Title: Dynamic Hyperinflation and Exertional Dyspnea in COPD Patients Pre- and Post-Lung Transplant
Thesis Supervisor: Dr. A. William Sheel
Committee members: Dr. Jordan Guenette, Dr. Donald McKenzie, Dr. Robert Levy
Defence Chair: Dr Daniel Gamu
Abstract: The pathophysiological hallmark of Chronic Obstructive Pulmonary Disease (COPD) is dynamic hyperinflation and progressive impairment of ventilatory mechanics with exercise and contributes to intolerable perceptions of dyspnea. Patients with the most deteriorated health status may be candidates for lung transplantation. While lung mechanics generally improve post-transplant, affective and sensory perceptions of exertional dyspnea vary. PURPOSE: The purpose of this thesis was to compare ratings of dyspnea with lung and chest wall mechanics in COPD patients pre- and post-bilateral lung transplantation during incremental exercise to exhaustion and steady-state exercise breathing a helium-hyperoxia gas mixture. METHODS: Two older males (n=2) and one older female (n=1) between the ages of 60-70 waitlisted for transplantation participated in this study. All three subjects were GOLD stage IV COPD, defined as “very severe” with an FEV1 < 30% predicted. Both male participants completed a pre-transplant visit and returned to the lab for a second visit 28-30 weeks post-bilateral lung transplantation. The female participant is still waitlisted and only completed the first experimental visit. The first visit included pulmonary function testing, incremental exercise to exhaustion, and a 5-minute steady-state exercise bout at 50% peak workload breathing a helium-hyperoxia mixture. Optoelectronic plethysmography (OEP) was used to capture compartmental changes in chest wall mechanics during exercise. The second visit mimicked day one exactly. RESULTS: Results are presented as individual case reports. Case 1: between conditions, there is an increase in rib cage contribution as well as an increase in IC and a reduction in EELV. Perception of dyspnea unpleasantness was reduced between conditions. Case 2: post-transplant, dynamic hyperinflation was not identified with the plateau in end-expiratory lung volume (EELV) and increase in inspiratory capacity (IC) during incremental exercise. Dyspnea perceptions were unchanged between conditions post-transplant. Case 3: post-transplant, during incremental exercise and steady-state exercise, EELV gradually increased accompanied with a reduction in IC. Affective responses to dyspnea are unchanged pre- to post-transplant as well as between conditions. CONCLUSION: The present study details the idiosyncratic compensatory mechanisms, respiratory kinematic changes, and subjective responses to dyspnea during exercise in patients waitlisted for and transplanted for COPD.