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    Inaccuracy assessment of pulse oximeter in black-skinned adults admitted to ICU in Tikur Anbessa Specialized Hospital
    (Addis Ababa University, 2024-03) Mahammed,Jafar; Bekele,Amsalu( MD, Ass.Prof.); Yusuf,Hanan(MD, MPH, Ass.Prof.); Kebede,Dawit( MD, Ass.Prof.); Haisch,Deborah A( MD, Ass.Prof.); Fogarty,Andrew W(MD)
    Background:The measurement of oxygen saturation via pulse oximeter is a safe and noninvasive method to approximate arterial oxygen saturation (SpO2), which is an important vital sign in clinical assessment [1-3]. According to manufacturers, reported values ranging from 70 to 100 percent are considered accurate within 2 to 3 percent of the true value, as per FDA standards [12,13]. Any variation in oxygen saturation measured by the pulse oximeter (SpO2) compared to the gold standard measurement by Arterial Blood Gas (ABG) measured oxygen saturation (SaO2) of ≥4% is considered inaccurate [12,13]. There have been recent reports of systemic racial bias where pulse oximeter-measured oxygen saturation (Spo2) has been found to overestimate true arterial oxygen saturation (SaO2) in patients with darkly pigmented skin, leading to concerns about the clinical accuracy of pulse oximetry [6]. Though this finding is deeply relevant to Africa, there is no data from Africa including Ethiopia. Objective: To determine the frequency of Pulse Oximeter inaccuracies in black-skinned adults admitted to the ICU at TASH in Addis Ababa, Ethiopia between July 2023, and February 2024. Methodology:We conducted a cross-sectional observational study at a tertiary medical center. While collecting an arterial blood gas, we utilized a pulse oximeter to measure oxygen saturation in the opposite arm. Pulse oximeter readings were recorded after 10 seconds of stable measurement. We used Fitzpatrick skin color tone classification to scale skin color of the patients. Patients with shock, severe anemia, profound hypoxemia and hypothermia were excluded [3, 5,15]. Statistical Analysis Quantitative analysis was conducted to compare the oxygen saturation estimates obtained from the pulse oximeter with the gold standard measurement from the arterial blood gases. The resulting discrepancies were documented and entered into SPSS for analysis. Descriptive statistics were then employed to determine the mean discrepancy and the prevalence of pulse oximeter error. Result:During our study, we simultaneously measured SpO2 and SaO2 for 72 patients. 37 patients were excluded due to shock, severe anemia, profound hypoxemia and hypothermia, leaving 35 patients for preliminary result analysis. The skin color of the patients according to Fitzpatric classification (Table1) were Class III (16 patients), Class IV (12 patients), Class V(6patients) and Class VI(1patient). The SpO2 readings taken by pulse oximetry showed that 31 patients (88.6%) had SpO2 ≥ 92%. Among the 4 patients who had SpO2 of ˂92%, 2 (5.7%) had SpO2 between 88-˂ 92%, 1(2.9%) had SpO2 between 80-˂88%, and 1 (2.9%) had SpO2 between 70-˂80%. On ABG, we found that 17 patients (48.8%) had SaO2 readings of ˂92%. 16 patients (45.7%) had a pulse oximeter inaccuracy/error. The mean discrepancy of SpO2 to SaO2 was 5.4666 (SD= ± 8.39870, range=-4.8 to 33.4). The prevalence and mean discrepancy percentages of pulse oximeter error at different ranges of SpO2 sequentially were as follows: SpO2 ≥ 92% (38.7%,4.95), 88-˂92 % (100%,6.95%), 80-˂88% (100%,5.6%), and 70-˂80% (100%, 29.4%). Even if the proportion of patients with SpO2 <92% is low, this study indicated that mean discrepancy might be even more as saturation drops. Discussions and Conclusion:The results indicate a higher frequency/prevalence of error compared to other studies conducted in different settings, which reported 11.7% (7) and 17% (9) prevalence of pulse oximeter error in black patients. While these preliminary findings suggest that the pulse oximeter overestimates arterial oxygen saturation relative to ABG-measured arterial oxygen saturation in our sample, it is important to note that a larger sample size is required to draw a more definitive conclusion. Recommendations We should be cautious in interpreting SpO2 in Dark-skinned patients, especially when patients have low oxygen saturation. Pragmatic studies with larger sample size are needed to observe differences in Pulse oximeter error across different ranges of SpO2 and skin color classes.