Endoscopic thoracic sympathectomy (ETS) is the preferred surgery for treatment of intractable palmar hyperhidrosis (PH). General anesthesia with onelung collapsed ventilation (OLCV) using single-lumen tracheal tube (SLT), is our preferred anesthetic technique for ETS. Intrapleural CO(2) insufflation (capnothorax) was used to ensure lung collapse. The current study examined the effects of capnothorax on dynamic lung compliance (DLC) of the ventilated lung during ETS. After obtaining written informed consent, 10 adult male patients ASA I&II undergoing ETS were studied. Their average age and weight were 25 +/- 7 yr and 67 +/- 8 kg. General anesthesia with SLT and OLCV technique was used. Capnothorax with intrapleural pressure (IPP) of 10 mmHg was initially used, then it was reduced and maintained at 5 mmHg throughout the operation. Anesthesia delivery unit (Datex Ohmeda type A_Elec, Promma, Sweden) was used where airway pressures and DLC were displayed during OLCV. A computer program (SPSS 9.0 for Windows; SPSS Inc., Chicago, IL) was used for statistical analysis of the data obtained. One way analysis of variance (ANOVA) was used for analysis of data before, during and after OLCV. P<0.05 was considered significant. The mean values of the DLC were 52 +/- 6, 30 +/- 3, 39 +/- 5 and 53 +/- 9 ml/cmH(2)O before, during (at 10 and 5 mmHg IPP) and after OLCV respectively with significant differences before and at 10 and 5mmHg IPP. In conclusions, during OLCV and capnothorax for ETS, DLC tends to decrease with increasing of intrapleural CO(2) insufflation pressure. However, in short procedures it has no deleterious postoperative effect. To the best of our knowledge this is the first study performed to investigate DLC changes during OLCV with capnothorax.