Does fractal quantitative endoscopic evaluation of the upper airway in patients with obstructive sleep apnea syndrome (OSAS) provide objectivity in the interpretation of these studies?
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September 2010Study Design: Diagnostic test assessment
Setting: Tertiary care private hospital sleep laboratory in Athens, Greece
Background: Fiberoptic nasopharyngolaryngeal endoscopic examination with Müller’s Maneuver (FNPMM) has been used over the years for the evaluation of patients with OSAS. Computer-assisted quantification of the results of this examination is desirable and is limited by the fact that most methods reported have been scale dependent. Slight variations in the position of the scope can affect these results. Fractal geometry creates a fractal dimension that is scale independent.
Synopsis: Researchers used fiberoptic endoscopic nasopharyngolaryngeal examination with and without Müller’s Maneuver to study 25 patients with OSAS and 17 chronic snorers (controls). These examinations were done in awake, non-sedated patients in the erect position. The images recorded in the retropalatal area were analyzed with fractal dimension calculator software. Fractal dimensions (FD) during quiet inspiration (FDI) and during Müller’s maneuver (FDM) were calculated. The degree of area collapsibility (FDAC) was calculated as (FDI – FDM)/FDI.
The FDI was no different in patients with OSAS than in controls. The differences in the FDM and FDAC between OSAS and control patients were significant (p<0.0001). A correlation was found between FDM and apnea-hypopnea index (AHI) (r=-0.481, p<0.01) and between FDAC and AHI (r=0.518, p<0.01).
In differentiating between a positive and negative FDAC, a receiver operating characteristic (ROC) curve was generated and a cutoff point of 0.095 was set. A positive test was defined as FDAC>0.095 and a negative result as FDAC>0.095. The calculated sensitivity was 92 percent, specificity was 82.4 percent and the positive predictive value was 88.5 percent with rather wide confidence intervals for each of these calculations.
Bottom line: Fractal analysis provides some measure of objectivity for the interpretation of endoscopic evaluation of patients with obstructive sleep apnea; however, the real population estimate for sensitivity and specificity needs further study.
Citation: Delides A, Viskos A. Fractal quantitative endoscopic evaluation of the upper airway in patients with obstructive sleep apnea syndrome. Otolaryngol Head Neck Surg. 2010;143(1):85-89.
—Reviewed by Pell Wardrop, MD