Central versus peripheral adaptations after lung transplantation in patients with end-stage chronic obstructive pulmonary disease

Background: Oxygen delivery to contracting limb muscle is diminished in patients with chronic obstructive pulmonary disease (COPD), which may contribute to the development of peripheral muscle dysfunction. We hypothesized that lung transplantation (LTx) in patients with end-stage COPD would improve exercise capacity both centrally and peripherally. Methods: Patients with end-stage COPD eligible for LTx were included and followed for 6 months after LTx. We performed lung function testing and maximal workload during incremental one-leg knee-extensor exercise (one-leg WLmax), DEXA, 6 min walking distance (6MWD), leg accelerometers for 7 days (Axivity AX3) and COPD Assessments test (CAT). Results: 10 patients (female/male: 6/4, age 55±2 years) were included. Lung function (FEV1: 31±17% vs. 81±27%) and diffusion capacity (DLCO 2.38±1.19 vs. 5.76 ± 1.5) increased after LTx. Whole body exercise capacity (6 min walking distance: 251±47 m to 475±69 m) increased, and symptom burden (COPD Assessment Test score: 26 to 9) was reduced. Daily step count increased (3646±1739 vs 6195±2251). However, leg muscle endurance (one-leg WLmax 21±1 W vs. 26±2), and leg lean mass (6.3±1.5 vs. 6.7±1.9kg) remained unaltered. Conclusion: In contrary to our hypothesis, the limb muscle dysfunction persisted even though lung function was normalized in end-stage COPD. These data add to debate regarding the etiology of the muscle abnormalities in COPD by suggesting a pulmonary independent myopathy. The LTx recipients were still quite physically inactive at 6-month follow-up, thus we cannot rule out some degree of deconditioning, that might be targeted with exercise training.