• Luigi Camporota, Barnaby Sanderson, Stephanie Worrall, Marlies Ostermann, Nicholas A Barrett, Andrew Retter, Mattia Busana, Patrick Collins, Federica Romitti, Beverley J Hunt, Louise Rose, Luciano Gattinoni, and Davide Chiumello.
• Guy's and St Thomas' NHS Foundation Trust, St Thomas' Hospital, London SE1 7EH, UK; Centre of Human Applied Physiological Sciences, King's College London, London, UK.
• J Crit Care. 2023 Oct 1; 77: 154313154313.

BackgroundDespite its diagnostic and prognostic importance, physiologic dead space fraction is not included in the current ARDS definition or severity classification. ARDS caused by COVID-19 (C-ARDS) is characterized by increased physiologic dead space fraction and hypoxemia. Our aim was to investigate the relationship between dead space indices, markers of inflammation, immunothrombosis, severity and intensive care unit (ICU) mortality.ResultsRetrospective data including demographics, gas exchange, ventilatory parameters, and respiratory mechanics in the first 24 h of invasive ventilation. Plasma concentrations of D-dimers and ferritin were not significantly different across C-ARDS severity categories. Weak relationships were found between D-dimers and VR (r = 0.07, p = 0.13), PETCO2/PaCO2 (r = -0.1, p = 0.02), or estimated dead space fraction (r = 0.019, p = 0.68). Age, PaO2/FiO2, pH, PETCO2/PaCO2 and ferritin, were independently associated with ICU mortality. We found no association between D-dimers or ferritin and any dead-space indices adjusting for PaO2/FiO2, days of ventilation, tidal volume, and respiratory system compliance.ConclusionsWe report no association between dead space and inflammatory markers in mechanically ventilated patients with C-ARDS. Our results support theories suggesting that multiple mechanisms, in addition to immunothrombosis, play a role in the pathophysiology of respiratory failure and degree of dead space in C-ARDS.Copyright © 2023 Elsevier Inc. All rights reserved.

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