THE EFFECT OF TWO DIFFERENT LEVELS OF POSITIVE END EXPIRATORY PRESSURE (PEEP) ON THE INCIDENCE RATE OF ATELECTASIS AND HEMODYNAMIC STATUS OF PATIENTS AFTER CORONARY ARTERY BYPASS SURGERY

Background: Due to the high incidence of atelectasis following coronary artery bypass surgery and the effects of different levels of positive end expiratory pressure (PEEP) in preventing this condition. Objectives: this study was designed aimed to investigate the effects of PEEP on the incidence of atelectasis after coronary artery bypass surgery. Material and methods: This study is a clinical trial with a control group conducted on 90 patients underwent coronary artery bypass surgery. After surgery and entering patients to the intensive care unit (ICU) the intervention group subjects were under PEEP = 10 cm / H2o and the control group subjects were under PEEP = 5 cm / H2o for 4 hours. For the final diagnosis of atelectasis, a chest radiograph was performed six hours after extubation and 5 days after surgery, saturation pulse oximetry was also examined. The systolic and diastolic blood pressure before and after the intervention were measured in order to evaluate hemodynamic status of patients. Chi-square and independent t-tests were used to statistical analysis. Results: The observed difference in the incidence of atelectasis between the two groups 6 hours after extubation were statistically significant (P=0/03). There was also no statistical significant difference between the two groups 5 days after surgery (P=0/3). The difference between the two groups in terms of the average of saturation pulse oximetry was statistically significant (P=0/025). There was no statistical significant difference between the two groups in terms of systolic (P = 0.25) and diastolic (P = 0.14) blood pressure before intervention. There also was no statistical significant difference between the two groups in terms of systolic (P = 0.62) and diastolic (P = 0.67) blood pressure after intervention. Conclusion: this study indicated that applying PEEP=10 cm/H2O after the Coronary Artery Bypass Surgery can lead to decrease the incidence rate of atelectasis following the surgery, and considering that applying of two levels of PEEP with 5 and 10 cm of water has no effect on the hemodynamic status of patients, so it is proposed that this technique be used at intensive care unit to reduce the incidence of atelectasis. Keywords: positive end expiratory pressure (PEEP), coronary artery bypass graft surgery (CABG), atelectasis