The esophageal-tracheal Combitube (Kendall-Sheridan Catheter Corp., Argyle, NY) is an effective device for providing adequate gas exchange. However, tracheal suctioning is impossible with the Combitube placed in the esophageal position. To eliminate this disadvantage, the Combitube was redesigned by creating an enlarged hole in the pharyngeal lumen that allows fiberoptic access, tracheal suctioning, and tube exchange over a guide wire.
The two anterior, proximal perforations of regular Combitubes were replaced by a larger, ellipsoid-shaped hole. After the study was approved by the institutional review board, 20 patients with normal airways (Mallampati I or II) were studied. During general anesthesia, patients were esophageally intubated with the Combitube. A flexible bronchoscope was inserted and guided via the modified hole and glottic opening down the trachea. For the replacement procedure, a J tip guide wire was introduced through the bronchoscope. The bronchoscope and the Combitube were removed and a standard endotracheal tube was advanced over a guide catheter.
Bronchoscopic evaluation of the trachea and guided replacement of the Combitube by an endotracheal tube was successful in all 20 study patients. The average time needed to perform airway exchange was 90 +/- 20 s (mean +/- SD). Arterial oxygen saturation and end-tidal carbon dioxide levels remained normal in all patients. No case of laryngeal trauma was observed during intubation or the airway exchange procedure.
The redesigned Combitube enables fiberoptic bronchoscopy, fine-tuning of its position in the esophagus, and guided airway exchange in patients with normal airways. Further studies are warranted to demonstrate its value in patients with abnormal airways.
The esophageal-tracheal Combitube (Kendall-Sheridan Catheter Corp., Argyle, NY;Figure 1) has proved to be a valuable device for emergency airway management. In many potentially life-threatening situations, adequate ventilation and gas exchange has been re-established within seconds by blindly inserting a Combitube.  Consequently, the American Society of Anesthesiologists Task Force on Management of the Difficult Airway has recommended insertion of the Combitube as one of the options for managing the “cannot intubate, cannot ventilate” situation. 
However one limitation of the device is the inability to gain tracheal access when the Combitube is placed in the esophageal position.  This limitation is important when treating patients who have difficult airways and aspiration of gastric contents, vomitus, or blood. In these patients, immediate clearance of aspirated material by endotracheal suctioning or bronchoscopy is vital but impossible with the Combitube design.
The “pharyngeal lumen” is characterized by eight separated perforations (Figure 2) in the pharyngeal section.  These perforations ensure supralaryngeal ventilation when the Combitube is placed in the esophagus (as occurs in 96% to 100% of cases [1,4]). In our experience, the two proximal, anterior perforations are positioned directly in front of the laryngeal aperture. Thus we modified the standard model of the Combitube and created a larger single hole by connecting the two proximal perforations (Figure 2). We hypothesized that sufficient clearance of tracheal secretions might be possible by directing a fiberoptic bronchoscope through this larger hole into the trachea. Further, a guide wire might be placed into the trachea using a fiberoptic technique, thereby enabling the exchange of the Combitube for a regular endotracheal tube (ETT) while maintaining continuous access to the patient's airway.
The aim of this investigation was to prove the hypothesis that bronchoscopic suctioning of tracheal secretions and tube exchange is possible during airway management with the modified Combitube in the esophageal position in patients with normal airways.
Materials and Methods
Patients and Anesthetic Management
After the study was approved by the institutional ethics committee and patients' informed consent was obtained, 20 otherwise healthy persons (American Society of Anesthesiologists physical status I-II) scheduled for elective surgery for lower back pain at the Department of Neurosurgery were recruited. The Mallampati test,  as modified by Samsoon and Young,  was performed in each patient. Only patients within Mallampati classes I and II were recruited for the study.
Patients were premedicated with 0.06 mg/kg midazolam. Anesthesia was induced with 3 micro gram/kg fentanyl and 2 mg/kg propofol. Muscle relaxation was achieved with 0.1 mg/kg vecuronium. The onset of relaxation was tested using a nerve stimulator (MiniStim MS II; Professional Instruments, Houston, TX). Insertion of the Combitube was performed after disappearance of the fourth twitch of the train-of-four. Electric activity of the heart, noninvasive blood pressure, oxygen saturation, and expired carbon dioxide levels were monitored continuously (CMS-Monitor; Hewlett-Packard Products Group, Boblingen, Germany).
The Modified Esophageal-Tracheal Combitube
Standard esophageal-tracheal Combitubes were modified by replacing the two anterior, proximal perforations by a single larger hole in an ellipsoid shape (Figure 2). (This prototype is not commercially available and we do not recommend the use of any “self-made” modified Combitubes until the manufacturer releases the redesigned model.) Combitubes of adult size (41F) were used for men and the small adult size (37F) was used for women. With the 41F Combitube, the long and short diameters of the enlarged hole were 25 mm and 6 mm, respectively; with the 37F Combitube, 20-mm and 5-mm holes were used, respectively. In cadaver studies we found that when the Combitube was inserted to the recommended depth, the single larger perforation directly faced the laryngeal aperture (unpublished data).
After anesthesia was induced and ventilation was achieved via mask and until complete muscle paralysis, the lubricated Combitube was inserted until the printed ring marks were lying between the patient's teeth. Next the oropharyngeal balloon (blue port) was inflated (41F, 100 ml; 37F, 85 ml), followed by inflation of the distal balloon (white port) with 5 to 15 ml air. Test ventilation was always performed through the longer blue connector (pharyngeal lumen) at first. The potential risk of impaired venous blood flow and tissue swelling may be prevented by deflating the oropharyngeal balloon to the least volume that still allows a tight seal.
After establishing sufficient ventilation and adequate oxygenation in the esophageal position, a maximum-sized flexible lubricated fiberoptic bronchoscope was inserted into the pharyngeal lumen through an adapter equipped with a self-sealing diaphragm (Olympus, Tokyo, Japan; 3.8-mm outer diameter LF 2, for the 37F Combitube or 5-mm outer diameter BFP 30 for the 41F Combitube). The bronchoscope was advanced into the pharyngeal section of the Combitube until the modified large hole was found. The bronchoscope was guided through the enlarged perforation across the pharynx directly into the larynx and trachea. The trachea, main bronchi, and lobar bronchi of both sides were inspected (Figure 3(A)). During the entire procedure, ventilation was maintained with a peak airway pressure of 25 cm H2O, and adequate ventilation and oxygenation were checked by a second anesthesiologist as monitored by pulse oximetry and partial pressure of end-tidal carbon dioxide.
After inspection of the trachea and the clearance of tracheal secretions, a J tip guide wire (TSCM; 0.035-inch outer diameter, 145 cm long; William Cook Europe, Bjaeverskov, Denmark) was inserted into the suctioning channel of the scope and advanced under visualization until the carina was reached (Figure 3(B)). The bronchoscope and then the Combitube were removed over the guide wire (Figure 3(C)). A guide catheter (TFE catheter; 11F, 70 cm long; William Cook Europe) was fed over the guide wire. Tracheal intubation was performed by sliding reinforced spiral ETTs (Willy Ruesch Austria, Vienna, Austria;Figure 3(D)) of 7-mm inner diameters for women and 8-mm inner diameters for men over the guide wire-guide catheter combination. The exchange procedure was performed under direct laryngoscopy using a MacIntosh #3 blade to minimize the risk of soft-tissue trauma or laryngeal damage in our study patients. After removing the Combitube and before the ETT was inserted, soft tissues were screened for trauma and the laryngeal structures were graded according to Cormack and Lehane's  criteria: grade 1, visualization of the entire laryngeal aperture; grade 2, visualization of the posterior portion of the laryngeal aperture only; grade 3, visualization of the epiglottis only; and grade 4, visualization of the soft palate only.
Fourteen study patients had Mallampati class I airways and six patients had class II airways. Mean age, height, and weight of the patients were 47 +/- 10 yr, 170 +/- 8 cm, and 72 +/- 7 kg, respectively.
In all patients the Combitube was inserted into the esophagus without difficulty on the first attempt. Supralaryngeal ventilation via the pharyngeal perforations was normal in all respects and without air leak in all patients. The proximal single hole of the redesigned Combitube directly faced the laryngeal aperture, and the bronchoscope could be directed into the trachea on the first attempt in all patients. Pulse oximetry and partial pressure of end-tidal carbon dioxide were unchanged during the entire study and always remained greater than 95% and less than 45 mmHg, respectively.
The tube exchange process was successful in all study patients, and placement required an average of 90 +/- 20 s. All study patients had laryngoscopic views of grades 1 (n = 17) or 2 (n = 3).
We did not observe any complications or disadvantages of the newly designed model (such as affected pharyngeal secretions or instability of the device) as a result of the modification. No direct traumatizing effects (mucosal lacerations or blood present anywhere on the removed Combitube) were observed in any study patient.
Replacing the two anterior, proximal perforations of the esophageal-tracheal Combitube by one single larger hole enables flexible bronchoscopy, tracheal suctioning, and tube exchange even when the device is placed in the esophagus. In addition, the new design now allows fiberoptic fine tuning of the depth of insertion of the Combitube in all cases so that the pharyngeal ventilation holes are known to be supraglottic. No complications or disadvantages of the modified Combitubes have been observed in our 20 study patients, who had normal airways.
The Combitube is one of the generally accepted and recommended (by the American Society of Anesthesiologists, the American Heart Association, and the European Resuscitation Council) alternate rescue devices for managing potentially detrimental “can't intubate, can't ventilate” and other emergency situations. [1,9,10] Some of the primary indications for using the Combitube are severe hemorrhages or vomiting that impedes visualization of the glottic opening during direct laryngoscopy or fiberoptic intubation, especially when mask ventilation is difficult or impossible. In most of these patients, the airway can be secured quickly using the Combitube. In emergency situations, blind insertion of the Combitube results in esophageal intubation in nearly all patients. [1,4] Endotracheal suctioning through the Combitube in the esophageal position is impossible. The pressure exerted by the inflated oropharyngeal balloon of the Combitube may lead to impaired venous blood flow, swelling, and cyanosis of the tongue within 30 min of Combitube placement.  Consequently, as Combitube in situ time increases, the risk of exchanging a Combitube for a conventional ETT might increase, and thus the need for a surgical airway might also increase. Early exchange of the airway using a guide wire, tube exchanger, or a flexible fiberoptic bronchoscope was not possible until now.
These limitations might be eliminated by the modification of the device that we describe. Endotracheal suctioning using the fiberoptic bronchoscope can now be performed even with the Combitube in the esophageal position and may be repeated as needed. Further, an exchange of the Combitube for a standard ETT can be performed using a guide wire and guide catheter, tube exchanger, or the flexible bronchoscope. A guide catheter may be used as a jet styles, and transtracheal jet ventilation  also can be performed during the entire exchange procedure, thereby further increasing patient safety. Furthermore patient safety during exchange of the Combitube for an ETT might be enhanced by using a fiberoptic technique to introduce the guide wire into the trachea through the Combitube, removing the Combitube and bronchoscope, again sliding the bronchoscope and ETT over the guide wire (instead of a guide catheter), and intubating the trachea over the guide wire using a fiberoptic technique.
Clinically we observed maintenance of pulse oximetry and partial pressure of end-tidal carbon dioxide and good respiratory mechanics during the exchange of the Combitube for an ETT. The approximate internal radius and surface area of the semicircular pharyngeal lumen for the 41F and 37F Combitubes are 5 mm/39 mm2and 4.2 mm/28 mm2, respectively. The outside surface area of the 5-mm and 3.8-mm bronchoscopes are 19.6 mm2and 11.3 mm2, respectively. Therefore the space available to ventilate both the 41F Combitube and the 5-mm outer diameter fiberscope and the 37F Combitube/3.8-mm outer diameter fiberscope combinations are approximately 17–20 mm2, which corresponds to a 4.5–4.9-mm inner diameter conventional ETT. The ventilation space for a 41F Combitube/3.8-mm outer diameter fiberscope combination corresponds to a 6-mm inner diameter ETT. Thus these simple calculations are consistent with our ability to sufficiently ventilate around the fiberscope during the Combitube-to-ETT exchange.
The primary limitation of our investigation is that, because of ethical considerations, we recruited only healthy patients with normal airways. Thus we cannot exclude the possibility of a poorer performance of the modified Combitube in persons with less normal or with frankly abnormal airways. Studies investigating the utility of the modified Combitube in difficult airways and during emergency situations are under way.
In conclusion, replacing the two proximal perforations of the esophageal-tracheal Combitube by a single larger hole enables fiberoptic bronchoscopy, tracheal suctioning, and airway exchange even with the device positioned in the esophagus. Because we observed no complications or disadvantages of the redesigned Combitube in our study patients with normal airways, we speculate that this minor modification might improve the intubation of patients with abnormal airways. Further studies are warranted to determine whether these results can be reproduced in patients with difficult airways.