Chronic Obstructive Pulmonary Disease (COPD) is a leading cause of morbidity and mortality worldwide. The vast COPD symptomatology and features are usually accompanied by weakness and deconditioning of the respiratory muscles, with particular impairment described in strength and endurance of the musculature involved with inspiration. Several local and systemic mechanisms contribute to an imbalance between the load placed on the inspiratory muscle pump and its capacity in COPD. Inspiratory muscle dysfunction is independently associated with dyspnea, poorer functional capacity and decreased health-related quality of life in this population.
This dissertation aimed at evaluating a novel inspiratory muscle assessment and training method which had not been previously examined in COPD called the Test of Incremental Respiratory Endurance (TIRE). Besides the traditionally studied measure of maximal inspiratory pressure (MIP), the TIRE provides values of sustained maximal inspiratory pressure (SMIP) and inspiratory duration (ID) which are obtained from residual volume to total lung capacity, reflecting inspiratory muscle endurance. Three aims were proposed: 1. to examine the psychometric properties of MIP, SMIP and ID in subjects with COPD; 2. to investigate the association between the TIRE measures and COPD-related clinical outcomes; and 3. to explore the feasibility and efficacy of the TIRE as a home-based inspiratory muscle training method.
We hypothesized that a greater clinical, functional and prognostic value would exist in the assessment and training of the capacity of the inspiratory muscles to maintain a particular force over time when compared to the evaluation and buildup of inspiratory muscle strength alone in COPD.