Diffusing capacity limitations of the extent of lung volume reduction surgery in an animal model of emphysema

Abstract

Objective: The purpose of this study was to investigate in an elastase-induced emphysema rabbit model the effects of increasing resection volumes during lung volume reduction surgery on pulmonary compliance, forced expiratory air flow, and diffusing capacity to assess factors limiting optimal resection. Methods: Emphysema was induced in 68 New Zealand White rabbits with 15,000 units of aerosolized elastase. Static respiratory system compliance, forced expiratory flow, and single-breath diffusing capacity were measured before the induction of emphysema, after the induction of emphysema, and 1 week after a bilateral upper and middle lobe lung volume reduction operation. Results: Static respiratory system compliance with 60 mL insufflation above functional residual capacity increased with emphysema induction and then decreased progressively with resection of larger volumes of lung tissue ( P = .001 by analysis of variance). Expiratory flow improved after lung resection in the rabbits with large resection volumes. In contrast, diffusing capacity tended to deteriorate with larger resection volumes ( P = .18). Conclusion: Improvements in respiratory system compliance and forced expiratory flow after lung volume reduction operations may account for the improvements seen clinically. Declines in diffusing capacity with extensive lung reduction may limit the clinical benefits associated with greater tissue resection volumes. Future investigations with animal models may reveal other physiologic parameters that may further guide optimal lung volume reduction procedures. (J Thorac Cardiovasc Surg 1999;117:728-35)