Evaluation of the performance of using mean absolute amplitude analysis of thoracic and abdominal signals for immediate indication of sleep apnoea events.

AIM: To evaluate the sensitivity of mean absolute amplitudes of the thoracic and the abdominal signals as a prompt indicator of the occurrence of sleep apnoea events. BACKGROUND: To provide symptomatic management of sleep apnoea, a reliable method of detecting sleep apnoea is essential to ensure that the intervention can be applied only when needed. It is also crucial to identify the threshold for the trigger of an intervention using a deployed sensor. DESIGN: Twenty-six subjects aged between 18-65 years who were diagnosed with obstructive or central sleep apnoea underwent an overnight sleep study. METHOD: Signals of nasal and oral airflow, thoracic and abdominal efforts and pulse oximetry level were recorded using a polysomnography device. RESULTS: With a 95% CI, the overall area under the receiver operating characteristic of the thoracic signal, the abdominal signal and the combination of the thoracic and the abdominal signals were 84.56, 87.48 and 90.91%, respectively. Using -20, -25 and -30% as a cut-off point, the sensitivity values of thoracic signal, abdominal signal and combination of the thoracic and the abdominal signals ranged from 70.29-86.25% and the specificity values ranged from 74.82 to 90.09%. CONCLUSIONS: Using mean absolute amplitude analysis, the results of this study showed that combination of the thoracic and the abdominal signals achieved the best overall and individual performances compared with thoracic signal and abdominal signal. Overall, thoracic signal, abdominal signal and combination of the thoracic and the abdominal signals have a good performance with an receiver operating characteristic value higher than 80%. The thoracic and the abdominal signals were good parameters for the identification of the occurrence of sleep apnoea, being as quick as the nasal airflow signal. RELEVANCE TO CLINICAL PRACTICE: These results suggested that sleep apnoea events could be identified through constant monitoring of the patient's thoracic and abdominal signals. Knowledge of these signals could help nurses to manage sleep apnoea in patients.

Using pulse oximetry level to indicate the occurrence of sleep apnoea events.

The aim of this research study was to identify an alternative to nasal airflow as a prompt and unobtrusive indicator of sleep apnoea events. This study attempted to select pulse oximetry (SpO2) level as an alternative parameter to indicate the occurrence of sleep apnoea. Ten subjects diagnosed with sleep apnoea underwent an overnight polysomnography (PSG) study. Signals of nasal flow and SpO2 level were recorded. Time differences were compared between the "onset of nasal airflow cessation" (ONAC) and the "onset of three percent oxygen desaturation from the baseline" (OOD) during sleep apnoea events. The results of this study showed that measuring SpO2 level was more comfortable for patients, but that there was around a twenty second delay after the onset of the cessation of nasal airflow. It was concluded that the measurement of SpO2 level was useful for screening suspected sleep apnoea patients, but it might not be able to provide "online detection" of the occurrence of sleep apnoea events.