Inspiratory muscle training based on anaerobic threshold on the functional capacity of patients after coronary artery bypass grafting: clinical trial

Abstract Introduction: Coronary artery bypass grafting (CABG) is associated with reduced ventilatory muscle strength and consequent worsening of functional capacity (FC). Inspiratory Muscle Training (IMT) can be indicated, but there is still a lack of knowledge about the use of the anaerobic threshold (AT) as a basis for prescription. The objective of this study is to evaluate if IMT based on AT modifies FC and inspiratory muscle strength of patients submitted to CABG. Methods: This is a clinical trial. On the first postoperative day, the patients were divided into two groups: the conventional group (IMT-C), which performed IMT based on 40% of maximal inspiratory pressure (MIP), and the IMT-AT group, which performed IMT based on AT. All patients underwent preoperative and postoperative assessment of MIP and performed a six-minute walk test (6MWT). Results: Forty-two patients were evaluated, 21 in each group. Their mean age was 61.4±10 years and 27 (64%) of them were male. There was a reduction of inspiratory muscle strength with a delta of 23±13 cmH2O in the IMT-C group vs. 11±10 cmH2O in the IMT-AT group (P<0.01) and of the walking distance with a delta of 94±34 meters in the IMT-C group vs. 57±30 meters in the IMT-AT group (P=0.04). Conclusion: IMT based on AT minimized the loss of FC and inspiratory muscle strength of patients submitted to CABG.

Behavior of pulmonary function after discharge in patients submitted to myocardial revascularization / Comportamento da função pulmonar após a alta em pacientes submetidos à revascularização do miocárdio

Background: Coronary artery bypass grafting (CABG) is a type of surgery where there is a compromise in one or more coronary arteries, with the objective of restoring function to the areas that have been compromised in the heart, possibly leading to respiratory compromise and postoperative complications. The return time of the pulmonary function to the preoperative condition is still indeterminate in the literature. Objective: To describe the behavior of pulmonary function after hospital discharge in patients submitted to CABG. Methods: This is a prospective cohort study. Only patients undergoing MRI, whose lung function was evaluated preoperatively, at hospital discharge and 30 days after surgery, were evaluated. This evaluation consisted of maximum inspiratory pressure (MIP) and expiratory (MEP), vital capacity (VC) and expiratory flow peak (EFP). Results: A total of 30 patients were evaluated, of which 18 (60%) were males, mean age 62 ± 9 years. A reduction in lung function from preoperative time to hospital discharge was observed in all variables. There was improvement in MIP (88 ± 9 vs 109 ± 5, p < 0.001), MEP (67 ± 10 for 90 ± 8, p < 0.001) and EFP (310 ± 59 for 390 ± 32, p < 0.001), high for review. At the time of the review, no variables returned to their preoperative value: MIP (116 ± 5 for 109 ± 5, p = 0.43), MEP (111 ± 8 for 90 ± 8, p < 0.001), VC (45 ± 12 for 39 ± 7, p = 0.33) and EFP (430 ± 40 for 390 ± 32, p < 0.001). Conclusion: It is concluded that MRI surgery reduces lung function and is not reestablished after 30 days of the procedure. Being the expiratory muscular force and the peak of expiratory flow the most affected