Department of Anaesthesiology, Kansai Medical University, 1015 Fumizono-cho, Moriguchi City, Osaka, 570-8507, Japan
* Corresponding author. E-mail: asait{at}takii.kmu.ac.jp
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Abstract |
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Keywords: airway ; complications, difficult intubation ; equipment, laryngeal tube
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Introduction |
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Standard laryngeal tube
The initial design of the laryngeal tube has been modified. The current device consists of an airway tube with a small cuff attached at the tip (distal cuff) and a larger balloon cuff at the middle part of the tube (proximal cuff) (Figs 1 and 2). The cuffs are inflated through a single pilot tube and balloon, through which cuff pressure can be monitored. There are three black lines on the tube near a standard 15-mm connector, which indicate adequate depth of insertion when aligned with the teeth. The device is made of silicone (latex free) and is re-usable, after sterilization in an autoclave, up to 50 times. There are six sizes, suitable for neonates up to large adults (Table 1).
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Anatomical position |
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Insertion and removal of the laryngeal tube |
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Inflation of the cuffs
The cuff should be inflated to a pressure of 60 cm H2O.18 It may be easier to inflate the cuffs to a higher pressure and then adjust them to 6070 cm H2O. This can be done either with a cuff inflator or a 100 ml syringe with the marks for the recommended volumes for each size of the laryngeal tube (Fig. 4; Table 1).
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Concern has been expressed that the intracuff pressure of 60 cm H2O is too high and could cause ischaemic changes to the pharynx.4 Nevertheless, what is important is the pressure exerted by the cuff on the oropharyngeal tissues, because the exerted pressure may be unrelated to the intracuff pressure.5
Asai and Kawachi8 studied the exerted pressure by calculating the difference between intracuff pressures measured with the device in place in the patient and held in air, with the cuffs inflated with the same volume of air. The exerted pressure was 29 (range 2436) cm H2O at an intracuff pressure of 60 cm H2O.8 Brimacombe and colleagues28 directly measured the exerted pressure, by applying gauge microchip sensors to the cuffs of a size 4 laryngeal tube. At the recommended cuff volume of 80 ml, the intracuff pressure was 70 (range 5593) cm H2O, and the exerted pressure to the posterior pharynx was 37 (2660) cm H2O.
Using the cuffed oropharyngeal airway (COPA), Brimacombe and colleagues27 have shown that blood vessels in the pharyngeal mucosa started to be compressed when the exerted pressure on the pharynx exceeded 34 cm H2O and collapsed when the exerted pressure reached 73 cm H2O. Because the exerted pressure by the cuffs of the laryngeal tube is somewhere 3035 cm H2O (with an intracuff pressure of 60 cm H2O) the perfusion of the pharynx would not be reduced markedly. When nitrous oxide is used, the intracuff pressure may increase up to 120 cm H2O during 2 h of anaesthesia,22 and at this pressure, the exerted pressure can reach
50 cm H2O.28 Therefore, when nitrous oxide is used, the pressure on the pharynx may be high enough to compress, if not collapse, the blood vessels in the pharynx. Nevertheless, factors other than the cuff pressure, such as the shape, material and compliance of the cuff, have an important effect on the incidence of ischaemia of oropharyngeal tissues.5 As with any other airway device, vigilance is required during the use of the laryngeal tube, and excessive gas should be regularly removed from the cuffs.
Adjustment of the device position
If it is not possible to ventilate the lungs after insertion of the laryngeal tube, the following adjustments may enable ventilation: lifting the angle of the mandible vertically upwards, further extension of the patient's head on the neck, turning the patient's head to the side and a gentle push or pull of the device.12 18 31 If insertion or ventilation fails after two to three attempts, the laryngeal tube should be abandoned and an alternative airway used.
Removal of the laryngeal tube
The laryngeal tube may be removed while the patient is still deeply anesthetized or after the patient has regained consciousness and has responded to verbal command to open the mouth.18 31 The cuffs of the laryngeal tube should be deflated before removal.
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Efficacy |
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The standard laryngeal tube
The insertion of the standard laryngeal tube is generally easy. The reported success rate of insertion of, and ventilation through, the laryngeal tube ranges 92100% for the earlier prototype10 12 18 26 33 35 37 53 and 97100% for the newest type.22 24 31 32
Three studies reported that the laryngeal tube provided a clear airway during controlled ventilation in a majority of patients.18 24 33
There have been four studies comparing the standard laryngeal tube and laryngeal mask airway classic during controlled ventilation.12 31 53 58 These studies are in agreement on a number of points: the ease of insertion of the laryngeal tube is similar to that of the laryngeal mask airway classic and may provide a better seal and the peak airway pressure generated in the laryngeal tube is higher than that for the laryngeal mask airway,31 53 due probably to a narrower breathing tube and smaller distal apertures. However, the difference between the two devices is 2 cm H2O and thus may not be clinically relevant.31 The incidence of complications associated with the use of the laryngeal tube is similar to that for the laryngeal mask, although the laryngeal tube may require more re-adjustments of its position to obtain a clear airway. Lastly, similar to the laryngeal mask airway, the laryngeal tube can be left in place until the patient has regained consciousness, without major respiratory complications.12 31 53 58 Therefore, it can be concluded that the laryngeal tube is generally as effective as the laryngeal mask airway classic.
There have been two studies comparing the efficacy of the laryngeal tube and the ProSealTM laryngeal mask.26 32 Brimacombe and colleagues studied 120 patients and reported that the success rate for the insertion of the laryngeal tube at the first attempt was similar to that for the ProSeal, but the success rate after three attempts was lower for the laryngeal tube (55 of 60 patients) than for the ProSeal (all 60 patients). The leak pressure was similar, but the expiratory tidal volume was lower, and the end-tidal carbon dioxide concentration was higher, for the laryngeal tube. More adjustments of the device position, inspiratory oxygen concentration and respiratory rate, were required for the laryngeal tube. The incidence of postoperative complications was similar. Cook and colleagues32 reported that the success rate of insertion within two attempts was similar between the laryngeal tube and ProSeal, but insertion of the laryngeal tube took longer. The leak pressure and the number of adjustments of position were similar, but the peak airway pressure was higher for the laryngeal tube. In addition, airway patency was better with the ProSeal. From these results, it appears that the laryngeal tube is less effective than the ProSeal during controlled ventilation under general anaesthesia.
There are only a few reports of the efficacy of the laryngeal tube during spontaneous ventilation. Miller and colleagues50 assessed the efficacy of a prototype laryngeal tube and had to abandon its use in 25 of 27 occasions. Figueredo and colleagues35 studied 35 patients and reported that insertion of a prototype laryngeal tube was successful at the first attempt in only 18 patients (51%). These reports could simply indicate that the laryngeal tube is not useful during spontaneous breathing, but other interpretations may be made. One possibility is that as the device that Miller and colleagues used was a prototype7 its efficacy was not satisfactory. A subsequent study by Miller found that the success rate of adequate ventilation through the new laryngeal tube was higher than that for the prototype.31 Another possibility is that the high failure rates in their study were due to technical problems.50 This may be a more likely reason, because even when ventilation was controlled, insertion of, and ventilation through, the laryngeal tube, failed far more frequently in their studies compared with other studies.18 22 31 32 In addition, in these other studies, the airway did not obstruct even when the patient started to breathe spontaneously (after controlled ventilation) during emergence from anaesthesia.31 32
There have been only three studies of the use of the laryngeal tube in children, and all are available only as abstracts.41 42 56 These reports indicate that repeated attempts may be required for successful insertion, and the device may be less effective in children than in adults.
The laryngeal tube-Suction
The efficacy of the laryngeal tube-Suction II is yet to be determined, because there have been only a few reports on the first type of this device with inconsistent results.30 38 57 Gaitini and colleagues38 studied 150 patients and found that the success rate of insertion, leak pressure and the number of adjustments of the device position were similar to those for the laryngeal tube-Suction and the ProSeal laryngeal mask. In addition, the success rate of passing a gastric tube through the laryngeal tube-Suction into the stomach (96%) was similar to that for the ProSeal. Roth and colleagues57 studied 50 patients and concluded that the laryngeal tube Suction was as effective as the ProSeal laryngeal mask. In contrast, in 32 patients, Cook and colleagues30 concluded that the quality of airway maintenance and the ability to ventilate the patient's lungs through the laryngeal tube-Suction was inferior to that through the ProSeal. The laryngeal tube-Suction required more time to insert and more frequent adjustments of the device position and was associated with a higher incidence of respiratory complications.30
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Complications |
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The laryngeal tube may be displaced during repositioning the patient's head and neck for operation. One study showed that the tidal volume decreased more frequently during repositioning the head and neck with the laryngeal tube (24%) than with the ProSeal (7%).2 In contrast, another study has reported that airway obstruction did not occur when the patient's head and neck were extended for mastectomy or rotated to the side for operation on the clavicle.24
One major drawback of the laryngeal tube is airway obstruction,31 32 occurring 240%.24 26 31 32 35 Compared with the laryngeal mask airway classic or ProSeal, adjustments of the position of the laryngeal tube may be required more frequently during anaesthesia.26 35
In one study, apparent ischaemic changes to the tongue were found in 2 of 36 patients during the use of the laryngeal tube, and in these patients, ischaemia disappeared after deflating the cuffs.31 Another study also reported an incidence of 3% (1 of 35 patients).35 Therefore, the cuff volume should be kept minimum, and when nitrous oxide is used, the cuff volume should be re-adjusted during maintenance of anaesthesia.
The laryngeal tube may cause injury to the pharynx. Blood was detected on the device at removal in 07% of cases.24 26 31 35 37 This range is similar to, or possibly lower than, the incidence caused by the laryngeal mask airway (0.450%)25 (Table 3).
The reported incidence of postoperative airway complications, such as sore throat, dysphagia, dysphonia or numb mouth, ranges from 0 to 34%. The incidence and the degree of postoperative complications are similar to those after the use of the classic laryngeal mask airway or the ProSeal laryngeal mask airway.31 32
Because the cuffs are thin and relatively large, they may be torn during use. One study reported that 2 of 18 laryngeal tubes broke during a study involving 36 patients. The damage was caused either by teeth during insertion or by sterilization.31 In another study by the same authors, the incidence of the damage was 2 of 18 laryngeal tubes during use in 32 patients32 and 4 of 32 patients for the laryngeal tube Suction.30 Recently, a worrying case has been reported for a single-use laryngeal tube.52 In a female patient, a size 4 was inserted and the cuffs were inflated with 80 ml of air. Ten minutes after the start of anaesthesia with sevoflurane, 66% nitrous oxide in oxygen, the proximal cuff ruptured, due possibly to expansion of the cuff by diffusion of nitrous oxide, causing a haematoma in the tongue and some damage to the pharyngeal mucosa. Full recovery took 7 days.52
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Indications and uses |
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There have been several reports of the successful use of the laryngeal tube in patients with a difficult airway,11 15 49 including patients in whom insertion of the laryngeal mask had failed.15 49 Insertion of a laryngeal mask or a laryngeal tube may be difficult in some circumstances.4 14 25 An understanding of the causes of difficult insertion of the laryngeal mask and of laryngeal tube would help establish the role of these devices in patients with a difficult airway. One possible factor which may differentiate the ease of insertion between these devices is the pharyngeal space. If the pharyngeal space is narrowed by, for example, swollen tonsils, insertion of the laryngeal tube may be easier than of the laryngeal mask airway, because the width of the laryngeal tube is narrower than that of the laryngeal mask airway.15
Fibreoptic intubation is useful in patients with a difficult airway, but it may be difficult to locate the glottis, to advance a tracheal tube over the fibrescope, and to ventilate the lungs during the procedure.23 54 The laryngeal tube may provide a clear airway and enable delivery of oxygen and inhalation anaesthetics during attempts at fibreoptic nasotracheal intubation.3 19 After insertion of a laryngeal tube, a tracheal tube is inserted through a nostril and the fibrescope is then advanced through the tube into the trachea, and the tube passed over the fibrescope into the trachea, while the lungs are ventilated through the laryngeal tube (Fig. 5). This method may also facilitate location of the glottis through a fibrescope, because the laryngeal tube indicates the centre of the oral cavity, and the distal cuff indicates that the glottis should be just anterior to the cuff. This method was successfully used in a patient in whom laryngoscopy, conventional fibreoptic intubation and insertion of the laryngeal mask airway had failed.3 This method may also be useful in a patient with an unstable neck, in whom stabilization of the head and neck makes fibreoptic intubation more difficult.2 23 One possible problem in a patient with an unstable neck is that insertion of the laryngeal tube may be difficult when the patient's head and neck are stabilized by manual in-line method.14 46 Another possible problem of the use of the laryngeal tube is that inflated cuffs could damage an unstable neck. Although the cuffs should not exert high pressure on the upper cervical spine, this possible risk should be weighed against the usefulness of the laryngeal tube in this group of patients.
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Cardiopulmonary resuscitation
Because of the ease of insertion and a good airtight seal, the laryngeal tube may, potentially, have a role in airway management during cardiopulmonary resuscitation. Insertion of the laryngeal tube is easy for paramedical staff.6 9 In one report,6 28 Fire Defence Academy students, who had no experience of the laryngeal tube but had used a laryngeal mask airway, were all able to insert the laryngeal tube at first attempt in mannequins. The majority of the participants stated that its insertion was easier than that of the laryngeal mask.6
Genzwuerker and colleagues39 reported a case of the use of the laryngeal tube by a physician during cardiopulmonary resuscitation. Subsequently, Asai and colleagues16 reported five cases of the use of the laryngeal tube by paramedical staff. Manual ventilation was possible without airleak around the laryngeal tube in four of five patients. During the transport of the patients to the hospital, cardiac massage was continued, and the laryngeal tube was used for up to 30 min without airway obstruction or vomiting, until the trachea could be intubated. In the remaining patient, in whom ventilation was not satisfactory, there was no improvement in ventilation with tracheal intubation. Kett and colleagues43 reported the use of the laryngeal tube by nurses during cardiopulmonary resuscitation of 30 patients, and ventilation through the laryngeal tube was successful in 24 patients (80%).
From these reports, it may be concluded that, although the laryngeal tube may share similar possible limitations with the laryngeal mask airway,17 55 the laryngeal tube has a potential role in providing a clear airway during cardiopulmonary resuscitation. In Japan, since 2002, the laryngeal tube has been licensed for use during cardiopulmonary resuscitation, and paramedical staff has been allowed to use it,9 along with the laryngeal mask airway and Combitube. It would be useful to study the efficacy of the laryngeal tube-Suction II during cardiopulmonary resuscitation, as this device has a theoretical advantage over the standard laryngeal tube or the laryngeal mask airway classic.
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Conclusions |
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Footnotes |
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References |
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2 Asai T. Use of the laryngeal tube in a patient with an unstable neck. Can J Anaesth 2002; 49: 6423
3 Asai T. Use of the laryngeal tube for difficult fibreoptic tracheal intubation. Anaesthesia 2005; 60: 826[Medline]
4 Asai T. Difficulty in insertion of the laryngeal mask. In: Latto IP and Vaughan RS eds. Difficulties in Tracheal Intubation, 2nd edn. London: W.B. Saunders Company Ltd, 1997; 197214
5 Asai T, Brimacombe J. Cuff volume and size selection with the laryngeal mask. Anaesthesia 2000; 55: 117984[CrossRef][ISI][Medline]
6 Asai T, Hidaka I, Kawachi S. Efficacy of the laryngeal tube by inexperienced personnel. Resuscitation 2002; 55: 1715[CrossRef][ISI][Medline]
7 Asai T, Hidaka I, Kubota T. Efficacy of the laryngeal tube. Eur J Anaesthesiol 2002; 19: 3056[ISI][Medline]
8 Asai T, Kawachi S. Pressure exerted by the cuff of the laryngeal tube on the oropharynx. Anaesthesia 2001; 56: 9112[Medline]
9 Asai T, Kawachi S. Insertion of the laryngeal tube by paramedical staff. Anaesthesia 2004; 59: 4089[CrossRef][ISI][Medline]
10 Asai T, Kawashima A, Hidaka I. Laryngeal tube: its use for controlled ventilation. Masui (Japanese J Anesthesiol) 2001; 50: 13401
11 Asai T, Kawashima A, Hidaka I. Use of the laryngeal tube in patients without teeth. Resuscitation 2001; 51: 2134[CrossRef][ISI][Medline]
12 Asai T, Kawashima A, Hidaka I. The laryngeal tube compared with the laryngeal mask: insertion, gasleak pressure and gastric insufflation. Br J Anaesth 2002; 89: 72932
13 Asai T, Koga K, Vaughan RS. Respiratory complications associated with tracheal intubation and extubation. Br J Anaesth 1998; 80: 76775
14 Asai T, Marfin AG, Thompson J. Ease of insertion of the laryngeal tube during manual-in-line neck stabilization. Anaesthesia 2004; 59: 11636[CrossRef][ISI][Medline]
15 Asai T, Matsumoto S, Shingu K. Use of the laryngeal tube after failed laryngeal mask airway. Anaesthesia 2005; 60: 8256[CrossRef][ISI][Medline]
16 Asai T, Moriyama S, Nishita Y. Use of the laryngeal tube during cardiopulmonary resuscitation by paramedical staff. Anaesthesia 2003; 58: 3934[CrossRef][ISI][Medline]
17 Asai T, Morris S. The laryngeal mask airway: Its features, effects and role (Review). Can J Anaesth 1994; 41: 93060
18 Asai T, Murao K, Shingu K. Efficacy of the laryngeal tube during intermittent positive-pressure ventilation. Anaesthesia 2000; 55: 1099102[CrossRef][ISI][Medline]
19 Asai T, Shingu K. Use of the laryngeal tube for nasotracheal intubation. Br J Anaesth 2001; 87: 1578[CrossRef][Medline]
20 Asai T, Shingu K. Use of the laryngeal tube during emergence from anaesthesia in a patient with unstable neck. Anaesthesia 2004; 59: 3001[CrossRef][Medline]
21 Asai T, Shingu K. Appropriate cuff volume of the laryngeal tube. Anaesthesia 2005; 60: 4869[CrossRef][ISI][Medline]
22 Asai T, Shingu K. Time-related cuff pressures of the laryngeal tube: with and without the use of nitrous oxide. Anesth Analg 2004; 98: 18036
23 Asai T, Shingu K. Difficulty in advancing a tracheal tube over a fibreoptic bronchoscope: incidence, causes and solutions (Review). Br J Anaesth 2004; 92: 87081
24 Asai T, Shingu K, Cook T. Use of the laryngeal tube in 100 patients. Acta Anaesthesiol Scand 2003; 47: 82832[CrossRef][ISI][Medline]
25 Brimacombe JR. Laryngeal Mask Anesthesia: Principles and Practice, 2nd edn. Philadelphia: Saunders, 2005
26 Brimacombe J, Keller C, Brimacombe L. A comparison of the laryngeal mask airway ProSealTM and the laryngeal tube airway in paralyzed anesthetized adult patients undergoing pressure-controlled ventilation. Anesth Analg 2002; 95: 7706
27 Brimacombe J, Keller C, Puhringer F. Pharyngeal mucosal pressure and perfusion: a fiberoptic evaluation of the posterior pharynx in anesthetized adult patients with a modified cuffed oropharyngeal airway. Anesthesiology 1999; 91: 16615[CrossRef][ISI][Medline]
28 Brimacombe J, Keller C, Roth W. Large cuff volumes impede posterior pharyngeal mucosal perfusion with the laryngeal tube airway. Can J Anaesth 2002; 49: 10847
29 Cook TM. Novel airway devices: spoilt for choices? Anaesthesia 2003; 58: 10710
30 Cook TM, Cranshaw J. Randomized crossover comparison of ProSeal laryngeal mask airway with laryngeal tube Sonda during anaesthesia with controlled ventilation. Br J Anaesth 2005; 95: 2616
31 Cook TM, McCormick, Asai T. Randomized comparison of the laryngeal tube and the classic laryngeal mask airway for anaesthesia with controlled ventilation. Br J Anaesth 2003; 91: 3738
32 Cook TM, McKinstry C, Hardy R. Randomized crossover comparison of the ProSealTM laryngeal mask airway with the laryngeal tube during anaesthesia with controlled ventilation. Br J Anaesth 2003; 91: 67883
33 Dörges V, Ocker H, Wenzel V. The laryngeal tube: a new simple airway device. Anesth Analg 2000; 90: 12202
34 Devitt JH, Wenstone R, Noel AG. The laryngeal mask airway and positive-pressure ventilation. Anesthesiology 1994; 80: 5505[ISI][Medline]
35 Figueredo E, Martinez M, Pintanel T. A comparison of the ProSeal laryngeal mask and the laryngeal tube in spontaneously breathing anesthetized patients. Anesth Analg 2003; 96: 6005
36 Gaitini LA, Vaida SJ, Mostafa S. The effect of nitrous oxide on the cuff pressure of the laryngeal tube. Anaesthesia 2002; 57: 506[Medline]
37 Gaitini LA, Vaida SJ, Somri M, et al. An evaluation of the laryngeal tube during general anesthesia using mechanical ventilation. Anesth Analg 2003; 96: 17505
38 Gaitini LA, Vaida SJ, Somri M, Yanovski B, Ben-David B, Hagberg CA. A randomized controlled trial comparing the ProSeal Laryngeal Mask Airway with the Laryngeal Tube Suction in mechanically ventilated patients. Anesthesiology 2004; 101: 31620[CrossRef][ISI][Medline]
39 Genzwuerker HV, Dhonau S, Ellinger K. Use of the laryngeal tube for out-of-hospital resuscitation. Resuscitation 2002; 52: 2214[CrossRef][ISI][Medline]
40 Genzwurker H, Finteis T, Hinkelbein J. First clinical experiences with the new LTS. A laryngeal tube with an oesophageal drain (German). Anaesthesist 2003; 52: 697702
41 Genzwuerker HV, Fritz A, Finteis T. A randomized, prospective comparison of laryngeal tube and laryngeal mask airway in pediatric patients undergoing elective interventions. ASA Annual Meeting Abstract 2004; A1422
42 Genzwuerker HV, Hohl EC, Elinger K. Laryngeal tube (LT) for ventilation during ambulatory paediatric surgery requiring general anesthesia. ASA Annual Meeting Abstract 2003; A24
43 Kett F, Reffo I, Giordani G, et al. The use of laryngeal tube by nurses in out-of-hospital emergencies: preliminary experience. Resuscitation 2005; 66: 2215[CrossRef]
44 Khan SA, Siddiqi MMH, Khan RM. Diffusion of nitrous oxide into the cuff of the laryngeal tube. Anaesthesia 2003; 58: 291[Medline]
45 Koga K, Asai T, Vaughan RS. Respiratory complications associated with tracheal extubation. Timing of tracheal extubation and use of the laryngeal mask during emergence from anaesthesia. Anaesthesia 1998; 53: 5404[CrossRef][ISI][Medline]
46 Komatsu R, Nagata O, Kamata K. Comparison of the intubating laryngeal mask airway and laryngeal tube placement during manual in-line stabilisation of the neck. Anaesthesia 2005; 60: 1137[CrossRef][ISI][Medline]
47 Mandal NG. A new device has to be safe and reliable too. Anaesthesia 2001; 56: 382[Medline]
48 Magill IW. Technique in endotracheal anaesthesia. Br Med J 1930; ii: 8179
49 Matioc AA, Olson J. Use of the laryngeal tube in two unexpected difficult airway situations: lingual tonsillar hyperplasia and morbid obesity. Can J Anaesth 2004; 51: 101821
50 Miller DM, Youkhana I, Pearce AC. The laryngeal mask and VBM laryngeal tube compared during spontaneous ventilation. A pilot study. Eur J Anaesthesiol 2001; 18: 5938[CrossRef][ISI][Medline]
51 Nandi PR, Nunn JF, Charlesworth CH, et al. Radiogical study of the laryngeal mask. Eur J Anaesthesiol 1991; 4(Suppl.): 339
52 Niemi-Murola L, Rautomia V-P, Castren M, Pere P. Two consective ruptures of the upper cuff of disposable laryngeal tubes during anaesthesia of a single patient. Acta Anaesthesiol Scand 2005; 49: 125[Medline]
53 Ocker H, Wenzel V, Schmucker P, Steinfath M, Dörges V. A comparison of the laryngeal tube with the laryngeal mask airway during routine surgical procedures. Anesth Analg 2002; 95: 10947
54 Ovassapian A. Fiberoptic Endoscopy and the Difficult Airway, 2nd edn. New York: Lippincott-Raven Press, 1996
55 Results of a multicentre trial. The use of the laryngeal mask by nurses during cardiopulmonary resuscitation. Anaesthesia 1994; 49: 37[ISI][Medline]
56 Richebe P, Semjen F, El Hammer F, Marie S, Cros A-M. Clinical evaluation of the laryngeal tube (LT) in pediatric anesthesia. Anesthesiology 2000; 93: A1268[CrossRef]
57 Roth H, Genzwuerker HV, Rothhaas A, Finteis T, Schmeck J. The ProSeal laryngeal mask airway and the laryngeal tube Suction for ventilation in gynaecological patients undergoing laparoscopic surgery. Eur J Anaesthesiol 2005; 22: 11722[CrossRef][ISI][Medline]
58 Wrobel M, Grundmann U, Wilhelm W, Wagner S, Larsen R. Laryngeal tube versus laryngeal mask airway in anaesthetised non-paralysed patients. A comparison of handling and postoperative morbidity (German). Anaesthesist 2004; 53: 7028[ISI][Medline]