Structural changes underlying compensatory increase of diffusing capacity after left pneumonectomy in adult dogs.

Abstract

To determine if the functional compensation in diffusing capacity of the remaining lung following pneumonectomy is due to structural growth, we performed morphometric analysis of the right lung in three adult foxhounds -2 yr after left pneumonectomy (removal of 42% of lung) and compared the results to those in normal adult dogs previously studied by the same techniques. Diffusing capacity was calculated by an established morphometric model and compared to physiologic estimates at peak exercise in the same dogs after pneumonectomy. The major structural changes after left pneumonectomy are hyperinflation of the right lung, alveolar enlargement, and thinning of the alveolar-capillary tissue barrier. These changes confer significant functional compensation for gas exchange by reducing the overall resistance to 02 diffusion. The magnitude of compensation in diffusing capacity estimated either morphometrically or physiologically is similar. In spite of morphometric and physiologic evidence of functional compensation, there is no evidence of significant growth of structural components. After pneumonectomy, morphometric estimates of diffusing capacity are on average 23% higher than physiologic estimates in the same dogs at peak exercise. We conclude that the previously reported large differences between morphometric and physiologic estimates of diffusing capacity reflects the presence of large physiologic reserves available for recruitment. (J. Clin.

Compensatory lung growth occurs in adult dogs after right pneumonectomy.

“…1 c), the alveolar spaces and mean septal thickness were normal. The alveolar enlargement previously reported in adult dogs after left pneumonectomy (3) was less evident in dogs after right pneumonectomy, either at 5 or 16 mo.…”

“…It is generally believed that postpneumonectomy compensatory lung growth occurs in immature dogs but not in fully mature dogs (1)(2)(3). In adult dogs, postpneumonectomy compensation is largely attributed to use of existing functional reserves in the remaining lung.…”

Quantitative morphology of compensatory lung growth

“…As long as the remaining lung is relatively normal, this modest diffusion limitation is readily tolerated. Comparable diffusion impairment in well-trained adult dogs following left pneumonectomy (45% lung resection) elicits a budding alveolar cellular response but no overt growth of septal tissue [11,12]. The remaining lung increases by nearly 80% in volume; alveolar capillaries are enlarged, as would be expected from an increased blood flow.…”

Neoalveolarisation contributes to compensatory lung growth following pneumonectomy in mice

“…Although detailed quantitative morphological studies demonstrated that alveolar and capillary surface area, alveolar septal tissue volume and morphometric lung diffusing capacity are completely restored after PNX [15,17,18], the structural basis of how new alveolar tissue is added remains incompletely understood [5]. In particular, it is unclear whether regeneration is accomplished solely by growth of existing alveoli, as indicated by early studies [18][19][20], or if neoalveolarisation contributes to the restoration of lung parenchyma.…”