Inverse association between blood pressure and pulse oximetry accuracy: an observational study in patients with suspected or confirmed COVID-19 infection

Abstract

BackgroundPulse oximeters are a standard non-invasive tool to measure blood oxygen levels, and are used in multiple healthcare settings. It is important to understand the factors affecting their accuracy to be able to use them optimally and safely. This analysis aimed to explore the association of the measurement error of pulse oximeters with systolic BP, diastolic BP and heart rate (HR) within ranges of values commonly observed in clinical practice.MethodsThe study design was a retrospective observational study of all patients admitted to a large teaching hospital with suspected or confirmed COVID-19 infection from February 2020 to December 2021. Data on systolic and diastolic BPs and HR levels were available from the same time period as the pulse oximetry measurements.ResultsData were available for 3420 patients with 5927 observations of blood oxygen saturations as measured by pulse oximetry and ABG sampling within 30 min. The difference in oxygen saturation using the paired pulse oximetry and arterial oxygen saturation difference measurements was inversely associated with systolic BP, increasing by 0.02% with each mm Hg decrease in systolic BP (95% CI 0.00% to 0.03%) over a range of 80–180 mm Hg. Inverse associations were also observed between the error for oxygen saturation as measured by pulse oximetry and with both diastolic BP (+0.03%; 95% CI 0.00% to 0.05%) and HR (+0.04%; 95% CI 0.02% to 0.06% for each unit decrease in the HR).ConclusionsCare needs to be taken in interpreting pulse oximetry measurements in patients with lower systolic and diastolic BPs, and HRs, as oxygen saturation is overestimated as BP and HR decrease. Confirmation of the oxygen saturation with an ABG may be appropriate in some clinical scenarios.

The Use of End-Tidal CO2 and Integrated Pulmonary Index to Predict Postspinal Hypotension in Cesarean Section

“…Similarly, Crooks et al demonstrated an inverse relationship between blood pressure and pulse oximetry accuracy. It has been reported that at low blood pressure, signal integrity received from translucent tissue is compromised due to poor peripheral perfusion, resulting in false overestimation of pulse oximetry readings [35].…”

The Use of End-Tidal CO2 and Integrated Pulmonary Index to Predict Postspinal Hypotension in Cesarean Section

“…Similarly, Crooks et al demonstrated an inverse relationship between blood pressure and pulse oximetry accuracy. It has been reported that at low blood pressure, the signal integrity received from translucent tissue is compromised due to poor peripheral perfusion, resulting in the false overestimation of pulse oximetry readings [ 31 ].…”

Defining the role of skin pigmentation in the accuracy of pulse oximetry in COVID-19 subjects receiving domiciliary oxygen supplementation

“…A more recent study, which reported an inverse association between blood pressure and pulse oximetry accuracy in the context of COVID-19 infection, comprised 4330 white participants, 200 black participant, and 260 asian participants. Ethnicity did not appear to be a confounding factor in the outcome but, again, there was no specification of the degree of skin pigmentation in any of the ethnic subgroups, let alone a distinction between dark skinned asians versus light skinned white subjects [ 6 ].…”

“…The sum total of these studies [ [1] , [2] , [3] , 5 , 6 ] represents a missed opportunity to clarify, more accurately, the significance of skin pigmentation in the management of subjects in whom pulse oximetry plays an important clinical role. Future studies should be based on the recognition that categorization by ethnicity(such as white versus black, versus asian) is no substitute for categorization by degree of skin pigmentation, given the recognition that the intensity of skin pigmentation varies enormously both in “black” subjects and in, for example, “asian” subjects from the Indian subcontinent.…”