IJCS | Volume 31, Nº3, May/ June 2018

246 Cordeiro et al. Respiratory mechanics and oxygenation International Journal of Cardiovascular Sciences. 2018;31(3)244-249 Original Article Table 1 presents the characteristics of the patients included in the study. The mean static compliance was 35.5 ± 9.1 cmH 2 O, the mean airway resistance was 6.0 ± 2.3 cm H 2 O, and the mean duration of ICU stay was 2.9 ± 1.1 days. No significant correlation was found between IMV duration with static compliance and resistance (p = 0.73 and p = 0.51, respectively) (Table 2). Table 3 shows the static compliance and resistance as functions of the duration of hospitalization in the ICU, analyzed with the Spearman test. No statistically significant relationship was observed (p = 0.83 and p = 0.98, respectively). On the other hand, a strong correlation was observed between static compliance and gas exchange (228.0 ± 33.4, r = 0.8, p < 0.001) (Figure 1). Discussion The results of this study show that ventilatory mechanics (static compliance and resistance) had no influence on the IMV duration and length of ICU Table 1 - Clinical, demographic, and surgical data of the patients who underwent cardiac surgery Variables Mean/SD N (%) Age (years) 57 ± 13 Gender Male 24 (48) Female 26 (52) Type of surgery CABG 37 (74) Valve replacement 12 (24) Correction of congenital malformations 1 (2) ECC duration (minutes) 72 ± 22 MV duration (hours) 8 ± 3 PaO 2 /FiO 2 228.0 ± 33.4 Successful weaning 50 (100) SD: standard deviation; N: number of patients; CABG: coronary- artery bypass grafting; MV: mechanical ventilation; ECC: extracorporeal circulation; PaO 2 : arterial oxygen pressure; FiO 2 : fraction of inspired oxygen. Table 2 - Analysis of the ventilatory mechanics and duration of invasive mechanical ventilation (IMV) in patients undergoing cardiac surgery Variable Static compliance (cm H 2 O) 35.5 ± 9.1 IMV duration (hours) 8 ± 3 p a 0.73 Resistance (cm H 2 O) 6.0 ± 2.3 IMV duration (hours) 8 ± 3 p* 0.51 Data are presented as mean ± standard deviation. *Pearson's test. Table 3 - Analysis of the ventilatory mechanics and duration of hospitalization in the intensive care unit (ICU) in patients undergoing cardiac surgery Variable Static compliance (cm H 2 O) 35.5 ± 9.1 Duration of ICU stay (days) 2.9 ± 1.1 p* 0.83 Resistance (cm H 2 O) 6.0 ± 2.3 Duration of ICU stay (days) 2.9 ± 1.1 p* 0.98 Data are presented as mean ± standard deviation. *Spearman test. stay. However, static compliance presented a strong correlationwith gas exchange in the postoperative period of cardiac surgery. For Arcênio et al., 7 both anesthesia and certain surgeries predispose patients to changes in respiratory mechanics, pulmonary volumes, and gas exchange. Cardiac surgery, which is considered a large procedure, can trigger in the postoperative period respiratory changes related to several factors, including pulmonary and cardiac function in the preoperative period, use of ECC, and degree of sedation. According to Badenes et al., 8 cardiac surgery associated with MV in the postoperative period causes significant structural and functional changes at a pulmonary level due to the inflammatory process that is also associated