LUNG-VOLUME REDUCTION SURGERY AND AIR-FLOW LIMITATION

Interest has recently been renewed in lung volume reduction surgery (L VRS) for end-stage emphysema. However, numerous questions about its ro le in the treatment of emphysema remain, including the clinical charac teristics of optimal candidates and its mechanism of improvement in pu lmonary function. In this report, we develop a mathematical analysis a nd graphic depiction of the mechanism of improvement in expiratory air flow and vital capacity. This analysis is based on consideration of th e interaction between lung function and respiratory muscle function. W e also reexamine previously published pulmonary mechanics in patients with alpha(1)-antitrypsin deficiency, chronic obstructive pulmonary di sease, and asthma. We find a major determinant of airflow limitation c ommon to these diseases is the ratio of residual volume to total lung capacity (RV/TLC). Moreover, RV/TLC is found to be the single most imp ortant determinant of the improvement in pulmonary function after LVRS . Regardless of the specific underlying lung disease, the impairment o f airflow is due primarily to mismatch between the sizes of the lung a nd the chest wall, and the effects of LVRS are almost exclusively due to improvement of that match. This analysis can be used to develop tes table hypotheses to guide patient selection for this procedure.