Objective:To determine whether treatment with patient-controlled analgesia (PCA) alone or in combination with nonsteroidal anti-inflammatory drugs can prevent postoperative pulmonary complications after cardiac surgery, when compared with conventional nurse-controlled analgesia.Design:Randomized controlled trial.Setting:University Medical Center.Patients:A total of 120 patients undergoing elective coronary artery bypass grafting.Interventions:After extubation of the trachea, 120 patients were randomly allocated to three different methods of postoperative pain relief for 72 hrs. In group 1, patients received PCA with a bolus of 1.5 mg piritramide combined with a 10-min lockout interval. Group 2 patients were treated with a combination of PCA and administration of nonsteroidal anti-inflammatory drugs prescribed three times per day. Patients of group 3 received conventional nurse-controlled analgesia. Postoperative assessment included daily visual analog pain scoring (VAS) and chest radiographs. All chest radiographs were graded for the extent of atelectasis by a radiologist blinded as to treatment using a scale from 0 to 9 for each of the three lung fields of the right and left lungs.Measurements and Main Results:Chest radiograph atelectasis scores and VAS values were similar among the three groups on the first and second days. On the third day, the chest radiograph atelectasis scores of the left lower and the right middle lung field were significantly better in the groups treated with PCA alone (4.7 ± 3.0; 0.3 ± 1.0) and in combination with nonsteroidal anti-inflammatory drugs (3.9 ± 1.1; 0.4 ± 1.2) than in the control group (5.5 ± 3.1; 0.8 ± 1.8). Furthermore, on the third day, the VAS values for maximum pain were higher in the control group (42.6 ± 19.7) compared with the VAS values in the two groups with PCA (32.2 ± 17.9 and 34.5 ± 21.0).Conclusions:PCA significantly decreases postoperative pulmonary atelectasis in patients after coronary artery bypass grafting when compared with nurse-controlled analgesia. In addition, patients treated with PCA experienced a higher quality of analgesia. We therefore conclude that treatment with PCA may reduce respiratory complications after coronary artery bypass grafting.