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Volume Reduction Surgery Impairs Immediate Postoperative Pulmonary Function in Canine Emphysema

Departments of Surgery and Internal Medicine, University of Manitoba, Winnipeg, Manitoba, Canada

Correspondence and requests for reprints should be addressed to Steven N. Mink, M.D., GF-221, Health Sciences Centre, Winnipeg, MB, R3E-0Z3 Canada. E-mail: minksn{at}cc.umanitoba.ca

Rationale: In severe pulmonary emphysema, lung volume reduction surgery (LVRS) improves pulmonary function over a 2-yr period in selected patients. However, the changes in lung function and maximal flow (max) occurring immediately postoperatively are not clear and may contribute to the high morbidity observed. In the present study, we used a chronic canine model of upper lobe emphysema to address this question.

Methods: Bilateral upper lobe emphysema was produced by the intrabronchial administration of papain. Measurements were made before and immediately after LVRS was performed. A vacuum-assisted surgical system (VALR Surgical System; Spiration, Redmond, WA) that deploys a compression sleeve over portions of the disease tissue was used to produce LVRS. Changes in max were interpreted in terms of the wave-speed theory of flow limitation in which a pressure sensor was placed into the airway to determine the site of limitation and intrabronchial pressures.

Results: In the emphysema group, total lung capacity postemphysema increased to approximately 20% above the preemphysema value, whereas max was reduced as compared with a control group. After LVRS, tidal respiratory compliance and max decreased, whereas lung elastic recoil and frictional resistance increased in both the emphysema and control groups as compared with presurgery.

Conclusion: The acute effect of LVRS leads to an impairment in lung mechanical properties. These changes could contribute to ventilatory complications, including the difficulty of weaning patients from mechanical ventilation and the mortality observed from this procedure.

Key Words: chronic obstructive lung disease • maximum expiratory flow • tidal compliance • wave-speed theory of flow limitation

AT A GLANCE COMMENTARY Scientific Knowledge on the Subject Although most investigations have centered on the long-term effects of lung volume reduction surgery (LVRS) on pulmonary function where the effects have been beneficial, there is only limited information about the changes that evolve in the immediate postoperative period. What This Study Adds to the Field We show that the acute effect of LVRS in a canine model of upper lobe emphysema is to impair lung mechanics and maximal expiratory flow. This study points out that an acute impairment in pulmonary function post-LVRS may contribute to the respiratory compromise that frequently develops after this procedure is performed.

 

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