1 Bath, UK 2 Mannheim, Germany 3 Bruchsal, Germany
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EditorWe were interested to read Genzwuerker and colleagues article on fibreoptic guided intubation via the Laryngeal TubeTM (LT).1 They report a 90% success rate for tracheal intubation in 10 patients with the procedure performed by an experienced fibreoptic intubator after previous practice with the device on a mannequin. In one of the nine successful patients the first attempt led to oesophageal intubation. The glottis was seen via the laryngeal tube in six of the 10 cases without manipulation of the LT; in another three, rotation of the device brought at least part of the glottis into view.
The authors comment that the specific configuration of the aperture of the laryngeal tube guides the tip of the flexible fibreoptic bronchoscope more towards the glottis than would be the case with the standard laryngeal mask. This statement is unsupported by a reference, and we would find it difficult to agree with.
The LT was modified in September 2001 (Personal Communication, VBM). Amongst several changes, the distal part of the proximal cuff was modified and the orifices between the two cuffs were altered and increased in number to lessen the likelihood of airway obstruction (Fig. 1). The shape of the proximal cuff was also modified. From the figures published, it is unclear whether Genzwuerker and colleagues1 performed their study with the old version of the LT (which is no longer marketed in the UK), or with the currently available device.
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Our results (studying patients of similar height and weight to those in Genzwuerkers article, but including six patients with Mallampati scores of 3), suggest that the glottis is visible through the ventilation holes of the LT in <50% of cases. We would therefore question whether the LT is the best device to use for catheter exchange tracheal intubation, even when a fibrescope is used. In our study, the PLMA offered a far better view of and access to the glottis. It is recognized, from other studies, that the classic LMA provides at least as good a view as the PLMA.2 3
T. M. Cook
R. Hardy
C. McKinstry
S. Twigg
Bath, UK
EditorThank you for the opportunity to reply to Cook and colleagues. In the discussion of our paper, we suggested that the flexible fibreoptic bronchoscope is guided towards the glottis by the configuration of the aperture of the LTs aperture.1 Inside the lumen of the LT, a ramp with an angle of approximately 40° leads from the posterior wall towards the main anterior ventilatory outlet. While intended to guide the air-stream, it will also guide the bronchoscope inserted through the LT. The lumen of the classic LMA ends in a steeper angle, as shown in Figure 2.
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Cook and colleagues provide their own data from a comparison of the PLMA and the current version of the LT. While we used a classification published by Brimacombe and Berry in 1993,4 who proposed a standardized assessment of LMA position ranging from 4 to 0, with the highest score describing complete visualization of the vocal cords, Cook uses his own classification from 1 to 4, assigning the lowest score to the optimal view. For the PLMA, but not the LMA ClassicTM, significantly better grades of view are described. Unfortunately, the standardized position of the tip of the bronchoscope, as suggested by Brimacombe and Berry,4 is not mentioned. When slight manipulation leads to a vast improvement in the fibreoptic view through the LT without impairment of ventilation,5 including such manoeuvres in fibreoptic studies might be helpful. Other authors also describe a much higher incidence of glottic visualization through the LT than that described by Cook and colleagues: Galli and colleagues6 described an 80% incidence with ventilation possible in all patients; Doerges and colleagues7 described fibreoptic verification of the correct position of the Laryngeal Tube and of the tip in the oesophageal inlet in 30 patients after successful insertion at the first attempt in all cases; and we were able to pass the fibreoptic bronchoscope inserted into the LT through the vocal cords in 9 out of 10 patients.1
Although a tube exchange manoeuvre was not attempted by Cook and colleagues through the PLMA, they suggest it might be superior to the LT from their fibreoptic view results. Whether the fibreoptic view through the LMA ClassicTM is comparable with the view through the PLMA must be questioned in the light of studies reporting partial visualization of the oesophagus in up to 15% of cases, and a correct, central position in only 59% of patients successfully ventilated with the standard LMA.8 The PLMA provides a better seal of the airway, allowing higher peak pressures compared with the LMA ClassicTM, because of its different shape and an additional posterior cuff.3 Other authors found significant differences in the airway seal in favour of the LT compared with the LMA ClassicTM.9 10 For the old version of the LT, oropharyngeal leak pressure was comparable with the PLMA.11 A comparison of the PLMA and the new LTS (Laryngeal Tube Suction), which was introduced in 200212 13both devices providing an additional oesophageal drain tubehas not been published to date, but studies are under way.
Ventilatory characteristics, airway seal, ease of insertion, and acceptance by personnel are variables that should be considered as well as the fibreoptic view when searching for the best airway device to perform not only fibreoptic-aided tube exchange manoeuvres, butmore importantlyemergency ventilation, as an alternative to tracheal intubation and face mask ventilation in a cannot intubatecannot ventilate situation. We described the possibility of a manoeuvre in a high percentage of patients using the standard LT, a flexible fibreoptic bronchoscope and a tube exchange catheter after adequate ventilation was achieved in all patients.
H. V. Genzwuerker1
T. Vollmer2
1Mannheim, Germany
2Bruchsal, Germany
References
1 Genzwuerker HV, Vollmer T, Ellinger K. Fibreoptic tracheal intubation after placement of the laryngeal tube. Br J Anaesth 2002; 89: 7338
2 Brimacombe J, Keller C, Boehler M, Pühringer F. Positive pressure ventilation with ProSeal versus Classic laryngeal mask airway: a randomized, crossover study of healthy female patients. Anesth Analg 2001; 93: 13513
3 Brimacombe J, Keller C, Fullekrug B, et al. A multicenter study comparing the ProSealTM and ClassicTM laryngeal mask airway in anesthetized, nonparalyzed patients. Anesthesiology 2002; 96: 28995[CrossRef][ISI][Medline]
4 Brimacombe J, Berry A. A proposed fiber-optic scoring system to standardize the assessment of laryngeal mask airway position. Anesth Analg 1993; 76: 457
5 Vollmer T, Genzwuerker HV, Ellinger K. Fibreoptic control of the laryngeal tube position. Eur J Anaesthesiol 2002; 19: 3067[Medline]
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8 Fullekrug B, Pothmann W, Werner C, Schulte am Esch J. The laryngeal mask airway: anesthetic gas leakage and fiberoptic control of positioning. J Clin Anesth 1993; 5: 35763[CrossRef][ISI][Medline]
9 Asai T, Kawashima A, Hidaka I, Kawachi S. The laryngeal tube compared with the laryngeal mask: insertion, gas leak pressure and gastric insufflation. Br J Anaesth 2002; 89: 72932
10 Ocker H, Wenzel V, Schmucker P, et al. A comparison of the Laryngeal Tube with the Laryngeal Mask Airway during routine surgical procedures. Anesth Analg 2002; 95: 10947
11 Brimacombe J, Keller C, Brimacombe L. A comparison of larnygeal mask airway and the laryngeal tube airway in paralyzed anesthetized patients undergoing pressure-controlled ventilation. Anesth Analg 2002; 95: 7706
12 Dorges V, Ocker H. The Laryngeal Tube S (LTS)a modified simple airway device. Eur J Anaesthesiol 2002; 19: 175
13 Genzwuerker HV, Finteis T, Hundt A, Ellinger K. Comparison of Laryngeal Tube and new LTS in a resuscitation model. Resuscitation 2002; 55: 62