The effect of positive end expiratory pressure on incidence rate of atelectasis after coronary artery bypass graft

Background & Objectives: Positive end expiratory pressure (PEEP) can reduce atelectasis after general anesthesia by lung expansion and increase in alveolar pressure. Considering high incidence of atelectasis after open heart surgery and presence of reports on usefulness of PEEP in decreasing its incidence, this study was done to evaluate the effects of PEEP on incidence of atelectasis after CABG.

 Materials and Methods: Sixty patients (48 males) were divided into two groups of experiment and control (30 patients in each group). Two groups were similar with regard to age, sex, duration of cigarette smoking, aortic clamping time, cardiopulmonary bypass time, anesthesia time, ejection fraction, intubation time.     The experiment group received 5-10 cm/H2O PEEP after operation. The control group did not receive BEEP. The diagnosis of atelectasis was made using a combination of radiographic findings, WBC counts, temperature, Pao2, Paco2 and O2 saturation. Data were analyzed using t-test and chi ².

Results: Incidence of atelectasis in experimental group was 26.7% (8 patients) and in control group 56.7% (17 patients). The difference was significant (P<0.02). Mean   Pao2 and Paco2 in the first and second days after surgery in experimental group were significantly higher than in the control group. There was no significant difference in mean temperature or o2 saturation. 

Discussion:  Use of PEEP after CABG can decrease the incidence of atelectasis in intensive care unit.