Background and Goal of Study: 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 (MA) bite block was developed for EGD using computer-assisted design and three-dimensional printing techniques. The mandible is advanced 6 mm 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 study was to compare the inspired oxygen concentration (FiO2) provided by nasal cannulas and MA bite blocks in sedated EGD. 

Materials and Methods: For bench study, a manikin head was connected to a ventilator to mimic “patient” inspiratory effort. FiO2 was evaluated continuously via the endotracheal tube connected to manikin under different oxygen flow rates, tidal volumes, and different mouth opening sizes. For clinical study, eligible patients undergoing sedative EGD were randomly assigned to standard bite block with nasal cannula and MA bite block groups. The primary endpoint was the oxygen saturation nadir. The secondary endpoints were upper airway obstruction and rescue event episodes.

Results and Discussion: In bench study, the MA bite block provided higher FiO2 under the same supplemental oxygen flow and the FiO2 were not as influenced by nasal or oral breathing compared to nasal cannulas. The measured FiO2 using the MA bite block at oxygen flow of 5L/min was 62% during normoventilation. A low respiratory rate with a smaller tidal volume has a relative high FiO2. In clinical study, oxygen saturation nadir was significantly higher for MA bite blocks vs. the standard bite block (95.42 vs. 93.57%, p= 0.025), as well as a significant reduction in adverse events such as subclinical airway obstruction, severe airway obstruction, or airway rescue interventions (p= 0.007). Patients with moderate risk for obstructive sleep apnea syndrome benefitted best (p=0.040).

Conclusions: In conclusion, the MA bite blocks deliver a higher FiO2 during EGD. The orifice size of the mouth opening, supplemental oxygen flow, tidal volume, and respiratory rate influenced the FiO2 provided. The MA bite block could decrease hypoxemia, prevent airway obstruction and decrease the need for rescue intervention during sedative EGD.


03 / Novel mandibular advancement bite block improve oxygenation during sedative esophagogastroduodenoscopy