System Automatically Monitors Apnea-Hypopnea Index

Does a new, full-night automatic system for the detection of snoring provide information on the acoustic characteristics of snores that differ in relation to the apnea-hypopnea index (AHI)?

Background: The probability of obstructive sleep apnea syndrome (OSAS) is 3.2 times higher in snorers than in non-snorers. Although several studies have shown differences in acoustic snoring characteristics between patients with OSAS and simple snorers, usually only a few manually isolated snores have been analyzed, with an emphasis on postapneic snores in OSAS patients.

Although automatic snore detection systems may offer more objective measurement over a longer period of sleep, they have not been applied to full-night analysis, mainly because of problems of recording noise from ambient sounds.

Study Design: Thirty-seven nonsmoking snorers were monitored for six hours.

Setting: Sleep Disorders Laboratory, University Hospital Germans Trias i Pujol, Badalona, Spain

Synopsis: Full-night polysomnography was performed in patients classified as either simple snorers, snorers with an AHI <5, snorers with an AHI ≥5 and <15 and snorers with an AHI ≥15. Snoring sounds were recorded for six hours using a unidirectional electric condenser microphone coupled to the skin through a conic air cavity. The microphone was placed over the trachea at the level of the cricoid cartilage using an elastic band.

The snoring episodes were identified by an automatic detector and analyzer developed by the Spanish research group. Snore number, average intensity and power spectral density parameters were computed for each subject and compared among AHI groups. The system was able to identify and isolate snores from other noises, relate each snore to body position and provide statistical results for the entire night of study.

Bottom Line: The automatic analyzer, which takes into consideration all snoring episodes detected throughout the night, showed that snoring intensity and the snore frequency spectrum seem to be significantly different in snorers with different AHIs. This could be a tool for automatic screening for OSAS, but further validation is needed.

Citation: Fiz JA, Jané R, Solà-Soler J, et al. Continuous analysis and monitoring of snores and their relationship to the apnea-hypopnea index. Laryngoscope. 2010;120(4):853-861.

—Reviewed by Sue Pondrom