Correlation between hypoxaemia and lung ultrasound score in patients presenting to an emergency department with interstitial syndrome: a prospective physiological study

Objective: To assess for the presence of a correlation between lung ultrasound score (LUSS) and ratio between arterial partial pressure of oxygen (PaO(2)) and the fraction of inspired oxygen (FiO(2)) in patients presenting to an emergency department (ED) with interstitial syndrome (IS). Design: Prospective, multicentre, physiological study. Setting: Four Belgian hospitals: one tertiary academic centre and three secondary centres. Participants: A convenience sample of adult patients who presented to an ED with acute dyspnoea and needed an arterial blood gas (ABG) analysis (those with a LUSS < 2 were secondarily excluded). Main outcome measure: Correlation between PaO(2)/FIO(2) and LUSS determined using Pearson correlation. Results: In total, 162 adult patients were included. A statistically significant negative linear correlation between PaO(2)/FIO(2) and LUSS was found (correlation coefficient, –0.4860 [95% CI, –0.5956 to –0.3587]; P < 0.0001). Conclusions: Our data provide evidence of a statistically significant negative linear correlation between PaO(2)/FIO(2) and LUSS for ED patients with lung IS. Given the representativeness of PaO(2)/FIO(2) for hypoxaemia and the fact that hypoxaemia indicates IS severity, our findings suggest that LUSS could contribute to the evaluation of IS severity. If confirmed by future studies that include patient follow-up, a noninvasive approach using LUSS could decrease the need for ABG analysis in patients who do not require repeated measurement of ABG values other than PaO(2), and thereby improve patient comfort.