PEEP levels in COVID-19 pneumonia
Vasiliki Tsolaki, Ilias Ι. Siempos, Eleni Magira, Stelios Kokkoris, George Ε. Zakynthinos, Spyros Zakynthinos
Abstract
To the Editor:Recently, the Surviving Sepsis Campaign COVID-19 guidelines and ATS suggest that a ventilatory strategy complying with the ARDSnet protocol should be applied to manage COVID-19 pneumonia [1-3].However, "COVID-19 lung" pathophysiology seems to be divergent from the "ARDS lung"; hence, heart-lung interactions may be more pronounced than initially considered [2,3].We studied 17 patients (March 20-April 14, 2020) treated in two Greek University Intensive Care Units.Patients had COVID-19 pneumonia fulfilling the Berlin criteria of acute respiratory distress syndrome (ARDS) and were on the 2nd or 3rd day of invasive mechanical ventilation.Positive endexpiratory pressure (PEEP) was set according to predefined criteria [1-3].Mean tidal volume (± standard deviation) was 6.8 ± 0.9 ml/kg ideal body weight (469 ± 64 ml), respiratory rate was 29.5 ± 3.7 breaths/min, and the fraction of inspired oxygen was 82 ± 12%.After measuring respiratory mechanics, arterial blood gases, and hemodynamics, we decreased PEEP by 25-30% (other mechanical ventilation variables remained stable).We re-evaluated measurements (1 h later) focusing on the effects of PEEP reduction on respiratory mechanics, hemodynamics, and fluid balance in a 12-h window before and after the PEEP change.Mean PEEP reduction by 29% significantly increased respiratory system compliance and reduced hypercapnia, while oxygenation (PaO 2 /FiO 2 ) did not worsen (Table 1).PEEP reduction was not accompanied by lung derecruitment, as oxygenation was not deteriorated.Rather PEEP reduction decreased lung overdistension as interpreted by the increase in respiratory system compliance and decrease in dead space ventilation (reduced PaCO 2 ).Concerning hemodynamics, PEEP reduction was followed by a substantial decrease in noradrenaline dose,