Detection of sleep apnea with the forced oscillation technique compared tothree standard polysomnographic signals

Background: The forced oscillation technique (FOT) allows analysis of the u pper airway impedance and, hence, detection of obstructive sleep apnea. Obj ective: To evaluate FOT with respect to sensitivity and to specificity in o nline detection of sleep-disordered breathing patterns and to compare algor ithmic onset detection time with manual onset time markers of staff physici ans. Methods: We compared the absolute value ZI of the impedance with three routinely obtained polysomnographic signals - nasal airflow (V) over dot ( nasal), thoracic excursion Thox and esophageal pressure P-es - by retrospec tive analysis of the diagnostic polysomnograms of 51 patients. For each sig nal we evaluated algorithms for online detection of respiratory events. For each out of five apnea classes, 50 respiratory events marked by staff phys icians were drawn randomly from the 51 polysomnograms to optimize the onlin e detection algorithms (learning set). The algorithm analyzes relative chan ges of signal baseline and amplitude. Again 50 respiratory events were draw n randomly for each apnea class to examine to what extent it is possible to detect event onsets with the algorithms (test set). Results: The sensitivi ty of the signals varied between 56 and 94% and was on average 74%, The spe cificity was 96 +/- 1.5% on average. The onset was detected 4-6 s after the initially evaluated onset of the staff physicians, Conclusion: We conclude that nasal airflow and FOT are equivalent sensitive measurands for detecti on of respiratory events, Copyright (C) 2000 S. Karger AG, Basel.