Rapid and effective airway control is the primary objective in cardiopulmonary resuscitation (CPR), and tracheal intubation is the best method to protect the airway and to adequately ventilate the lungs of patients .
The 2000 European Resuscitation Council Guidelines for Adult Advanced Life Support  state that the endotracheal tube remains the gold standard for securing the airway during CPR, when undertaken by experienced personnel. However, the laryngeal mask airway and the oesophageal-tracheal Combitube® are acceptable alternatives to endotracheal intubation, when healthcare providers have little experience with this airway technique. While endotracheal intubation skills are difficult to learn [3,4], and require long practice before successfully acquired , the teaching skills for the laryngeal mask airway and the Combitube® are more easily obtained [6-9].
Despite the importance of teaching airway management for medical students and its retention, only one publication has evaluated the process of acquisition and retention of skills for laryngeal mask airway and Combitube® . Since a clerkship in anaesthesia is mandatory during the fifth year of the medical course in the Faculty of Health Sciences of the Ben Gurion University of the Negev, we decide to conduct a study to compare the acquisition and retention of insertion skills of the endotracheal tube, the laryngeal mask airway and the Combitube®.
Sixty-fifth year medical students underwent their mandatory clerkship in the Division of Anesthesiology and Critical Care Medicine of the Soroka Medical Center during the period March 1998 to July 1998. Although we proposed to all that they should participate in this project, only 47 of them volunteered to take part.
The first morning of the clerkship was dedicated to instruction on laryngoscopy and endotracheal intubation, insertion of the laryngeal mask airway and Combitube®. The instructor used audio-visual aids to instruct the students about the theoretical aspects of each device and the proper insertion techniques. The instructor next demonstrated laryngoscopy and endotracheal intubation, as well as laryngeal mask airway and Combitube® insertion in a Laerdal® Airway Management Trainer mannikin.
After these two steps, each student inserted the devices into the mannikin. We defined successful endotracheal intubation as visual confirmation of the tube in the trachea, and satisfactory positioning of the laryngeal mask airway and Combitube®, when full inflation of the lungs was obtained after one attempt.
The participants in this study were asked to complete an anonymous questionnaire to ascertain exposure to the equipment and its previous use; expectancy of successful insertion (i.e. if they felt able to per-form the proposed procedure successfully) just before instruction and training, and to grade the difficulty of insertion on a four-point scale (very easy, easy, difficult and very difficult) after the insertion (phase 1) (Table 1). Six months later, the participants were requested to repeat the procedures; this time without the audio-visual presentation or the instructor demonstration. A second questionnaire was instituted just before the re-testing and, again, the students were asked to grade the difficulty of the procedure, using the same four-value scale (phase 2).
Statistical analysis was performed using the EPI-INFO (CDC Atlanta) software package, the two-tailed Fisher's exact test applied for 2 × 2 contingency tables and t-test for normally distributed values. The non-parametric Kruskal-Wallis test for two groups was used for other analysis. P < 0.05 was considered significant.
Forty-seven medical students volunteered to participate in the phase 1 of the study and 29 of them replied to the phase 2 invitation. At phase 1, 100% of the students had previous knowledge and were exposed to insertion (but they did not insert the devices themselves) of the endotracheal tube, 42 of the laryngeal mask airway, and 10 of the Combitube®. This difference was significant only for the Combitube® (P = 0.03 for the endotracheal tube vs. the laryngeal mask airway, and 0.000 for the Combitube® vs. the endotracheal tube and the laryngeal mask airway). However, only 38 students had inserted an endotracheal tube; 15, the laryngeal mask airway and nobody the Combitube® (P = 0.07 for endotracheal tube vs. the laryngeal mask airway, and P = 0.001 for the Combitube® vs. the endotracheal tube and laryngeal mask airway).
The expectation for successful insertion of the devices among the students with previous exposure to the devices was similar in the three groups (40/47 for the endotracheal tube, 29/42 for the laryngeal mask airway and 8/10 for the Combitube®) (P = 0.52). The success rate was different for the endotracheal tube (28/47), laryngeal mask airway (47/47) and Combitube® (47/47) (P = 0.000).
Endotracheal intubation was graded as difficult/very difficult 27 of 27 questionnaires, while all participants graded insertion of the laryngeal mask airway and Combitube® as easy/very easy (P = 0.000). Twelve of the 29 students that had participated in phase 2 of the study performed endotracheal intubation during the 6-month period between the two phases, while only three had inserted the laryngeal mask airway, and two others the Combitube®. Airway manipulation was done in anaesthetized patients. This difference was significant (P = 0.001). Tracheal intubation was successful in 63% of attempts during phase 2, compared to 93% and 96% for the laryngeal mask airway and the Combitube®, respectively (P <0.001 for the endotracheal tube vs. the laryngeal mask airway and the Combitube®; P = 1.0 for the laryngeal mask airway and Combitube® comparison).
Endotracheal intubation was graded as difficult/very difficult in 20 questionnaires, while insertion of the laryngeal mask and the Combitube® was considered easy/very easy in all questionnaires (P = 0.000).
Interestingly, the success of positioning for endotracheal intubation did not increase in phase 2 of the study, despite the fact that 41% of the students had performed tracheal intubation during the 6-month interval (57% in phase 1 vs. 63% in phase 2, P = 0.85). The results of phase 1 and 2 are summarized in Tables 2 and 3.
It was previously argued that insertion skills for both the laryngeal mask airway and the Combitube® are easy to learn for medical and paramedical personnel [8-11], whereas endotracheal intubation skills are difficult to learn and retain [3,4], and an average of 57 attempts at endotracheal intubation are needed to achieve a 90% success rate .
Airway control and effective lung ventilation are major objectives during CPR, and tracheal intubation is still the gold standard for a secure airway during CPR. It is acknowledged that, with infrequent use, tracheal intubation skills are poorly maintained and much time may be lost trying to intubate patients with cardiac arrest . Manual lung ventilation using a facemask and Guedel airway is a good alternative during CPR . However, facemask ventilation may increase the risk of pulmonary aspiration of gastric contents . This risk seems to be lower with either the laryngeal mask or the Combitube® .
Our results clearly demonstrate that laryngeal mask airway and Combitube® insertion skills are easily learned and better retained than those for endotracheal intubation. The utilization of either a laryngeal mask airway or a Combitube® may provide rapid and effective airway control, with faster initiation of ventilation, during CPR when unskilled medical personnel are called upon to initiate resuscitation, until an operator with enough experience of endotracheal intubation arrives at the scene. Despite the fact that the rate of successful insertion and skills retention with the Combitube® and the laryngeal mask is similar, the laryngeal mask airway seems to be superior because it is less traumatic  and produces less adverse haemodynamic responses . It is important to be aware that severe traumatic complications, such as perforation of the piriform sinus  and the oesophagus , have been reported, and a higher incidence of complications should be considered when the Combitube® is used .
The ideal period of time for assessment of skills retention has not been yet established. Atherton and Johnson  showed that after 15 months between initial training and reassessment, the performance of paramedics with the Combitube® was very poor. However, this interval may be too long. On the other hand, Roberts and colleagues  demonstrated good retention of skills, when nurses repeated laryngeal mask airway insertion after 3 months of initial training. Nevertheless, this period can be too short. We arbitrarily choose a 6-month interval for our study.
The clinical application of this research may be questioned, since the training and skills acquisition were performed in mannikins and not in patients. Roberts and colleagues  compared laryngeal mask airway insertion training programs for nurses without prior experience with the use of the laryngeal mask in anaesthetized patients or mannikins. They were unable to detect any difference in skill performance and retention between the two methods, proposing that mannikins alone may be adopted as a training modality.
In conclusion, using a mannikin training programme, skill acquisition and retention were superior with the laryngeal mask airway and the Combitube® than with endotracheal intubation. We believe that because of the better skill retention seen with the laryngeal mask airway and the Combitube®, rather than with the endotracheal tube, these techniques should be taught to medical students, we can improve future emergency airway manipulation. However, further studies are recommended to assess the validity of this hypothesis.
1. Donegan JH. New concepts in cardiopulmonary resuscitation. Anesth Analg
2. de Latorre F, Robertson C, Chamberlain D, Baskett P. European Resuscitation Council Guidelines 2000 for Adult Advanced Life Support. Resuscitation
3. Nelson MS. Medical student retention of intubation
skills. Ann Emerg Med
4. O'Flaherty D, Adams AP. Endotracheal intubation
skills of medical students. J Royal Soc Med
5. Konrad C, Schupfer G, Wietlishbach M, Gerber H. Learning
manual skill in anesthesiology: is there a recommended number of cases for anesthetic procedures? Anesth Analg
6. Choyce A, Avidan MS, Patel C, et al
. Comparison of laryngeal mask and intubating laryngeal mask insertion by the naïve intubator. Br J Anaesth
7. Davies PR, Tighe SQ, Greenslade GL, Evans GH. Laryngeal mask airway and tracheal tube by unskilled personnel. Lancet
8. Pennant JH, Walker MB. Comparison of the endotracheal tube
and laryngeal mask in airway management by paramedic personnel. Anesth Analg
9. Reinhart DJ, Simmons G. Comparison of placement of the laryngeal mask airway with endotracheal tube
by paramedics and respiratory therapists. Ann Emerg Med
10. Atherton GL, Johnson JC. Ability of paramedics to use the Combitube in prehospital cardiac arrest. Ann Emerg Med
11. Alexander R, Hodgson P, Lomax D, Bullen C. A comparison of the laryngeal mask airway and Guedel airway, bag and facemask for manual ventilation following formal training. Anaesthesia
12. Tolley PM, Watts AD, Hickman JA. Comparison of the use of laryngeal mask and facemask by inexperienced personnel. Br J Anaesth
13. Martin PD, Cyna AM, Hunter WAH, Henry J, Ramayya GP. Training nursing staff in airway management for resuscitation. A clinical comparison of the facemask and laryngeal mask. Anaesthesia
14. Oczenski W, Krenn H, Dahaba AA, et al
. Complications following the use of the Combitube, tracheal tube and laryngeal mask airway. Anaesthesia
15. Oczenski W, Krenn H, Dahaba AA, et al
. Hemodynamic and catecholamine stress responses to insertion of Combitube, laryngeal mask airway or tracheal intubation
. Anesth Analg
16. Richards CF. Piriform sinus perforation during esophageal-tracheal Combitube placement. J Emerg Med
17. Vezina D, Lessard MR, Bussieres J, Topping C, Trepanier CA. Complications associated with the use of the esophageal-tracheal Combitube. Can J Anaesth
18. Tagnigawa K, Shigematsu A. Choice of airway devices for 12,020 cases of nontraumatic cardiac arrest in Japan. Prehosp Emerg Care
19. Roberts I, Allsop P, Dickinson M, Curry P, Eastwick-Field P, Eyre G. Airway management training using the laryngeal mask airway: a comparison of two different training programmes. Resuscitation