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BJA Advance Access originally published online on September 19, 2006
British Journal of Anaesthesia 2006 97(6):878-882; doi:10.1093/bja/ael252
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© The Board of Management and Trustees of the British Journal of Anaesthesia 2006. All rights reserved. For Permissions, please e-mail: journals.permissions@oxfordjournals.org

An evaluation of poor LMA CTrachTM{ddagger} views with a fibreoptic laryngoscope and the effectiveness of corrective measures,{dagger}

E. H. C. Liu1,2,*, R. W. L. Goy2 and F. G. Chen1,2

1 Department of Anaesthesia, Yong Loo Lin School of Medicine, National University of Singapore Singapore
2 Department of Anaesthesia, National University Hospital Singapore

*Corresponding author: Department of Anaesthesia, National University Hospital, 5 Lower Kent Ridge Road, Singapore 119074. E-mail: analiue{at}nus.edu.sg

Accepted for publication July 9, 2006.


   Abstract
Top
 Abstract
Introduction
 Methods
 Results
 Discussion
 References
 
Background. The LMA CTrachTM{ddagger} system has integrated fibreoptics to enable viewing of the glottis to aid tracheal intubation via a laryngeal mask conduit. Earlier evaluations of this system had shown high success rates of insertion, ventilation and tracheal intubation, but frequent difficulty or failure to view the glottis.

Method. We evaluated CTrach views in 100 patients. In 69 patients with partial or no views of the glottis, we evaluated the causes with the aid of an Olympus LF-DP fibreoptic laryngoscope passed through the CTrach. In those with poor views, we tested the effectiveness of simple corrective measures to improve the views and optimize CTrach placement. These included pushing the CTrach deeper in, partial withdrawal by 6 cm and reinsertion to correct epiglottic downfolding, withdrawal by 1 cm and applying forward lift to correct obstruction by the arytenoids, and complete removal to clean the fibreoptic ports followed by reinsertion when secretions were the problem.

Results. Downfolding of the epiglottis caused poor views in 57 patients, which was correctable in 51. Obstruction of the view by the arytenoids occurred in seven patients and by secretions in five, all of which were correctable. With the Ctrach, we were able to ventilate the lungs in all patients, view the glottis in 94 and intubate the trachea in 97 patients.

Conclusion. Despite the ability to ventilate the lungs in all patients with the CTrach, poor initial views were very frequent, indicating suboptimal placement, although most poor views can be improved, leading to a high intubation success rate.

Keywords: equipment, laryngeal mask; equipment, LMA CTrachTM; intubation, endotracheal; larynx, fibreoptic laryngoscope


   Introduction
Top
 Abstract
 Introduction
Methods
 Results
 Discussion
 References
 
The LMA CTrachTM system (The Laryngeal Mask Company, Singapore) is a development of the Intubating Laryngeal Mask Airway (Fastrach), incorporating fibreoptic channels in the laryngeal mask conduit and a detachable LCD viewer. This system enables viewing of the glottis to guide tracheal intubation via the laryngeal mask conduit. In our recent evaluation of this system, we found high success rates of insertion, lung ventilation and tracheal intubation.1 However, we found it difficult or impossible to view the glottis in 48% of our patients. We were unable to confirm the causes of poor and failed views, particularly when no glottic or pharyngeal anatomy was recognizable on the viewer.

As poor views may indicate suboptimal placement and limit the usefulness of the LMA CTrachTM system, in this study we evaluated the causes of poor or failed views using a fibreoptic laryngoscope. We also assessed the effectiveness of simple measures to achieve a full view of the glottis and optimize placement of the CTrach.


   Methods
Top
 Abstract
 Introduction
 Methods
Results
 Discussion
 References
 
After institutional review board approval and written informed consent from all patients for this study, we recruited 100 adult patients, 21–75 yr of age and ASA grade I–III, who required general anaesthesia with tracheal intubation for elective surgery. We excluded patients who were pregnant, non-fasted, morbidly obese, had gastro-oesophageal reflux, delayed gastric emptying or severe respiratory disease. We also excluded patients with loose teeth or teeth in poor condition.

The LMA CTrachTM system comprises the LMA CTrach AirwayTM (CTrach) and LMA CTrach ViewerTM, and has been described previously.1 2 In the version used in this study, the aperture of the epiglottis elevator bar (EEB) on the CTrach was enlarged. This reduces the risk of obstruction of the fibreoptic ports by lateral displacement of the EEB after insertion. Second, the EEB colour was changed from beige to blue, to make its identification on the viewer easier. Third, there was a new coating for the fibreoptic tips and an improved connection between the CTrach airway and viewer, to enhance image quality.

We chose the CTrach size according to the patient's body weight.3 We used a size 3 CTrach and 7 mm inner diameter tracheal tube (TT) for patients with body weight <50 kg, a size 4 CTrach and 7.5 mm TT for patients 50–70 kg, and a size 5 CTrach and 8 mm TT for patients >70 kg. The CTrach length is longer in the larger sizes and weight-based sizing may not always be appropriate. In a few tall but very thin patients, we used a larger CTrach size than that indicated by weight, and in a few short but heavy patients, we used a smaller CTrach. We used flexible, cuffed, wire reinforced silicone Fastrach TT (The Laryngeal Mask Company, Singapore) for all patients. The system was focused, then the viewer was detached and no further adjustments made.

After preoxygenation, anaesthesia was induced in all patients with propofol 2–2.5 mg kg–1 and maintained with isoflurane 1–1.5% end tidal concentration. After checking that the lungs could be ventilated by bag and mask, neuromuscular block was induced with atracurium 0.5 mg kg–1. Two investigators (E.H.C.L. and R.W.L.G.) carried out all the CTrach and fibreoptic laryngoscopy procedures, while a third anaesthetist administered the anaesthetic drugs and monitored the patient. Our anaesthetic colleagues, who had worked in anaesthesia for at least 3 yr, performed direct laryngoscopy with a Macintosh laryngoscope before we inserted the CTrach. They placed the patient's head and neck in the ‘sniffing’ position, graded the difficulty of conventional laryngoscopy with the Cormack and Lehane scale4 and only revealed their gradings after all the airway procedures were completed.

We supported the patient's occiput on a silicone jelly doughnut of 4 cm height with the head and neck in neutral posture, and inserted the CTrach with minimal neck movement. We then inflated the CTrach cuff and checked our ability to ventilate the lungs. If necessary, we partially withdrew and reinserted the CTrach to improve ventilation. During the subsequent procedures, we continued ventilation via the CTrach as far as possible, except during fibreoptic laryngoscopy, tracheal intubation and removal of the CTrach over the TT.

After ventilation was established, we attached the viewer and graded the view of the glottis as full or good view of glottis, partial view (<50%), completely no view and no recognizable glottic or pharyngeal anatomy. We determined the causes of poor views both from the CTrach view and by passing a 3.1 mm LF-DP tracheal intubation fibreoptic laryngoscope (Olympus Optical Co. Ltd, Tokyo, Japan) through the CTrach to reach the EEB, but without lifting the EEB. The causes were noted to be the epiglottis, arytenoids or secretions. Where we identified the epiglottis as the cause of a poor view, we first tried pushing the CTrach deeper in. If this did not improve the view, we then partially withdrew the CTrach 6 cm (guided by the markings on the tube) and reinserted it without deflating the cuff.3 We tried this measure, also called the ‘up-down manouevre’, up to four times. If we were still unable to achieve a view, we removed and reinserted the CTrach, and tried this up to two times. Where the arytenoids obstructed a view of the glottis, we partially withdrew the CTrach 1 cm, and applied a forward lift to centre the view on the glottis. In patients in whom no anatomical features could be recognized on the viewer, but in whom there were good fibreoptic laryngoscopic views of the glottis, we suspected the cause to be the secretions obscuring the fibreoptic ports. We removed the CTrach to check for and clean any secretions obscuring the ports, before reinserting and trying again.

We limited the total time for all attempts to achieve and optimize the view to 3 min. The anaesthetist monitoring the patient ensured that the patient's oxygen saturation did not decrease below 95% at any time. After optimizing the CTrach view, we carried out tracheal intubation via the CTrach. Where we had failed to view the glottis despite the corrective measures, we carried out ‘blind’ intubation via the CTrach. We confirmed correct tracheal intubation with end tidal capnography, and then removed the CTrach over the TT with the aid of the stabilizer rod. We limited the number of attempts to three, before removing the CTrach and carrying out intubation with a Macintosh laryngoscope.

Our primary outcome measures were the success of viewing the glottis with the CTrach, the causes of poor views and the effectiveness of simple corrective measures. We noted the success rates of lung ventilation and of tracheal intubation with the CTrach. Based on our earlier evaluation, we estimated that in this evaluation of 100 patients, we would encounter poor views in 50 patients and that this number would provide meaningful information. Means and SD were used to describe parametric data, medians and interquartile ranges for non-parametric data, and rates and percentages for success rates and nominal data. We used Pearson {chi}2-tests to evaluate any relationship between the difficulty of conventional laryngoscopy and success rates of viewing the glottis, and tracheal intubation with the CTrach.


   Results
Top
 Abstract
 Introduction
 Methods
 Results
Discussion
 References
 
Of 101 eligible patients who were approached 100 (44 male) agreed to participate in this study. The patients had a mean age of 45.8 (21–75) yr, mean weight of 62.8 (14.2) kg and a mean BMI of 23.4 (4.2) kg m–2. There were 58, 38 and 4 patients of ASA status I, II and III, respectively. There were 55, 29 and 16 patients with Grades 1, 2 and 3 direct laryngoscopy views, respectively. Anaesthesia was uncomplicated in all patients.

We were able to insert the CTrach at the first attempt in all patients and were able to ventilate the lungs in all patients. In 41 patients, partial withdrawal and reinsertion was required to improve ventilation, before attaching the viewer. Immediately after insertion and attachment of the viewer, we were able to obtain full views of the glottis in 31 patients. (Fig. 1) Overall, we were able to achieve full or partial views of the glottis in 94 patients.


Figure 1
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  		Fig 1 The grade of initial views with the LMA CTrachTM system, causes of poor views determined with fibreoptic laryngoscopy, grade of final views after corrective measures and success of tracheal intubation via the LMA CTrachTM.

 
Downfolding of the epiglottis was the main cause of poor views, occurring in 57 patients. In 11 of these patients, we were able to achieve a full view by pushing the CTrach deeper in. In the other 46 patients, pushing deeper in did not improve the view, and we carried out partial withdrawal and reinsertion. We were eventually able to achieve a full or partial view in 51 of these 57 patients. In the remaining six patients, we were unable to achieve a view of the glottis even after removal and reinsertion.

The arytenoids obstructed the view of the glottis in seven patients and we were able to obtain full views in all of them. In five patients, secretions caused failure to identify any anatomy on the viewer, but we were able to obtain full views in all patients after cleaning and reinsertion.

In two patients in whom we had obtained full views of the glottis, ventilation via the CTrach resulted in obstruction of the view during the inspiratory phase. Using the fibreoptic laryngoscope, a partially downfolded epiglottis could be seen and this was corrected by partial withdrawal and reinsertion. During the later stage of this study, we found that reducing the viewer's brightness could help in identification of the downfolded epiglottis when nothing could be distinguished on the initial ‘white out’ view. After correcting epiglottic downfolding by partial withdrawal and reinsertion, we increased the brightness to illuminate the glottis to guide tracheal intubation.

We were able to intubate the trachea in 97 patients using the CTrach. In the 94 patients whose glottis could be seen fully or partially with the CTrach system, tracheal intubation was successful in all patients at the first attempt. In the remaining six patients in whom epiglottic downfolding could not be corrected, blind intubation was successful at the first attempt in only three patients. We failed after three attempts and carried out tracheal intubation with a Macintosh laryngoscope in the other three patients, among whom there was one patient each with direct laryngoscopy grades of 1, 2 and 3.

The median time for the entire process was 118 (IQR 90–175) (range 68–310) s. We found no relation between the grade of conventional laryngoscopy and success of viewing the larynx, Pearson {chi}2 value=0.50, P=0.78. We found no relation between the grade of conventional laryngoscopy and success of tracheal intubation with the CTrach, Pearson {chi}2-value=0.87, P=0.65.


   Discussion
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
References
 
Our study showed that poor initial views were very common when using the CTrach, and that downfolding of the epiglottis was the most common cause. Significantly, it was possible to ventilate the lungs in all patients despite these poor views and the presence of epiglottic downfolding. In the majority of patients with poor initial views, full views of the glottis could be obtained after applying simple measures. The first attempt success rate of tracheal intubation was very high if the glottis could be seen, suggesting that it is worth the time and effort to achieve a full view when using the CTrach. Conversely, where failed views as a result of epiglottic obstruction were not corrected, ‘blind’ intubation had a low probability of success.

Possible limitations of our study are as follows. First, we did not try changing the CTrach size in patients in whom we were unable to correct a persistently downfolded epiglottis. We had tried passing the TT, to raise the EEB and the downfolded epiglottis in these patients. Although we had succeeded in intubation at the first attempt in half of these patients, we do not recommend doing so as it may cause trauma to the epiglottis. Second, we inserted the CTrach with the head and neck in neutral posture and with minimal neck movement, and did not investigate if changing the posture improved the success and ease of insertion. Third, only 16 patients were of Grade 3 and none of Grade 4 and our patients had modest BMI values. This will limit the applicability of our findings.

In this study, using a fibreoptic laryngoscope enabled us to diagnose or confirm the causes of poor views. This was particularly helpful when no anatomical features could be identified on the viewer, where it helped us distinguish between a downfolded epiglottis and secretions as the cause. The simple corrective measures were easy to apply, without the need to change the CTrach size. Although improving the view of the glottis takes time, ventilation of the lungs can be maintained.

This study confirmed that downfolding of the epiglottis was very frequent, and that partial withdrawal and reinsertion was an effective corrective measure, both to improve ventilation and to improve the view. This measure uses the inflated cuff as a hook to elevate the epiglottis during the partial withdrawal movement,3 but this may need to be applied multiple times to be successful. Even though we did not have complete success in correcting epiglottic downfolding, partial withdrawal and reinsertion can still be tried when no anatomy can be identified and fibreoptic laryngoscope guidance is unavailable. Although we did not have any patients in whom both epiglottic downfolding and secretions occurred together, partial withdrawal and reinsertion may also help when more than one cause of a poor view is suspected. The frequency and causes of poor initial views and suboptimal placement, and the corrective measures in this study, may be of relevance to the Fastrach system.5–7

In this study, we had emphasized focusing the system before insertion of the CTrach, and adjusting the level of brightness to reduce glare, for every patient. This ensured that the optical quality of the system was adequate and that poor focusing was not the cause of poor views. Even more importantly, we emphasized not adjusting the focus as part of any attempt to correct poor views as this may be counterproductive, and concentrated instead on optimizing placement. However, adjusting the brightness may help when anatomy abutting against the fibreoptic ports causes a ‘white out’ view where nothing can be distinguished.

In conclusion, we found high success rates of insertion, ventilation and tracheal intubation with the CTrach. However, we obtained a full view of the glottis in only 31% of patients immediately after insertion of the CTrach and attachment of the viewer. Although we could correct poor views with simple measures in most patients, we failed to correct epiglottic downfolding and failed in tracheal intubation in a small number of patients.


   Acknowledgments
 
The authors thank colleagues in the Department of Anaesthesia and the anaesthesia nurses of the Operating Theatres Department at the National University Hospital, Singapore for their help and patience with this study. We thank Dr Chandy Verghese, Consultant Anaesthetist, Royal Berkshire Hospital, Reading, UK, for his guidance on using the LMA CTrachTM system and his advice on this study. We thank the Laryngeal Mask Company (Singapore) Private Limited for providing the equipment for this study.


   Footnotes
 
{dagger}Declaration of interest. The LMA Company Singapore supplied the LMA CTrachTM equipment for this study and supported the costs of fibreoptic laryngoscopy and sterilization of equipment. The Department of Anaesthesia, National University Hospital, Singapore has been paid by the LMA Company Singapore for teaching on other laryngeal mask devices in Singapore, China and Malaysia. The authors have evaluated other airway equipment. The Department of Anaesthesia, National University Hospital, Singapore and the authors have not accepted any payment for their evaluations of the LMA CtrachTM or any other airway equipment. None of the authors has any personal financial relationship with or stock holdings in any company whose product is mentioned in this report or with any competing company. Part of this work was presented at the European Society of Anaesthesiology Annual Meeting in June 2006 in Madrid, Spain. Back

{ddagger}LMA CTrachTM is the property of LMA International N.V. Back


   References
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
1 Liu EH, Goy RW, Chen FG. The LMA CTrach, a new laryngeal mask airway for endotracheal intubation under vision: evaluation in 100 patients. Br J Anaesth 2006; 96:396–400[Abstract/Free Full Text]

2 Timmermann A, Russo S, Graf BM. Evaluation of the CTrach—an intubating LMA with integrated fibreoptic system. Br J Anaesth 2006; 96:516–21[Abstract/Free Full Text]

3 LMA CTrachTM. Instruction Manual2005.Singapore The Laryngeal Mask Company Limited

4 Cormack RS and Lehane J. Difficult tracheal intubation in obstetrics. Anaesthesia 1984; 39:1105–11[Web of Science][Medline]

5 Kapila A, Addy EV, Verghese C, Brain AI. The intubating laryngeal mask airway: an initial assessment of performance. Br J Anaesth 1997; 79:710–13[Abstract/Free Full Text]

6 Baskett PJ, Parr MJ, Nolan JP. The intubating laryngeal mask. Results of a multicentre trial with experience of 500 cases. Anaesthesia 1998; 53:1174–9[CrossRef][Web of Science][Medline]

7 Keller C and Brimacombe J. Pharyngeal mucosal pressures, airway sealing pressures, and fiberoptic position with the intubating versus the standard laryngeal mask airway. Anesthesiology 1999; 90:1001–6[CrossRef][Web of Science][Medline]


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