PATTERNS OF MUSCLE-ACTIVITY IN LEGS IN SLEEP-APNEA PATIENTS BEFORE AND DURING NCPAP THERAPY

Nocturnal muscle activity in legs (MAL) was studied in 19 patients wit h sleep apnea syndrome before and during nCPAP. We distinguished perio dic (P-MAL) and nonperiodic (N-MAL) as well as apnea-associated and in dependent MALs. N-MALs were strongly associated with apneas and disapp eared during nasal continuous positive airway pressure (nCPAP). P-MALs showed a rather long intermovement interval (IMI) of about 54 s when associated with respiratory disturbances and a shorter one of about 38 s when occurring independently. In 5 patients with predominantly inde pendent P-MALs and a short IMI before and during nCPAP an incidental c oexistence of sleep apnea with periodic leg movements in sleep syndrom e (PLMS) was postulated. Five patients with an equal number of apnea-a ssociated and independent MALs before nCPAP had a long IMI which short ened under nCPAP, while the majority of MALs become independent. This could indicate a facilitating or an unmasking effect of nCPAP on PLMS. Four patients with predominantly apnea-associated MALs with a long IM I before nCPAP showed an unchanged MAL pattern under nCPAP, despite th e disappearance of apneas. Since some arousals persisted in these pati ents, insufficient nCPAP pressure with an upper airway resistance synd rome was suspected. We conclude that when P-MALs persist under nCPAP t herapy a long IMI may indicate an upper airway resistance syndrome, wh ereas a short IMI may indicate a coexisting or even induced PLMS.