The laryngeal tube
2005; Elsevier BV; Volume: 95; Issue: 6 Linguagem: Inglês
10.1093/bja/aei269
ISSN1471-6771
Autores Tópico(s)Foreign Body Medical Cases
ResumoThe laryngeal tube (VBM Medizintechnik, Sulz, Germany) is a relatively new extraglottic airway, designed to secure a patent airway during either spontaneous breathing or controlled ventilation. In this review article, we have assessed the potential role of the laryngeal tube during anaesthesia and during cardiopulmonary resuscitation. There are four variations of the laryngeal tube: standard laryngeal tube, disposable laryngeal tube, laryngeal tube-Suction II and disposable laryngeal tube-Suction II. The design of the device has been revised several times. Insertion of the standard laryngeal tube is as easy as with the laryngeal mask airway classic. The laryngeal tube may provide a better sealing effect than the laryngeal mask. The incidence of complications with the two devices is similar, although the laryngeal tube may require more re-adjustments of its position to obtain a clear airway. Compared with the ProSeal™ laryngeal mask, the laryngeal tube may be less effective. The efficacy of the standard laryngeal tube is unclear, particularly in patients breathing spontaneously or in children. The efficacy of the laryngeal tube Suction-II and disposable devices is also not clear. From the limited number of studies and reports available, it can be concluded that the laryngeal tube is potentially useful in maintaining a clear airway during anaesthesia and cardiopulmonary resuscitation. In addition, the device may be useful as an aid to tracheal intubation. The laryngeal tube (VBM Medizintechnik, Sulz, Germany) is a relatively new extraglottic airway, designed to secure a patent airway during either spontaneous breathing or controlled ventilation. In this review article, we have assessed the potential role of the laryngeal tube during anaesthesia and during cardiopulmonary resuscitation. There are four variations of the laryngeal tube: standard laryngeal tube, disposable laryngeal tube, laryngeal tube-Suction II and disposable laryngeal tube-Suction II. The design of the device has been revised several times. Insertion of the standard laryngeal tube is as easy as with the laryngeal mask airway classic. The laryngeal tube may provide a better sealing effect than the laryngeal mask. The incidence of complications with the two devices is similar, although the laryngeal tube may require more re-adjustments of its position to obtain a clear airway. Compared with the ProSeal™ laryngeal mask, the laryngeal tube may be less effective. The efficacy of the standard laryngeal tube is unclear, particularly in patients breathing spontaneously or in children. The efficacy of the laryngeal tube Suction-II and disposable devices is also not clear. From the limited number of studies and reports available, it can be concluded that the laryngeal tube is potentially useful in maintaining a clear airway during anaesthesia and cardiopulmonary resuscitation. In addition, the device may be useful as an aid to tracheal intubation. The laryngeal tube (VBM Medizintechnik, Sulz, Germany) is one of several new extraglottic (supraglottic) airways that have become available since the introduction of the laryngeal mask airway into clinical practice in 1988. Each device may have theoretical advantages or disadvantages over other devices. However, it is necessary to study the efficacy and safety of each device to determine whether the new device performs to an acceptable standard29Cook TM Novel airway devices: spoilt for choices?.Anaesthesia. 2003; 58: 107-110Crossref PubMed Scopus (81) Google Scholar and to establish which airway device is more appropriate for different clinical circumstances. We have reviewed the current knowledge of the laryngeal tube's performance and its role during anaesthesia and during cardiopulmonary resuscitation. 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).Table 1Size selection and recommended cuff volumesSizePatientsBody sizeRecommended cuff volumes (ml)Connector colour0Newborn<5 kg10Clear1Infants5–12 kg20White2Children12–25 kg35Green3Adults: small 180 cm90Purple Open table in a new tab There are three other modified versions of the laryngeal tube: single-use laryngeal tube, laryngeal tube-Suction II and single-use laryngeal tube-Suction II (Fig. 2). The laryngeal tube-Suction is a further development of the laryngeal tube, which aims to separate the respiratory and alimentary tracts. This device has two lumens: one for ventilation and the other for the passage of a gastric tube. Recently, the design of the laryngeal tube-Suction has been revised (laryngeal tube-Suction II). When inserted, the laryngeal tube lies along the length of the tongue and the distal tip is positioned in the hypopharynx (Fig. 3). The proximal cuff provides a seal in the upper pharynx and the distal cuff seals the oesophageal inlet. The distal aperture should face the glottic aperture, although fibreoptic bronchoscopy has shown that this may not be so.32Cook TM McKinstry C Hardy R Randomized crossover comparison of the ProSeal™ laryngeal mask airway with the laryngeal tube during anaesthesia with controlled ventilation.Br J Anaesth. 2003; 91: 678-683Crossref PubMed Scopus (57) Google Scholar37Gaitini LA Vaida SJ Somri M et al.An evaluation of the laryngeal tube during general anesthesia using mechanical ventilation.Anesth Analg. 2003; 96: 1750-1755Crossref PubMed Scopus (45) Google Scholar However, similar to the laryngeal mask airway,17Asai T Morris S The laryngeal mask airway: Its features, effects and role (Review).Can J Anaesth. 1994; 41: 930-960Crossref PubMed Scopus (173) Google Scholar51Nandi PR Nunn JF Charlesworth CH et al.Radiogical study of the laryngeal mask.Eur J Anaesthesiol. 1991; 4: 33-39Google Scholar ventilation through the laryngeal tube may often be adequate even if the distal aperture is not facing the glottis directly.31Cook 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: 373-378Crossref PubMed Scopus (74) Google Scholar Initial recommendations suggested selection of airway size based on the patient's weight. However, in an early study, it was found that, by the weight-based selection, ventilation was often not adequate when the patient's height was 180 cm; size 4 when 155–180 cm; and a size 3 when <155 cm. Since then, the success rate of ventilation through the laryngeal tube has been increased even in patients of short stature.24Asai T Shingu K Cook T Use of the laryngeal tube in 100 patients.Acta Anaesthesiol Scand. 2003; 47: 828-832Crossref PubMed Scopus (38) Google Scholar The device should be inserted while the patient's head and neck are placed either in the sniffing position (Magill48Magill IW Technique in endotracheal anaesthesia.Br Med J. 1930; ii: 817-819Crossref Scopus (82) Google Scholar position) or in the neutral position. The tip of a well-lubricated laryngeal tube is placed against the hard palate behind the upper incisors. The device is then slid down the centre of the mouth until resistance is felt or the device is almost fully inserted. Care should be taken not to push the tongue towards the posterior pharynx, to minimize a possible obstruction of the airway. When the laryngeal tube is inserted properly, the second bold black line on the tube should have just passed between upper and lower teeth, but this has not been studied formally. When ventilation is adequate, a bite block provided is inserted, the laryngeal tube snagged into its wedge and both are fixed in place. The cuff should be inflated to a pressure of 60 cm H2O.18Asai T Murao K Shingu K Efficacy of the laryngeal tube during intermittent positive-pressure ventilation.Anaesthesia. 2000; 55: 1099-1102Crossref PubMed Scopus (94) Google Scholar It may be easier to inflate the cuffs to a higher pressure and then adjust them to 60–70 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). Asai and Shingu21Asai T Shingu K Appropriate cuff volume of the laryngeal tube.Anaesthesia. 2005; 60: 486-489Crossref PubMed Scopus (5) Google Scholar sought adequate cuff volume by measuring the volume of air with which there was no gas leak around the cuffs at the intracuff pressure of 60 cm H2O and the airway pressure of 18 cm H2O. The mean volume was 62 ml for size 3 and 84 ml for size 4. These results are in agreement with the manufacturer's recommended cuff volumes (60 ml for size 3, 80 ml for size 4).21Asai T Shingu K Appropriate cuff volume of the laryngeal tube.Anaesthesia. 2005; 60: 486-489Crossref PubMed Scopus (5) Google Scholar They21Asai T Shingu K Appropriate cuff volume of the laryngeal tube.Anaesthesia. 2005; 60: 486-489Crossref PubMed Scopus (5) Google Scholar also found that, although the cuff volume was correlated with both the patient's height and weight, the height was a better indicator, as the variability of the predicted cuff volume was narrower for the height than the weight (Table 2).Table 2The fitted values, 95% confidence intervals and 95% reference intervals (which include intracuff volumes of 95% of future subjects), of the intracuff volumes of the laryngeal tube, at several different patients' heights.21Asai T Shingu K Appropriate cuff volume of the laryngeal tube.Anaesthesia. 2005; 60: 486-489Crossref PubMed Scopus (5) Google ScholarHeightFitted value (ml)95% confidence intervals (ml)95% reference intervals (ml)1405751–6234–791506763–7045–881607775–7955–981708784–9066–109180*There was only one patient whose height was 180 cm9792–10375–119* There was only one patient whose height was 180 cm Open table in a new tab When nitrous oxide is used during anaesthesia, the intracuff pressure of the laryngeal tube increases progressively over time22Asai T Shingu K Time-related cuff pressures of the laryngeal tube: with and without the use of nitrous oxide.Anesth Analg. 2004; 98: 1803-1806Crossref PubMed Scopus (13) Google Scholar36Gaitini LA Vaida SJ Mostafa S The effect of nitrous oxide on the cuff pressure of the laryngeal tube.Anaesthesia. 2002; 57: 506Crossref PubMed Scopus (8) Google Scholar44Khan SA Siddiqi MMH Khan RM Diffusion of nitrous oxide into the cuff of the laryngeal tube.Anaesthesia. 2003; 58: 291Crossref PubMed Scopus (6) Google Scholar and may increase up to 120 cm H2O within 2 h.22Asai T Shingu K Time-related cuff pressures of the laryngeal tube: with and without the use of nitrous oxide.Anesth Analg. 2004; 98: 1803-1806Crossref PubMed Scopus (13) Google Scholar In contrast, when nitrous oxide is not used, the intracuff pressure remains stable.22Asai T Shingu K Time-related cuff pressures of the laryngeal tube: with and without the use of nitrous oxide.Anesth Analg. 2004; 98: 1803-1806Crossref PubMed Scopus (13) Google Scholar Concern has been expressed that the intracuff pressure of 60 cm H2O is too high and could cause ischaemic changes to the pharynx.4Asai T Difficulty in insertion of the laryngeal mask.in: Latto IP Vaughan RS Difficulties in Tracheal Intubation. 2nd edn. W.B. Saunders Company Ltd, London1997: 197-214Google Scholar 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.5Asai T Brimacombe J Cuff volume and size selection with the laryngeal mask.Anaesthesia. 2000; 55: 1179-1184Crossref PubMed Scopus (56) Google Scholar Asai and Kawachi8Asai T Kawachi S Pressure exerted by the cuff of the laryngeal tube on the oropharynx.Anaesthesia. 2001; 56: 911-912PubMed Google Scholar 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 24–36) cm H2O at an intracuff pressure of 60 cm H2O.8Asai T Kawachi S Pressure exerted by the cuff of the laryngeal tube on the oropharynx.Anaesthesia. 2001; 56: 911-912PubMed Google Scholar Brimacombe and colleagues28Brimacombe J Keller C Roth W Large cuff volumes impede posterior pharyngeal mucosal perfusion with the laryngeal tube airway.Can J Anaesth. 2002; 49: 1084-1087Crossref PubMed Scopus (22) Google Scholar 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 55–93) cm H2O, and the exerted pressure to the posterior pharynx was 37 (26–60) cm H2O. Using the cuffed oropharyngeal airway (COPA), Brimacombe and colleagues27Brimacombe 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: 1661-1665Crossref PubMed Scopus (83) Google Scholar 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 ∼30–35 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,22Asai T Shingu K Time-related cuff pressures of the laryngeal tube: with and without the use of nitrous oxide.Anesth Analg. 2004; 98: 1803-1806Crossref PubMed Scopus (13) Google Scholar and at this pressure, the exerted pressure can reach ∼50 cm H2O.28Brimacombe J Keller C Roth W Large cuff volumes impede posterior pharyngeal mucosal perfusion with the laryngeal tube airway.Can J Anaesth. 2002; 49: 1084-1087Crossref PubMed Scopus (22) Google Scholar 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.5Asai T Brimacombe J Cuff volume and size selection with the laryngeal mask.Anaesthesia. 2000; 55: 1179-1184Crossref PubMed Scopus (56) Google Scholar 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. 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.12Asai T Kawashima A Hidaka I The laryngeal tube compared with the laryngeal mask: insertion, gasleak pressure and gastric insufflation.Br J Anaesth. 2002; 89: 729-732Abstract Full Text Full Text PDF PubMed Scopus (72) Google Scholar18Asai T Murao K Shingu K Efficacy of the laryngeal tube during intermittent positive-pressure ventilation.Anaesthesia. 2000; 55: 1099-1102Crossref PubMed Scopus (94) Google Scholar31Cook 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: 373-378Crossref PubMed Scopus (74) Google Scholar If insertion or ventilation fails after two to three attempts, the laryngeal tube should be abandoned and an alternative airway used. 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.18Asai T Murao K Shingu K Efficacy of the laryngeal tube during intermittent positive-pressure ventilation.Anaesthesia. 2000; 55: 1099-1102Crossref PubMed Scopus (94) Google Scholar31Cook 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: 373-378Crossref PubMed Scopus (74) Google Scholar The cuffs of the laryngeal tube should be deflated before removal. In this section, studies of the efficacy of the standard laryngeal tube and the laryngeal tube-Suction will be reviewed separately. The efficacy of the single-use device will not be reviewed here, as there are insufficient studies from which to draw any conclusions. The use in adults and in children will also be discussed separately. The insertion of the standard laryngeal tube is generally easy. The reported success rate of insertion of, and ventilation through, the laryngeal tube ranges 92–100% for the earlier prototype10Asai T Kawashima A Hidaka I Laryngeal tube: its use for controlled ventilation.Masui (Japanese J Anesthesiol). 2001; 50: 1340-1341PubMed Google Scholar12Asai T Kawashima A Hidaka I The laryngeal tube compared with the laryngeal mask: insertion, gasleak pressure and gastric insufflation.Br J Anaesth. 2002; 89: 729-732Abstract Full Text Full Text PDF PubMed Scopus (72) Google Scholar18Asai T Murao K Shingu K Efficacy of the laryngeal tube during intermittent positive-pressure ventilation.Anaesthesia. 2000; 55: 1099-1102Crossref PubMed Scopus (94) Google Scholar26Brimacombe J Keller C Brimacombe L A comparison of the laryngeal mask airway ProSeal™ and the laryngeal tube airway in paralyzed anesthetized adult patients undergoing pressure-controlled ventilation.Anesth Analg. 2002; 95: 770-776Crossref PubMed Google Scholar33Dörges V Ocker H Wenzel V The laryngeal tube: a new simple airway device.Anesth Analg. 2000; 90: 1220-1222Crossref PubMed Scopus (153) Google Scholar35Figueredo 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: 600-605Crossref PubMed Google Scholar37Gaitini LA Vaida SJ Somri M et al.An evaluation of the laryngeal tube during general anesthesia using mechanical ventilation.Anesth Analg. 2003; 96: 1750-1755Crossref PubMed Scopus (45) Google Scholar53Ocker 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: 1094-1097Crossref PubMed Google Scholar and 97–100% for the newest type.22Asai T Shingu K Time-related cuff pressures of the laryngeal tube: with and without the use of nitrous oxide.Anesth Analg. 2004; 98: 1803-1806Crossref PubMed Scopus (13) Google Scholar24Asai T Shingu K Cook T Use of the laryngeal tube in 100 patients.Acta Anaesthesiol Scand. 2003; 47: 828-832Crossref PubMed Scopus (38) Google Scholar31Cook 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: 373-378Crossref PubMed Scopus (74) Google Scholar32Cook TM McKinstry C Hardy R Randomized crossover comparison of the ProSeal™ laryngeal mask airway with the laryngeal tube during anaesthesia with controlled ventilation.Br J Anaesth. 2003; 91: 678-683Crossref PubMed Scopus (57) Google Scholar Three studies reported that the laryngeal tube provided a clear airway during controlled ventilation in a majority of patients.18Asai T Murao K Shingu K Efficacy of the laryngeal tube during intermittent positive-pressure ventilation.Anaesthesia. 2000; 55: 1099-1102Crossref PubMed Scopus (94) Google Scholar24Asai T Shingu K Cook T Use of the laryngeal tube in 100 patients.Acta Anaesthesiol Scand. 2003; 47: 828-832Crossref PubMed Scopus (38) Google Scholar33Dörges V Ocker H Wenzel V The laryngeal tube: a new simple airway device.Anesth Analg. 2000; 90: 1220-1222Crossref PubMed Scopus (153) Google Scholar There have been four studies comparing the standard laryngeal tube and laryngeal mask airway classic during controlled ventilation.12Asai T Kawashima A Hidaka I The laryngeal tube compared with the laryngeal mask: insertion, gasleak pressure and gastric insufflation.Br J Anaesth. 2002; 89: 729-732Abstract Full Text Full Text PDF PubMed Scopus (72) Google Scholar31Cook 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: 373-378Crossref PubMed Scopus (74) Google Scholar53Ocker 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: 1094-1097Crossref PubMed Google Scholar58Wrobel 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: 702-708PubMed Google Scholar 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,31Cook 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: 373-378Crossref PubMed Scopus (74) Google Scholar53Ocker 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: 1094-1097Crossref PubMed Google Scholar 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.31Cook 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: 373-378Crossref PubMed Scopus (74) Google Scholar 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.12Asai T Kawashima A Hidaka I The laryngeal tube compared with the laryngeal mask: insertion, gasleak pressure and gastric insufflation.Br J Anaesth. 2002; 89: 729-732Abstract Full Text Full Text PDF PubMed Scopus (72) Google Scholar31Cook 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: 373-378Crossref PubMed Scopus (74) Google Scholar53Ocker 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: 1094-1097Crossref PubMed Google Scholar58Wrobel 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: 702-708PubMed Google Scholar 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 ProSeal™ laryngeal mask.26Brimacombe J Keller C Brimacombe L A comparison of the laryngeal mask airway ProSeal™ and the laryngeal tube airway in paralyzed anesthetized adult patients undergoing pressure-controlled ventilation.Anesth Analg. 2002; 95: 770-776Crossref PubMed Google Scholar32Cook TM McKinstry C Hardy R Randomized crossover comparison of the ProSeal™ laryngeal mask airway with the laryngeal tube during anaesthesia with controlled ventilation.Br J Anaesth. 2003; 91: 678-683Crossref PubMed Scopus (57) Google Scholar 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 colleagues32Cook TM McKinstry C Hardy R Randomized crossover comparison of the ProSeal™ laryngeal mask airway with the laryngeal tube during anaesthesia with controlled ventilation.Br J Anaesth. 2003; 91: 678-683Crossref PubMed Scopus (57) Google Scholar 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 colleagues50Miller DM Youkhana I Pearce AC The laryngeal mask and VBM laryngeal tube compared during spontaneous ventilation. A pilot study.Eur J Anaesthesiol. 2001; 18: 593-598Crossref PubMed Scopus (42) Google Scholar assessed the efficacy of a prototype laryngeal tube and had to abandon its use in 25 of 27 occasions. Figueredo and colleagues35Figueredo 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: 600-605Crossref PubMed Google Scholar 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 prototype7Asai T Hidaka I Kubota T Efficacy of the laryngeal tube.Eur J Anaesthesiol. 2002; 19: 305-306Crossref PubMed Scopus (7) Google Scholar 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.31Cook 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: 373-378Crossref PubMed Scopus (74) Google Scholar Another possibility is that the high failure rates in their study were due to technical problems.50Miller DM Youkhana I Pearce AC The laryngeal mask and VBM laryngeal tube compared during spontaneous ventilation. A pilot study.Eur J Anaesthesiol. 2001; 18: 593-598Crossref PubMed Scopus (42) Google Scholar 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.18Asai T Murao K Shingu K Efficacy of the laryngeal tube during intermittent positive-pressure ventilation.Anaesthesia. 2000; 55: 1099-1102Crossref PubMed Scopus (94) Google Scholar22Asai T Shingu K Time-related cuff pressures of the laryngeal tube: with and without the use of nitrous oxide.Anesth Analg. 2004; 98: 1803-1806Crossref PubMed Scopus (13) Google Scholar31Cook 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: 373-378Crossref PubMed Scopus (74) Google Scholar32Cook TM McKinstry C Hardy R Randomized crossover comparison of the ProSeal™ laryngeal mask airway with the laryngeal tube during anaesthesia with controlled ventilation.Br J Anaesth. 2003; 91: 678-683Crossref PubMed Scopus (57) Google Scholar 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.31Cook 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: 373-378Crossref PubMed Scop
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