Background: Lung transplantation improves pulmonary function and quality of
life for patients with end-stage cystic fibrosis; however, a systematic ev
aluation 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 res
ults were compared with those of 10 age-similar healthy volunteers. Breath-
by-breath measurements of gas exchange and ventilation were obtained, arter
ial blood was sampled each minute, and cardiac output determined at rest an
d peak exercise by radionuclide ventriculography. The arterial-venous O-2 c
ontent 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. Compar
ed with control subjects, the lactate threshold occurred early, both before
and after transplantation. Peak exercise cardiac output and arterial O-2 c
ontent were not different from normal, either before or after transplantati
on. In contrast, the peak exercise arterial-venous O-2 content difference w
as 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 fibrosi
s improves after lung transplantation but remains well below normal. Reduce
d systemic O-2 extraction is an important factor limiting exercise in patie
nts with cystic fibrosis after transplantation and may also contribute to t
he exercise limit before transplantation.