Protective intraoperative ventilation with higher versus lower levels of positive end-expiratory pressure in obese patients (PROBESE): study protocol for a randomized controlled trial

Abstract

BackgroundPostoperative pulmonary complications (PPCs) increase the morbidity and mortality of surgery in obese patients. High levels of positive end-expiratory pressure (PEEP) with lung recruitment maneuvers may improve intraoperative respiratory function, but they can also compromise hemodynamics, and the effects on PPCs are uncertain. We hypothesized that intraoperative mechanical ventilation using high PEEP with periodic recruitment maneuvers, as compared with low PEEP without recruitment maneuvers, prevents PPCs in obese patients.Methods/designThe PRotective Ventilation with Higher versus Lower PEEP during General Anesthesia for Surgery in OBESE Patients (PROBESE) study is a multicenter, two-arm, international randomized controlled trial. In total, 2013 obese patients with body mass index ≥35 kg/m2 scheduled for at least 2 h of surgery under general anesthesia and at intermediate to high risk for PPCs will be included. Patients are ventilated intraoperatively with a low tidal volume of 7 ml/kg (predicted body weight) and randomly assigned to PEEP of 12 cmH2O with lung recruitment maneuvers (high PEEP) or PEEP of 4 cmH2O without recruitment maneuvers (low PEEP). The occurrence of PPCs will be recorded as collapsed composite of single adverse pulmonary events and represents the primary endpoint.DiscussionTo our knowledge, the PROBESE trial is the first multicenter, international randomized controlled trial to compare the effects of two different levels of intraoperative PEEP during protective low tidal volume ventilation on PPCs in obese patients. The results of the PROBESE trial will support anesthesiologists in their decision to choose a certain PEEP level during general anesthesia for surgery in obese patients in an attempt to prevent PPCs.Trial registrationClinicalTrials.gov identifier: NCT02148692. Registered on 23 May 2014; last updated 7 June 2016.Electronic supplementary materialThe online version of this article (doi:10.1186/s13063-017-1929-0) contains supplementary material, which is available to authorized users.

A perioperative surgeon-controlled open-lung approach versus conventional protective ventilation with low positive end-expiratory pressure in cardiac surgery with cardiopulmonary bypass (PROVECS): study protocol for a randomized controlled trial

“…We opted for a binary collapsed composite of single PPCs that have a real clinical meaning in daily practice. With a consensual and unambiguous definition of PPCs, we facilitate the assessment of the primary outcome, prevent the risk of wrong diagnoses and allow for comparisons with previous or ongoing studies [ 20 , 28 , 29 , 37 ]. For example, the “respiratory failure” outcome, based on hypoxemia evaluated with SpO2 tolerance to room air ventilation, has previously been described in different trials interested in PPCs.…”

“…The primary endpoint, the proportion of PPCs, is defined as a composite endpoint taking the presence of at least one of the following items during the first 7 postoperative days into account. These PPCs have been defined, in accordance with previous or ongoing studies [ 20 , 29 , 37 ], as follows: Mild respiratory failure: SpO2 < 90% or PaO2 < 60 mmHg after breathing ambient air for 10 min (excluding hypoventilation) and corrected with an oxygen supply of 1–3 L/min with a nasal cannula Moderate respiratory failure: SpO2 < 90% or PaO2 < 60 mmHg despite a 3 L/min oxygen supply with a nasal cannula (excluding hypoventilation) and corrected with an oxygen supply from 4 to 10 L/min with a face mask. Severe respiratory failure: SpO2 < 90% or PaO2 < 60 mmHg despite a 10 L/min oxygen supply with a face mask (excluding hypoventilation) and corrected with an oxygen supply > 10 L/min with a high-flow face mask or with non-invasive ventilation or with high-flow nasal oxygen therapy or with invasive mechanical ventilation Fast-track extubation failure associated with hypoxemia: delayed extubation after the first 6 h postoperative, associated with PaO2/FiO2 < 300 New invasive mechanical ventilation associated with hypoxemia, defined as PaO2/FiO2 < 300 Bronchospasm: new wheezing, indicating bronchodilator treatment (except preoperative chronic obstructive pulmonary disease (COPD) or asthma) Severe tracheobronchial congestion: audible ronchi associated with disturbance in respiratory mechanics Post-extubation respiratory acidosis defined by pH ≤ 7.30 and PaCO2 > 45 mmHg Suspected pneumonia: new pulmonary infiltrate on a chest x-ray, plus at least two of the following: temperature > 38.5 °C or < 35.5 °C, leukocytosis or leukopenia (white blood cells > 12,000 cells/mm 3 or < 4000 cells/mm 3 ), purulent secretions and antibiotic treatment Confirmed pneumonia: new pulmonary infiltrate on a chest x-ray plus microbiological documentation (> 10 7 CFU/mm 3 on expectorated sputum, > 10 5 CFU/mm 3 on trans-tracheal aspiration or > 10 4 CFU/mm 3 on bronchoalveolar lavage) Pleural effusion with need for further postoperative pleural drainage Radiological atelectasis: new lung opacity on a chest x-ray with a shift in the mediastinum or ipsilateral hemi-diaphragm Acute respiratory distress syndrome (ARDS) as defined by the Berlin definition [ 38 ].…”

Airway Closure during Surgical Pneumoperitoneum in Obese Patients

“…This should be taken into account when assessing the effects on obese patients of PEEP-setting strategies, such as those currently under evaluation in ongoing randomized studies during general anesthesia. [34][35][36][37][38][39][40] Of note, when PEEP is set below airway opening pressure, distal airways suffer from cyclic opening and closing, and this may yield bronchiolar injury. 41 Whether this may clinically jeopardize the population of surgical patients is unknown.…”

High flow nasal oxygen after bariatric surgery (OXYBAR), prophylactic post-operative high flow nasal oxygen versus conventional oxygen therapy in obese patients undergoing bariatric surgery: study protocol for a randomised controlled pilot trial

“…PPCs are defined in this study as any pulmonary abnormality, disease or dysfunction that adversely affects the clinical course of a patient in the post-operative period. This includes mild, moderate or severe respiratory failure, acute respiratory distress syndrome (ARDs) new onset bronchospasm, new pulmonary infiltrates on chest x-ray, pulmonary infection and the presence of new plural effusions, atelectasis, cardiopulmonary oedema or pneumothorax [ 45 ].…”