In Patients With Obstructive Airway Disease, Investigate the Effects of Different Breathing Strategies and Pedaling Rates on the Physiological Response to Bicycle Exercise

Obstructive airway disease is defined as forced expiratory volume in one second (FEV1) / forced vital capacity (FVC) <0.7. It includes chronic obstructive pulmonary disease (COPD), asthma, lymphangioleiomyomatosis (LAM) and bronchiolitis obliterans syndrome. Pulmonary rehabilitation is widely utilized in patients with obstructive airway disease. Comprehensive intervention based on a thorough patient assessment followed by patient-tailored therapies that include, but are not limited to, exercise training, education, and behavior change, designed to improve the physical and psychological condition of people. The exercise prescription for pulmonary rehabilitation is often determined based on exercise capacity. The exercise capacity includes peaked VO2 (oxygen consumption), peaked work rate, and anaerobic threshold. They are all measured in cardiopulmonary exercise test (CPET). However, patients often struggle to achieve training goals due to severe dyspnea. Dynamic hyperinflation is a common cause of shortness of breath on exertion in obstructive airway disease.

Generally, end-expiratory lung volume (EELV) is relative constant during exercise. Inspiratory capacity (IC) is increasing during exercise. The IC maneuver is used to monitor exercise-induced dynamic hyperinflation. Dynamic hyperinflation caused by air trapping, which increases residual air volume, is a common cause of shortness of breath on exertion in obstructive lung disease. There are many diagnostic criteria, including a decrease in dynamic IC of >140mL, a decrease of ≥5% in IC during maximal exercise, or a decrease of ≥10% in IC during maximal exercise. In a prospective observational study, dynamic hyperinflation occurred at a higher prevalence (55%) in patients with LAM. Dynamic hyperinflation was associated with a reduction in FEV1 and higher dyspnea intensity at exercise cessation (R = -0.53, P-value < 0.001). COPD patients develop dynamic hyperinflation during symptom-limited incremental work exercise with cycle ergometer. The increase in EELV seems to be the best predictor of dyspnea.

The pedaling rate is typically set at 60 revolutions per minute in National Taiwan University Hospital. The average respiratory rate for a total of 31 patients is 29 breaths per minute. 2019 European respiratory society suggested that maintaining over a wide range of pedaling rates (40-70 revolutions per minute) in CPET. The evidence of the optimal pedaling rate during exercise obstructive airway disease is limited. The current consensus remains inconclusive on whether a lower pedaling rate will result in a reduction of breathing speed, subsequently improving dynamic hyperinflation, and ultimately leading to an improvement in exercise capacity. This prospective observational study, employing a crossover design, aims to investigate the impact of pedaling rate during exercise tests on dynamic hyperinflation and exercise capacity in individuals with obstructive airway disease.