Silent Hypoxemia in Covid-19 and Non-Covid-19 Pneumonias

ABSTRACT

Rationale Multiple anecdotal reports describe patients with COVID-19 presenting with what is referred to as silent hypoxemia (without dyspnea, tachypnea, or respiratory distress). However, there is a paucity of literature on this problem. We conducted a study to determine the prevalence of silent hypoxemia in patients with COVID-19 infection at presentation in the emergency department (ED) or on admission, and compared it with that of patients with pneumonia by any other etiology at Memorial Hermann Health System. In addition, we analyzed the differences between clinical, laboratory, hospital utilization, and mortality. Methods From electronic medical records, we identified pneumonia patients with a positive result for coronavirus on reverse transcriptasepolymerase chain reaction (RT-PCR) nasopharyngeal swab test, or diagnosis of pneumonia by influenza or any other etiology for one year, presenting to the ED or admitted to any MHHS hospital. We extracted age, sex, race/ethnicity, vital signs, oxygen saturation, intensive care unit (ICU) admission, and hospital stay for all patients. Results A total of 17,475 COVID-19 patients were compared with 2,343 patients with influenza/pneumonia of any etiology. The two groups were similar with respect to age, sex, and ethnicity. The frequency of silent hypoxemia was greater in the COVID-19 (n=232, 1.3%) group compared to influenza/pneumonia (n= 3, 0.13%) patients (p<0.001). For patients with an oxygen saturation < 90, the proportion who had silent hypoxemia was 11.7% (232/1981) in the COVID-19 patients and 2.6% (3/117) in the influenza and other viral pneumonia patients. Between COVID-19 patients admitted to the hospital, patients with symptomatic hypoxemia had a longer hospital stays (median 11 days, IQR 6-22) compared to those with silent hypoxemia (median 8 days, IQR 4-18) (p=0.001). The symptomatic hypoxemia group was more likely to be admitted to the ICU (n=457, 26.1%) compared to the silent hypoxemic patients (n=33, 15.5%) (p<0.001) and the mortality rate was higher (n=454, 26.0%) vs (36, 15.5%) (p=0.001). Conclusion The prevalence of silent hypoxemia for adults with viral pneumonia who were seen in the ED or hospitalized in a 17- hospital system in Houston, was higher in the COVID-19 infection patient group compared to patients with other pneumonias or any other etiology. Among the COVID-19 subjects, those with symptomatic hypoxemia had worse outcomes compared to those with silent hypoxemia. More studies are needed to confirm these findings.