Role of Alveolar-Arterial Difference in Estimation of Extravascular Lung Water in COVID-19-Related ARDS.

Background: The dominant feature of COVID-19-associated ARDS is gas exchange impairment. Extravascular lung water index is a surrogate for lung edema and reflects the level of alveolocapillary disruption. The primary aim was the prediction of extravascular lung water index by the alveolar-arterial oxygen difference. The secondary aims were in determining the relationship between the extravascular lung water index and other oxygenation parameters, the [Formula: see text], end-tidal oxygen concentration, pulmonary oxygen gradient ([Formula: see text] minus end-tidal oxygen concentration), and [Formula: see text].

Methods: This observational prospective single-center study was performed at the Department of Anaesthesiology and Intensive Care, The University Hospital in Ostrava, The Czech Republic, during the COVID-19 pandemic, from March 20, 2020, until May 24, 2021.

Results: The relationship between the extravascular lung water index and alveolar-arterial oxygen difference showed only a mild-to-moderate correlation (r = 0.33, P < .001). Other extravascular lung water index correlations were as follows: [Formula: see text] (r = 0.33, P < .001), end-tidal oxygen concentration (r = 0.26, P = .0032), [Formula: see text] minus end-tidal oxygen concentration (r = 0.15, P = .0624), and [Formula: see text] (r = -0.15, P = .01).

Conclusions: The alveolar-arterial oxygen difference does not reliably correlate with the extravascular lung water index and the degree of lung edema in COVID-19-associated ARDS.