The Impact of Routine Pulse Oximetry Use on Outcomes in COVID-19-Infected Patients at Increased Risk of Severe Disease: A Retrospective Cohort Analysis

Background: A phenomenon of silent hypoxaemia has been described in patients with COVID-19 pneumonia, which is characterised by low oxygen saturation levels of < 90% in patients who appear clinically well and do not show signs of significant respiratory distress. We assessed the impact on clinical outcomes for high-risk COVID-19 patients using a pulse oximeter to monitor oxygen saturation levels in a home setting.Methods: We performed a retrospective cohort analysis using data from a large South African insurance administrator. Patients were categorised as high risk, based on age or if they had specific underlying clinical conditions, or if they were classified as high risk from predictive models based on medical scheme administrative claims data. The impact of pulse oximetry home monitoring on COVID-19 clinical outcomes were investigated by use of Cox proportional hazard models.Findings: Between 2 March 2020 and 31 October 2020, of 38 645 patients analysed, 8 113 were in the intervention group. The 60-day mortality rate for the evaluated high-risk population was 1·35%. After adjusting for the age and co-morbidity differences, the intervention group was found to have an adjusted hazard ratio (HR) of 0·52 (p<0·0001). No statistical significance was found between the intervened and control groups for admission to hospital, admission to ICU and, use of mechanical ventilation. The intervention group had a lower median CRP on admission (p=0·03), and after adjustment for admission CRP levels, elevated CRP was associated with increased mortality (p<0·0001), and the statistical significance in mortality between the intervention and the control group was lost.Interpretation: High-risk COVID19 patients who used a pulse oximeter to monitor oxygen saturation levels had significantly lower mortality rates, compared to other high-risk patients. The mortality benefit was explained by earlier presentation to hospital, as suggested by lower initial CRP levels.Funding Statement: None.Declaration of Interests: None.Ethics Approval Statement: Ethics clearance was obtained from the Human Research Ethics Committee (Medical) of the University of the Witwatersrand.