Exercise performance in cystic fibrosis before and after bilateral lung transplantation

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.

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 O2 content difference was derived by the Fick principle.

After transplantation, peak O2 uptake improved (31% +/- 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 O2 content were not different from normal, either before or after transplantation. In contrast, the peak exercise arterial-venous O2 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 < or = .0001 for each) and without significant improvement.

Exercise performance in patients with end-stage cystic fibrosis improves after lung transplantation but remains well below normal. Reduced systemic O2 extraction is an important factor limiting exercise in patients with cystic fibrosis after transplantation and may also contribute to the exercise limit before transplantation.