Background: The Lung Ultrasound (LUS) is routinely used as a point-of-care imaging tool in Emergency Department (ED) and its role in COVID-19 is being studied. The Lung UltraSound Score (LUSS) is a semi quantitative score of lung damage severity. Alongside instrumental diagnostic, the PaO2/FiO2 (P/F) ratio, obtained from arterial blood gas analysis, is the index used to assess the severity of the acute respiratory distress syndrome (ARDS), according to the Berlin definition.
Objectives: The primary objective of the study was to evaluate a possible correlation between the LUSS score and the P/F Ratio, obtained from the arterial sampling in COVID-19 positive patients.
Materials and methods: This was a cross-perspective monocentric observational study and it was carried out in the Emergency Department of the "AOU delle Marche" (Ancona, Italy), from 1 January 2023 to 28 February 2023. The study foresaw, once the patient was admitted to the ED, the execution of the LUS exam and the subsequent calculation of the LUSS score.
Results: The sample selected for the study was of 158 patients. The proportion of LUSS ≤4 was statistically higher in those with a P/F >300 (76.2%), compared to those with a P/F ≤300 (13.2%). On the other end, the proportion of LUSS >4 was lower in those who have P/F >300 (23.8%), while it was higher in those who have P/F ≤300 (86.8%). Those patients with a LUSS >4 were 1.76 (95% CI: 1.57 - 1.99) times more likely to have a P/F ≤300, compared to those with LUSS ≤4. The Odds Ratio of having a P/F ≤300 value in those achieving a LUSS >4, compared to those achieving a LUSS ≤4, was 21.0 (95% CI: 8.4 - 52.4). The study identified pO2, Hb and dichotomous LUSS as predictors of the level of P/F ≤300 or P/F >300.
Discussion: We found that the LUSS score defined by our study was closely related to the P/F ratio COVID-19 positive patients. Our study presented provides evidence on the potential rule of the LUSS for detecting the stage of lung impairment and the need for oxygen therapy in COVID-19 positive patients.