Some COVID-19 patients visiting EDs are not sick enough to be admitted to the hospital, but that could change shortly after discharge.

Researchers wanted to see if patient-reported oxygen saturation levels of less than 92% could identify the need for hospitalization.1

“One criterion that became a clear indicator for admission at the beginning of the pandemic was hypoxia,” says Sonia Shah, DO, chief resident of emergency medicine at Swedish Hospital in Chicago.

However, not all patients were hypoxic when they came to the ED. Many people showed only mild symptoms or no symptoms at all. “Before telemedicine became more popular, many of the patients within the population that we served did not have easy access to primary care physicians who could follow up on them after an ED visit,” Shah notes.

Portable home pulse oximeters seemed like a possible solution; patients could monitor themselves. “But there was no data on how well it would work to predict the need for future hospitalization in patients with COVID-19, or even people with viral pneumonias,” Shah says.

A group of 77 patients who tested positive for COVID-19 (and who were discharged home from the ED) received a home pulse oximeter and learned how to use it. Patients were told to record oxygen saturation levels every eight hours and return to the ED if they saw levels of less than 92%. Of this group, 22 ended up coming back to the ED and were hospitalized. “Our findings did surprise us. While the concept of silent hypoxia was only spoken of anecdotally, we had the evidence and data to prove that this was happening to COVID-19 patients at home who were otherwise asymptomatic,” Shah reports.

Patients with resting home oxygen saturation levels of less than 92% were more likely to be hospitalized, admitted to the ICU, and were at risk for acute respiratory distress syndrome and septic shock. Of those who were not hospitalized, one-third said if they did not have a pulse oximeter to check their levels at home, they would have returned to the ED. Those patients were reassured by home pulse oximetry readings and did not return to the ED. “Presumably, returning to the ED with normal pulse oximeter readings would not warrant admission unless patients had other concerning symptoms,” Shah suggests.

Such a visit would use up PPE and increase ED providers’ COVID-19 exposure. “Discharging patients with a low-cost tool to monitor their own health can improve patient safety outcomes,” Shah concludes.

Some patients in the study returned to the ED specifically because of a persistently low pulse oximeter reading. Of the 22 patients who were admitted, some improved; others progressed to requiring supplemental oxygen and even mechanical ventilation. “We found that it was only because of the home pulse oximeter reading that some patients sought medical attention earlier than they otherwise would have, potentially preventing worse outcomes,” Shah says.


  1. Shah S, Majmudar K, Stein A, et al. Novel use of home pulse oximetry monitoring in COVID-19 patients discharged from the emergency department identifies need for hospitalization. Acad Emerg Med 2020 doi: 10.1111/acem.14053.