Abstract
Evidence shows that pulmonary problems in coronavirus disease 2019 (COVID-19) may set off from vascular injury that progresses to physiological disturbances through a compromised gas exchange, following an infection with the severe acute respiratory syndrome coronavirus 2. In this process, inefficient gas exchange in the alveolar could precipitate silent nonclinical hypoxemia. Unfortunately, patients with "silent hypoxemia" do not necessarily experience any breathing difficulty (dyspnea) at the early stage of COVID-19 while the disease progresses. As a result, several asymptomatic, presymptomatic and patients with mild symptoms may escape quarantine measure and thus continue to spread the virus through contacts. Therefore, early diagnosis of "silent hypoxemia", which attracts no clinical warnings, could be an important diagnostic measure to prevent acute respiratory distress syndrome from the risk of pulmonary failure among the presymptomatic and as a screening tool in the asymptomatic who are hitherto potential spreaders of the virus.