Abnormal blood-oxygen, breathing strong predictors of poor COVID-19 outcomes, study finds

Respiration rate and blood-oxygen saturation are distinctly predictive of higher mortality among novel coronavirus (COVID-19) patients, according to a new study published in the journal Influenza and Other Respiratory Viruses.

For the study, the researchers examined the cases of 1,095 patients age 18 and older who were admitted with COVID-19 to UW Medicine hospitals in Seattle or to Rush University Medical Center in Chicago. The study span was March 1, 2020 to June 8, 2020. The lone exclusions were people who chose "comfort measures only" at time of their admission.

While patients frequently had hypoxemia, or low blood-oxygen saturation at 91 percent or below for this study, or tachypnea, or fast, shallow breathing at 23 breaths per minute for this study, few reported feeling short of breath or coughing regardless of blood oxygen.

The study's primary measure was all-cause in-hospital mortality. Overall, 197 patients died in the hospital. Compared to those admitted with normal blood oxygen, hypoxemic patients had a mortality risk 1.8 to 4.0 times greater, depending on the patient's blood oxygen levels. Similarly, compared to patients admitted with normal respiratory rates, those with tachypnea had a mortality risk 1.9 to 3.2 times greater. By contrast, other clinical signs at admission, including temperature, heart rate, and blood pressure, were not associated with mortality, according to the study

Nearly all patients with hypoxemia and tachypnea required supplemental oxygen, which, when paired with inflammation-reducing glucocorticoids, can effectively treat acute cases of COVID-19.

The authors said anyone who receives a positive COVID-19 screening test can easily monitor for these two signs at home. The findings have relevance for family-medicine practitioners and virtual-care providers, who typically are first-line clinical contacts for people who have received a positive COVID-19 test result and want to monitor meaningful symptoms.

The researchers recommended that people with positive COVID-19 test results, particularly those at higher risk of adverse outcomes due to advanced age or obesity, buy or borrow a pulse oximeter and monitor for blood-oxygen below 92 percent. The clip-like devices fit over a fingertip and can be purchased for under $20.

"These findings apply to the lived experience of the majority of patients with COVID-19, being at home, feeling anxious, wondering how to know whether their illness will progress and wondering when it makes sense to go to the hospital,” said Neal Chatterjee, MD, co-lead author of the study from the University of Washington School of Medicine, in a statement. “We recommend that the CDC and [World Health Organization] consider recasting their guidelines to account for this population of asymptomatic people who actually merit hospital admission and care.”

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