Continuous Versus High Intensity Interval Exercise in Chronic Obstructive Pulmonary Disease

Chronic Obstructive Pulmonary Disease (COPD) is characterized by exercise intolerance, which is a prognostic factor of disease severity and mortality and is usually attributed to ventilatory limitations. Emerging evidence indicates that cerebral oxygenation may also be an important contributor, being impaired both at rest and during exercise in COPD patients. Furthermore, abnormal systemic hemodynamic responses and autonomic nervous system (ANS) dysfunction have been observed, which may further impair cerebral oxygenation. The type of exercise training applied in pulmonary rehabilitation (continuous versus interval) appears to influence these mechanisms differently, yet evidence on their impact on cerebral oxygenation in COPD remains scarce. The aim of this study is to compare, for the first time, the acute changes in cerebral oxygenation, CPET parameters, systemic hemodynamic responses, and autonomic responses in patients with COPD who undergo a high-intensity interval aerobic exercise (HIIE) protocol versus a moderate-intensity continuous aerobic exercise (MICE) protocol. These findings will have important clinical implications, as they may guide the choice of the most appropriate exercise modality in pulmonary rehabilitation.

Inclusion Criteria: * Clinical diagnosis of COPD based on smoking history (pack/years) or exposure to other risk factors and post bronchodilation forced expiratory volume (FEV1) to forced vital capacity (FVC) ratio \60 mmHg, according to recent (within a week) arterial blood gases assessment * Disease being stable and treated optimal, based on current GOLD guidelines. * Provision of informed written signed consent prior to study entry Exclusion Criteria: * Recent respiratory infection or exacerbation (as indicated by deterioration of respiratory symptoms, hospital admission and/or change in medication within the previous month), within the past 3 months * Changes in COPD medication with the past month * History of asthma and/or reversible airway obstruction (post bronchodilation FEV1/ FVC \>0.7) * Pulmonary hypertension * Congestive heart failure (Left Ventricle Ejection Fraction \ 200 mm Hg systolic, \> 120 mm Hg diastolic blood pressure), orthopedic impairment that compromises exercise performance.