IMAGE-BASED IN VIVO QUANTITATIVE ASSESSMENT OF HUMAN AIRWAY OPENING AND CONTR ACTILITY BY FIBER OPTICAL NA SOPH A RYNGOSCOPY IN HEALTHY AND ASTHMATIC SUBJECTS

Assessment of human airway humen opening is important in diagnosing and understanding the mechanisms of airway dysfunctions such as the excessive airway narrowing in asthma and chronic obstructive pulmonary disease(COPD).Although there are indirect methods to evaluate the airway calibre,direct in vivo measurement of the airway calibre has not been commonly available.With recent advent of the flexible fiber optical nasopharyngoscope with video recording it has become possible to directly visualize the passages of upper and lower airways.However,quan-titative analysis of the recorded video images has been technically challenging.Here,we describe an automatic image processing and analysis method that allows for batch analysis of the images recorded during the endoscopic procedure,thus facilitates image-based quantification of the airway opening.Video images of the airway lumen of volunteer subject were acquired using a fiber optical nasopharyngoscope,and subsequently processed using Gaussian smoothing filter,threshold segment ation,differentiation,and Canny image edge detection,respectively.Thus the area of the open airway lumen was identified and computed using.a predetermined converter of the image scale to true dimension of the imaged object.With this method we measured the opening/narrowing of the glottis during tidal breathing with or without making“Hee"sound or cough.We also used this met hod to measure the opening/narrowing of the primary bronchus of either healthy or asthmatic subjects in response to hist amine and/or albuterol treatment,which also provided an indicator of the airway contractility.Our results demonstrate that the image-based method accurately quantifed the area change waveform of either the glottis or the bronchus as observed by using the optical nasopharygoscope.Importantly,the opening/nar-rowing of the airway lumen generally correlated with the airAow and resistance of the airways,and could differentiate the level of airway contr actility between the healthy and asthmatic subjects.Thus,this quant itative assessment of airway opening may provide a useful tool to ssist clinical diagnosis of airway dysfunctions and understanding the mechanisms of associated pathophysiologies.