Influence of Morphometry and Airway Patency on Response to Inhaled Methacholine

• Published in: Aerosol science and technology Vol. 47; no. 5; pp. 574 - 579
• Main Authors: Oldham, Michael J., Clinkenbeard, Rodney E., Moss, Owen R.
• Format: Journal Article
• Language: English
• Published: Colchester Taylor & Francis Group 01.05.2013; Taylor & Francis; Taylor & Francis Ltd
• Subjects: Aerosols; Airways; Chemical compounds; Chemistry; Circumferences; Colloidal state and disperse state; Computed tomography; Copyrights; Deposition; Effectiveness; Exact sciences and technology; General and physical chemistry; Inclination; Lungs; Respiration; Surface area; Tomography; Volume; Aerosols; Morphometry
• ISSN: 0278-6826; 1521-7388
• DOI: 10.1080/02786826.2013.773580

For some individuals, the degree of response to inhaled allergens or the efficacy of inhaled pharmaceuticals may be influenced by their lung morphometry. Fourteen healthy, nonsmoking subjects received a high-resolution computed tomography (HRCT) scan just prior to performance of a methacholine challenge. Following the methacholine challenge, subjects were given a bronchodilator and received a second HRCT scan. HRCT scans were reconstructed and measurements of airway length, diameter, branch angle, and inclination to gravity were made for the first six tracheobronchial airway generations. The average length (L) and diameter (d) of each airway generation were used to calculate the average airway generation circumference (πd) and surface area (πLd). The product of airway circumference and surface area was incorporated into an airway volume factor (Ld 2 ), inversely proportional to the fractional decrease in airway circumference due to deposited methacholine. Ld 2 was used to compare methacholine challenge responders with nonresponders. Six subjects did not respond to the methacholine challenge, while eight subjects responded with a greater than 3% decrease in their forced expiratory volume in 1 s. Compared with the nonresponders, these responders had smaller airway volume factors (from about the same in airway generation 1 to 36% smaller in airway generation 5). They also entered the study with less airway patency (the largest difference was in airway generation 5; 28% compared with 13% in the nonresponsive). Comparison of first and second (after bronchodilation) CT scans indicated that all subjects started the study with each airway generation having a unique degree of airway patency (2-33%). Copyright 2013 American Association for Aerosol Research