Daytime predictors of nocturnal hypercapnic hypoventilation in children with neuromuscular disorders.

Objectives: To examine objective daytime predictors of nocturnal hypercapnic hypoventilation (NHH) and identify a forced vital capacity (FVC) z-score cut off that predicts NHH using the 2012 Global Lung Function Initiative (GLI) reference equations in pediatric neuromuscular patients.

Design: Single-centre retrospective medical record review.

Setting: Tertiary pediatric hospital in Australia.

Patients: Children (<18 years old) with a neuromuscular disorder (NMD) who had a diagnostic sleep study over a 5-year period.

Results: Fifty children were included, median age 11.9 years (interquartile range [IQR]: 4.5-14.3). The majority of children had a diagnosis of Duchenne Muscular Dystrophy (32%). NHH was diagnosed in 18 children (36%). Multivariate logistic regression analysis performed for the entire cohort confirmed a statistically significant association between NHH and scoliosis (odds ratio [OR]: 3.3, p = 0.03), but not age (OR: 1.01, p = 0.26), body mass index z-score (OR: 0.86, p = 0.26) or use of a wheelchair for mobility (OR: 1.25, p = 0.72). For the subset of 29 children who had spirometry testing (median age 12.9 years [IQR: 10.2-14.3]), FVC z-score was the only statistically significant predictor of NHH (OR: 0.45, p = 0.02). NHH was predicted by an FVC z-score <-3.24 (sensitivity 78%, specificity 73%), or FVC <60% predicted (sensitivity 78%, specificity 73%). There was a strong positive correlation between FVC and forced expiratory volume in 1 s z-scores (r  = 0.98, p = 0.00) and FVC and peak expiratory flow  z-scores (r  = 0.72, p = 0.00).

Conclusion: Children with a NMD and scoliosis or a lower FVC z-score have increased odds of having NHH.