Methods: Sixty adult patients at >18 years of age undergoing CABG surgery under cardiopulmonary bypass with median sternotomy were assigned into two groups, including Control group (n=30) and COPD group (n=30). Preoperative and postoperative values of pulmonary function (FEV1, FVC) and respiratory muscle strength (Pimax, SNIP, PEmax) were obtained.

Results: Preoperative values of pulmonary function and respiratory muscle strength did not differ significantly between groups (p>0.05), except FEV₁ value (p=0.00). The values of FEV1 (p=0.00, p=0.00, respectively), FVC (p=0.00, p=0.00, respectively), Pimax (p=0.00, p=0.00, respectively), SNIP (p=0.00, p=0.00, respectively) and PEmax (p=0.00, p=0.00, respectively) decreased postoperatively both in Control and COPD groups. No significant difference was found in the values of pulmonary function and respiratory muscle strength between the groups at the third postoperative day (p>0.05). The percentage decreases of the values of FEV₁ (p=0.01) and FVC (p=0.02) within the control group were significantly higher than those of within the COPD group. No significant difference was found in the percentage decreases of intragroup respiratory muscle strength values between the groups (p>0.05).

Conclusion: While low preoperative FEV₁ was obtained in patients with COPD, the values of FVC and respiratory muscle strength were similar in patients with and without COPD. The values of pulmonary function and respiratory muscle strength decreased as a result of the surgical procedure in all patients. The values of FEV₁ and FVC decreased more in patients without coexisting pulmonary disease compared to patients with COPD. However, the presence of COPD did not affect the preoperative respiratory muscle strength values and the changes in these values caused by surgery.