New Airway Will Not Replace Laryngeal Mask Airway
ABSTRACT & COMMENTARY
A new upper airway device, the cuffed oropharyngeal airway (COPA), which is a guedel airway modified with a large cuff and a standard connector (Mallinckrodt Medical, Athlone, Ireland), was randomly compared to the laryngeal mask airway (LMA) in 120 patients undergoing anesthesia for elective surgery. The broad, flat, large-volume, low-pressure pharyngeal cuff on the new device is designed to displace the tongue and elevate the epiglottis. The standard connector allows manual or spontaneous ventilation with ordinary equipment. The new airway is available in three adult sizes: 90, 100, and 110 mm, indicating the flange to distal tip distance.
After informed consent, 120 patients judged suitable for mask general anesthesia were randomly assigned to receive either a COPA or an LMA for the procedure. Problems with insertion, number of airway manipulations, airway stability with changes in head and neck position, cardiovascular stability, and postoperative problems were assessed. A standard anesthetic technique consisting of midazolam and fentanyl sedation followed by propofol induction with nitrous oxide, oxygen, and isoflurane with spontaneous ventilation was used in all patients. If adequate assisted ventilation could not be achieved with a leak pressure of more than 10 cm H2O, usual airway manipulations were attempted, and, if these failed, the device was changed for a different size. At the end of surgery, head and neck positions were varied and the quality of gas exchange with spontaneous and assisted ventilation graded. Visual injury to the mouth, tongue, and gums, as well as the incidence and degree of sore throat, were assessed during recovery room discharge and the next day by a blinded observer.
The patients were well matched in demographic and surgical variables and anatomic markers of having a difficult airway. Drug doses were identical in the groups. First-time success for the LMA was 97% vs. 55% for the COPA. In 10 patients, the COPA was never able to achieve an adequate airway and the device had to be abandoned. All LMA patients were successfully managed. Once the device was successfully placed, additional airway support was needed in 68% of COPA patients during the anesthetic compared to less than 0.5% in those with the LMA. Hemodynamic stability was identical with both devices, as was the incidence of airway trauma identified in the recovery room. Patients complained of a sore throat more than twice as frequently the day following use of the COPA (32%) as the LMA (13%). (Brimacombe JR, et al. Anesth Analg 1998;87:147-152.)
COMMENT BY CHARLES G. DURBIN, Jr., MD, FCCM
This is an important study introducing a note of caution regarding a new airway device. In the search for a less expensive, effective, disposable, and less invasive airway device (compared to the LMA), the COPA has been introduced into clinical use. It is a deceptively simple concept, attaching a large cuff to a standard airway to move the tongue forward and achieve a pharyngeal seal for positive pressure ventilation. Unfortunately, the device is difficult to use, unreliable, and associated with more airway injuries than the LMA. It is possible that with more user experience, some of the initial problems of placement may improve, however, it is unlikely that this device will replace the LMA in elective anesthesia.
There is a great need for improved airway management techniques during emergencies (cardiac arrest, trauma, airway obstruction, difficult intubation), especially by individuals not trained in respiratory care or anesthesia. Standard mask ventilation is a difficult skill to learn and perform correctly but is the "gold standard" for emergency airway management. Emergency mask ventilation is frequently ineffective in restoring adequate gas exchange, and additional devices have been suggested to improve success. Airway adjuvants, including the esophageal obturator airway (EOA), the pharyngeal-tracheal tube airway, the Combi-tube, and the LMA have been promoted as solutions to the difficult-to-manage airway in inexperienced hands. The LMA has been the most successful of these. The LMA is now available as a single-use, disposable device (although relatively expensive at $36). From this preliminary study, it appears that the COPA is not likely to replace the LMA as the emergency airway device of choice. What role, if any, this device will have in emergency airway management remains to be determined.
None of the devices mentioned above, including the LMA, provides a secure airway. Only a cuffed, translaryngeal (oral or nasal endotracheal intubation) or transtracheal (surgical airway) allows endotracheal suctioning and high pressure ventilation. Prevention of aspiration is not provided by any of the devices, although the esophageal balloon devices may reduce passive regurgitation. Since a high level of skill and specialized equipment are required for placement of a secure airway, maintenance of adequate gas exchange and prevention of hypoxemia using simple devices is the goal of emergency airway management. The COPA is probably not as effective as the LMA for this purpose.
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