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Correspondence to Dr Hazel J Evans, Respiratory Medicine, Southampton Children's Hospital, Southampton SO16 6YD, UK; hazel.evans@uhs.nhs.uk In 2020 we published data defining reference ranges for pulse oximetry parameters generated from oximeters which use short averaging times and contain motion rejecting algorithms in healthy children under 12 years of age.1 This paper reported the minimum saturation (SAT min), which is the lowest oxygen saturation recorded, a value that is commonly reported in the paediatric literature.1 2 This is limited by the fact that it takes into account the single most severe dip, without reflecting the pattern of desaturations occurring throughout the period of sleep. Full details of the study have been published previously1 and published oximetry indices from this cohort are provided in table 1.Table 1 Descriptive statistics for oximetry desaturation events and indices for the entire study group (n=66): number of oxygen desaturations >4% and >3% from baseline per hour (DI4 and DI3), Delta Index 12 s (DI12s) and percentage time with saturations below 92% and 90% Parameter Mean SD Mean 95% CI Median Median 95% CI 90th centile 95th centile 97.5th centile DI4 1.14 0.84 0.93 to 1.34 0.92 0.73 to 1.15 2.60 3.00 3.38 DI3 2.90 1.65 2.50 to 3.29 2.58 1.96 to 3.10 5.65 6.43 7.06 DI12s 0.35 0.09 0.33 to 0.38 0.34 0.31 to 0.38 0.48 0.53 0.57 Time <92% 0.02 0.03 0.01 to 0.03 0.00 0.00 to 0.01 0.05 0.11 0.15 Time <90% 0.005 0.015 0.002 to 0.009 0.00 0.00 to 0.00 0.01 0.05 0.07 Here we report data previously collected but not reported for MDN DI3 and DI4. Data analysis for MDN DI3 and DI4 for a total cohort of 65 children was performed using SPSS (V.28).

Background and objectiveCardiorespiratory polygraphy (CRP) is the predominant technology used to diagnose obstructive sleep apnoea (OSA) in tertiary centres in the UK. Nocturnal pulse oximetry (NPO) is, however, cheaper and more accessible. This study evaluated the ability of NPO indices to predict OSA in typically developing (TD) children.MethodsIndices from simultaneous NPO and CRP recordings were compared in TD children (aged 1–16 years) referred to evaluate OSA in three tertiary centres. OSA was defined as an obstructive apnoea–hypopnoea index (OAHI) ≥1 event/hour. Receiver operating characteristic curves assessed the diagnostic accuracy of NPO indices including ODI3 (3% Oxygen Desaturation Index, ODI4 (4% Oxygen Desaturation Index), delta 12 s index and minimum oxygen saturation. Two-by-two tables were generated to determine the sensitivities and specificities of whole number cut-off values for predicting OAHIs ≥1, 5 and 10 events/hour.ResultsRecordings from 322 TD children, 197 male (61.2%), median age 4.9 years (range 1.1–15.6), were reviewed. OAHI was ≥1/hour in 144 (44.7%), ≥5/hour in 61 (18.9%) and ≥10/hour in 28 (8.7%) cases. ODI3 and ODI4 had the best diagnostic accuracy. ODI3 ≥7/hour and ODI4 ≥4/hour predicted OSA in TD children with sensitivities/specificities of 57.6%/85.4% and 46.2%/91.6%, respectively. ODI3 ≥8/hour was the best predictor of OAHI ≥5/hour (sensitivity 82.0%, specificity 84.3%).ConclusionRaised ODI3 and ODI4 predict OSA in TD children with high specificity but variable sensitivity. NPO may be an alternative to diagnose moderate-severe OSA if access to CRP is limited. Low sensitivities to detect mild OSA mean that confirmatory CRP is needed if NPO is normal.