Accuracy of Pulse Oximetry in COVID-19 Patients Stepping Down from Intensive Care

Abstract

Background: UK Guidelines suggest pulse oximetry, rather than blood gas sampling, is adequate for monitoring of patients with COVID-19 if CO2 retention is not suspected. However, pulse oximetry has impaired accuracy in certain patient groups, and data are lacking on its accuracy in patients with COVID-19 stepping down from Intensive Care Units (ICU) to non-ICU settings or being transferred to another ICU. Methods: We assessed agreement between pulse oximetry (SpO2) and arterial blood gas analysis (SaO2) in patients with COVID-19, deemed clinical stable to step down from an ICU to a non-ICU ward, or be transferred to another ICU. We used 90 paired SpO2 and SaO2 from 30 patients (3 paired samples per patient). Findings: Mean difference between SaO2 and SpO2 (bias) was -0.42%, with a standard deviation of 2.4 (precision). The limits of agreement between SpO2 and SaO2 were, lower limit of -5.16% (95% CI -6.51 to -4.20), upper limit of 4.32% (CI 3.36 to 5.67). Interpretation: In our setting, pulse oximetry showed a poor level of agreement with SaO2 measurement in people with COVID-19 judged clinically ready to step down from ICU to a non-ICU ward, or who were being transferred to another hospital’s ICU. In such patients, SpO2 should be interpreted with caution. Arterial blood gas assessment of SaO2 may still be clinically indicated. Funding: Imperial College London. Declaration of Interests: No authors declare any conflict of interest. Ethics Approval Statement: This evaluation was authorized by the Royal Brompton and Harefield NHS Foundation Trust Quality and Safety team. No external ethical approvals were required.