In Reply:—
We appreciate the interest and the comments of Dr. Mandal regarding our findings pertaining to the Combitube (Tyco-Kendall-Sheridan, Mansfield, MA). We agree that it is important to conduct a thorough safety evaluation of the various supraglottic airway devices, and it is to this end that we have conducted this and other studies. Indeed, our article suggests only that continued airway management with a Combitube that has been previously placed is a reasonable option in many cases. Having thus secured the airway, it may not be necessary to abort the anesthetic or to continue with further airway management efforts. The point of our study was not to advocate or promote the use of the Combitube as a preferred method of airway management, but rather to address the question “What now?” after one has used the device, typically in a difficult airway situation. We have shown that in most cases, the device can be used as the definitive airway for an anesthetic of at least moderate duration with the use of either spontaneous or mechanical ventilation.
Certainly, the issue of aspiration is of concern, and in cases of increased risk of aspiration (e.g. , full stomach, obesity), it may be wise to awaken the patient or secure an endotracheal tube, such as we have described previously. 1However, we note that in these 200 cases and in the many other cases in which we have used the Combitube, aspiration has not occurred. One of the advantages of the Combitube in comparison with other supraglottic airway devices is, in fact, that it is designed to allow regurgitated gastric contents to be diverted away from the airway as well as to be suctioned.
We share Dr. Mandal’s concern regarding potential injury from excessive pressure exerted by the oropharyngeal balloon of the Combitube. The high intracuff pressure of the supraglottic airway devices is a common feature, and awareness of this problem is increasing. For example, the new Laryngeal Tube®(VBM Medizintechnik Gmbh, Sulz a.N, Germany) has a high-volume, low-pressure oropharyngeal balloon that is inflated by the aid of a manometer to a intracuff pressure of 60 cm H2O. In this study, we tried to avoid excessive pressure on the pharyngeal mucosa and tongue by deflating the oropharyngeal balloon every 20 min for 1 min. Overinflation of the oropharyngeal balloon with an additional 15–20 ml of air was not performed routinely, but only in 15 of 200 patients when a gas leak was detected at a ventilation pressure of 25 cm H2O. Recently, we have shown that in most patients, significantly smaller cuff volumes than those recommended by the manufacturer are needed to form an effective seal by the oropharyngeal balloon of the Combitube. 2Smaller filling volumes of the oropharyngeal balloon result in lower cuff pressures and may thus reduce mucosal or lingual injury. As Urtubia and Medina 3suggest, a redesigned Combitube with a high-volume, low-pressure oropharyngeal balloon could minimize this problem.
