Volumen
16 Número 3 Julio - Septiembre 2004
Combitube for Emergency Intubation and the Cannot Ventilate Situation
| Michael Frass MD * |
* Department of Internal Medicine 1, MICU ** Intensive Care and Anesthesia Unit |
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A large elastic oropharyngeal balloon occupies the oropharyngeal cavity after inflation for sealing both mouth and nose. After inflation, the balloon presses against the root of the tongue in ventro-caudal direction, and closes the soft palate in dorso-cranial direction. Then, the anterior wall of the balloon is positioned just behind the posterior part of the hard palate. Thereby, strong anchoring during ventilation and transportation is guaranteed without danger of accidental extubation. In esophageal position, air flows through the holes into the hypopharynx and from there into the trachea, while mouth, nose, and esophagus are sealed by the oropharyngeal and distal balloon. Furthermore, the double lumen ETC exhibits a second distally open lumen for use after tracheal intubation.
The ETC is available in two sizes, the ETC 37 F SA (small adult) is to be used in patients with a height between 4 and 6 ½ feet (about 120 to 200 cm), the ETC 41 F is used in patients taller than 6 ½ feet (about 200 cm) following the results of studies by Urtubia,2 Gaitini,3 Walz and Panning,4 and Krafft.5 The kit of the ETC 37 F SA comes with a large color-coded syringe, pre-drawn to 85 mL (41 F: 100 mL), and a small syringe, pre-drawn to 12 mL (41 F: 15 mL). The kit also contains a 10 F (41 F: 12 F) suction catheter as well as a deflection elbow to avoid soiling of the rescuer by gastric contents.
Three types of packaging are available: Hard tray, roll-up kit (both kits containing all accessories), and single kit (containing ETC only). Recent studies show that the ETC may be reused observing special precautions.6 So, the ETC has become affordable to be used in elective cases. However, in emergencies, a new kit should be used.
The ETC may be either positioned into the esophagus or into the trachea. The two lumens are divided by a partition. The so-called "pharyngeal lumen" 7 is blind at the distal end and bears eight oval-shaped holes positioned at the level of the lower pharynx following correct placement. At the proximal part, this lumen ends in a longer blue tube No. 1 with a connector for any ventilating systems. The so-called "tracheal lumen", is open at the distal end and forms a shorter transparent tube No. 2 at its proximal end with another connector. It is recommended to check the function of both balloons before insertion. Lubrication of the ETC may be performed complimentary.
The ETC is easy to insert in flaccid patients experiencing cardiac arrest. In elective cases, the patient should be well anesthetized. To avoid adverse effects,8 we recommend use of propofol and fentanyl with or without relaxation. The use of the ETC in elective cases should be limited to patients younger than 70 years without signs of esophageal disease. With professional anesthesia, use of laryngoscope,2-5 and minimal inflation technique 2,9 the danger of esophageal injury can be circumvented. Do not use force during insertion of the ETC.
While some clinicians prefer to extend the head, and/or to use a small cushion, placement of the ETC is usually performed with the patient's head in a neutral, semi-flexed position opposite to standard intubation. Sniffing position, however, should be avoided! Neutral position is advantageous in patients with suspected or evident cervical spine injury. Insertion is aided by full muscle relaxation, but may be unnecessary with the use of propofol. The position of the operator may be behind the patient, to one side of the patient's head, or face to face. Similar to the EOA, the back of the patient's tongue and lower jaw are grasped between the thumb and forefinger of the non-dominant hand, while a jaw lift is performed (Figure 1). Then, the ETC is inserted blindly with a gentle downward curved dorso-caudal movement along the tongue until the two printed ring marks lie between teeth (Figure 2), or alveolar ridges in edentulous patients. Opposite to the laryngeal mask airway, the ETC should be inserted along the tongue rather than the hard palate.
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Figure 1. Insertion of the Combitube |
Figure 2. Inflation of the balloons |
Complete inflation of the recommended volume is mandatory in emergency situations. In elective cases, however, the minimal leakage technique should be used2,9 in order to avoid any potential stress to the pharyngeal mucosa: starting with 40 mL of air, the function of the balloon should be tested with respect to leakage (auscultation over the neck, comparison of inspiratory and expiratory tidal volume, observation of flow-volume curve). In case of a leak, additional increments of 10 mL each are instilled until a sufficient seal is achieved. Usually, 40 to 85 mL of air are sufficient to obtain a tight seal.2,9 However, higher amounts up to 150 mL of air may be necessary in some individuals.6 Then, the distal balloon is inflated with 5 to a maximum of 12 mL (41 F: 5 to a maximum of 15 mL) of air through the port no. 2 with the white pilot balloon using the small syringe. This balloon seals the esophagus or the trachea.
There is a high probability (up to 98%) of esophageal placement after blind insertion (Figure 3). Therefore, test ventilation is recommended through the longer blue tube, no. 1 leading to the pharyngeal lumen. By ventilating through this distally blocked lumen, air is forced through the holes into the pharynx. Since the oropharyngeal balloon forms a seal against nose and mouth and the distal cuff against the esophagus, air passes over the epiglottis into the trachea. Expiration also occurs through the same holes into the pharyngeal lumen. Please confirm adequate bilateral breath sounds over the lungs by auscultation in the absence of gastric insufflation when the ETC has been placed in the esophagus. Capnography (Easycap, Tyco Nellcor, Pleasanton , CA ) and/or esophageal detection method may be used for confirmation. Ventilation is then continued through this lumen. The second lumen allows for immediate decompression of esophagus and stomach (the deflection elbow prevents the rescuer from soiling) and for suctioning with the help of a thin suction catheter.
If auscultation over the lungs is negative, the ETC has been positioned into the trachea (Figure 4). Now, ventilation is performed via the shorter transparent tube no. 2, leading to the tracheal lumen. Evaluation has to be performed again. Air flows directly into the trachea.
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Figure 3. Esophageal position of the Combitube |
Figure 4. Tracheal position of the Combitube |
In rare cases, ventilation does not function neither via the esophageal nor the tracheal lumen. Then it might have happened that the ETC had been positioned too deeply with the oropharyngeal balloon occluding the laryngeal aperture. Then, the balloons should be deflated, the tube be pulled back for about 2 to 3 cm, and both balloons re-inflated.
While the ETC is easy to insert and to use, it should be trained in a few elective cases observing the above mentioned preliminary measures. Furthermore, clinical judgment as in any anesthetic procedure is mandatory to avoid any possible adverse effect. While the ETC may be inserted blindly, the use of a laryngoscope is recommended.
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There are many ways to replace an ETC by a conventional endotracheal tube (ETT). The maximum duration of ventilation observed with the ETC was eight hours. A simple maneuver to replace the ETC is to deflate the oropharyngeal balloon completely with the distal cuff still being inflated. Then, a conventional ETT is placed by inserting a laryngoscope, a fiberoptic bronchoscope, etc. around the ETC. After successful insertion of the ETT, the distal cuff is deflated and the ETC removed under continuous suctioning via the so-called tracheal lumen, thereby preventing the danger of aspiration. In case of failed endotracheal intubation, the oropharyngeal balloon has to be re-inflated and ventilation be continued via the ETC until another method of ventilation is installed.
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Gaitini10 studied the replacement of the ETC by nasotracheal fiberoptic bronchoscopy in 40 patients with Mallampati class III or IV. The oropharyngeal balloon was partially deflated while the fiberscope was introduced posteriorly around the balloon. The advantage of this method is that there is no interruption of airway control and/or ventilation. In his study, replacement was performed quicker in spontaneously breathing than in mechanically controlled ventilated patients. This technique of replacing without interruption of ventilation is unique for an alternate airway and is of special value in patients with severe pulmonary dysfunction.
Besides the above mentioned non-invasive techniques of replacement, also cricothyrotomy or tracheotomy may be performed 11,12 during ventilation over the ETC. The advantage is that the trachea is not occupied by an ETT.
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Several studies show that ventilation and oxygenation via the ETC are comparable to endotracheal intubation in patients experiencing surgery or cardiac arrest.10,13,14 Oxygenation is even better with the same respiratory setting.13,14 This phenomenon was studied13 in 12 patients undergoing general anesthesia during routine surgery. A thin catheter was placed with its tip 10 cm below the vocal cords into the trachea for measuring intratracheal pressures. In randomized order, each patient was ventilated by mask, by an ETT, and by the ETC in esophageal position for 20 min with each airway. Pressures were recorded in the trachea and at the airway openings. At the end of each period arterial blood samples were taken for gas analysis. In the ETC group, arterial oxygen tension was significantly higher than in the ETT group. Significant differences in arterial carbon dioxide tension and pH could be found between all groups, with mask ventilation being associated with the highest PaCO2 and lowest pH, followed by ETC and endotracheal intubation. The greater anatomic dead space may be responsible for this difference. Furthermore, with the ETC the hypopharynx is integrated into the dead space opposite to the ETT. Differences found with respect to intratracheal pressures were: A smaller rising pressure with the ETC; a longer expiratory flow time; and presentation of a small positive end expiratory pressure (PEEP; 2.1±1.2 mm Hg) similar to mask ventilation. The prolonged expiratory flow and the PEEP effect seems to be due to an increase in expiratory resistance caused by the perforations in the pharyngeal lumen. The Auto-PEEP phenomenon might also be caused by integration of the vocal cords into the airway with the ETC. It may be speculated, that the smaller rising pressure, prolonged expiratory-flow time, and auto-PEEP improve conditions for alveolar-arterial-gas exchange.
While the ETC is primarily designed to bridge the gap of an otherwise hypoxic situation for a relatively short period of time, it may also be used for prolonged ventilation.1,6,5 In seven critically ill and mechanically ventilated patients, the ETC was used over a period of two to eight hours. On several occasions, the ETC has been used during emergencies for hours, e.g. emergency cardiac bypass surgery, etc. As a conclusion from the available literature the ETC provides excellent oxygenation and ventilation as comparable to standard endotracheal intubation.2,10 Urtubia describes the value of the ETC 37 F SA in patients from 122 to 185 cm in height during routine surgery.2 Airway protection as evaluated by oral administration of methylene blue appeared to be adequate. He also established a direct relationship between the oropharyngeal balloon volume and patient height by using linear regression models. The volume of air required to prevent an air leak around the pharyngeal balloon varied between 40 and 85 mL. Similar results could be found by Hartmann10 when using the ETC 37 SA during gynecological laparoscopy. In 100 patients, the ETC was compared to endotracheal intubation. An airtight seal was obtained using air volumes of 55 ± 13 mL for the oropharyngeal, and 10 ± 1 mL for the distal cuff in the esophagus. The ETC provided a patent airway during laparoscopy with non-traumatic insertion and an airtight seal at airway pressures of up to 30 cm H2O.
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Insertion of the ETC takes a very short time: 12 to 23 seconds,16 16 ± 3 sec.10 Coincidentally, intubation time was significantly shorter when compared to placement of an ETT in a crossover study of patients undergoing in-hospital CPR.14 Opposite to endotracheal intubation, the skills required for ETC placement are easier to maintain. In another study, intensive care unit nurses placed the ETC successfully in cardiopulmonary arrest patients within 30 seconds after having received only 2 hours of theory and mannequin demonstration.17 This study supports the hypothesis that personnel can successfully use the ETC with the proper training. In an unpublished study on 1498 patients in Quebec , Canada , a 95 % insertion success and 91 % ventilation success rate were found.18
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The primary idea of the ETC was its use by medical and non-medical personnel during prehospital resuscitation.19,20 Moreover, several independent studies have been published documenting the effectiveness of this device in routine surgery,2,3,4,10 cardiopulmonary resuscitation,14,18,19 and in mechanical ventilation in the ICU.15 As an advantage, the device represents the “All-in-one” concept: It may be used equally well in different situations regarding procedure and level of skills. There is no need to carry different types of a device misleading to confusion. The ETC is mainly used for airway control in emergencies in and out of hospital whenever establishment of an ETT is not immediately possible.19,20,21 As a major advantage in trauma patients, the ETC can be inserted blindly without moving of the head or neck.21,22 The use of the ETC has been documented also in patients suffering from massive bleeding or regurgitation,23 since intubation with the ETC does not require visualization of the vocal cords. The extraordinary sealing of the oropharyngeal balloon prevents swallowing or inspiring of blood, secretions, and foreign bodies. In non-fasting patients, either immediate decompression of the esophagus may be observed (in these situations the elbow deflector should be mounted on the outer end of the “pharyngeal” lumen), or gastric contents may be suctioned via the open “pharyngeal” lumen. Further advantages include the easiness to introduce the ETC in patients exhibiting difficult airway anatomy (such as bull neck, lockjaw) or under difficult circumstances with respect to space (such as difficult access when the patient is lying with his head close to the wall or in the ICU with many lines at the side, or in patients trapped in a car after an accident) and under difficult illumination (bright light might inhibit direct laryngoscopy). To avoid any surprise in emergencies, we recommend to train the ETC in elective cases.
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The ETC is accepted as a valuable tool in the "cannot intubate, cannot ventilate" situation. 24,25 As described before, insertion of the ETC is possible without visualization of the vocal cords, which is beneficial in the presence of blood and/or vomitus.23
Case reports describe the value of the ETC when rapidly developing cervical hematomas following inadvertent carotid puncture prevented visualization of the glottis.26 The ETC was also successfully used as a rescue device in a patient with massive oropharyngeal hemorrhage following thrombolytic therapy23 and in a patient with extreme nasal hemorrhage after unsuccessful nasotracheal intubation despite all precautions.27 There are numerous case reports including limited spine mobility in severe rheumatoid arthritis. The American Society of Anesthesiologists task force on difficult airway management24 concluded the ETC to be included in a portable kit for the management of difficult airways, with particular reference to its potential use in the "cannot intubate, cannot ventilate" scenario. The two other techniques recommended for the "cannot intubate-cannot mask ventilate" situation are transtracheal jet ventilation (TTJV) and the laryngeal mask airway (LMA). While TTJV requires special equipment and some degree of skill in locating the cricothyroid membrane, the LMA does not offer the same level of protection against aspiration and applicability of ventilatory pressures greater than approximately 16 to 18 cm H20. While the ETC is ready to use in its package, the LMA should be lubricated and its cuff deflated before insertion. Wissler has inserted the ETC during obstetric anesthesia,28 concluding that the ETC is his first choice for the anesthetized parturient who cannot be intubated or mask ventilated with cricoid pressure. The strong anchoring of the ETC behind the hard palate may be beneficial in emergency situations. Therefore, in patients at risk for aspiration, such as obese, obstetric, or emergency patients, the ETC offers advantages over the LMA. Another advantage of the ETC is that there is no need for neck movement in patients with suspected or evident cervical spine injury.
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In many studies, application of the ETC during CPR has been evaluated. In the first of these studies,29 effectiveness of ventilation was assessed in 31 patients requiring CPR following non-traumatic cardiac arrest calls in-hospital. In the first part, the adequacy of ventilation by ETC was examined, in the second part the efficiency of ventilation with the ETC with a conventional ETT (internal diameter 8 mm) was compared. An adequate level of ventilation and oxygenation could be shown in the first part. In the second part, patients ventilated via the ETC again exhibited significantly higher mean arterial oxygen tensions compared to endotracheal airway. In postmortem examinations there was neither macroscopic nor microscopic evidence of pulmonary aspiration. The promptness and effectiveness of ventilation via the ETC during CPR was investigated in another study.15 Intubation time was significantly shorter in the ETC group (27.3 ± 8.4 sec) compared to the ETT group (39.7 ± 10.0 sec) and mean arterial oxygen tensions higher.
Tanigawa20 found the ETC to be the most successful device with respect to insertion and ventilation in CPR of non-traumatic, out of hospital cardiac arrest patients when compared to LMA and esophageal gastric tube airway (EGTA) in a review of 10,020 cases. In a study performed by Rumball,19 the ETC was rated superior to LMA and PTLA by the emergency medical technicians despite LMA was trained in the operating room. The results with respect to ventilation success rates, tidal volumes, arterial blood gas analyses, and prevention of aspiration were all in favor of the ETC. In a bench model comparing bag-valve, LMA and ETC, the ETC was superior with respect to sealing the airway.30
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The advantages of the ETC comprise: non-invasive, easy to learn and effective, safe in elective cases as well as in emergencies, no need of preparations, it allows blind insertion as well as insertion under laryngoscopical view, neck flexion not necessary, minimizing the risk of aspiration, no need for additional fixation of the ETC after inflation of the oropharyngeal balloon, possibility to perform controlled mechanical ventilation at ventilatory pressures up to 50 cm H2O, no need of power supply (e.g., batteries of laryngoscope), well suited for obese patients, extremely useful in paralyzed patients who cannot be intubated or mask ventilated, helpful under difficult circumstances with respect to space and illumination, optimal in cases of bleeding when visualization of vocal cords is impossible, works equally well in either tracheal or esophageal position
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La aspiración de las secreciones traqueales es imposible cuando el ETC está en la posición esofágica. No obstante, el ETC se diseñó originalmente para ser usado en el ¨puente¨ del intervalo relativamente corto entre el ambiente prehospitalario y la admisión de los pacientes al departamento de urgencias. En caso de ser necesaria la ventilación prolongada, la administración de bromuro de glicopirrolato suprime las secreciones traqueales.16
Como una modificación, 31 las dos perforaciones anteriores y proximales en el lumen faríngeo del ETC se pueden remplazar por una sola perforación más grande, en forma de un agujero elipsoide, permitiendo un acceso para el fibroscopio y así realizar succión traqueal, y cambio de tubo sobre una guía metálica. Por fortuna, los broncoscopios modernos (Storz, Alemania) con un diámetro externo muy pequeño permiten el paso a través de los orificios del ETC en su versión actual.
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Contraindications are: Patient height less than 4 feet (approximately 123 cm) with the ETC SA ("small adult"), intact gag reflex,8 presence of known esophageal disease or prior ingestion of caustic substances, obstruction of the upper airways.
In a 1999 prospective, randomized, and controlled trial, about hemodynamic and catecholamine stress responses to insertion of the ETC, LMA or ETT, the ETC insertion was associated with a significant increase in mean maximal systolic arterial pressure and diastolic arterial pressure. The mean maximal epinephrine and norepinephrine plasma concentrations after insertion of the ETC were significantly increased, too. Authors suggested that this might be attributed to the pressure of the pharyngeal cuff of the ETC on the anterior pharyngeal wall. Adequate anesthesia, use of a laryngoscope, and application of the minimal leakage technique avoid these problems. A final contraindication is upper airway (supralaryngeal) obstruction, such as the presence of a foreign body, severe glottic edema, or epiglottitis.
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Until now, just few complications have been reported in the literature using the ETC. Small amounts of blood may be present on the ETC after removal. While Ovassapian [Ovassapian A, personal communication, 1994] observed livid discoloration of the tongue indicating venous gorging during ventilation with the ETC without further sequelae, minimal leakage technique is able to avoid this phenomenon.
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During the years, the ETC has gained world-wide interest and is now an integral part of airway equipment in many anesthesiology departments and ambulance services. The ETC has been included into the "Practice Guidelines for Management of the Difficult Airway" of the American Society of Anesthesiologists,24 into the "Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiac Care" of the American Heart Association already in 1992;25 in 2000 the AHA has rated the ETC as a class IIa device for advanced cardiac life support), and into the Guidelines of the European Resuscitation Council in 1996,34 besides many national guidelines and algorithms. Ongoing studies show its safety and effectiveness in elective surgery as well as in emergencies.35,38
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In many worldwide studies, the ETC has been shown to be a safe device securing the airways and providing adequate oxygenation and ventilation in elective patients as well as in emergencies in- and out-of-hospital. In elective cases, the use of a laryngoscope in conjunction with the minimal leakage technique is recommended. The advantages of the ETC include ease and quick insertion, blind or visualized placement, strong anchoring of the oropharyngeal balloon behind the hard palate after inflation, sufficient ventilation and oxygenation in both esophageal and tracheal position, applicability of high ventilatory pressures and prevention of aspiration. Several national and international medical societies including ASA, AHA, and European Resuscitation Council have incorporated the ETC as a primary non-invasive device in their respective guidelines for “cannot ventilate – cannot intubate” situations. Training of the ETC under controlled elective conditions is mandatory to gain expertise for emergency situations. The ETC is non-invasive alternative to endotracheal intubation in cases of predicted or unpredicted difficult airways.
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- Frass M. The Combitube: esophageal/Tracheal double-lumen airway. In Benumof JL, editor: Airway Management Principle and Practice , S. Louis, Missouri , 1996, Mosby
- Urtubia RM, Aguila CM, Cumsille MA: Combitube: A study for proper use. Anesth Analg 2000;90:958-962.
- Gaitini LA, Vaida SJ, Mostafa S, Yanovski B, Croitoru M, Capdevila MD, Sabo E, Ben-David B, Benumof J. The Combitube in elective surgery: A report of 200 cases. Anesthesiology 2001;94:79-82.
- Walz R, Davis S, Panning B. Is the Combitube a useful emergency airway device for anesthesiologists? Anesth Analg 1999;88:233.
- Krafft P, Nikolic A, Frass M. Esophageal rupture associated with the use of the Combitube. Anesth Analg 1998;87:1457.
- Lipp M, Jaehnichen G, Golecki N, Fecht G, Reichl R, Heeg P. Microbiological, microstructure, and material science examinations of reprocessed Combitubes after multiple reuse. Anesth Analg 2000;91:693-697.
- Urtubia R, Aguila C. Combitube: a new proposal for a confusing nomenclature. Anesth Analg 1999;89:803.
- Klein H, Williamson M, Sue-Ling HM, Vucevic M, Quinn AC. Esophageal rupture associated with the use of the Combitube. Anesth Analg 1997;85:937-939.
- Hartmann T, Krenn CG, Zoeggeler A, Hoerauf K, Benumof JL, Krafft P. The oesophageal - tracheal Combitube small adult. An alternative airway for ventilatory support during gynaecological laparascopy. Anaesthesia 2000;55:670-675.
- Gaitini LA, Vaida SJ, Fradis M, Somri M, Yanovski B, Kalderon N. Replacing the combitube by an endotracheal tube using a fibre-optic bronchoscope during spontaneous ventilation. Journal Laryngology Otol 1998;112,786-787.
- Mallick A, Quinn AC, Bodenham AR, Vucevic M. Use of the Combitube for airway maintenance during percutaneous dilatational tracheostomy. Anaesthesia 1998;53: 249-255.
- Wiltschke C, Kment G, Swoboda H. Ventilation with the combitube during tracheostomy. Laryngoscope 1994;104:763-765.
- Frass M, Rödler S, Frenzer R, Ilias W, Leithner C, Lackner F. Esophageal tracheal combitube, endotracheal airway, and mask: comparison of ventilatory pressure curves. J Trauma 1989;29:1476-1479.
- Frass M, Frenzer R, Rauscha F, Schuster E, Glogar D. Ventilation with the esophageal tracheal combitube in cardiopulmonary resuscitation. Promptness and effectiveness. Chest 1988;93:781-784.
- Frass M, Frenzer R, Mayer G, Popovic R, Leithner C. Mechanical ventilation with the esophageal tracheal combitube (ETC) in the intensive care unit. Arch Emerg Med 1987;4:219-225.
- Lipp M, Thierbach A, Daubländer M, Dick W. Clinical evaluation of the Combitube. 18th Annual Meeting of the European Academy of Anaesthesiology, August 29 to September 1, 1996, Copenhagen, Denmark, p 43
- Staudinger T, Brugger S, Watschinger B. Emergency intubation with the combitube: comparison with the endotracheal airway. Ann Emerg Med 1993;22: 1573-1575.
- Lefrancois DP, Dufour DG. Use of the esophageal tracheal combitube by basic emergency medical technicians. Resuscitation 2002;52:77-83.
- Rumball CJ, MacDonald D. The PTL, Combitube, laryngeal mask, and oral airway: a randomized prehospital comparative study of ventilatory device effectiveness and cost-effectiveness in 470 cases of cardiorespiratory arrest. Prehosp Emerg Care 1997;1:1-10.
- Tanigawa K, Shigematsu A. Choice of airway devices for 12,020 cases of nontraumatic cardiac arrest in Japan . Prehosp Emerg Care 1998;2:96-100.
- Blostein PA, Koestner AJ, Hoak S. Failed rapid sequence intubation in trauma patients: esophageal tracheal combitube is a useful adjunct. J Trauma 1998; 44: 534-537.
- Mercer MH, Gabbott DA. The influence of neck position on ventilation using the Combitube airway. Anaesthesia 1998;53:146-150.
- Klauser R, Röggla G, Pidlich J, Leithner C, Frass M. Massive upper airway bleeding after thrombolytic therapy: successful airway management with the combitube. Ann Emerg Med 1992;21:431-433.
- Practice Guidelines for Management of the Difficult Airway. An updated report by the American Society of Anesthesiologists Task Force on management of the difficult airway. Anesthesiology 2003 98:1269-1277.
- American Heart Association (AHA) Emergency Cardiac Care (ECC) Guidelines, Part 6: Advanced Cardiovascular Life Support, Section 3: Adjuncts for Oxygenation, Ventilation, and Airway Control. Airway Adjuncts. Circulation 2000;102:I-95 - I-104
- Bigenzahn W, Pesau B, Frass M. Emergency ventilation using the combitube in cases of difficult intubation. Eur Arch Otorhinolaryngol 1991;248:129-131.
- Kulozik U, Georgi R, Krier C. Intubation with the Combitube-TM in massive hemorrhage from the locus Kieselbachii. Anasthesiol Intensivmed Notfallmed Schmerzther 1996;31:191-193.
- Wissler R. The esophageal-tracheal combitube. Anesthesiol Rev 1993;20:147.
- Frass M, Frenzer R, Zdrahal F, Hoflehner G, Porges P, Lackner F. The esophageal tracheal combitube: Preliminary results with a new airway for CPR. Ann Emerg Med 1987;16:768-772.
- Doerges V, Sauer C, Ocker H, Wenzel V, Schmucker P. Airway management during cardiopulmonary resuscitation--a comparative study of bag-valve-mask, laryngeal mask airway and combitube in a bench model. Resuscitation 1999; 41: 63-69.
- Krafft P, Röggla M, Fridrich P, Locker GJ, Frass M, Benumof JL. Bronchoscopy via a redesigned Combitube in the esophageal position. A clinical evaluation. Anesthesiology 1997;86:1041-1045.
- Vezina D, Lessard MR, Bussieres J, Topping C, Trepanier CA. Complications associated with the use of the Esophageal-Tracheal Combitube. Can J Anaesth 1998;45:76-80.
- Oczenski W, Krenn H, Dahaba AA. Hemodynamic and catecholamine stress responses to insertion of the Combitube, laryngeal mask airway or tracheal intubation. Anesth Analg 1999;88:1389-1394.
- Baskett PJF, Bossaert L, Carli P. Guidelines for the advanced management of the airway and ventilation during resuscitation. Resuscitation 1996;31:201-230.
- Gaitini LA, Vaida SJ, Mostafa S, Yanovski B, Croitoru M, Capdevila MD, Sabo E, Ben-David B, Benumof J. The Combitube in elective surgery: A Report of 200 Cases. Anesthesiology 2001;94:79-82.
- Hoerauf KH, Hartmann T, Acimovic S, Kopp A, Wiesner G, Gustorff B, Jellinek H, Krafft P. Waste gas exposure to sevoflurane and nitrous oxide during anaesthesia using the oesophageal-tracheal Combitube small adultTM. Br J Anaesth 2001;86:124-126.
- Ochs M, Vilke GM, Chan TC, Moats T, Buchanan J. Successful prehospital airway management by EMT-Ds using the combitube. Prehosp Emerg Care 2000;4:333-337.
- Davis DP, Valentine C, Ochs M, Vilke GM, Hoyt DB. The Combitube as a salvage airway device for paramedic rapid sequence intubation. Ann Emerg Med 2003;42:697-704.