Physiological basis of improvement after lung volume reduction surgery for severe emphysema: where are we?

Abstract

Physiological basis of improvement after lung volume reduction surgery for severe emphysema: where are we? E. Marchand, G. Gayan-Ramirez, P. De Leyn, M. Decramer. #ERJ Journals Ltd 1999. ABSTRACT: Lung volume reduction surgery has become an accepted therapeutic option to relieve the symptoms of selected patients with severe emphysema. In a majority of these patients, it causes objective as well as subjective functional improvement. A proper understanding of the physiological determinants underlying these beneficial effects appears very important in order to better select patients for the procedure that is currently largely carried out on an empirical basis.Lung volume reduction surgery has two distinct effects. Firstly, it causes an increased elastic recoil, which at least partially explains the enhanced maximal expiratory flow. Secondly, it is associated with a reduction of hyperinflation which allows for an increase in global inspiratory muscle strength and in diaphragmatic contribution to tidal volume as well as a decrease in the inspiratory elastic load imposed by the chest wall. Taken together, these effects result in a reduced work of breathing and in an enhanced maximal ventilation which both contribute to the increased exercise capacity and reduced dyspnoea after surgery. The improved lung recoil and the reduced hyperinflation after volume reduction surgery were the primary postulates upon which the usual selection criteria for the procedure were based. It is now likely that these are correct. Nevertheless, some patients do not benefit from lung volume reduction surgery and the current literature does not allow for a refinement of the selection process from a physiological point of view.The exact mechanisms underlying the improvement in lung recoil, lung mechanics, and respiratory muscle function remain incompletely understood. Moreover, the effects of lung volume reduction surgery on gas exchange and pulmonary haemodynamics still need to be more fully investigated. An analysis of the characteristics of patients who do not benefit from the procedure and the development of an animal model for lung volume reduction surgery would probably help address these important issues. Eur Respir J 1999; 13: 686±696.

Treatment of chronic respiratory failure: lung volume reduction surgery versus rehabilitation

“…A comprehensive discussion is clearly beyond the scope of the present publication, and has already been published [79]. The hypotheses explaining the improvement include: improved lung mechanics, increased lung elastic recoil [80,81], reduced intrinsic positive inspiratory pressure [82], reduced hyperinflation, increased respiratory muscle strength due to geometric factors [74][75][76][77][78], improved ventilation/perfusion matching, and reduced pulmonary vascular resistance.…”

Lung volume reduction surgery versus conservative treatment in severe emphysema

“…It reduces the overall lung volume by multiple wedge excisions of the most diseased portions of the lung. The exact physiological effect of LVRS has not been investigated in full detail [5]. Possible benefits of reduction of hyperinflation are restoration of the elastic recoil of the lung [5,6] and improvement in the economics of the work of breathing [5,7].…”

Aerosolized methacholine-induced bronchoconstriction and pulmonary hyperinflation in rats

“…One possible mechanism is continuous activation of inspiratory muscles [15]; another is air trapping, i.e., a check valve mechanism [16]. The disadvantages of pulmonary hyperinflation on respiratory mechanics have been previously described as reflected by significant improvement in pulmonary function after volume reduction surgery in patients with COPD [17]. Recent studies have shown that pulmonary hyperinflation plays important roles in restriction of diaphragmatic motion and in development of dyspnea in obstructive lung diseases [3,4].…”