Does dynamic hyperinflation of the lung affect exercise ability and prognosis in patients with cystic fibrosis?
Why is this important?
In chronic chest diseases the diameter of the airways in the lung become smaller. This makes it harder to breathe out air during exercise, when breathing is increased. As a result, air becomes trapped in the lung and less “fresh air” can be breathed in. This is known as dynamic hyperinflation. In bronchitis / emphysema (COPD) dynamic hyperinflation is suggested to be the major limitation to exercise performance. However, little is known about how common it is and the impact of dynamic hyperinflation during exercise in cystic fibrosis.
What did you do?
We performed exercise testing on 109 adult patients with cystic fibrosis. The exercise test was performed on a bike and every minute the pedals became harder to turn, making the test more difficult. The patient exercised until they could not go on any longer. During each exercise test we measured how much air the patient breathed in and out. We also measured how short of breath they felt during the exercise. We then recorded the patient’s lung function and number of pulmonary exacerbations over the next two years.
What did you find?
We found that dynamic hyperinflation during exercise is very common in patients with cystic fibrosis. 58% of patients in our study experienced dynamic hyperinflation during exercise testing. We also found that patients with poorer lung function experienced greater dynamic hyperinflation. Patients with dynamic hyperinflation during exercise had reduced exercise performance and experienced greater shortness of breath at peak exercise.
What does this mean and reasons for caution?
The assessment of dynamic hyperinflation during exercise testing may help identify patients who could benefit from increased airway clearance management (physiotherapy, some inhaled medicines). Despite a relationship between poorer lung function and increased dynamic hyperinflation, our study showed that responding to exercise with dynamic hyperinflation didn’t predict future lung function and how many exacerbations a patient would have in the near future.
Studies investigating the use of medicines that increase the size of the airways (bronchodilators) and pulmonary rehabilitation to reduce dynamic hyperinflation during exercise in cystic fibrosis may help improve the patient’s ability to exercise.