Longitudinal changes in compliance, oxygenation and ventilatory ratio in COVID-19 versus non-COVID-19 pulmonary acute respiratory distress syndrome

Crit Care. 2021 Jul 15;25(1):248. doi: 10.1186/s13054-021-03665-8.

Abstract

Background: Differences 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.

Methods: 135 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.

Results: The 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).

Conclusions: For 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.

Keywords: Acute Respiratory Distress Syndrome; Covid-19; Dead space; Mechanical ventilation; Respiratory failure; Respiratory mechanics.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Blood Gas Analysis
  • Body Mass Index
  • COVID-19 / physiopathology
  • COVID-19 / therapy*
  • Female
  • Humans
  • Intensive Care Units
  • Male
  • Middle Aged
  • Positive-Pressure Respiration / methods*
  • Propensity Score
  • Pulmonary Gas Exchange / physiology
  • Respiration, Artificial / methods
  • Respiratory Distress Syndrome / physiopathology
  • Respiratory Distress Syndrome / therapy*
  • Respiratory Function Tests
  • Respiratory Mechanics / physiology
  • SARS-CoV-2

Associated data

  • ClinicalTrials.gov/NCT04385004