NREM sleep instability changes following rapid maxillary expansion in children with obstructive apnea sleep syndrome.

OBJECTIVE: To evaluate NREM sleep microstructure in children with obstructive sleep apnea syndrome (OSAS) before and after one year of rapid maxillary expander (RME) treatment by means of the cyclic alternating pattern (CAP). METHODS: Nine children with OSAS aged 4-8 years (6 males, mean age 6.4+/-1.97 years) and age-matched normal controls were included. All subjects underwent an overnight polysomnography in the sleep laboratory after one adaptation night, as a baseline evaluation; children with OSAS were recorded again after one year of RME treatment. RESULTS: After one year of treatment the OSAS group showed a longer duration of time in bed and sleep period time, a reduction in number of stage shifts compared to baseline recordings, and the apnea-hypopnea index decreased significantly. At baseline, the OSAS group had a higher CAP rate during slow-wave sleep and an increased A2 index compared to normal controls. After one year of RME application, children with OSAS showed an increase in CAP rate associated with an increase of A1 index during slow-wave sleep. CONCLUSIONS: RME treatment almost normalized sleep architecture and improved sleep respiratory disturbances; however, sleep microstructure and respiratory parameters did not completely recover. The persistence of increased CAP rate in slow-wave sleep associated with an increase of A1 index might reflect a partial failure of orthodontic treatment. On the other hand, the rebound of A1 subtypes might be an indirect sign of an attempt to normalize sleep that has been disturbed by the respiratory events.