IMAGE-BASEDIN VIVOQUANTITATIVE ASSESSMENT OF HUMAN AIRWAY OPENING AND CONTRACTILITY BY FIBER OPTICAL NASOPHARYNGOSCOPY IN HEALTHY AND ASTHMATIC SUBJECTS

Linhong Deng

doi:10.1142/s1793545813500132

Abstract

Assessment of human airway lumen 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, quantitative 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 segmentation, 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 method to measure the opening/narrowing of the primary bronchus of either healthy or asthmatic subjects in response to histamine and/or albuterol treatment, which also provided an indicator of the airway contractility. Our results demonstrate that the image-based method accurately quantified the area change waveform of either the glottis or the bronchus as observed by using the optical nasopharygoscope. Importantly, the opening/narrowing of the airway lumen generally correlated with the airflow and resistance of the airways, and could differentiate the level of airway contractility between the healthy and asthmatic subjects. Thus, this quantitative assessment of airway opening may provide a useful tool to assist clinical diagnosis of airway dysfunctions and understanding the mechanisms of associated pathophysiologies.

Highlights

Bronchial airways in the lungs of a human body constantly open and narrow due to the action of various respiratory muscles as the person breaths
The results demonstrate that the image-based method could accurately measure the area of individual airway's open lumen, and detect abrupt changes of the glottis aperture during respiratory manoeuvre such as coughing and sound-making, or bronchus opening/narrowing in response to bronchoconstrictor/dilator exposure
From each image of the coin, the diameter of the coin was calculated by the number of pixels corresponding to the centerline of the imaged coin and the conversion factor for the distance (d)

Summary

Introduction

Bronchial airways in the lungs of a human body constantly open and narrow due to the action of various respiratory muscles as the person breaths. In airway disease such as asthma, the airways can narrow excessively when being irritated by certain irritants such as allergen, and restrict the air°ow through the airways and eventually cause breathing di±culty.[1] asthma is characterized by bronchial airways that narrow too much and too in response to exposure of a variety of contractile stimuli such as histamine. The opening/narrowing of the airways is the ultimate determinant of lung function, it has been di±cult to directly assess for pulmonary lung function test. Instead, it is usually measured by indirect methods such as spirometry[3] and forced oscillatory technique (FOT).[4]

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Discussion

Conclusion