Exercise Capacity in Patients With Cystic Fibrosis vs. Non-cystic Fibrosis Bronchiectasis

Introduction:

Bronchiectasis is a chronic lung disease in which the underlying condition causes permanent damage to the conducting airways. Bronchiectasis is associated with considerable morbidity and poor quality of life. Patients with respiratory diseases show reduced daily functional physical ability (habitual physical activity). Reasons may be due to pulmonary limitation (in severe diseases), peripheral muscular changes or due to secondary factors such as deconditioning or overly cautious caregivers restraining patient's physical activity. Deconditioning due to reduced habitual activity leads to further reduction in exercise capacity increasing the severity of their condition. While CF is the most common cause of bronchiectasis in childhood, non-CF bronchiectasis is associated with a wide variety of disorders. The etiology for non-CF bronchiectasis include: primary ciliary dyskinesia (PCD), post infectious, aspiration, primary and secondary immunodeficiency, congenital malformation, and others. Children with CF tend to perform poorly at a moderate-intensity physical activity compared to non-CF children of same age. In the last several decades, exercise has been encouraged in CF patients to improve sputum expectoration and lung function. There is evidence that exercise in addition to respiratory physical therapy, improves lung function and reduces the rate of lung function deterioration, compared with respiratory physical therapy alone. Another study showed that an aerobic training program in children contributed to significantly higher peak aerobic capacity, activity level, and subjective quality of life than children who received a resistance training program. In conclusion, higher levels of physical activity in addition to good muscular and pulmonary functions are associated with a high aerobic capacity in cystic fibrosis.

Although the exact physiologic mechanism by which exercise improves clearing of airways secretions in CF is not entirely clear, possible explanations are attributed to increased airflow and mechanical clearing of mucus. Following physical exertion there is an increase in tidal volume and respiratory flow to meet tissue demands. Increasing peak expiratory flow (PEF) to peak inspiratory flow (PIF) ratio may help drive the mucus past the oropharynx to clear more easily. Additional benefits of exercise in patients with CF are similar to the healthy population and includes overall improvement in cardiovascular health, musculoskeletal health, and quality of life. Maximal oxygen consumption (VO2peak) serves as a strong prognosis marker associated with an approximate 8-year survival in CF patients and correlates with the number of hospital admissions due to respiratory exacerbations. There is paucity of data regarding exercise capacity in non-CF bronchiectasis.

3. Research Aim: To evaluate and compare exercise capacity in CF and non-CF bronchiectasis patients.

4. Significance: There is limited data regarding exercise capability in non-CF bronchiectasis. CPET is increasingly gaining importance in clinical medicine. The test helps the clinician objectively evaluate the physiological functions, may help predict the outcome and mortality in different clinical circumstances and may serve as a basis for creating individualized exercise prescription within the context and limitation of the disease.