Arousals in sleep-disordered breathing: patterns and implications.

STUDY OBJECTIVE

To describe the whole spectrum of electroencephalographic (EEG) transients associated with the termination and recovery of obstructed respiratory events and, thus, widen the recognized spectrum of arousal phenomena from sleep.

DESIGN

Retrospective review of diagnostic polysomnograms.

SETTING

American Academy of Sleep Medicine (AASM)-accredited multidisciplinary sleep disorders center.

PATIENTS

17 patents with obstructive sleep-disordered breathing.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

Nasal airflow using a nasal-cannula-pressure-transducer system and oral flow by a thermistor were used to score apneas and hypopneas; the latter included flow-limitation events. The EEG patterns that crested or occurred within 2 to 3 seconds of respiratory recovery were recorded, and posthoc categories were created for the purpose of tabulation ranging from an AASM 3-second arousal to a single K-complex with no electromyographic increase. Chi-square statistic was calculated to assess the difference in EEG patterns at event termination between apneas and hypopneas. Score-rescore agreement was tested. Apneas were significantly more likely to be associated with a 3-second arousal than were hypopneas, but all types of EEG change were seen with both types of events. Spindles were rarely seen with arousal-linked K-complexes. The majority of events in rapid eye movement sleep were terminated with visible electromyography tone increase.

CONCLUSIONS

The spectrum of EEG change associated with the termination of respiratory events identified by using a nasal-cannula-pressure-transducer system is wider than that recognized as arousal phenomena by the 1992 AASM criteria. Scoring arousals with the 3-second rule may falsely minimize the apparent impact of abnormal breathing on sleep. The time may be right to update arousal recognition rules.