IJCS | Volume 32, Nº2, March/April 2019

107 Table 3 - Behavior of pulmonary function at different operative moments Variable Preoperative period Hospital discharge Surgical revision MIP (cmH 2 O) P 116 ± 5 88 ± 9 < 0.001 a 109 ± 5 < 0.001 b 0.43 c MEP (cmH 2 O) P 111 ± 8 67 ± 10 < 0.001 a 90 ± 8 < 0.001 b < 0.001 c VC (ml/kg) P 45 ± 12 31 ± 9 < 0.001 a 39 ± 7 0.09 b 0.33 c PEF (L/min) P 430 ± 40 310 ± 59 < 0.001 a 390 ± 32 < 0.001 b < 0.001 c a: Comparison of preoperative period with hospital discharge; b: Comparison of hospital discharge with surgical revision; c: Comparison of preoperative period with surgical revision. MIP: maximum inspiratory pressure; MEP: maximum expiratory pressure; VC: vital capacity; PEF: peak expiratory flow. All analyses were conducted using the Student’s paired t-test. Cordeiro et al. Pulmonary function after hospital discharge Int J Cardiovasc Sci. 2019;32(2)104-109 Original Article discharge and surgical revision. These findings were evidenced in other studies on pulmonary function after cardiac surgeries, which showed that pulmonary function remains 25% to 30% lower even after 3.5 months of surgery. 11,12 Urell et al., 13 state that respiratory muscle strength is not compromised two months after cardiac surgery. In the study by Jonsson et al., 14 it was evidenced that after two months of cardiac surgery there is an increase in pulmonary function (vital capacity, functional residual capacity and total lung capacity) associatedwith increased physical activity level and, consequently, functionality. These results were not replicated in this study and may be related to the smaller sample size than the study by Jonsson et al., 14 Another cause for this difference in results may lie in the possibility of pain impacting lung function for up to 45 days due to the scarring process. As the patients in this study were evaluated after thirty days, there may be some interference, as opposed to the study by Jonsson et al. 14 Pain has a significant negative correlation with the decreased values ​in the variables of the study of Baumgarten et al. 15 In this study, pain was not evaluated, but this may be a possible explanation for a reduction in the variables of this study. Mueller and Lima 16 state in their study that most patients that underwent cardiac surgery complain of intense postoperative pain, being one of the main causes of pulmonary complications due to the lower thoracic expansion, thus generating a shallow breathing. Static and dynamic complacencies that reflect pulmonary function may be significantly reduced even after one year of surgery. 17 In the study by Annoni et al., 1 patients undergoing coronary artery bypass grafting presented increased expiratory muscle strength and, consequently, peak expiratory flow, in addition to showing improvement in quality of life. As opposed to the results of this study, which shows inconsistent responses, since the PEF, MIP, MEP and VC values were smaller, thus showing loss of muscle strength. These differentiated results can be associated with several factors. In the study by Annoni et al., 1 all patients were followed up by physiotherapy that prescribed individualized exercises at least twice a day. All patients were encouraged to perform a 6-minute walk test (6MWT) over 50 meters with medium intensity in the preoperative period. According to Laizo, 18 the 6-minute walk test (6MWT) is a method that has been used to evaluate functional capacity and is also used as a predictor of morbidity and mortality in patients with cardiovascular and respiratory diseases. Another justification may be the sample size, which was only twelve patients undergoing coronary artery bypass grafting, as opposed to this study, in which thirty patients were evaluated.