Cameron Gee’s PhD Thesis Defence

Title:Heart-lung interactions following spinal cord injury”

Supervisory Committee:  Dr. Christopher West (Research Supervisor), Dr. Bill Sheel, Dr. Neil Eves
University Examiners: Dr. Tania Lam, Dr. Glen Foster
External Examiner: Dr. Dennis Jensen (McGill University)
Chair: Dr. Thomas Oxland

Abstract: Cervical spinal cord injury (C-SCI) is a devastating condition that leads to significant

impairments in both the cardiovascular and respiratory response to aerobic exercise. As

the heart and lungs share space within the thoracic cavity it follows that changes in one

system will affect the other. Therefore, the purpose of this thesis was to examine heartlung

interactions in C-SCI and to utilize this knowledge to enhance exercise capacity in

athletes with C-SCI.

The aims of this thesis were to (1) compare the cardiorespiratory response to maximal

and sub-maximal exercise following C-SCI to able-bodied individuals, with a particular

focus on operating lung volumes (Study #1, Chapter 3); (2) to examine the effects of

respiratory loading on lung volumes and left-ventricular function during head-up tilt

(Study #2, Chapter 4); and (3) to assess the effects of a combined inspiratory and

expiratory respiratory muscle training (i.e. RMT) intervention in elite athletes with C-SCI

(Study 3, Chapter 5).

Laboratory-based incremental arm ergometry testing demonstrated that C-SCI is

associated with a limited exercise capacity compared to able-bodied individuals along

with an altered respiratory pattern that is characterized by dynamic hyperinflation and

reduced VT. By manipulating inspiratory and expiratory in individuals with C-SCI, it was

demonstrated that expiratory loading elicited dynamic hyperinflation that was associated

with impaired left-ventricular filling, likely due to direct ventricular interaction and/or

mediastinal constraint. Finally, a six-week RMT intervention in elite athletes with C-SCI

was found to significantly enhance respiratory muscle strength and measures of

pulmonary function and prevent dynamic hyperinflation during exercise. These changes

in pulmonary function were accompanied by enhanced exercise capacity during an

incremental arm ergometry test and were partly ameliorated following six-weeks of

wash-out (i.e., no RMT).

This thesis demonstrates that dynamic hyperinflation in individuals with C-SCI limits left

ventricular filling and is associated with impaired exercise capacity. RMT, improved

respiratory muscle strength and prevented dynamic hyperinflation in individuals with CSCI

that was associated with enhanced exercise capacity.