Published ahead of print on October 20, 2005, doi:10.1164/rccm.200507-1148OC Am. J. Respir. Crit. Care Med., Volume 173, Number 2, January 2006, 226-233 A more recent version of this article appeared on January 15, 2006
Submitted on July 26, 2005 Quantitative Upper Airway Imaging with Anatomical Optical Coherence TomographyJulian J Armstrong1*,1 Optical+Biomedical Engineering Laboratory, University of Western Australia, School of Electrical, Electronic and Computer Engeneering, Crawley, WA, Australia, 2 Department of Pulmonary Physiology, Sir Charles Gairdner Hospital, West Australian Sleep Disorders Research Institute, Nedlands, WA, Australia, 3 Department of Pulmonary Physiology, Sir Charles Gairdner Hospital, West Australian Sleep Disorders Research Institute, Nedlands, WA, Australia; University of Western Australia, School of Anatomy and Human Biology, Crawley, WA, Australia * To whom correspondence should be addressed. E-mail: julian-a{at}ee.uwa.edu.au.
Background: Measurements of upper airway size and shape are important in investigating the pathophysiology of obstructive sleep apnea (OSA) and in devising, applying and determining the effectiveness of treatment modalities. We describe an endoscopic optical technique (anatomical optical coherence tomography, aOCT) that provides quantitative real-time imaging of the internal anatomy of the human upper airway. Methods: Validation studies were performed by comparing aOCT- and CT-derived measurements of cross-sectional area (CSA) in: (i) conduits in a wax phantom; and (ii) the velo-, oro- and hypopharynx during wakefulness in 5 volunteers. aOCT scanning was performed during sleep in one subject with OSA. Results: aOCT generated images of pharyngeal shape, and measurements of CSA and internal dimensions that were comparable to radiographic CT images. The mean difference between aOCT- and CT-derived measurements of CSA in (i) the wax phantom was 2.1 mm2 with limits of agreement (2SD) from -13.2 to 17.4 mm2 and intra-class correlation coefficient of 0.99 (p<0.001), and (ii) the pharyngeal airway was 14.1 mm2 with limits of agreement from -43.7 to 57.8 mm2 and intra-class correlation coefficient of 0.89 (p<0.001). aOCT generated quantitative images of changes in upper airway size and shape before, during and after an apneic event in an individual with OSA. Conclusions: aOCT generates quantitative, real-time measurements of upper airway size and shape with minimal invasiveness, allowing study over lengthy periods during both sleep and wakefulness. These features should make it useful for study of upper airway behavior to investigate OSA pathophysiology and aid clinical management. Key words: upper airway anatomy, optical coherence tomography, sleep apnea
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