Modulation of ventilatory mechanics during exercise in ventilation-limited populations

The aim of this thesis was to examine the impact of modifications to ventilatory constraint in populations who have reductions in expiratory flow and ventilatory limitations during exercise. The first study examined the effect of the self-contained breathing apparatus (SCBA) regulator on work of breathing (WOB) and lung volume changes in healthy subjects. The second study further examined the effect of the SCBA on the above outcomes, as well as on pulmonary function and respiratory muscle fatigue during stair-stepping (in healthy subjects). In addition, the effect of breathing heliox on the aforementioned variables was studied. The third thesis study examined the effect of heliox on ventilatory constraint, exercise tolerance, and leg muscle fatigue in patients with chronic obstructive pulmonary disease (COPD). The main results of the first study were that, compared with a low-resistance breathing valve (RV), the SCBA regulator increased inspiratory elastic (32%), expiratory resistive (59%), and total WOB ...