Longitudinal changes in compliance, oxygenation and ventilatory ratio in COVID-19\xa0versus\xa0non-COVID-19 pulmonary acute respiratory distress syndrome

François Beloncle,Laurent Brochard,Antoine Studer,Ferhat Meziani,Jean-Christophe Richard,Sibylle Cunat,Christophe Desprez,Nicolas Fage,Hamid Merdji,Valérie Seegers,Bertrand Pavlovsky,Alain Mercat,Julie Helms,Satar Mortaza,Julien Demiselle

doi:10.1186/s13054-021-03665-8

Abstract

BackgroundDifferences in physiology of ARDS have been described between COVID-19 and non-COVID-19 patients. This study aimed to compare initial values and longitudinal changes in respiratory system compliance (CRS), oxygenation parameters and ventilatory ratio (VR) in patients with COVID-19 and non-COVID-19 pulmonary ARDS matched on oxygenation.Methods135 patients with COVID-19 ARDS from two centers were included in a physiological study; 767 non-COVID-19 ARDS from a clinical trial were used for the purpose of at least 1:2 matching. A propensity-matching was based on age, severity score, oxygenation, positive end-expiratory pressure (PEEP) and pulmonary cause of ARDS and allowed to include 112 COVID-19 and 198 non-COVID pulmonary ARDS.ResultsThe two groups were similar on initial oxygenation. COVID-19 patients had a higher body mass index, higher CRS at day 1 (median [IQR], 35 [28–44] vs 32 [26–38] ml cmH2O−1, p = 0.037). At day 1, CRS was correlated with oxygenation only in non-COVID-19 patients; 61.6% and 68.2% of COVID-19 and non-COVID-19 pulmonary ARDS were still ventilated at day 7 (p = 0.241). Oxygenation became lower in COVID-19 than in non-COVID-19 patients at days 3 and 7, while CRS became similar. VR was lower at day 1 in COVID-19 than in non-COVID-19 patients but increased from day 1 to 7 only in COVID-19 patients. VR was higher at days 1, 3 and 7 in the COVID-19 patients ventilated using heat and moisture exchangers compared to heated humidifiers. After adjustment on PaO2/FiO2, PEEP and humidification device, CRS and VR were found not different between COVID-19 and non-COVID-19 patients at day 7. Day-28 mortality did not differ between COVID-19 and non-COVID-19 patients (25.9% and 23.7%, respectively, p = 0.666).ConclusionsFor a similar initial oxygenation, COVID-19 ARDS initially differs from classical ARDS by a higher CRS, dissociated from oxygenation. CRS become similar for patients remaining on mechanical ventilation during the first week of evolution, but oxygenation becomes lower in COVID-19 patients.Trial registration: clinicaltrials.gov NCT04385004

Highlights

Most of the patients admitted to ICU for coronavirus disease 2019 (COVID‐19) present severe respiratory failure fulfilling acute respiratory distress syndrome (ARDS) criteria according to the Berlin definition [1,2,3]
Based on clinical observations reported in small series, it has been advocated that part of the patients with COVID-19 ARDS may be characterized by severe hypoxemia and relatively normal respiratory system compliance (CRS) and may beneficiate from a “less protective” ventilation compared to the “classical form” of ARDS [4]
Ventilatory parameters at day 1, day 3 and day 7 in patients with COVID‐19 and non‐COVID‐19‐associated ARDS Ventilatory parameters changes in matched COVID19-associated ARDS and pulmonary non-COVID-19-associated ARDS at day 1, day 3 and day 7 are presented in Table 2 and Fig. 1

Summary

Introduction

Most of the patients admitted to ICU for coronavirus disease 2019 (COVID‐19) present severe respiratory failure fulfilling acute respiratory distress syndrome (ARDS) criteria according to the Berlin definition [1,2,3]. Cumulating evidence coming from larger series tends to demonstrate that variability in clinical presentation (depending on ARDS severity) exists in COVID-19 as it has been described in non-COVID19-associated ARDS, challenging this interesting conceptual “new phenotype” specific to COVID-19-associated ARDS [12,13,14,15,16]. Based on this statement, these authors advocated that the well-described “lung protective strategy” should be adapted to a systematic daily physiological evaluation in COVID-19 and non-COVID-19-associated ARDS patients [12, 14, 16, 17]. This study aimed to compare initial values and longitudinal changes in respiratory system compliance (CRS), oxygenation parameters and ventilatory ratio (VR) in patients with COVID-19 and non-COVID-19 pulmonary ARDS matched on oxygenation

Objectives

Methods

Results