Most ER patients with COVID-19 had COVID pneumonia, even those without respiratory complaints or breathing problems. However, chest X-rays do show diffuse pneumonia, and the patient's oxygen saturation level was below normal. This makes a pulse oximeter a handy tool for detecting such "silent hypoxia." This topic was featured in The New York Times op-ed last April 20, 2020: https://www.nytimes.com/2020/04/20/op...​.