Postpneumonectomy alveolar growth does not normalize hemodynamic and mechanical function

Immature foxhounds underwent 55% lung resection by right pneumonectomy (n = 5) or thoracotomy without pneumonectomy (Sham, n = 6) at 2 mo of age. Card iopulmonary function was measured during treadmill exercise on reaching mat urity 1 yr later. In pneumonectomized animals compared with Sham animals, m aximal oxygen uptake, ventilatory response, and cardiac output during exerc ise were normal. Arterial and mixed venous blood gases and arteriovenous ox ygen extraction during exercise were also normal. Mean pulmonary arterial p ressure and resistance were elevated at a given cardiac output. Dynamic ven tilatory power requirement was also significantly elevated at a given minut e ventilation. These long-term hemodynamic and mechanical abnormalities are in direct contrast to the normal pulmonary gas exchange during exercise in these same pneumonectomized animals reported elsewhere (S. Takeda, C. C. W . Hsia, E. Wagner, M. Ramanathan, A. S. Estrera, and E. R. Weibel. J. Appl. Physiol. 86: 1301-1310, 1999). Functional compensation was superior in ani mals pneumonectomized as puppies than as adults. These data indicate a limi ted structural response of conducting airways and extra-alveolar pulmonary blood vessels to pneumonectomy and suggest the development of other sources of adaptation such as those involving the heart and respiratory muscles.