Non-invasive detection of respiratory effort-related arousals (RERAs) by anasal cannula/pressure transducer system

Study Objectives: The published AASM guidelines approve use of a nasal cann ula/pressure transducer to detect apneas/hypopneas, but require esophageal manometry for Respiratory Effort-Related Arousals (RERAs). However, esophag eal manometry may be poorly tolerated by many subjects. We have shown that the shape of the inspiratory flow signal from a nasal cannula identifies fl ow limitation and elevated upper-airway resistance. This study tests the hy pothesis that detection of flow limitation events using the nasal cannula p rovides a non-invasive means to identify RERAs. Design: N/A Setting: N/A Patients: 10 UARS/OSAS and 5 normal subjects Interventions: N/A Measurements and Results: All subjects underwent full NPSG. Two scorers ide ntified events from the nasal cannula signal as apneas, hypopneas, and flow limitation events. Two additional scorers identified events from esophagea l manometry. Arousals were scored in a separate pass. Interscorer reliabili ty and intersignal agreement were assessed both without and with regard to arousal. The total number of respiratory events identified by the two score rs of the nasal cannula was similar with an Intraclass Correlation (ICC) = 0.96, and was essentially identical to the agreement for the two scorers of esophageal manometry (ICC = 0.96). There was good agreement between the nu mber of events detected by the two techniques with a slight bias towards th e nasal cannula (4.5 events/hr). There was no statistically significant dif ference (bias 0.9/hr, 95%CI -0.3-2.0) between the number of nasal cannula f low limitation events terminated by arousal and manometry events terminated by arousal (RERAs). Conclusion: The nasal cannula/pressure transducer provides a non-invasive r eproducible detector of all events in sleep disordered breathing; in partic ular, it detects the same events as esophageal manometry (RERAs).