Novel mandibular advancement bite block with supplemental oxygen to both nasal and oral cavity improves oxygenation during esophagogastroduodenoscopy: a bench comparison

Abstract

Drug-induced respiratory depression is a major cause of serious adverse events. Adequate oxygenation is very important during sedated esophagogastroduodenoscopy (EGD). Nasal breathing often shifts to oral breathing during open mouth EGD. A mandibular advancement bite block was developed for EGD using computer-assisted design and three-dimensional printing techniques. The mandible is advanced when using this bite block to facilitate airway opening. The device is composed of an oxygen inlet with one opening directed towards the nostril and another opening directed towards the oral cavity. The aim of this bench study was to compare the inspired oxygen concentration (FiO) provided by the different nasal cannulas, masks, and bite blocks commonly used in sedated EGD. A manikin head was connected to one side of a two-compartment lung model by a 7.0 mm endotracheal tube with its opening in the nasopharyngeal position. The other compartment was driven by a ventilator to mimic "patient" inspiratory effort. Using this spontaneously breathing lung model, we evaluated five nasal cannulas, two face masks, and four new oral bite blocks at different oxygen flow rates and different mouth opening sizes. The respiratory rate was set at 12/min with a tidal volume of 500 mL and 8/min with a tidal volume of 300 mL. Several Pneuflo resistors of different sizes were used in the mouth of the manikin head to generate different degrees of mouth opening. FiO was evaluated continuously via the endotracheal tube. All parameters were evaluated using a Datex anesthesia monitoring system. The mandibular advancement bite block provided the highest FiO under the same supplemental oxygen flow. The FiO was higher for devices with oxygen flow provided via an oral bite block than that provided via the nasal route. Under the same supplemental oxygen flow, the tidal volume and respiratory rate also played an important role in the FiO. A low respiratory rate with a smaller tidal volume has a relative high FiO. The ratio of nasal to oral breathing played an important role in the FiO under hypoventilation but less role under normal ventilation. Bite blocks deliver a higher FiO during EGD. The ratio of nasal to oral breathing, supplemental oxygen flow, tidal volume, and respiratory rate influenced the FiO in most of the supplemental oxygen devices tested, which are often used for conscious sedation in patients undergoing EGD and colonoscopy.

High-Flow Nasal Cannula and Mandibular Advancement Bite Block Decrease Hypoxic Events during Sedative Esophagogastroduodenoscopy: A Randomized Clinical Trial

“…The MA bite block in this study is equipped with an oxygen inlet directing oxygen flow to both nasal and oral routes, increasing oxygen delivery efficacy. In our previous bench study, when given oxygen flow of 5 L min −1 , the MA bite block delivered 63% FiO2 during normoventilation and a high 80% during hypoventilation [21]. During hypoventilation, FiO 2 increases to 86%.…”

“…The MA bite block was equipped with connectors for oxygen inlet directed to both nose and mouth and ETCO 2 detection catheter. ETCO 2 detection and 5 L min −1 oxygen were connected to the bite block in the MA bite block group [21] (Figure 1). Once the bite blocks were placed and the patients were preoxygenated for 5 minutes, midazolam intravenous bolus was administered at a dose of 0.05 mg kg −1 , and alfentanil at 0.2 mcg kg −1 .…”

“…It provides mandibular advancement, supplemental oxygen directed to both nasal and oral cavities, and inlet for endoscopic entry. In our previous bench study comparing eleven airway devices for EGD, the MA bite block was the most capable device to deliver a high fraction of inspired oxygen (FiO 2 ) [21]. Its clinical use has not been reported.…”