Airway Wall Structure Assessed by Endobronchial Ultrasonography and Bronchial Hyperresponsiveness in Patients With Asthma

Abstract

The purpose of this study was to evaluate the relationship between the wall structure assessed by using endobronchial ultrasonography (EBUS) and bronchial hyperresponsiveness in patients with asthma. Twenty-four patients with stable asthma and 11 individuals without asthma were studied. EBUS was performed with a radial 20-MHz ultrasonic probe inserted into the intermediate bronchus undergoing flexible bronchoscopy to assess the airway wall structure. The percentage of airway wall thickness {WT%; defined as [(ideal outer diameter-ideal luminal diameter)/ideal outer diameter]×100} was determined by EBUS. We measured bronchial hyperresponsiveness to methacholine [the provocative concentration of methacholine causing a decrease of 20% or more in forced expiratory volume in 1 s (PC20)]. Percentage wall thickness measured by EBUS was significantly greater in patients with asthma than that in subjects without asthma (P<0.01). The evaluation of the laminar structure using EBUS indicated that the thickness of the second layer in patients with asthma was greater than that in subjects without asthma (P<0.05). PC20 was negatively correlated with the thickness of the second layer (r=0.52, P<0.01) but was not significantly correlated with other layers in patients with asthma. The evaluation of the bronchial mural structure using EBUS might be advantageous for assessing the relationship between airway wall remodeling and bronchial hyperresponsiveness.