Progressive neuromuscular disorders.: Chronic respiratory muscle failure and sleep disordered breathing

Background. Chronic respiratory muscle failure is an inevitable complication of many progressive childhood neuromuscular disorders (NMD) that becomes evident as sleep disordered breathing (SDB) or daytime respiratory failure (RF). Patients. 50 children and adolescents with NMD (11.2+/-4.3 years). Methods. Measurement of inspiratory vital capacity (IVC), maximum inspiratory pressure (Pi(max)), arterial blood gases (PaO2, PaCO2) and complete polysomnography (PSG) including capnometry (PtcCO2). Results. There was a significant correlation between IVC (%predicted) and Pi(max) (r=0.77), IVC and daytime gas exchange [PaO2 (r=0.55), PaCO2 (r=0.63)] and IVC and nocturnal gas exchange [SaO2 (r=0.71), PtcCO2 (r=-0.74)]. Apnoeas, hypopnoeas or hypoventilation during sleep were seen in 36 patients (72%), 12 children (24%) had additional daytime RF. The severity of the respiratory disturbance correlated with IVC (r=0.82). The occurrence of SDB or RF could be predicted from IVC <60% and <25%, respectively; positive predictive values were 94% and 71%. Conclusion. SDB and RF are frequent complications of chronic respiratory muscle failure. The combination of lung and respiratory muscle testing with PSG gives a detailed description of respiratory function and reserve. This has important clinical implication for further disease management, assessment of prognosis and the indication of noninvasive ventilation in children with NMD.