Carli Monica Peters’ PhD Thesis Defence

Title: “Characterizing the relationship between airway anatomy and physiological function: Implications of sex and swim training”

Supervisory Committee: Dr. Bill Sheel (Research supervisor), Dr Stephen C T Lam, Dr. Don McKenzie, Dr Donald Sin
University Examiners: Dr. Jean-Sebastien Blouin, Dr. Patricia Schulte
External Examiner: Dr. Louis Phillipe Boulet
Chair: Dr. John A Fleetham

Purpose: Two optical coherence tomography (OCT) imaging studies were performed to examine how sex differences in airway anatomy affect respiratory mechanics during exercise and how airway anatomy may be altered due to swim training.

Methods: Study #1 was designed as a proof-of-concept and is presented in Chapters 2 and 3. Chapter 2 presents respiratory mechanics during exercise, airway diameter, airway luminal area (Ai), index of airway size, and Weibel model area data measured from OCT images. Chapter 3 describes development of OCT software to measure Ai, wall area (WA), wall area percent (WA%), and wall thickness (WT). Reproducibility of OCT-derived airway measures are presented. In Study #2, men and women (19-30 years) performed exercise to exhaustion and OCT airway images were obtained. Of the 25 subjects, 7 (6 women, 1 man) were competitive swimmers. Chapter 4 investigated whether sex differences in Ai affect mechanical ventilatory constraint and resistive work of breathing (Wb) during exercise. Chapter 5 investigated whether swim training leads to airway remodeling detectable with OCT.

Conclusions: Imaging the airways of healthy men and women with OCT provides measures of Ai across airway generations that are related to respiratory mechanics during exercise (Chapter 2). The software developed had a smaller coefficient of variation than other techniques and can detect smaller differences in OCT-derived airway measures between groups in future airway remodeling studies (Chapter 3). Women tend to have smaller 4th-6th generation Ai measures relative to men. When ventilation is high, resistance to inspired flow is larger in women and is associated with two measures of airway size: index of airway size and Weibel area. This study suggests that innate sex differences exist in Ai which result in a greater resistive Wb in women compared to men during exercise (Chapter 4). Lastly, OCT can be used to detect changes in airway wall structure in male and female swimmers (Chapter 5). Results of this thesis extend our understanding of how airway size is an important determinant of respiratory mechanics during exercise and provides evidence that OCT can be utilized to study airway anatomy in healthy humans and airway remodeling in swimmers.