Exercise testing in cystic fibrosis: Why (and how)?

Abstract

Exercise in CF is associated with improvements in physical and psychological wellbeing. Exercise testing may have an important role in assessing exercise ability and tailoring patient-specific exercise programmes, and exercise-related outcome measures may prove very useful for research intervention studies. Exercise capacity is of known prognostic importance in both adults and children with CF, and the degree of mutual exclusivity that separates fitness from lung function suggests that exercise testing is a vital diagnostic tool for identifying patients at risk of decline. The question of why exercise test in CF seems self-evident, but how to test is less clear-cut. A variety of field tests exist that are low-cost tests requiring minimal equipment. These act as surrogate tests of exercise capacity and can be submaximal in some cases. The gold standard test is CPET, a maximal test that provides precise exercise data. CPET is, however costly, needs highly specialized equipment and also requires technical expertise to supervise and interpret the test. The choice of test depends upon the question one is trying to answer. The chosen exercise test should be one that allows maximal exercise to be achieved, and may also be influenced by equipment and expertise that is held locally. Research outcomes may need the precision of CPET, whereas if one is looking for year on year within patient comparison, selection of a field test or incremental treadmill or ergometer test without metabolic measures may be appropriate. A desire for precise and reproducible data on exercise capacity in CF, however, may demand CPET as the test of choice of the future.