IJCS | Volume 31, Nº3, May/ June 2018

247 Figure 1 - Correlation between static compliance and gas exchange. 60.00 50.00 40.00 30.00 20.00 10.00 160 .00 180.00 200.00 220. 00 240.00 260.00 280.00 300.00 Cordeiro et al. Respiratory mechanics and oxygenation International Journal of Cardiovascular Sciences. 2018;31(3)244-249 Original Article with the ECC, leading to reduced compliance of the respiratory system. In the present study, it was not possible to assess the parameters of pulmonary function prior to surgery. Taking into consideration the pulmonary decline that occurs after cardiac surgery, Auler Jr et al. 9 investigated the effect of PEEP on respiratory mechanics in patients submitted to cardiac revascularization. The authors applied different PEEP levels (0, 5, 10, and 15 cm H 2 O) and demonstrated that with increases in positive pressure, there were decreases in airway resistance and elastance. It is worth mentioning that in the present study, all patients had the PEEP previously set at 5 cm H 2 O and a low resistance was also observed with a mean of 6 cm H 2 O. Another factor that may increase the length of stay of the patient in the IMV and in the ICU is the intraoperative ECC duration. Canver & Chanda 10 verified that ECC might be an independent factor for postoperative respiratory insufficiency, which consequently increases the duration of IMV and ICU stay. In an attempt to reduce the impact of ECC on the pulmonary function, Figueiredo et al. 11 evaluated 30 patients in the postoperative period of CABG to verify the impact of continuous positive airway pressure (CPAP) on gas exchange during ECC and showed that there was no lasting improvement with the use of ECC at 10 cm H 2 O. The causes of unsuccessful weaning in patients undergoing cardiac surgery are mainly related to the presence of cardiac dysfunction and prolonged ECC duration. The ECC duration is one of the main factors to delay MV weaning after cardiac surgery, due to the important physiological disorder caused by the inflammatory response to the extracorporeal circuit. 12 In a study conducted by Nozawa et al., 12 static pulmonary compliance was altered in patients undergoing cardiac surgery, showing values below the normal range, but this parameter was not sensitive enough to identify the prognosis of the patients in regards to MV weaning. Airway resistance was increased in all patients; however, no significant difference was observed between the patients who progressed toMV independence and those who evolved to weaning failure. In relation to gas exchange, the present study found that the lower the static compliance, the lower the