Assessment of respiratory function and sleep disorders in children with myopathy

Background: Impaired activity of respiratory muscles and poor lung mechanisms predispose to sleep disordered breathing in neuromuscular disorders. Although it may lead to major morbidity, its relation to respiratory function is poorly defined.

Objectives: To evaluate respiratory muscle function and sleep disorders in children with myopathy and their relations to daytime and nocturnal symptoms and oxygen saturation.

Method: A cross-sectional study was carried out on 30 children, 20 males and 10 females, diagnosed with myopathy at Abou El Reesh Paediatric Hospital, Cairo University. Arterial blood gases, creatine kinase (CK), aspartate transaminase (AST) and alanine transaminase (ALT) levels were measured. All subjects underwent respiratory function tests using spirometry, overnight polysomnography and diaphragmatic ultrasound.

Results: Patients were assigned into 2 groups based on respiratory function tests assessed by spirometry. Group A included 14 patients with normal respiratory function tests and Group B included 16 patients with abnormal respiratory function tests. A significant difference was noted as regards symptoms suggestive of poor sleep quality including somnolence, waking unrested and frequent awakening (p=0.005). Apnoea hypopnoea index (AHI) was significantly higher in group B patients (p=0.04) (AHI was abnormal in 43% of patients in group A and 69% of patients in group B). Obstructive apnoeic and hypopnoeic events were detected in all patients with abnormal AHI. No significant difference was noted regarding sleep staging, sleep efficiency or total sleep test (TST).There was no significant difference between both groups as regards arterial blood gases, CK, ALT, AST or diaphragmatic ultrasound.

Conclusions: Myopathic children with abnormal respiratory function had a significant increase in symptoms related to sleep deprivation as well as abnormal AHI. In the diagnosis of sleep disordered breathing in myopathic children polysomnography was useful but daytime blood gas analysis was not useful. Children with muscle disorders should be assessed by respiratory function tests and polysomnography even if they do not have symptoms suggestive of respiratory muscle involvement.

Sri Lanka Journal of Child Health, 2021; 50(2): 215-221