Comparison of pulse oximetry and earlobe blood gas with CO-oximetry in children with sickle cell disease: A retrospective review

Objectives To investigate the agreement between pulse oximetry (SpO 2) and oxygen saturation (SaO 2) measured by CO-oximetry on arterialised earlobe blood gas (EBG) in children and adolescents with sickle cell disease (SCD). Design and setting We retrospectively reviewed 39 simultaneous and paired SaO 2 EBG and SpO 2 measurements from 33 ambulatory patients with SCD (32 subjects with Haemoglobin SS and one with Haemoglobin Sß +, 52% male, mean±SD age 11.0±3.6, age range 5-18). Measurements were performed between 2012 and 2015 when participants were asymptomatic. Hypoxaemia was defined as SaO 2 ≤93%. A Bland-Altman analysis was performed to assess the accuracy of SpO 2 as compared with EBG SaO 2. Results The mean±SD SpO 2 and SaO 2 values in the same patients were, respectively, 93.6%±3.7% and 94.3%±2.9%. The bias SpO 2-SaO 2 was-0.7% (95% limits of agreement from-5.4% to 4.1%) and precision was 2.5%. In 9/39 (23%) cases, the difference in SpO 2-SaO 2 was greater than the expected error range ±2%, with SaO 2 more often underestimated by SpO 2 (6/9), especially at SpO 2 values ≤93%. Thirteen participants (33%) were hypoxaemic. The sensitivity of SpO 2 for hypoxaemia was 100%, specificity 85% and positive predictive value 76%. Conclusions Pulse oximetry was inaccurate in almost a quarter of measurements in ambulatory paediatric patients with SCD, especially at SpO 2 values ≤93%. In these cases, oxygen saturation can be confirmed through EBG CO-oximetry, which is easier to perform and less painful than traditional arterial blood sampling.