Airway narrowing assessed by anatomical optical coherence tomography in vitro: dynamic airway wall morphology and function

1 Division of Clinical Sciences, Telethon Institute for Child Health Research; ; 2 Physiology, School of Biomedical, Biomolecular and Chemical Sciences, University of Western Australia; ; 3 Optical + Biomedical Engineering Laboratory, School of Electrical, Electronic and Computer Engineering, University of Western Australia; ; 4 School of Anatomy and Human Biology, University of Western Australia; ; 5 Department of Pulmonary Physiology, Sir Charles Gairdner Hospital; and ; 6 West Australian Sleep Disorders Research Institute, Sir Charles Gairdner Hospital, Perth, Australia Submitted 13 May 2009 ; accepted in final form 10 November 2009 Regulation of airway caliber by lung volume or bronchoconstrictor stimulation is dependent on physiological, structural, and mechanical events within the airway wall, including airway smooth muscle (ASM) contraction, deformation of the mucosa and cartilage, and tensioning of elastic matrices linking wall components. Despite close association between events in the airway wall and the resulting airway caliber, these have typically been studied separately: the former primarily using histological approaches, the latter with a range of imaging modalities. We describe a new optical technique, anatomical optical coherence tomography ( a OCT), which allows changes at the luminal surface (airway caliber) to be temporally related to corresponding dynamic movements within the airway wall. A fiber-optic a OCT probe was inserted into the lumen of isolated, liquid-filled porcine airways. It was used to image the response to ASM contraction induced by neural stimulation and to airway inflation and deflation. Comparisons with histology indicated that a OCT provided high-resolution images of the airway lumen including mucosal folds, the entire inner wall (mucosa and ASM), and partially the cartilaginous outer wall. Airway responses assessed by a OCT revealed several phenomena in "live" airways (i.e., not fixed) previously identified by histological investigations of fixed tissue, including a geometric relationship between ASM shortening and luminal narrowing, and sliding and bending of cartilage plates. It also provided direct evidence for distensibility of the epithelial membrane and anisotropic behavior of the airway wall. Findings suggest that a OCT can be used to relate changes in airway caliber to dynamic events in the wall of airways. bronchoconstriction; lumen narrowing; imaging Address for reprint requests and other correspondence: P