PEEP levels in COVID-19 pneumonia

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,

Right ventricular dilation: The additive effect of mechanical ventilation on pulmonary embolism in Covid-19 patients

“…It is well known that mechanical ventilation in patients with acute respiratory distress syndrome may deteriorate RV function and even lead to acute cor pulmonale [ 6 ]; yet, heart-lung interactions may be pronounced in Covid-19 patients under mechanical ventilation. When lung compliance is relatively normal, as it has been reported in Covid-19 lung by Gattinoni and confirmed later by our group [ 7 , 8 ], substantial amount of the alveolar pressure is transmitted to the pleural pressure, restricting venous return and forcing the transition of lung Zone 3 regions to Zone 2 and even 1. A remarkable positive end-expiratory pressure (PEEP) de-escalation from the levels proposed by the ARDSnet, led to significant improvements in respiratory function (improving dead space ventilation and respiratory system compliance) and hemodynamics, decreasing by three-fold the need for vasopressors [ 8 ].…”

“…When lung compliance is relatively normal, as it has been reported in Covid-19 lung by Gattinoni and confirmed later by our group [ 7 , 8 ], substantial amount of the alveolar pressure is transmitted to the pleural pressure, restricting venous return and forcing the transition of lung Zone 3 regions to Zone 2 and even 1. A remarkable positive end-expiratory pressure (PEEP) de-escalation from the levels proposed by the ARDSnet, led to significant improvements in respiratory function (improving dead space ventilation and respiratory system compliance) and hemodynamics, decreasing by three-fold the need for vasopressors [ 8 ]. Moreover, PEEP effects may be rather exacerbated in the setting of non-recruitable lung regions, as in cases of focal but also in non-focal lung involvement, when extensive, multilobar ground glass opacifications are present (as in Fig.…”

Effect of early versus delayed or no intubation on clinical outcomes of patients with COVID-19 

“…ICU-mortality among patients admitted in the ICU was 26%. Data for 13 of those patients have been included in a previous report focusing on the application of positive end-expiratory pressure [9]. Table 1 also summarizes the baseline characteristics and outcomes of patients undergoing early versus delayed or no intubation.…”

Overview of the Pathogenesis and Treatment of SARS-CoV-2 for Clinicians: A Comprehensive Literature Review

“…Therefore, the study suggests that it may be helpful to adjust the ventilatory approach based on the patients underlying stage and physiology [25]. Additionally, a study examining 17 patients on their second or third day of ICU admission found that a 29% reduction of PEEP resulted in improved lung compliance, reduced hypercapnia, improved fluid balance, and decreased need for vasopressor therapy [26]. However, these findings have not been found among other studies and are thus not generalizable to all SARS-CoV-2 patients; therefore, these strategies cannot be recommended.…”