As doctors see more and more COVID-19 patients, they are noticing an odd trend: Patients whose blood oxygen saturation levels are exceedingly low but who are hardly gasping for breath. These patients are quite sick, but their disease does not present like typical acute respiratory distress syndrome (ARDS), a type of lung failure known from the 2003 outbreak of the SARS coronavirus and other respiratory diseases. Their lungs are clearly not effectively oxygenating the blood, but these patients are alert and feeling relatively well, even as doctors debate whether to intubate them by placing a breathing tube down the throat....