Night-to-night Variability of Overnight Pulse Oximetry in Children with Underlying Medical Conditions.

Children with underlying medical conditions, such as neuromuscular diseases, craniofacial malformations, or chromosomal abnormalities, are at increased risk of obstructive sleep apnea (OSA). Although polysomnography remains the diagnostic gold standard for OSA, its feasibility in children is limited. Overnight pulse oximetry is a widely used screening tool, but its diagnostic accuracy may be compromised by first-night effects and night-to-night variability, particularly in children with neurodevelopmental or craniofacial disorders. Therefore, we evaluated night-to-night agreement of pulse oximetry indices in children with underlying medical conditions using correlation and Bland-Altman analysis. We retrospectively analyzed thirty-two children with underlying medical conditions under 15 years of age (median age 3 years) who underwent two consecutive nights of overnight pulse oximetry to evaluate night-to-night agreement of oximetry indices. Oxygen desaturation indices (ODI3, ODI4) and desaturation times <90% (DT90) and <95% (DT95) were evaluated. Correlations between nights were moderate to high (ODI3: r =0.71; DT90: r =0.72), but Bland-Altman analysis revealed wide 95% limits of agreement for ODI3 (-7.06 to +8.14 events/h), comparable to the diagnostic threshold of 7/h, leading to diagnostic reclassification in 25% of cases. Despite moderate to strong correlations, Bland-Altman analysis demonstrated clinically meaningful variability near diagnostic thresholds. In children with underlying conditions, a single-night oximetry study may under- or over-diagnose OSA. While two-night assessments should remain the standard, we propose a stepwise diagnostic algorithm in which a markedly elevated first-night ODI3 (≥15/h) may justify immediate intervention, whereas further evaluation is warranted in cases suspected to represent mild-to-moderate disease.