Faculty Bibliography

BACKGROUND:Fingertip pulse oximeters are widely available, inexpensive, and commonly used to make clinical decisions in many settings. Device performance is largely unregulated and poorly characterised, especially in people with dark skin pigmentation. METHODS:Eleven popular fingertip pulse oximeters were evaluated using the US Food and Drug Administration (FDA) Guidance (2013) and International Organization for Standardization Standards (ISO, 2017) in 34 healthy humans with diverse skin pigmentation utilising a controlled desaturation study with arterial oxygen saturation (SaO 2) plateaus between 70% and 100%. Skin pigmentation was assessed subjectively using a perceived Fitzpatrick Scale (pFP) and objectively using the individual typology angle (ITA) via spectrophotometry at nine anatomical sites. FINDINGS/RESULTS:Five of 11 devices had a root mean square error (ARMS) > 3%, falling outside the acceptable FDA performance range. Nine devices demonstrated worse performance in participants in the darkest skin pigmentation category compared with those in the lightest category. A commonly used subjective skin colour scale frequently miscategorised participants as being darkly pigmented when compared to objective quantification of skin pigment by ITA. INTERPRETATION/CONCLUSIONS:Fingertip pulse oximeters have variable performance, frequently not meeting regulatory requirements for clinical use, and occasionally contradicting claims made by manufacturers. Most devices showed a trend toward worse performance in participants with darker skin pigment. Regulatory standards do not adequately account for the impact of skin pigmentation on device performance. We recommend that the pFP and other non-standardised subjective skin colour scales should no longer be used for defining diversity of skin pigmentation. Reliable methods for characterising skin pigmentation to improve diversity and equitable performance of pulse oximeters are needed. FUNDING/BACKGROUND:This study was conducted as part of the Open Oximetry Project funded by the Gordon and Betty Moore Foundation, Patrick J McGovern Foundation, and Robert Wood Johnson Foundation. The UCSF Hypoxia Research Laboratory receives funding from multiple industry sponsors to test the sponsors' devices for the purposes of product development and regulatory performance testing. Data in this paper do not include sponsor's study devices. All data were collected from devices procured by the Hypoxia Research Laboratory for the purposes of independent research. No company provided any direct funding for this study, participated in study design or analysis, or was involved in analysing data or writing the manuscript. None of the authors own stock or equity interests in any pulse oximeter companies. Dr Ellis Monk's time utilised for data analysis, reviewing and editing was funded by grant number: DP2MH132941.

BACKGROUND:Retrospective clinical trials of pulse oximeter accuracy report more frequent missed diagnoses of hypoxemia in hospitalized Black patients than White patients, differences that may contribute to racial disparities in health and health care. Retrospective studies have limitations including mistiming of blood samples and oximeter readings, inconsistent use of functional versus fractional saturation, and self-reported race used as a surrogate for skin color. Our objective was to prospectively measure the contributions of skin pigmentation, perfusion index (PI), sex, and age on pulse oximeter errors in a laboratory setting. METHODS:We enrolled 146 healthy subjects, including 25 with light skin (Fitzpatrick class I and II), 78 with medium (class III and IV), and 43 with dark (class V and VI) skin. We studied 2 pulse oximeters (Nellcor N-595 and Masimo Radical 7) in prevalent clinical use. We analyzed 9763 matched pulse oximeter readings (pulse oximeter measured functional saturation [Spo2]) and arterial oxygen saturation (hemoximetry arterial functional oxygen saturation [Sao2]) during stable hypoxemia (Sao2 68%-100%). PI was measured as percent infrared light modulation by the pulse detected by the pulse oximeter probe, with low perfusion categorized as PI < 1%. The primary analysis was to assess the relationship between pulse oximeter bias (difference between Sao2 and Spo2) by skin pigment category in a multivariable mixed-effects model incorporating repeated-measures and different levels of Sao2 and perfusion. RESULTS:Skin pigment, PI, and degree of hypoxemia significantly contributed to errors (bias) in both pulse oximeters. For PI values of 1.0% to 1.5%, 0.5% to 1.0%, and <0.5%, the P value of the relationship to mean bias or median absolute bias was <.00001. In lightly pigmented subjects, only PI was associated with positive bias, whereas in medium and dark subjects bias increased with both low perfusion and degree of hypoxemia. Sex and age was not related to pulse oximeter bias. The combined frequency of missed diagnosis of hypoxemia (pulse oximeter readings 92%-96% when arterial oxygen saturation was <88%) in low perfusion conditions was 1.1% for light, 8.2% for medium, and 21.1% for dark skin. CONCLUSIONS:Low peripheral perfusion combined with darker skin pigmentation leads to clinically significant high-reading pulse oximeter errors and missed diagnoses of hypoxemia. Darkly pigmented skin and low perfusion states are likely the cause of racial differences in pulse oximeter performance in retrospective studies.

UNLABELLED: < 0.01. In terms of opioid consumption and a majority of functional outcomes, our study demonstrates no overall benefits of adding an IPACK block in this ERAS pathway in TKA. Nevertheless, IPACK may have the potential of mitigating posterior knee pain after TKA. LEVEL OF EVIDENCE/METHODS:level 1. CLINICAL TRIAL NUMBER AND REGISTRY URL/BACKGROUND:NCT03653416. www. CLINICALTRIALS/RESULTS:gov.

It has long been known that many pulse oximeters function less accurately in patients with darker skin. Reasons for this observation are incompletely characterized and potentially enabled by limitations in existing regulatory oversight. Based on decades of experience and unpublished data, we believe it is feasible to fully characterize, in the public domain, the factors that contribute to missing clinically important hypoxemia in patients with darkly pigmented skin. Here we propose 5 priority areas of inquiry for the research community and actionable changes to current regulations that will help improve oximeter accuracy. We propose that leading regulatory agencies should immediately modify standards for measuring accuracy and precision of oximeter performance, analyzing and reporting performance outliers, diversifying study subject pools, thoughtfully defining skin pigmentation, reporting data transparently, and accounting for performance during low-perfusion states. These changes will help reduce bias in pulse oximeter performance and improve access to safe oximeters.