ABSTRACT
Exercise testing is an important tool in quantifying the functional capacity of a patient with cystic brosis (CF). Assessment of the exercise tolerance of patients with CF provides important information about disease severity1 and the overall well-being of the patient.2 Exercise testing can not only help ascertain if exercise capacity is reduced but also determine the etiology of the reduced exercise capacity. During the course of an exercise test, the pulmonary system is placed under stress and subtle decits in lung function may be identied that were not apparent during conventional static pulmonary function testing. Although spirometry, lung volumes, and lung clearance index have traditionally been useful in the diagnosis and guidance of management for patients with lung disease, these tests measure only resting lung function and do not reliably predict functional and exercise capacity.3 Peak aerobic capacity measured during an exercise test may also predict structural lung damage as seen on high-resolution computed tomography of the chest.4 Given these observations, exercise testing is an important diagnostic tool in the assessment of the cardiorespiratory status of the subject with CF. Subjects with CF may have reduced exercise capacity due to primary respiratory limitation and be negatively associated with chronic Pseudomonas aeruginosa infection but independent of static pulmonary function.5 During a formal exercise test, subjects with a respiratory limitation will be identied by a reduced breathing reserve and even hypoxia at peak exercise (Table 36.1). Subjects with CF may have reduced exercise capacity due to secondary causes such as deconditioning.5 During a formal laboratory-based exercise test, subjects who are deconditioned will be identied by a reduced peak aerobic capacity despite a normal breathing reserve and normal cardiac function (Table 36.2). A negative feedback loop may be created where reduced habitual activity leads to further deconditioning, prompting a further reduction in exercise capacity. Formal exercise tests
will help to determine if the etiology of reduced exercise capacity in subjects with CF is due to cardiorespiratory limitation or deconditioning.
