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Determinants of abnormal maximum oxygen uptake after lung transplantation for chronic obstructive pulmonary disease
D M Systrom1, P Pappagianopoulos, R S Fishman
1Pulmonary and Critical Care Unit, Massachusetts General Hospital, Harvard Medical School, Boston 02114, USA. systrom@helix.mgh.harvard.edu
Background:
Single lung transplantation for chronic obstructive pulmonary disease relieves a ventilatory limit to incremental exercise, but maximum oxygen uptake remains abnormal. The purpose of this study was to define the relative contributions of Fick principle variables to abnormal aerobic capacity after lung transplantation.
Methods:
Twelve paired incremental cardiopulmonary exercise test results obtained before and 3 to 6 months after single lung transplantation for chronic obstructive pulmonary disease were compared.
Results:
Maximum workload nearly doubled after operation (42.5+/-4.2 vs 25.5+/-4.7 watts, P < .05). Peak exercise minute ventilation increased (32.8+/-3.3 vs 21+/-2.4 L/min, n = 11, P < .05), but maximum oxygen uptake remained markedly abnormal after transplantation (46.6%+/-4.4% vs 32.1%+/-2.9% predicted, P < .05, n = 8). Peak exercise cardiac output was normal (11.0+/-1.4 L/min, 89% predicted), but arterial-mixed venous oxygen content difference at peak exercise was only half of normal (7.2+/-0.61 mL/dL), as a result in part of the failure of mixed venous oxygen saturation to fall normally (peak exercise SvO2 = 49.8%+/-2.8%).
Conclusions:
Lung transplantation for chronic obstructive pulmonary disease relieves a ventilatory limit to exercise, but maximum aerobic capacity remains abnormal, in part because of abnormal systemic O2 extraction.