Exercise performance in cystic fibrosis before and after bilateral lung transplantation

Background: Lung transplantation improves pulmonary function and quality of life for patients with end-stage cystic fibrosis; however, a systematic evaluation of exercise performance in lung transplant recipients with cystic fibrosis has not been reported. Methods: Ten patients with end-stage cystic fibrosis performed incremental exercise testing before and after bilateral lung transplantation; their results were compared with those of 10 age-similar healthy volunteers. Breath-by-breath measurements of gas exchange and ventilation were obtained, arterial blood was sampled each minute, and cardiac output determined at rest and peak exercise by radionuclide ventriculography. The arterial-venous O-2 content difference was derived by the Pick principle. Results: After transplantation, peak O-2 uptake improved (31% t+/- 3% vs 45% +/- 4% predicted, P =.03) but was still reduced versus normal (100% +/- 8% predicted, p <.0001). Exercise was Limited by pulmonary mechanics in all patients before transplantation but in only 2 after transplantation. Compared with control subjects, the lactate threshold occurred early, both before and after transplantation. Peak exercise cardiac output and arterial O-2 content were not different from normal, either before or after transplantation. In contrast, the peak exercise arterial-venous O-2 content difference was markedly reduced before and after transplantation versus normal(7.1 +/- 1.2 and 9.3 +/- 0.9 vs 17.1 +/- 1.2 mL/dL, p less than or equal to.0001 for each) and without significant improvement. Conclusions: Exercise performance in patients with end-stage cystic fibrosis improves after lung transplantation but remains well below normal. Reduced systemic O-2 extraction is an important factor limiting exercise in patients with cystic fibrosis after transplantation and may also contribute to the exercise limit before transplantation.