Investigation of a Novel Oropharyngeal Airway: The ManMaxAirway

Oropharyngeal airways are simple devices placed in the mouth that help to maintain an open oral airway in anesthetized or otherwise unconscious or semi-conscious patients and also help to facilitate assisted ventilation with a bag and mask. The current standard of care, the Guedel airway, was originally designed by Dr. Arthur Guedel in 1933 and has remained essentially unchanged since its inception. It is a narrow, curved plastic tube which slides over the tongue to lie in the back of the throat. While this device has withstood the test of time, proving to be largely safe and effective, it is known to have several drawbacks: 1) it is not held securely in place in the mouth which allows it to become easily mal-positioned or expelled, 2) it often triggers a gag reflex in even minimally conscious patients limiting its utility in emergency and prehospital settings, 3) there are case reports of serious complication and injury as a result of the poor fit and retention of the Guedel airway including aspiration and injury to the tongue, posterior pharynx, and teeth, and 4) the Guedel airway's narrow and rigid construction make it unsuitable for patients who may clench their teeth, such as in patients who are seizing.

The purpose of this study is to obtain preliminary data to help determine the utility of the ManMaxAirway (MMA) for ventilation and that will aid in future study designs for the device. The MMA is a novel oral airway that is similar in size and shape to an athletic mouth guard, and which fits between and is held in place by the teeth (or gums of the edentulous patient). The external portion of the airway contains a flange in the front which remains anterior to the teeth, allowing for ventilation in a similar fashion to the Guedel airway. It also has a central lumen that divides posterior to the flange into two lateral passages, such that air passes through the U-shaped device to the posterior-lateral aspect of the tongue behind the back teeth. Unlike the Guedel device, it makes little contact with the tongue and does not protrude into the posterior pharynx. Instead, the device will - in theory - force the mandible to rest slightly anterior to the maxilla: this slight mandible-maxilla displacement (similar to that achieved via the jaw thrust technique) will theoretically allow for a better opening of the airway without requiring direct depression of the tongue. We hypothesize that the ManMaxAirway will maintain a viable airway and allow for adequate ventilation of patients while demonstrating the following advantages over the Guedel airway: 1) improved tolerability and ease of insertion with decreased gag reflex stimulation in conscious patients 2) ability to act as a bite block in patients actively seizing or likely to seize.

Our proposed study will include two major aims in assessing the utility of the MMA. Our first aim will be to assess the mechanical effect of the device on the oropharyngeal anatomy. We will obtain MRI images of several healthy volunteers, with and without the MMA in place, in order to observe any displacement of the mandible relative to the maxilla, and any changes in positioning of the tongue. We will also assess the physical performance characteristics of the MMA vs. Guedel in terms of flow resistance in the simulation laboratory. Our second aim will be to determine whether there is any difference in tolerability between the Man Max Airway and the Guedel airway. To address the second aim we propose a crossover study using conscious, healthy volunteers, in which subjects will be asked to place each device in their mouth, one after the other. We will document the elapsed time and the number of breaths that subjects are able to take with each device in place (up to one minute), and will obtain ratings of device discomfort from each subject using a visual analog scale. We will also measure resistance to forced oscillatory airflow in a subset of subjects, with and without the airway in place, at a second visit.