Abstract
AimTo compare pulse oximetry in children with sickle cell anaemia (SCA) and controls and test the hypothesis that vitamin C deficiency (VCD; <11.4 μmol/L) is associated with nocturnal haemoglobin oxygen desaturation in SCA.MethodsWe undertook nocturnal and daytime pulse oximetry in 23 children with SCA (median age 8 years) with known steady-state plasma vitamin C concentrations and 18 siblings (median 7 years).ResultsMedian nocturnal delta 12 s index (delta12 s), a measure of haemoglobin oxygen saturation (SpO2) variability, was 0.38 (interquartile range 0.28–0.51) in SCA and 0.35 (0.23–0.48) in controls, with 9/23 and 6/18, respectively, having a delta12 s >0.4, compatible with obstructive sleep apnoea (OSA). Eleven of twenty-three with SCA had VCD; logged vitamin C concentrations showed a 66% decrease per 0.1 unit increase in delta12 s ([95% CI −86%, −15%]; p = 0.023) and delta12 s >0.4 was associated with VCD (odds ratio 8.75 [1.24–61.7], p = 0.029). Daytime and mean nocturnal SpO2 were lower in SCA but there was no association with vitamin C.ConclusionObstructive sleep apnoea (OSA), detected from nocturnal haemoglobin oxygen saturation variability, is common in Tanzanian children and associated with vitamin C Deficiency in SCA. The direction of causality could be determined by comparing OSA treatment with vitamin C supplementation.
Highlights
Erythrocytes containing haemoglobin S (HbS) experience chronic redox imbalance from increased production of hemichromes and reactive oxygen species (ROS)
In 71 children with sickle cell disease enrolled in the Sleep Asthma cohort (4), using the same cut-offs for delta[12] s and apnoea ⁄ hypopnea index (AHI), specificity and sensitivity were 100% and 89%, respectively (Gavlak et al, unpublished)
Daytime haemoglobin oxygen saturation was lower in the children with sickle cell anaemia (SCA) than in the controls and there was a trend for lower mean nocturnal haemoglobin oxygen saturation but there was no difference between children with SCA and controls in sleep duration, minimum overnight Haemoglobin oxygen saturation (SpO2), number of overnight SpO2 dips >3% ⁄ hr and the delta 12 s index (Table 1)
Summary
Erythrocytes containing haemoglobin S (HbS) experience chronic redox imbalance from increased production of hemichromes and reactive oxygen species (ROS). Abbreviations AHI, Apnoea ⁄ hypopnea index; BMI, Body mass index; CPAP, Continuous positive air pressure; delta[12] s, Delta 12 second index; FEV1, Forced expiratory volume at 1 second; Hb, Haemoglobin; MCHC, Mean cell haemoglobin concentration; OSA, Obstructive sleep apnoea; ROS, Reactive oxygen species; SCA, Sickle cell anaemia; SpO2, Haemoglobin oxygen saturation; VCD, vitamin C deficiency. In adults in the general population, delta[12] s values of >0.4 predict an apnoea ⁄ hypopnea index (AHI) of >15 with 88% specificity and 70% sensitivity (3). In 71 children with sickle cell disease enrolled in the Sleep Asthma cohort (4), using the same cut-offs for delta[12] s and AHI, specificity and sensitivity were 100% and 89%, respectively (Gavlak et al, unpublished)
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