEEP might be more suitable in non-focal rather than focal ARDS; whereas, patients with focal ARDS who respond poorly to recruitment manoeuvres and high PEEP might benefit more from prone positioning and low PEEP. Thus, the difference between focal and non-focal ARDS might be a matter of recruitability rather than morphology.

More data on recruitability in patients with COVID-19 are urgently needed to understand the heterogeneity within COVID-19 ARDS. If patients with COVID-19 have non-recruitable collapsed lung lesions, intensivists and intensive care nurses might want to use early prone positioning and low PEEP (ie, according to a low PEEP and FiO₂ table). However, if patients with COVID-19 have recruitable collapsed lung lesions, these health-care professionals might want to use recruitment manoeuvres and high PEEP (ie, according to a high PEEP and FiO₂ table) instead.

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