Lung ultrasound (LUS) has recently gained popularity among the imaging methods to perform bedside assessment of critically ill patients to guide clinical management. LUS is a non-invasive and easy-to-perform procedure that provides precise data on lung aeration, lung recruitment, lung morphology, and lung perfusion. Studies have shown that LUS is a useful tool in monitoring lung reaeration in intubated patients diagnosed with traditional ARDS undergoing prone positioning; however there are mixed findings in terms of the use of LUS in predicting potential prone positioning response. A recent study found that the non-intubated COVID-19 patients who responded to prone positioning had more pronounced disturbances of aeration in posterior regions, however, they only investigated patients' response to the first prone positioning and the information for the patients' outcome is lacking. In our previous study with intubated COVID-19 patients, we found that patients' response to the subsequent prone positioning had higher predictive value than the response to the first prone positioning. Therefore, the primary objective of this study is to explore the physiological mechanism of awake, self proning among patients with acute hypoxemic respiratory failure induced by COVID-19, using LUS in the first three days and explore the predictive value of LUS in patients' outcome.
