Exercise Limitation in IPF Patients: A Randomized Trial of Pulmonary Rehabilitation

Patients with idiopathic pulmonary fibrosis (IPF) have severely limited exercise capacity due to dyspnea, hypoxemia, and abnormal lung mechanics. This pilot study was designed to determine whether pulmonary rehabilitation were efficacious in improving the 6-min walk test (6-MWT) distance, exercise oxygen uptake, respiratory muscle strength [maximum inspiratory pressure (MIP)], and dyspnea in patients with IPF. Underlying physiological mechanisms and effects of the intervention were investigated.

Subjects were randomly assigned to a 3-month pulmonary rehabilitation program (n = 11) or to a control group (n = 10). All subjects initially underwent the 6-MWT and constant load exercise gas exchange studies.

Subjects in the rehabilitation group increased treadmill exercise [metabolic equivalent of task-minutes] over the first 14 sessions. Beneficial effects on physical function resulted in those who completed rehabilitation. Subjects who completed the program increased cycle ergometer time and maintained exercise oxygen consumption (exercise VO₂) at the baseline level over 3 months, while the control group suffered a significant decrease in exercise VO₂. Rehabilitation subjects also increased their MIP. Plasma lactate doubled and brain natriuretic peptide levels increased significantly after exercise, as did the plasma amino acids glutamic acid, arginine, histidine, and methionine. These changes were associated with significant decreases in arterial oxygen saturation and increases in 15-F_2t-isoprostanes after exercise.

Pulmonary rehabilitation effectively maintained exercise oxygen uptake over 3 months and lengthened constant load exercise time in patients with moderately severe IPF. Exercise endurance on cycle ergometry testing was limited by dyspnea and severe hypoxemia associated with systemic oxidant stress.