Inspiratory Muscle Training and Pulmonary Function in Patients Submitted to Bariatric Surgery

This is a controlled and randomized clinical trial that included 106 patients. The protocol was approved by the ethics committee (4.395.114; CAAE: 39118720.4.0000.0064).

Inclusion and exclusion criteria The sample consisted of patients for bariatric surgery from an outpatient clinic who were referred to physiotherapy by the medical team to be submitted to the preoperative protocol. The inclusion criteria are as follows: age over 18 years, body body mass index (BMI) ≥35 kg/m2, indication for elective bariatric surgery by videolaparoscopy. The patients would be excluded if they presented hemodynamic instability (systolic blood pressure [SBP] ˂ 90mmhg or reduction greater than 40mmhg; mean blood pressure [MAP] ˂ 65mmhg; tachycardia: heart rate ˃ 100bpm; altered level of consciousness; tachypnea: respiratory rate [RR] > 18rpm; and urine output: diuresis \< 0.5ml/kg/hr)17. Furthermore, patients who were not release from their health insurance to undergo the surgery, were not included in the study.

Randomization Patients will be randomized into two blocks with 42 patients each, therefore two treatment groups: control and intervention groups. Randomization will be performed by a researcher not involved in the recruitment or treatment of the patients through a random draw in Excel software. Opaque sealed envelopes were used to ensure blind randomization. The envelopes will be kept in a safe place and delivered to the responsible physiotherapist after the initial assessments. Before starting the intervention, the envelope will be opened by the researcher, revealing the group strategy (control or intervention).

Assessments Preoperative procedures The patients will be evaluated clinically and demographically by the same evaluator and had their data recorded: level of physical activity (time per week); musculoskeletal pain based on the visual analogue scale (VAS)18; cough peak flow (CPF) by a peak flow meter19; dyspnea (modified Borg scale)20; maximum inspiratory pressure (MIP) and maximum expiratory pressure (MEP) by a manovacuometer21; respiratory symptoms, such as dyspnea and cough; and vital signs, including systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate (HR), respiratory rate (RR), and pulse oxygen saturation (SpO2). All the patients will be submitted to a preoperative spirometry in order to exclude previous pulmonary diseases, and, at the end of the evaluation, the patients were randomized into the control group (CG) or the intervention group (IG). All patients will be underwent to 10 preoperative physiotherapy sessions, and the preoperative evaluations took place during the first and at the end of the 10th session.

Preoperative protocol The preoperative exercise protocol will be performed in both groups under a physiotherapist's supervision in 10 non-consecutive sessions in an outpatient setting twice a week, on average 30 days before the surgical procedure. The protocol consist of diaphragmatic breathing and lung re-expansion exercises, including fractional inspiration, maximum sustained inspiration and pursed lips strategy. All respiratory exercises will be performed associated with upper limb exercises and involved three sets of 10 repetitions each. Aerobic exercise will be performed on a treadmill or cycle ergometer for 20 minutes, with the load and speed set according to the individualized prescription for each patient. During the interval between the 10 sessions, the patients in both groups will be also instructed to perform standardized exercises daily at home until the moment before surgery. Pre- and postoperative instructions will be provided by the same physiotherapist that will be the responsible for the entire perioperative period. In addition to guidelines related to the surgical procedure, the patients will be instructed to perform respiratory physiotherapy according to preoperative guidance (control or intervention group) and to wear elastic socks before, during, and after surgery. All patients will be asked to keep a diary about the proposed activities.

Control group The patients will be performed all exercises in the preoperative protocol (breathing and aerobic exercises) in addition to incentive spirometry (Respiron®) in sets of 30 repetitions (level 1), 40 repetitions (level 2), or 50 repetitions (level 3) according to their weekly evolution. It will be recommended that the patients perform incentive spirometry at home, with a frequency of three times a day and an intensity as described above.

Intervention group The IMT will be associated to the same exercises offered in the preoperative protocol (breathing and aerobic exercises). It will be performed with Powerbreathe®, (Medic Plus mechanical model), with 60% of the obtained maximum inspiratory pressure in the first preoperative physical therapy evaluation. Powerbreathe®, a muscle training device, will be available to the patients, and they were instructed to also perform 30 repetitions at home three times a day.

In the immediate postoperative period, all patients will be kept for 24 hours in the intensive care unit (ICU). In addition to the guidance received about coughing, walking, and exercise practices for the lower limbs to prevent deep venous thrombosis, all patients will be performed exercises with an incentive spirometer, every hour, 30 times, and will be remained seated between intervals. As soon as possible, they will walk around the inpatient unit accompanied by the physiotherapist. Before hospital discharge (1st PO) and on the 30th postoperative day (30th PO), the patients will return to outpatient clinic to be evaluated for pain, dyspnea, MIP, MEP, CPF, and vital signs (SBP, DBP, HR, RR, and SpO2). Pulmonary complications in the period will be checked.

Statistical analysis The sample calculation was obtained from a previous study by Lloréns et al. (2015), who evaluated inspiratory muscle strength in clinically severe patients with obesity undergoing bariatric surgery after an IMT program22. A mean MIP difference of 12 (±2) cmH2O was detected between groups (sample power = 80%, alpha error = 5%, sample loss = 15%, 42 patients per group). The variables will be previously tested in relation to their distribution. Mixed linear models will be used to analyze the differences obtained between groups and to assess the intragroup evolution, a two-factor analysis of variance (ANOVA) (time and group) will be used for the following variables: MIP and MEP, CPF, and pain. Statistical Package for the Social Sciences for Windows (SPSS) version 23.0 will be used for the analysis, and a value of 5% was considered for rejection of the null hypothesis in all tests.