Clinical Comparison of the Airway Devices

During the past decade, several pharyngeal airways have been introduced into clinical practice for airway management, such as the Laryngeal Mask Airway (LMA), the Cuffed Oropharyngeal Airway (COPA), the Esophageal Tracheal Combitube (ETC), and most recently, the Laryngeal Tube (LT). These airway devices have become very popular because of their ability to maintain an airway without perturbing the trachea, and can be used in patients without muscle relaxation and who are only lightly anesthetized.

The LMA generally provides an adequate airway, but certain problems remain. (1) In 8-33% of LMA placements, more than one attempt is required. (2) It is sometimes difficult to advance the LMA without extending the neck (which is contraindicated in some patients). (3) The device does not protect the airway from aspiration of gastric contents. (4) It does not provide an airtight seal around the larynx (the usual pressures causing leakage of gas being 15-20 cm H20). Consequently, the device functions poorly during positive-pressure ventilation. (5) The esophagus is included within the rim of the LMA in 10-15% of patients, directly exposing the esophagus to positive airway pressures. This often results in insufflation of the stomach and postoperative discomfort.

The ETC is a disposable double-lumen tube that combines the features of a conventional endotracheal tube with those of an esophageal obturator airway. It is appropriate for prehospital, intraoperative, and emergency use and is especially useful for patients in whom direct visualization of the vocal cords is not possible, patients with massive airway bleeding or regurgitation, limited access to the airway, and patients in whom neck movement is contraindicated. Ventilation with the ETC is possible with either tracheal or esophageal intubation, as its distal cuff seals off the esophagus to prevent aspiration of gastric contents. The ETC has a 6.9% incidence of placement failure and a failed ventilation rate of 21.1%.

The Laryngeal Tube Suction (LTS; VBM Medizintechnik; King Systems, Noblesville, IN) is a supra-glottic airway device designed to provide a more effective seal than the LMA, thus eliminating problems 3-5 described above. The insertion of the standard laryngeal tube is generally easy. The reported success rate of insertion of, and ventilation through, the laryngeal tube ranges from 92-100% for the earlier prototype and 97-100% for the newest version. It is a flexible, curved tube that passes through the mouth, advances posterior to the epiglottis, and terminates in the upper esophagus. The multi-use, double-lumen, silicon LTS is designed with ventilation outlets located between an oropharyngeal and an esophageal, low-pressure cuff. The second lumen allows for an orogastric tube to be passed through for gastric drainage and pressure release. Patients at risk of regurgitation now have an alternative to tracheal intubation. This device has been used in a number of patients by anesthesiologists in Europe. There are many published scientific abstracts in the use of the LTS. A disposable version of the LTS is now available, the LTS-D. The LTS-D offers the same benefits as the LTS, but being disposable, it also eliminates the risk of cross-infection.

The ProSeal Laryngeal Mask Airway (PLMA, LMA North America Inc.) is the pre-existing double-lumen supra-glottic device that allows gastric drainage and pressure release. Its design is based on the LMA with an added lumen. It is reusable. The ProSeal exhibits an unsuccessful ventilation rate of 9%, and a first time insertion failure of 12.7%. Currently, the ProSeal exhibits a 3% incidence of foldover during insertion that prevents it from functioning properly. Due to differences in design, we postulate that the LTS-D will have a lower incidence of foldover than the PLMA.

This clinical study has been designed to compare the ProSeal, ETC and LTS-D as to the ease of placement and ventilation during controlled ventilation, proper positioning, the seal pressure with each placement, the patency of the drain tube by suctioning and measuring stomach contents, and finally, any complications with their use. Fiberoptic observations through each device will provide information in relation to the epiglottis and the distal opening of the device.