2010 OPEN FORUM Abstracts
SCREENING OF OBSTRUCTIVE SLEEP APNEA IN AWAKE SUBJECTS.
Paulo J. Caseiro1,2, Rui Fonseca-Pinto3,2, Alexandre R. Andrade2; 1Cardiopneumology, Superior School of Health and Technology of Coimbra, Coimbra, Portugal; 2Biophysics and Biomedical Engineering, Faculty of Sciences, University of Lisbon., Lisbon, Portugal; 3Mathematics, Polytechnic Institute of Leiria, Leiria, Portugal
Background: Polysomnographic signals are usually recorded from patients exhibiting symptoms related to sleep disorders such as Obstructive Sleep Apnea (OSA). OSA has a relatively high prevalence, occurring in 5% of the adult population, but the majority of these cases remain undiagnosed. The usual procedure entails an overnight recording several hours long. Our goal is to present a fast screening method to identify OSA during the awake period, in order to simplify the diagnosis and reduce costs and waiting time for diagnosis and treatment. Methods: This study presents a methodology to help with the screening of OSA using a 5-minute oronasal airway pressure signal emanating from a polysomnographic recording during the awake period, eschewing the need for an overnight recording. The HilbertHuang Transform (a recent time-frequency analysis method) was used to extract intrinsic oscillatory modes from the signals. The frequency distribution of both the first mode and the second mode and their sum was shown to differ significantly between non OSA subjects and OSA patients. Results: The clinical sample consisted of a total of 41 subjects, 20 non OSA individuals and 21 individuals with OSA. An index measure based on the distribution frequencies of the oscillatory modes yielded a sensitivity of 81.0% (for 95% specificity) for the detection of OSA. Two other index measures based on the relation between the area and the maximum of the 1st and 2nd halves of the frequency histogram both yielded a sensitivity of 76.2% (for 95% specificity). The data was mostly composed of severe OSA patients (12), however it also included 4 patients with mild OSA and 4 patients with moderate OSA. Efficiency of detection was not dependent on disease severity. No significant correlations were found between age, sex and the best correlated indexes. Conclusions: Although further studies will be needed to test the reproducibility of these results, the proposed measures seem to provide a fast method to screen OSA patients, in awake period, thus reducing the costs and the waiting time for diagnosis. The physiological mechanisms that underlie the differences between OSA patients and non OSA subjects highlighted in the present study can be due to differences in upper airway anatomy and could be associated with an increase in airway resistance that is a feature of the disease. Sponsored Research - None