Different strategies for mechanical VENTilation during CardioPulmonary Bypass (CPBVENT 2014): Study protocol for a randomized controlled trial

Background: There is no consensus on which lung-protective strategies should be used in cardiac surgery patients. Sparse and small randomized clinical and animal trials suggest that maintaining mechanical ventilation during cardiopulmonary bypass is protective on the lungs. Unfortunately, such evidence is weak as it comes from surrogate and minor clinical endpoints mainly limited to elective coronary surgery. According to the available data in the academic literature, an unquestionable standardized strategy of lung protection during cardiopulmonary bypass cannot be recommended. The purpose of the CPBVENT study is to investigate the effectiveness of different strategies of mechanical ventilation during cardiopulmonary bypass on postoperative pulmonary function and complications. Methods/design: The CPBVENT study is a single-blind, multicenter, randomized controlled trial. We are going to enroll 870 patients undergoing elective cardiac surgery with planned use of cardiopulmonary bypass. Patients will be randomized into three groups: (1) no mechanical ventilation during cardiopulmonary bypass, (2) continuous positive airway pressure of 5 cmH2O during cardiopulmonary bypass, (3) respiratory rate of 5 acts/min with a tidal volume of 2-3 ml/Kg of ideal body weight and positive end-expiratory pressure of 3-5 cmH2O during cardiopulmonary bypass. The primary endpoint will be the incidence of a PaO2/FiO2ratio <200 until the time of discharge from the intensive care unit. The secondary endpoints will be the incidence of postoperative pulmonary complications and 30-day mortality. Patients will be followed-up for 12 months after the date of randomization. Discussion: The CPBVENT trial will establish whether, and how, different ventilator strategies during cardiopulmonary bypass will have an impact on postoperative pulmonary complications and outcomes of patients undergoing cardiac surgery. Trial registration: ClinicalTrials.gov, ID: NCT02090205. Registered on 8 March 2014

Large cuff volumes impede posterior pharyngeal mucosal perfusion with the laryngeal tube airway

Purpose: The laryngeal tube airway (LTA) is a new extraglottic airway device with a large proximal cuff that inflates in the laryngopharynx and a distal conical cuff that inflates in the hypopharynx. We determine the influence of the cuff volume and anatomic location on pharyngeal mucosal pressures for the LTA. Methods: Fifteen fresh cadavers were studied. Microchip sensors were attached to the (anatomic location) anterior, lateral and posterior surface of the distal cuff (hypopharynx) and proximal cuff (laryngopharynx) of the size 4 LTA. Oropharyngeal leak pressure (OLP) and mucosal pressures were measured at 0-140 mL cuff volume in 20-mL increments. In addition, mucosal pressures for the proximal cuff were measured in three awake, topicalized volunteers. Results: OLP and mucosal pressure at all locations increased with cuff volume (all: P 80-100 mL. Mucosal pressures were similar for cadavers and awake volunteers. Conclusion: Mucosal pressures for the LTA increase with cuff volume, are highest posteriorly and potentially exceed mucosal perfusion pressure when cuff volume exceeds 80-100 mL

The influence of cuff volume and anatomic location on pharyngeal, esophageal, and tracheal mucosal pressures with the esophageal tracheal combitube

Background: The authors determined the influence of cuff volume and anatomic location on pharyngeal, esophageal, and tracheal mucosal pressures for the esophageal tracheal combitube.\ud \ud Methods: Twenty fresh cadavers were studied. Microchip sensors were attached to the anterior, lateral, and posterior surfaces of the distal and proximal cuffs of the small adult esophageal tracheal combitube. Mucosal pressure for the proximal cuff in the pharynx was measured at 0- to 100-ml cuff volume in 10-ml increments, and for the distal cuff in the esophagus and trachea were measured at 0- to 20-ml cuff volume in 2-ml increments. The proximal cuff volume to form an oropharyngeal seal of 30 cm H₂O was determined. In addition, mucosal pressures for the proximal cuff in the pharynx were measured in four awake volunteers with topical anesthesia.\ud \ud Results: There was an increase in mucosal pressure in the trachea, esophagus, and pharynx at all cuff locations with increasing volume (all:P < 0.001). Pharyngeal mucosal pressures were highest posteriorly (50-ml cuff volume: 99 ± 62 cm H₂O; 100-ml cuff volume: 255 ± 161 cm H₂O). Esophageal mucosal pressures were highest posteriorly (10-ml cuff volume: 108 ± 55 cm H₂O; 20-ml cuff volume: 269 ± 133 cm H₂O). Tracheal mucosal pressures were highest anteriorly (10-ml cuff volume: 98 ± 53 cm H₂O; 20-ml cuff volume: 236 ± 139 cm H₂O). The proximal cuff volume to obtain an oropharyngeal seal of 30 cm H₂O was 47 ± 12 ml. Pharyngeal mucosal pressures were similar for cadavers and awake volunteers.\ud \ud Conclusion: We conclude that mucosal pressures for the esophageal tracheal combitube increase with cuff volume, are highest where the cuff is adjacent to rigid anatomic structures, and potentially exceed mucosal perfusion pressure even when cuff volumes are limited to achieving an oropharyngeal seal of 30 cm H₂O

Airway management during spaceflight: A comparison of four airway devices in simulated microgravity

Background: The authors compared airway management in normogravity and simulated microgravity with and without restraints for laryngoscope-guided tracheal intubation, the cuffed oropharyngeal airway, the standard laryngeal mask airway, and the intubating laryngeal mask airway. Methods: Four trained anesthesiologist-divers participated in the study. Simulated microgravity during spaceflight was obtained using a submerged, full-scale model of the International Space Station Life Support Module and neutrally buoyant equipment and personnel. Customized, full-torso manikins were used for performing airway management. Each anesthesiologist-diver attempted airway management on 10 occasions with each device in three experimental conditions: (1) with the manikin at the poolside (poolside); (2) with the submerged manikin floating free (free-floating); and (3) with the submerged manikin fixed to the floor using a restraint (restrained). Airway management failure was defined as failed insertion after three attempts or inadequate device placement after insertion. Results: For the laryngoscope-guided tracheal intubation, airway management failure occurred more frequently in the free- floating (85%) condition than the restrained (8%) and poolside (0%) conditions (both, P 90%), and for the cuffed oropharyngeal airway, laryngeal mask airway, and intubating laryngeal mask airway, it was always a result of inadequate placement. Conclusion: The emphasis placed on the use of restraints for conventional tracheal intubation in microgravity is appropriate. Extratracheal airway devices may be useful when restraints cannot be applied or intubation is difficult