Prophylactic Use of Noninvasive Ventilation in the Postoperative Period of Bariatric Surgery

The study will be performed at the surgical center of the Hospital de Clínicas of Porto Alegre. After approval by the Research Ethics Committee, patients must sign the Term of Consent for inclusion in the study. A blinded investigator will record clinical, anthropometric, pulmonary function tests, and functional measures. Patients submitted to open bariatric surgery will be divided into two groups for the use of NIV: immediate post-extubation (IG) and non-intervention (standard group [GP]). Patients will be randomly assigned to the groups. All subjects will undergo general anesthesia and postoperative analgesia, using a standardized surgical team approach. Patients who present the contraindication criteria for the use of NIV will be excluded from the study.

After the surgical procedure and extubation, GP subjects will receive oxygen therapy through a nasal cannula with 4 to 6 L / min of oxygen according to the team routine and patient need. The subjects in the immediate intervention group (GI) will be extubated and placed in NIV the moment they enter the recovery room through a portable ventilator (Esprit ® or BiPAP Vision ®, Respironics) in face mask. The parameters will be adjusted as follows: FiO2 = 50%, positive expiratory pressure (EPAP, starting at 4-6 cmH2O and adjusting 1-2 cmH2O to avoid snoring, apnea, paradoxical breathing and desaturations) and adjusted inspiratory positive pressure (IPAP) to maintain a tidal volume of 400 to 500 ml, maintaining IPAP <15cmH2O17. Individuals will receive this ventilatory support for 1 hour. After this period the patients will be submitted to the same care of GP patients. Measurement of respiratory muscle strength and lung function will be recorded in Time 1 (in the preoperative period), Time 2 (at the time of entry of the recovery room) and Time 3 (1 hour after extubation, with withdrawal of the support ventilatory). Vital signs (heart rate, peripheral O2 Saturation and Blood Pressure) will also be recorded through the multi-parameter monitor (IntelliVue MP40).

The functional evaluation will be performed in the period of the initial data collection through the Functional Status Score for the ICU (FSS-ICU) and Functional Independence Measure (MIF). Patients will be monitored during the hospitalization period until hospital discharge and records of postoperative complications (radiological changes, infections and surgical anastomosis fistulas) will be recorded by blinded evaluator. The final evaluation will be done through the MIF, through telephone contact 1 month after the surgery.

During the study participation patients may present with discomfort, nausea, vomiting and / or pain related to the use of non-invasive ventilation and procedures performed to evaluate muscle strength, lung function and functionality. In a study with methodology and similar population, such risks / complications were not reported16, however, if they occur, the procedures will be immediately interrupted and patients will be assisted by the study researchers in order to preserve the patients and the reliability of the results.