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.