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Anesthesiology:
Correspondence

Is the Combitube Traumatic?

Urtubia, Ricardo M. M.D.*; Gazmuri, Rodrigo R. M.D.

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To the Editor:—
We read with interest the article published by Keller et al., 1 who tested the Combitube 37 F SA (Kendall-Sheridan Catheter Corp., Argyle, NY). Our main observations about the study are as follows.
First, contrary to their ethical consideration of not using the recommended volumes in elective surgery patients because of the high risk of trauma, the authors used much greater volumes than those they wanted to avoid. The manufacturer recommends 85 ml (not 100 ml) of air for the pharyngeal balloon and 12 ml (not 20 ml) for the distal cuff of the 37 F SA model, 2 which are inflation volumes for only emergency intubation. In elective cases, the minimal leakage technique should be used to minimize pressure exerted on the pharyngeal mucosa, which means that from 40 up to 85 ml and less than 12 ml, respectively, are usually sufficient to achieve a tight seal. 3,4
Furthermore, use of the Combitube is contraindicated when the gag reflexes are intact, as occurs in awake, nonanesthetized patients, a fact that the authors completely overlooked. This seems unethical to us because without sufficient knowledge of the basics of what they intended to test, the investigators exposed the volunteers to an increased risk of complications. In fact, all of them reported sore throat.
Second, the main implications of the study relate to the safety of using the Combitube in elective surgery patients. Other investigators 4–6 have tested the device in such a population, concluding that elective use of the Combitube is not only safe but also reliable and feasible in most patients. Thus, the results of a study involving only four patients must be interpreted cautiously.
Third, concerning the cause of pharyngeal–esophageal lesions, although it has not been fully investigated, our impression is that, as with other procedures in anesthesia, they relate much more to the performing hands than to the device itself. According to the American Society of Anesthesiologists closed claims database, 7 most claims for esophageal injuries were for esophageal perforation (43 of 48; 90%), which involved difficult tracheal intubation in 67% of cases (n = 29). In addition, the intubating laryngeal mask airway 8 has been reported to cause fatal esophageal perforation during elective general anesthesia.
Nevertheless, the authors do not label the laryngeal mask airway as risky as they so superficially did with the Combitube. The cited reports of esophageal lesions associated with Combitube use are incidental cases involving paramedics in an out-of-hospital emergency setting who, exactly like the authors themselves, did not follow the recommendations. According to the criteria of evidence-based medicine, such reports should be classified as class C evidence, and they represent a poor basis for analysis. 9
Fourth, we missed in this study some essential qualities of good trial design, such as randomization or blind assessment of outcome. 10,11
In conclusion, we are alarmed that colleagues who are not very experienced with these aspects of clinical investigation might falsely interpret this article. Finally, we are worried that biased studies could overshadow serious attempts to investigate in clinical practice.
Ricardo M. Urtubia, M.D.*
Rodrigo R. Gazmuri, M.D.
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References

1. Keller Ch, Brimacombe J, Boehler M, Loeckinger A, Puehringer F: The influence of cuff volume and anatomic location on pharyngeal, esophageal, and tracheal mucosal pressures with the esophageal tracheal Combitube. A nesthesiology 2002; 96: 1074–7

2. Frass M: The Combitube: esophageal/tracheal double lumen airway, Airway Management: Principles and Practice. Edited by Benumof JL. St. Louis, Mosby, 1996, pp 444–54

3. Urtubia RM, Aguila CM, Cumsille MA. Combitube: A study for proper use. Anesth Analg 2000; 90: 958–62

4. Hartmann T, Krenn CG, Zoeggeler A, Hoerauf K, Benumof JL, Krafft P: The oesophageal-tracheal Combitube Small Adult. Anaesthesia 2000; 55: 670–5

5. Gaitini LA, Vaida SJ, Mostafa S, Yanovski B, Croitoru M, Capdevilla MD, Sabo E, Ben-David B: The Combitube in elective surgery: A report of 200 cases. A nesthesiology 2001; 94: 79–82

6. Walz R, Davis S, Panning B: Is the Combitube a useful emergency airway device for anesthesiologists? Anesth Analg 1999; 88: 233

7. Domino KB, Posner KL, Caplan RA, Cheney FW: Airway injury: A closed claim analysis. A nesthesiology 1999; 91: 1703–11

8. Branthwaite MA: An unexpected complication of the intubating laryngeal mask. Anaesthesia 1999; 54: 166–7

9. Ackman ML, Druteika D, Tsuyuki RT: Levels of evidence in cardiovascular clinical practice guidelines. Can J Cardiol 2000; 16: 1249–54

10. Todd MM: Clinical research manuscripts in anesthesiology [editorial]. A nesthesiology 2001; 95: 1051–3

11. Pua HL, Lerman J, Crawford MW, Wright JG: An evaluation of the quality of clinical trials in anesthesia. A nesthesiology 2001; 95: 1068–73

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