Correlazione fra gradiente alveolo-arterioso, rapporto P su F e reperti TC nelle polmoniti associate a COVID-19 nel Dipartimento di Emergenza-Urgenza

Background. Since one of the most common COVID-19 presentation in the Emergency Department is pneumonia with respiratory failure, it is essential an early stratification of its severity. Study design and methods. In this single center, observational, retrospective study we analyzed 112 patients with COVID-19 pneumonia, with focus on the relationship between P/F, A-a gradient and CT findings. Lung involvement has been evaluated with CT scan, as percentage (<25%, 26-50%, >50%) and type of parenchymal damage (ground glass opacity, infiltrates). Results. We found strong correlation between gas exchange impairment and outcome with significant P/F decreasing and A-a gradient increasing in dead subgroup (p < 0.0001). Association between A-a and CT data resulted significant (p < 0.05) from mild to severe pneumonia; association between P/F and CT resulted significant (p < 0.05) only for severe disease (> 50%). Patients with CT pattern of ground glass opacity and infiltrates had the worst prognosis, but interpretation of these results is difficult due to overlap of values between subgroups. Conclusions. Severity of respiratory failure at ED presentation is associated with type and percentage of parenchymal damage and has prognostic value. Due to the small population, further studies are needed to establish if lung damage and severity illness can be reliably predicted by blood gas analysis findings alone, reserving CT scan for specific cases such as of suspected pulmonary thromboembolism.