Working accuracy of pulse oximetry in COVID-19 patients stepping down from intensive care: a clinical evaluation

• Published in: BMJ open respiratory research Vol. 7; no. 1; p. e000778
• Main Authors: Philip, Keir Elmslie James, Bennett, Benjamin, Fuller, Silas, Lonergan, Bradley, McFadyen, Charles, Burns, Janis, Tidswell, Robert, Vlachou, Aikaterini
• Format: Journal Article
• Language: English
• Published: England BMJ Publishing Group LTD 23.12.2020; BMJ Publishing Group
• Subjects: Accuracy; Adult; Aged; Agreements; Arterial lines; Clinical medicine; Coronaviruses; COVID-19; COVID-19 - diagnosis; COVID-19 - epidemiology; Critical Care; Critical Care - methods; Female; Follow-Up Studies; Gases; Hemoglobin; Humans; Intensive care; Intensive Care Units; Male; Methods; Middle Aged; Oximetry - standards; Oxygen - blood; Oxygen saturation; Patient safety; Pulse oximetry; Reproducibility of Results; Retrospective Studies; SARS-CoV-2; respiratory measurement
• DOI: 10.1136/bmjresp-2020-000778
• ISSN: 2052-4439

IntroductionUK guidelines suggest that 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 unit (ICU) to non-ICU settings or being transferred to another ICU.MethodsWe assessed the bias, precision and limits of agreement using 90 paired SpO2 and SaO2 from 30 patients (3 paired samples per patient). To assess the agreement between pulse oximetry (SpO2) and arterial blood gas analysis (SaO2) in patients with COVID-19, deemed clinically stable to step down from an ICU to a non-ICU ward, or be transferred to another ICU. This was done to evaluate whether the guidelines were appropriate for our setting.ResultsMean difference between SaO2 and SpO2 (bias) was 0.4%, with an SD of 2.4 (precision). The limits of agreement between SpO2 and SaO2 were as follows: upper limit of 5.2% (95% CI 6.5% to 4.2%) and lower limit of −4.3% (95% CI −3.4% to −5.7%).ConclusionsIn our setting, pulse oximetry showed a level of agreement with SaO2 measurement that was slightly suboptimal, although within acceptable levels for Food and Drug Authority approval, 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.