Fiber optic endoscopic optical coherence tomography (OCT) to assess human airways: The relationship between anatomy and physiological function during dynamic exercise

Airway luminal area (A(i)) influences respiratory mechanics during dynamic exercise; however, previous studies have investigated the relationship between airway anatomy and physiological function in different groups of individuals. The purpose of this study was to determine the effect of A(i) on respiratory mechanics by making in vivo measures of airway dimensions and work of breathing (Wb) in the same individuals. Healthy participants (3F/2M; 23-45 years) completed a cycle exercise test to exhaustion. During exercise, Wb was assessed using an esophageal balloon catheter, while simultaneously assessing minute ventilation (V-E). On a separate day, subjects underwent a bronchoscopy procedure to capture optical coherence tomography (OCT) measures of three airways in the right lung. Each participant's Wb-V-E data were fit to a non-linear regression equation (Wb = aV(E)(3) + bV(E)(2)) that partitions Wb into its turbulent resistive (a) and viscoelastic (b) components. Measures of A(i) and luminal diameter were made for the 4th-6th airway generations. A composite index of airway size was calculated as the sum of the A(i) for each generation and the total area of the 4th-6th generation was calculated based on Weibel's model. Constant a was significantly correlated to the Weibel model total airway area (r = -0.94, p = 0.017) and index of airway size (r = -0.929, p = 0.023), whereas constant b was not associated with either measure (both p > 0.05). We found that individuals who had the smallest A(i) had the highest resistive Wb and our findings provide the basis for further study of the relationship between airway size and respiratory mechanics during exercise.

Automated summary

This study investigated the impact of airway luminal area (Ai) on respiratory mechanics during dynamic exercise. It found that individuals with smaller Ai experienced higher resistive work of breathing, indicating a correlation between airway size and breathing efficiency during exercise. These findings lay the foundation for further research on the relationship between airway size and respiratory mechanics during physical activity.