BACKGROUND: Lung volume reduction surgery (LVRS) for severe emphysema can significantly improve maximal expiratory flow rates and ameliorate dyspnea on exertion, probably by reducing airway resistance and by reducing hyperinflation with corresponding improvement in inspiratory muscle function. We have recently experienced 12 cases of bilateral LVRS in patients with severe emphysema in an effort to improve pulmonary function. Among these patients we examined the relationship between intraoperative spirometry and prognosis of LVRS. METHODS: Intraoperative total dynamic lung compliance (CT) and % of breath exhaled in one second (V1.0%) obtained immediately pre-lung reduction was compared with immediate post-lung reduction. In addition we also compared a preoperative pulmonary function test (PFT) [FEV1, TLC, and FRC] with 3 month postoperative values. RESULTS: Six of the twelve patients demonstrated post-reduction improvement in dynamic CT and V1.0% during LVRS. These six patients demonstrated an increase in FEV1 and a decrease in TLC, and FRC 3 months after an LVRS. The other six patients without improvement in V1.0% during an LVRS had no change in the PFT three months after an LVRS. CONCLUSIONS: It appears that sidestream spirometry with immediate intraoperative measurement of dynamic CT and V1.0% could play a role in predicting the expected follow-up objective PFT; improvement in both CT and V1.0% may predict significant increases in PFT.