Understanding the use of pulse oximetry in COVID-19 disease

Pulse oximetry has been used in the assessment and management of patients in pre-hospital and primary care for over 30 years (Silverston, 1989; 1991). The use of pulse oximetry in primary care has increased steadily over that time, partly due to the availability of inexpensive, finger clip pulse oximeters and also in response to the incorporation of oxygen saturation readings (SpO₂) into the national guidelines for the assessment and management of patients with a wide variety of respiratory and non-respiratory illnesses (Ingram and Munro, 2005; Potter, 2007; Plüddemann et al, 2011). In 2020, the emergence of a new respiratory illness, COVID-19, led to pulse oximetry being used routinely in the assessment and management of large numbers of patients with COVID-19 respiratory illness. Pulse oximetry was seen as a non-invasive, simple to use and inexpensive technology that would enable clinicians working in primary care to identify patients with the respiratory form of COVID-19 disease and to categorise that illness as being either mild, moderate or severe (NHS England and Wales, 2020). National guidelines for the assessment and management of patients with COVID-19 disease recommend that pulse oximetry is performed routinely as part of the assessment, management and monitoring of patients. In many parts of the UK, patients were provided with a pulse oximeter to help them monitor their condition at home, as part of a ‘virtual ward at home’ programme (Greenhlagh et al, 2021). An understanding of the technical and physiological principles involved in pulse oximetry can help clinicians to avoid errors in diagnosis arising from the incorrect use of equipment, or from the misinterpretation of SpO₂ readings (Silverston, 2016).