Nocturnal hypoxaemia and hypercapnia in children with neuromuscular disorders

The aim of the study was to identify daytime predictors of nocturnal gas exchange anomalies in children with neuromuscular disease (NMD) and normal daytime gas exchange. Lung function tests, respiratory muscle evaluation and nocturnal gas exchange were obtained as part of routine evaluation. We included 52 consecutive children with Duchenne muscular dystrophy (n = 20), spinal muscular atrophy (n = 10) and other NMD (n = 22). 20 patients had nocturnal hypoxaemia, defined as minimal arterial oxygen saturation measured by pulse oximetry (S(p,O(2))) <90% for ≥ 2% of night time, and 22 had nocturnal hypercapnia, defined as maximal transcutaneous carbon dioxide tension (P(tc,CO(2))) >50 mmHg for ≥ 2% of night time. Forced vital capacity and helium functional residual capacity correlated with minimal nocturnal S(p,O(2)) (p = 0.009 and p = 0.01, respectively). Daytime pH correlated negatively with maximal nocturnal P(tc,CO(2)) (p=0.005) and daytime arterial carbon dioxide tension (P(a,CO(2))) correlated with the percentage of time with a P(tc,CO(2)) >50 mmHg (p = 0.02). Sniff nasal inspiratory pressure correlated with minimal nocturnal S(p,O(2)) (p = 0.02). Daytime P(a,CO(2)) was a weak predictor of nocturnal hypercapnia (sensitivity 80%; specificity 57%). Daytime lung function and respiratory muscle parameters correlate poorly with nocturnal hypoxaemia and hypercapnia in children with NMD and normal daytime gas exchange, which necessitates more systematic sleep studies in these children.