Central versus peripheral adaptations after lung transplantation in end-stage COPD

<bold>Background:</bold> Skeletal muscle blood flow is markedly diminished in patients with COPD, contributing to reduced exercise capacity. The aim was to assess adaptations in skeletal muscle blood flow regulation and exercise capacity after lung transplantation (LTx) in end-stage COPD. <bold>Methods:</bold> Hemodynamic responses during submaximal single-leg knee-extensor exercise (KEE) were measured before and 6 months after LTx in 10 patients with end-stage COPD. Stroke volume and cardiac output were assessed using finger photoplethysmography. Leg blood flow was assessed using Doppler ultrasound, with arterio-venous variables sampled across the exercising leg. Symptom burden, exercise capacity (6-minute walking distance, single-legged peak workload [WL_peak]), body composition, and physical activity were also assessed. <bold>Results:</bold> After LTx, responses in cardiac output (6.2±0.4 vs 7.5±0.4 L·min⁻¹) and stroke volume (71±4 vs 81±4 mL) to KEE at 10% WL_peak increased significantly, while MAP response decreased (131±5 vs 117±5 mm Hg). Leg blood flow (1026±98 vs 941±66 mL·min⁻¹) and oxygen uptake (117±12 vs 103±16 mL O₂·min⁻¹) responses to KEE were similarly after LTx. Symptom burden (CAT score 26±1 vs 9±2 points), walking distance (258±32 vs 458±48 meters), and physical activity (3199±515 vs 5152±776 steps·min⁻¹⁾ increased after LTx, whereas WL_peak and leg lean mass remained unaltered. <bold>Conclusion:</bold> Despite near-normalisation of lung function after LTx, perfusion of the exercising skeletal muscle remained unaltered, showing persistent peripheral exercise limitation despite central adaptations in COPD. However, some degree of deconditioning may exist 6 months after LTx, which might be targeted and reversed with exercise training.