Dwayne you brought up an excellent point! While there is a valve on the combitube that I lovingly call the "Puke valve" I understand what your saying about the pressure of the vomit meeting the airway device and how it can cause damage. So I researched it because I'm just as curious as you are. This might provide some insight. It might answer your question or it may not but I took a shot at this. Its a study some doctors did to compare seals in supraglottic airway devices.
A Comparison of Seal in Seven Supraglottic Airway Devices Using a Cadaver Model of Elevated Esophageal Pressure
Sven Bercker, MD*, Willi Schmidbauer, MD{dagger}, Thomas Volk, MD{ddagger}, Gottfried Bogusch, PhD§, Hans Peter Bubser, MD{dagger}, Mario Hensel, MD{ddagger}, and Thoralf Kerner, MD{ddagger}
From the *Department of Anesthesiology and Intensive Care Medicine, Leipzig University Hospital, Germany; {dagger}Department of Anesthesiology and Intensive Care Medicine, Bundeswehrkrankenhaus, Berlin, Germany; {ddagger}Department of Anesthesiology and Intensive Care Medicine, Campus Virchow-Klinikum and Campus Charité Mitte, and §Center for Anatomy, Charité-Universitaetsmedizin, Berlin, Germany.
Address correspondence and reprint requests to Dr. Sven Bercker, Klinik für Anästhesiologie und Intensivtherapie Universitätsklinikum Leipzig, Liebigstr.20, 04103 Leipzig Germany. Address e-mail to sven.bercker@medizin.uni-leipzig.de.
Abstract
BACKGROUND: Supraglottic airway devices are increasingly important in clinical anesthesia and prehospital emergency medicine, but there are only few data to assess the risk for aspiration. We designed this study to compare the seal of seven supraglottic airway devices in a cadaver model of elevated esophageal pressure.
METHODS: The classic laryngeal mask airway, laryngeal mask airway ProSealTM, intubating laryngeal mask airway FastrachTM, laryngeal tubeTM, laryngeal tube LTS IITM, CombitubeTM, and EasytubeTM were inserted into unfixed human cadavers with an exposed esophagus that had been connected to a water column of 130 cm height. Slow and fast increases of esophageal pressure were performed and the water pressure at which leakage appeared was registered.
RESULTS: The Combitube, Easytube, and intubating laryngeal mask Fastrach withstood the water pressure up to more than 120 cm H2O. The laryngeal mask airway ProSeal, laryngeal tube, and laryngeal tube LTS II were able to block the esophagus until 72–82 cm H2O. The classic laryngeal mask airway showed leakage at 48 cm H2O, but only minor leakage was found in the trachea. Devices with an additional esophageal drain tube drained fluid sufficiently without pulmonary aspiration.
CONCLUSIONS: Concerning the risk of aspiration, the use of devices with an additional esophageal drainage lumen might be superior for use in patients with an increased risk of aspiration. The Combitube, Easytube, and intubating laryngeal mask Fastrach showed the best capacity to withstand an increase of esophageal pressure.
http://www.anesthesia-analgesia.org/cgi/co...tract/106/2/445