Objective To investigate the effects of mechanical ventilation with lower tidal volume in patients with chronic obstructive pulmonary disease (COPD) undergoing elective lung resection. Methods Twenty-eight ASA II or m patients with COPD aged 65-84 yr undergoing elective lung resection were randomly divided into 2 groups (n=14 each):traditional tidal volume group (TV) and low tidal volume group (LV). The patients were premedicated with intramuscular atopinc 0.5 mg and phenobarbital 100 rag. Anesthesia was induced with midazolam, fentanyl and propofol. Vecuronium was used to facilitate insertion of double-lumen tube (DLT). Correct DLT position was confirmed by fiberoptic hronchoscopy. Anesthesia was maintained with continuous infusion of remifentanil, propofol and vccuronium and inhalation of 1%-2% sevoflurane. The patients were mechanically ventilated (I:E=1:2). Tidal volume (VT) was set at 10 ml/kg (PEEP=0) in group TV and at 5-6 ml/kg (PEEP =0-5 cm H2O) in group LV. Airway peak pressure (Ppeak), airway plateau pressure (Pplat), airway resistance (Raw) and dynamic lung compliance (Cd) were monitored by side stream spirometry. Arterial and venous blood samples were taken at 10 min of two-lung ventilation (TLV) in supine position (T1), at 90 min of one-lung ventilation (OLV) in lateral position (T2), at 10 min of two-lung ventilation in supine position after the end of operation (T3) and 24 h after operation (T4) for blood gas analysis and determination of serum concentrations of TNF-a and IL-6. PaO2/FiO2, P(A-a)O2 and P(A-a)O2/PaO2 were calculated. Results The serum concentrations of TNF-α and IL-6 were significantly increased at T2-4 as compared with the baseline at T1 in both groups. The serum concentrations of TNF-α and IL-6 at T2.4, Ppeak, Pplat and Raw at T1-3 were significantly lower and Cd at T2.3 was significantly higher in group LV than in group TV. There was no significant difference in PaO2/FiO2, P(A-a)O2 and P(A-a)O2/PaO2 at T1-4 between the 2 groups. Conclusion Mechanical ventilation with lower tidal volume can ameliorate the lung injury induced by mechanical ventilation through inhibition of inflammatory response in COPD patients undergoing lung resection. Key words: Respiration, artificial; Lung neoplasms; Pulmonary disease, chronic obstructive