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UBC Theses and Dissertations

Phenotyping exercise limitation in chronic obstructive pulmonary disease to enhance exercise prescription Gelinas, Jinelle Crystal Marie


Introduction: Phenotyping patients with COPD according to their specific exercise limitation could be important to enhancing our understanding of the integrative physiological responses that limit exercise and how to optimize aerobic exercise prescription for pulmonary rehabilitation. Three studies were performed to identify distinct phenotypes of exercise limitation in COPD based on the ventilatory, cardiovascular and metabolic responses during incremental exercise. Differences in the physiological factors governing submaximal exercise tolerance in each phenotype were also assessed to accurately predict exercise tolerance at two novel indices of sustainable intensity; the highest workload that could be sustained for 30-minutes (critical power 30 [CP30]) and maximal dyspnea steady-state (MDSS). Methodology: Study 1: Ninety-five COPD patients performed an incremental cardiopulmonary exercise test to assess the physiological exercise responses associated with three different phenotypes of exercise limitation. Study 2: Thirty patients with a ventilatory, cardiovascular or combined (ventilatory and cardiovascular) phenotype performed three constant load exercise tests (CLTs) to determine the individual power-duration relationships and calculate critical power and CP30. An exercise session was performed at CP30. Study 3: In twenty-three patients with different exercise limitation phenotypes, the workload associate with MDSS was calculated from the individual dyspnea responses during the CLTs. A verification trial was performed at MDSS. Results and Conclusion: Study 1 demonstrated that patients with a ventilatory, cardiovascular or combined exercise limitation phenotype have distinct physiological responses to incremental exercise, that are not solely dependent on FEV₁. Study 2 found that patients with a cardiovascular or combined phenotype could sustain continuous exercise for 30-minutes at a higher workload and blood lactate concentration while maintaining a lower end-expiratory lung volume compared to the ventilatory phenotype. Study 3 confirmed that MDSS can be successfully predicted in COPD but found that MDSS was more applicable to the ventilatory phenotype, supporting that dyspnea may not be the primary limiting symptom in all patients with a cardiovascular or combined phenotype. These results demonstrate the importance of classifying patients with COPD according to their exercise limitation phenotype. These phenotypes may be clinically relevant and can be used to develop innovative methods to optimize exercise prescription for rehabilitative purposes.

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