Asymptomatic hypoxia in Covid-19

Abstract

<b>Background:</b> A bewildering aspect of Covid-19 is the presentation of a proportion of patients with respiratory failure, but no perception of dyspnea. The aim of this study was to investigate frequency, characteristics and outcomes of Covid-19 patients with asymptomatic hypoxia compared with a symptomatic severity-matched group.&nbsp;Methods: patients were hospitalized at ASST Papa Giovanni XXIII, in Bergamo, Italy, from February 23rd&nbsp;to April 7th&nbsp;2020. Data were derived from electronic medical records.&nbsp;Results:&nbsp;1316 Covid-19 patients were evaluated, a third of them (N 469, 35.6%) did not report dyspnea at hospital admission. Overall 28-days mortality was 26.9% (N 354). In the unmatched analysis, patients with dyspnea had a more severe respiratory failure and a higher 28-day mortality (29.3%&nbsp;vs.&nbsp;22.6%, p=0.009). The matching analysis led to the identification of two groups of dyspneic (N = 254), and not dyspneic (N = 254) patients with comparable radiological impairment, and respiratory failure severity at admission (median PaO2/FiO2&nbsp;ratio of 229 [135 - 286], bilateral chest X ray involvement in 81.1% of them). In matched analysis, 28-day mortality resulted similar (26.4%&nbsp;vs.&nbsp;21.7%, p=0.21), while endotracheal intubation (ETI) rate resulted significantly higher in patients with shortness of breath at admission (17.7%&nbsp;vs.&nbsp;10.2%, p=0.015).&nbsp;Conclusions:&nbsp;In Covid-19, up to a third of the patients could be asymptomatic for dyspnea on admission. Dyspneic patients at presentation generally have worst clinical outcomes and higher mortality when compared to those without breathlessness. However, when patients are matched for severity at presentation, mortality is similar between groups, in spite of a lower ETI rate during hospitalization for not dyspneic patients.