Can sleep microstructure improve diagnosis of OSAS? Integrative information from CAP parameters

Giulia Milioli, Marcello Bosi, Andrea Grassi, Silvia Riccardi, Mario Giovanni Terzano, Pietro Cortelli, Venerino Poletti, Liborio Parrino


Purpose: The scoring of American Academy of Sleep Medicine (AASM) arousal is mandatory for the definition of respiratory event-related arousal (RERA). However there are other EEG activation phenomena, such as A phases of cyclic alternating pattern (CAP) which are associated with respiratory events in non rapid eye movements (NREM) sleep.

This study aims at quantifying the additional value of CAP for the definition of respiratory events and  sleep alterations in OSAS.

Methods: Analysis of polysomnographic recordings from nineteen OSAS patients was carried out. Scoring was focused on investigation of the cerebral response to flow limitation  (FL) events. For this purpose we used both  CAP rules and AASM arousal criteria.

Main Results: While no difference was demonstrated in the arousal index between mild and moderate-severe OSAS patients, CAP time showed a progressive enhancement from normal subjects (152,5±20,76) to mild (180,64±34,76) and moderate-severe (282,27±58,02) OSAS patients.

In NREM sleep, only 41.1% of FL events met the criteria for the definition of RERA, while, 75.5% of FL events ended with a CAP  A phase and most FL CAP  (69.1%) terminated with a CAP phase A3 subtype.

Conclusions: Our data indicate that the RERA scoring has a limited accuracy in the detection of  FL events. In NREM sleep, CAP rules provided more information than AASM arousal  for the definition of respiratory events and  sleep alterations in OSAS.


Obstructive Sleep Apnea Syndrome; Respiratory Event-Related Arousal; Flow Limitation Events; Cyclic Alternating Pattern; Arousal

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