Inverse linear association between blood haemoglobin and oxygen saturation accuracy measured by pulse oximetry: a cross-sectional analysis in individuals with COVID-19 infection.

Background: Pulse oximetry measures oxygen saturation non-invasively by using differential absorption of infrared signals which are dependent on the oxyhaemoglobin:deoxyhaemoglobin ratio. We tested the hypothesis that pulse oximetry error in measurements of blood oxygen saturations may be associated with blood haemoglobin levels.

Methods: The study design was an observational study of all adult patients admitted to a large teaching hospital with suspected or confirmed COVID-19 infection from February 2020 to December 2021 who had arterial blood gases (ABG) drawn.

A requirement for the use of supplementary oxygen to guide medical treatment decisions may introduce bias against non-white individuals.

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Respiratory rate responses to both hypercapnia and acidaemia are modified by age in patients with acidosis.

Objective: To explore the associations between arterial pO, pCO and pH and how these are modified by age.

Methods: An analysis of 2598 patients admitted with a diagnosis of Covid-19 infection to a large UK teaching hospital.

Results: There were inverse associations for arterial pO, pCO and pH with respiratory rate.