Pulmonary function tests after different techniques for coronary artery bypass surgery

Pulmonary function tests were measured in 33 male patients undergoing elective coronary artery bypass surgery. Three modes of surgical technique were used: Bilateral internal mammary artery graft (BIMA), single internal mammary artery graft (SIMA) and saphenous vein grafts (VS). Following parameters were recorded: patient's age, length, body weight, preoperative forced vital capacity (FVC) and forced expiratory volume at one second (FEV 1), preoperative end-diastolic pressure and function of the left ventricle, smoking habitus, the fact that the pleural cavity was entered, duration of the cardiopulmonary bypass period, perioperative fluid balance and postoperative FVC and FEV 1 on the first eight postoperative days. In the BIMA group two pleural cavities, the SIMA group one pleural sac and the VS group none of the pleural cavities was entered. The BIMA group was younger (50.1±7.6 versus 57.7±7.28 and 60.1±6.9 years (p< 0.05)) than the SIMA and VS group. Postoperative external blood loss was lower in the VS group compared to the SIMA and BIMA groups (839±255 ml versus 1346±654 ml and 1259±396 ml (p< 0.05)). The FVC shows a dramatic decrease especially on the second postoperative day and was most markedly diminished in the BIMA and SIMA compared to VS (31%±9% and 35%±8% versus 45%±10% of preoperative values (p< 0.05)). Full recovery of the FVC was not achieved eight days after surgery: BIMA and SIMA showing the same tendency versus VS (61%±10%, 60%±8% versus 71%±8% preoperative FVC (p< 0.05)). FEV 1 had the same evolution: on the second postoperative day a significant reduction for BIMA and SIMA versus VS group (32%±10%, 34%±8% versus 46%±9% of preoperative values (p< 0.05)) and incomplete recovery after eight days (59%±8% (BIMA), 59%±11% (SIMA) versus 69%±7% (VS) (p< 0.05)). No statistical difference between SIMA and BIMA group could be shown for FVC and FEV 1. We conclude that coronary artery bypass surgery causes a substantial decrease in FVC and FEV 1 especially when one or two pleural cavities are violated. The reduction of FVC in BIMA is so important that this technique should be restricted to patients with adequate pulmonary reserves.