Evaluation of PEEP and prone positioning in early COVID-19 ARDS

Abstract

Background In face of the Coronavirus Disease (COVID)-19 pandemic, best practice for mechanical ventilation in COVID-19 associated Acute Respiratory Distress Syndrome (ARDS) is intensely debated. Specifically, the rationale for high positive end-expiratory pressure (PEEP) and prone positioning in early COVID-19 ARDS has been questioned. Methods The first 23 consecutive patients with COVID-19 associated respiratory failure transferred to a single ICU were assessed. Eight were excluded: five were not invasively ventilated and three received veno-venous ECMO support. The remaining 15 were assessed over the first 15 days of mechanical ventilation. Best PEEP was defined by maximal oxygenation and was determined by structured decremental PEEP trials comprising the monitoring of oxygenation, airway pressures and trans-pulmonary pressures. In nine patients the impact of prone positioning on oxygenation was investigated. Additionally, the effects of high PEEP and prone positioning on pulmonary opacities in serial chest x-rays were determined by applying a semiquantitative scoring-system. This investigation is part of the prospective observational PA-COVID-19 study. Findings Patients responded to initiation of invasive high PEEP ventilation with markedly improved oxygenation, which was accompanied by reduced pulmonary opacities within 6 h of mechanical ventilation. Decremental PEEP trials confirmed the need for high PEEP (17.9 (SD ± 3.9) mbar) for optimal oxygenation, while driving pressures remained low. Prone positioning substantially increased oxygenation ( p <0.01). Interpretation In early COVID-19 ARDS, substantial PEEP values were required for optimizing oxygenation. Pulmonary opacities resolved during mechanical ventilation with high PEEP suggesting recruitment of lung volume. Funding German Research Foundation, German Federal Ministry of Education and Research.

Mechanical ventilation in early COVID-19 ARDS

“…The present study indicates that also CARDS requires PEEP levels we are accustomed to from usual ARDS. Importantly, from the present study [2] we again learn that PEEP should be applied in an individualized manner. The amount of recruitable lung, an important determinant of harm and benefit from PEEP, varies considerably across patients with ARDS and more PEEP does not necessarily translate into improved gas exchange [5].…”

“…In this sense it is difficult to predict PEEP effects in individual patients as the clinical presentations of these patients are manifold. Interestingly, after careful titration, optimal PEEP in study patients was always lower than the initially applied PEEP [2]. The data suggest that in some patients, even lower levels of PEEP would have been acceptable with regard to oxygenation possibly giving more protection to the right ventricle.…”

“…Just by changing the body position, collapsed alveoli in dependent lung zones are recruited, V/Q mismatching is decreased and lower concentrations of oxygen may be used [9]. In their study, Mittermaier and colleagues [2] presented the effects of PP over a period of a least 12 h. However, PP probably did not change opacity indices in chest x-rays, as COVID-19 may cause a very dissiminated infestation of the lungs.…”

“…Respiratory failure due to Coronavirus disease 2019 (COVID-19) sparked a debate on when and how to apply IMV in these patients, as it has been proposed that severe COVID-19 causes "atypical" ARDS [1]. As published in EClinicalMedicine, Mittermaier and colleagues [2] investigated the effects of IMV, positive end-expiratory pressure (PEEP) and prone positioning (PP) on oxygenation and lung recruitability in patients with COVID-19-related ARDS (CARDS). All three interventions led to markedly improved oxygenation in CARDS.…”

“…There is definitely a lot to learn about CARDS, and it seems that the treatment principles are the same as in usual ARDS. The practices will be informed be a plethora of studies, and the study by Mittermaier et al [2] is one of those helping to guide the way.…”