Physiological and quantitative CT-scan characterization of COVID-19 and typical ARDS: a matched cohort study

Davide Chiumello; Mattia Busana; Silvia Coppola; Federica Romitti; Paolo Formenti; Matteo Bonifazi; Tommaso Pozzi; Maria Michela Palumbo; Massimo Cressoni; Peter Herrmann; Konrad Meissner; Michael Quintel; Luigi Camporota; John J Marini; Luciano Gattinoni

doi:10.1007/s00134-020-06281-2

Physiological and quantitative CT-scan characterization of COVID-19 and typical ARDS: a matched cohort study

Intensive Care Med. 2020 Dec;46(12):2187-2196. doi: 10.1007/s00134-020-06281-2. Epub 2020 Oct 21.

Authors

Affiliations

¹ Department of Anesthesiology and Intensive Care, ASST Santi e Paolo Hospital, University of Milan, Milan, Italy.
² Department of Anesthesiology, Intensive Care and Emergency Medicine, Medical University of Göttingen, Robert-Koch Straße 40, Göttingen, Germany.
³ Department of Radiology, San Gerardo Hospital, Monza, Italy.
⁴ Department of Adult Critical Care, Guy's and St Thomas' NHS Foundation Trust, Health Centre for Human and Applied Physiological Sciences, London, UK.
⁵ Department of Pulmonary and Critical Care Medicine, University of Minnesota and Regions Hospital, St. Paul, Minnesota, USA.
⁶ Department of Anesthesiology, Intensive Care and Emergency Medicine, Medical University of Göttingen, Robert-Koch Straße 40, Göttingen, Germany. [email protected].

Abstract

Purpose: To investigate whether COVID-19-ARDS differs from all-cause ARDS.

Methods: Thirty-two consecutive, mechanically ventilated COVID-19-ARDS patients were compared to two historical ARDS sub-populations 1:1 matched for PaO₂/FiO₂ or for compliance of the respiratory system. Gas exchange, hemodynamics and respiratory mechanics were recorded at 5 and 15 cmH₂O PEEP. CT scan variables were measured at 5 cmH₂O PEEP.

Results: Anthropometric characteristics were similar in COVID-19-ARDS, PaO₂/FiO₂-matched-ARDS and Compliance-matched-ARDS. The PaO₂/FiO₂-matched-ARDS and COVID-19-ARDS populations (both with PaO₂/FiO₂ 106 ± 59 mmHg) had different respiratory system compliances (Crs) (39 ± 11 vs 49.9 ± 15.4 ml/cmH₂O, p = 0.03). The Compliance-matched-ARDS and COVID-19-ARDS had similar Crs (50.1 ± 15.7 and 49.9 ± 15.4 ml/cmH₂O, respectively) but significantly lower PaO₂/FiO₂ for the same Crs (160 ± 62 vs 106.5 ± 59.6 mmHg, p < 0.001). The three populations had similar lung weights but COVID-19-ARDS had significantly higher lung gas volume (PaO₂/FiO₂-matched-ARDS 930 ± 644 ml, COVID-19-ARDS 1670 ± 791 ml and Compliance-matched-ARDS 1301 ± 627 ml, p < 0.05). The venous admixture was significantly related to the non-aerated tissue in PaO₂/FiO₂-matched-ARDS and Compliance-matched-ARDS (p < 0.001) but unrelated in COVID-19-ARDS (p = 0.75), suggesting that hypoxemia was not only due to the extent of non-aerated tissue. Increasing PEEP from 5 to 15 cmH₂O improved oxygenation in all groups. However, while lung mechanics and dead space improved in PaO₂/FiO₂-matched-ARDS, suggesting recruitment as primary mechanism, they remained unmodified or worsened in COVID-19-ARDS and Compliance-matched-ARDS, suggesting lower recruitment potential and/or blood flow redistribution.

Conclusions: COVID-19-ARDS is a subset of ARDS characterized overall by higher compliance and lung gas volume for a given PaO₂/FiO₂, at least when considered within the timeframe of our study.

Keywords: ARDS; COVID-19; CT scan; Mechanical ventilation; Respiratory system mechanics.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Adult
Aged
Blood Gas Analysis / methods
COVID-19 / physiopathology*
COVID-19 / therapy
Cohort Studies
Female
Humans
Intensive Care Units / organization & administration
Intensive Care Units / statistics & numerical data
Italy
Length of Stay / statistics & numerical data
Lung Compliance / physiology
Male
Middle Aged
Prospective Studies
Pulmonary Gas Exchange / physiology
Respiratory Distress Syndrome / physiopathology*
Respiratory Distress Syndrome / therapy
Simplified Acute Physiology Score
Tomography, X-Ray Computed / methods