Obesity affects the respiratory system through various mechanisms, including systemic inflammation and direct mechanical hindrance due to fat deposition in the chest and abdomen. In addition, changes in the neural control of respiration and increases in thoracic blood volume can promote abnormalities in lung function. Thus, determining relationships between the distance covered in the 6-min walk test (6MWT) and demographic and lung function variables may help us better understand the mechanisms involved in reduced functional exercise capacity in obesity. To explore the determinants of the 6-min walking distance (6MWD) and evaluate the influence of lung function on the distance covered, 263 obese Brazilian women performed the 6MWT and underwent spirometry and respiratory muscle strength measurement. The mean age was 41.8±11.1 years. The mean body mass index (BMI) was 45±8 kg/m 2 . The 6MWD showed correlations with height (r=0.319), age (r=-0.281), weight (r=-0.370), BMI (r=-0.561), forced vital capacity (FVC, r=0.443), expiratory peak flow (r=0.278), maximal inspiratory pressure (MIP, r=0.326), and maximal expiratory pressure (r=0.259), all with P<0.0001. In the stepwise forward regression analysis, BMI, FVC, age, and MIP were the independent predictive variables for 6MWD, explaining 41% of its variability. The reference equation including lung function was as follows: 6MWD (m) = 513.6 - (4.439 × BMI kg/m2 ) + (1.136 × FVC %predicted ) - (1.048 × age yrs ) + (0.544 × MIP %predicted ). Thus, the inclusion of lung function in a reference equation for 6MWD contributes to a better prediction of the distance covered in this population.

Papel da eletroanalgesia na função respiratória de pacientes submetidos à operação de revascularização do miocárdioThe role of electroanalgesia in patients undergoing coronary artery bypass surgery Abstract Objective: To assess the electroanalgesia as an effective method in the reduction of pain and consequent improvement in lung function in patients undergoing coronary artery bypass graft surgery.Methods: During the period of one year were studied 30 patients undergoing surgery for treatment of the ischemic coronary disease. After randomization, 15 patients were allocated in the study group (that received electroanalgesia) and 15 patients from the control group (placebo). From the 1 st until the 5 th postoperative day were performed two applications of eletroanalgesia or the placebo current, according to the group where the patient was allocated.Results: There was a reduction in the levels of pain in the study group compared to the control group, evidenced by the value P<0,05; however, there is no evidence of statistical difference of the spirometric variables between them.Conclusion: The group that did eletroanalgesia presented reduction in the intensity of postoperative pain, which however did not mean improvement in respiratory function of these patients. Rev Bras Cir Cardiovasc 2009; 24(3): 391-396 Descriptors

Background. Obesity has several effects on the mechanics of the rib cage that may impair the exercise performance of obese individuals and therefore impact the assessment of surgical risk. This study aimed to establish a reference value for the 6-minute walk distance (6 MWD) in obese Brazilian men in the preoperative period of bariatric surgery that considers the effect of lung function. Methods. This was a cross-sectional study in which 104 obese men underwent the six-minute walk test (6 MWT) before bariatric surgery. They also underwent the spirometry test and respiratory muscle strength measurement before the 6 MWT. Results. The 6 MWD was correlated with age (r = −0.388, p = 0.0005 ), weight (r = −0.365, p = 0.0007 ), height (r = 0.285, p = 0.022 ), body mass index (BMI) (r = −0.543, p < 0.0001 ), forced vital capacity (FVC) (r = 0.472, p < 0.0001 ), peak expiratory flow (r = 0.253, p = 0.031 ), and maximal inspiratory pressure (r = 0.313, p = 0.017 ). In the stepwise forward regression analysis, BMI, FVC, and age were the only variables that independently predicted the 6 MWD and explained 40% of its variability. The reference equation proposed for obese Brazilian men is 6 MWD (m) = 570.5 − (3.984 × BMIkg/m2) + (1.093 × FVC%predicted) − (0.836 × ageyrs). Conclusion. In this sample of obese Brazilian men, lung function contributed to poor performance in the 6 MWT. In these individuals, BMI, FVC, and age were the variables that composed the reference equation for the 6 MWD. Thus, in several clinical settings, such as in the evaluation before bariatric surgery, pulmonary function data are important to determine the reference value for the 6 MWD.

Background. Changes in lifestyle, a carbohydrate-rich diet, and decreased physical activity are part of the context that led to an obesity pandemic. Treating obesity is a task that requires multidisciplinary care; however, in many cases, conventional therapy has no effect, requiring surgical intervention. This, in turn, is not without risks and causes important changes in lung function. Therefore, the aim of this study is to evaluate the effect of electroanalgesia through conventional transcutaneous electrical nerve stimulation (TENS) on the pain and lung function in the postoperative period of bariatric surgery. Methods. This is a controlled and blinded clinical trial with 66 subjects who underwent bariatric surgery. The participants were randomized into 2 groups as follows: an intervention group treated with TENS ( n = 33 ) and a placebo group ( n = 33 ). The participants underwent 4 TENS sessions, and the effect on pain was assessed using a visual analogue scale (VAS pain). Lung function was measured by spirometry. Results. There were no differences between the 2 groups regarding time of surgery and time of mechanical ventilation. Compared to placebo, TENS reduced pain in the intervention group ( p = 0.001 ). Regarding the effect of electroanalgesia on pulmonary function, the spirometric parameters were similar between the groups. However, regarding muscle strength between the preoperative and postoperative periods, maximal inspiratory pressure (MIP) was maintained in the intervention group and decreased in the placebo group ( p = 0.03 ). Compared with that in the intervention group, the respiratory rate in the placebo group increased during the application of TENS ( p = 0.003 ). Conclusion. Electroanalgesia reduces pain in patients who underwent bariatric surgery. Importantly, in these patients, the MIP is maintained between the preoperative and postoperative periods. However, electroanalgesia does not contribute to improvements in spirometric data. This trial is registered with NCT04800640.