Intubating laryngeal mask as a ventilatory device
Reading, UK
* E-mail: chandy.verghese{at}virgin.net
Editor—We read with interest the article by Linstedt and colleagues1 and agree with the authors' conclusions and support their findings. We would like to add the following comments based on our experience of the technique.2 First, the authors do not make it clear whether the endotracheal tube (ETT) was completely removed at the beginning of the procedure. In our series, the ETT was electively removed at the start of the procedure after the insertion of the intubating laryngeal mask (ILMA), behind the ETT; that is, the ILMA was the ventilatory device for percutaneous dilatational tracheostomy (PDT). It also allowed the passage of a fibreoptic laryngoscope (FOL) without interruption of ventilation during PDT.
Secondly, the initial leakage and subsequent reduction in minute ventilation can be reduced by optimizing the position of the ILMA using the Chandy manoeuvre: the metallic handle of the ILMA can be used to lift the device in the direction used for direct laryngoscopy. We found this manoeuvre useful, though a bit uncomfortable for the user, in patients requiring high PEEP. Finally, we question the use of oxygen saturation at 1 min as the end point for PDT. We consider this to be too early to judge that the procedure has been successful, and would suggest 5 min as a more appropriate end point, as per the ILMA group in this paper.
The ILMA allows complete control of the airway in patients for PDT in the intensive care unit; with control of the airway, a conduit for rapid re-insertion of an ETT either blindly or using the fibreoptic scope if required; and the continuous application of PEEP using the Chandy manoeuvre. We agree with the authors that a randomized trial is needed to confirm the benefits of the ILMA in PDT.
Dr C. Verghese receives an annual honorarium from The LMA Company, Jersey, Channel Islands. Dr P. Dimitrov is an SpR from the Oxford Deanery.
Bath, UK
* E-mail: gmarkhaslam{at}doctors.org.uk
Editor—We read with interest the study by Linstedt and colleagues describing their experience of the ILMA as a ventilatory device during PDT.1 Their conclusion that the ILMA can be recommended as a standard device for ventilation during bronchoscope-guided PDT and that a prospective randomized trial of ILMA and ETT for PDT should be considered is to be welcomed. However, our accumulated experience of using the ProSeal laryngeal mask airway (PLMA, Intavent Orthofix) during PDT would suggest the need for a study arm examining the use of the PLMA during PDT.
Although several different supraglottic airway devices (SADs) have been advocated for this procedure,3 4 we believe the PLMA has several advantageous features. The main potential benefit of an SAD rather than an ETT is that bronchoscopy can include the whole of the trachea, enabling correct identification of the site and level of tracheal puncture. This is not possible when an ETT is in place. Use of the PLMA eliminates the risk of damaging a tracheal tube cuff and ‘spearing’ a Murphy eye, and reduces the risk of puncturing the bronchoscope. In selecting the SAD for this role in patients with ‘at risk lungs’, various features are desirable including easy insertion, reliable ventilation even in patients with reduced pulmonary compliance (and with a bronchoscope placed within the device tube), easy access to the larynx with a bronchoscope, and protection from the consequences of regurgitation and aspiration.
Several features of the PLMA favour its use over the ILMA for PDT. The ILMA is the laryngeal mask least likely to sit directly over the glottis,5 whereas the PLMA, like the LMA-classic (cLMA), sits over the glottis in more than 90% of insertions.6 The greater capacity of the PLMA bowl and absence of aperture bars or an epiglottic elevator is likely to make it easier to access the larynx. Unlike the ILMA, the PLMA is designed to minimize the risk of gastric distension, regurgitation, and aspiration during use.6 Perhaps, the only caveat to the use of the PLMA is the belief that it is harder to insert than other laryngeal masks. Brimacombe's study showed that when a gum elastic bougie (GEB) guided technique is used, the PLMA can be inserted with almost complete first-time success and without increasing airway trauma or patient sequelae.7
We described this technique in 23 patients in 2003.8 Since then we have gained further experience and refined our technique. As with all such procedures the patient's lungs are ventilated with 100% oxygen, and the patient anaesthetized and given a neuromuscular blocking drug before airway manipulation. The ETT is kept in place while the straight end of a lubricated GEB is passed into the oesophagus. A PLMA of the appropriate size is ‘rail-roaded’ over the GEB, using the oesophageal drainage channel, until it is fully inserted. Once the PLMA cuff is inflated and the PLMA tied in place the ETT is removed. The ventilator tubing is immediately attached to the PLMA with almost no interruption to ventilation. The combination of the GEB in the oesophagus and the ETT in the trachea optimizes the position of the PLMA.9 Bronchoscopy is then achieved through the PLMA with all the advantages listed by the authors.
We have performed over 250 PDTs in the last 5 yr, the majority of which have been performed with the PLMA. Problems have been minor and largely restricted to difficulties with PLMA placement and adequacy of ventilation. The problems occurred mainly during the learning curves of individual practitioners and have reduced as experience has increased and since the technique has evolved to include GEB-guided PLMA placement. Problems have also occurred during the same period with PDT performed with an ETT partially withdrawn or placed outside the vocal cords. These have included loss of airway control, puncture of the ETT cuff and damage to the bronchoscope with the advancing needle.
The fact that several techniques are advocated for this routine procedure suggests that none are ideal. The technique chosen at present appears to be largely based on personal experience and opinion. A recently presented randomized controlled study comparing the PLMA with ETT for airway management for PDT was performed in 52 patients. Although there were no differences in performance between the groups, we consider this study was too small to identify clinically important differences in performance and should be considered as a pilot for a larger study. We quite agree with the authors that a prospective study comparing techniques for airway management during PDT would be useful but believe strongly that the PLMA should be one of the designs evaluated.
Dr T. M. Cook has been paid by the LMA Company and Intavent Orthofix (both of whom manufacture the ILMA and PLMA) for lecturing.
Acknowledgements
We acknowledge the contributions of all of the consultant intensivists at our hospital in contributing to the information contained in this letter.
Flenburg, Germany
* E-mail: linstedtul{at}diako.de
Editor—We would like to thank Drs Dimitrov and Verghese and Dr Haslam and colleagues for their letters in response to our article. We are delighted and encouraged to hear about the use of the LMA by such experienced teams. Colleagues who routinely use an ETT during PDT can be difficult to convince of the advantages and benefits of LMAs.
First, we would like to respond to Dimitrov and Verghese's first and third questions. In our study, the change over from the ETT to an ILMA was performed just before the tracheostomy. To do this, the ILMA was inserted behind the ETT in situ, immediately followed by removing the ETT and then connecting the ILMA to the ventilator.
The question as to when after PDT lowest oxygen saturation occurs is, clearly, judged differently. We observed a very rapid recovery of oxygenation after connecting the ventilator to the tracheostomy tube. Therefore, we considered values taken 1 min after surgery to be meaningful.
The second question from Dimitrov and Verghese, and the comment by Haslam and colleagues, refers to the same issue. Which is the best LMA for PDT? Obviously, different authors prefer different types of LMA and achieved good results with them. When planning our proposed study to compare LMA and ETT, we did not choose the ILMA or ProSeal-LMA, but the LMA-classic. The ILMA appears not to be the ideal LMA, because in our study breathing difficulties occurred in 21% of cases (n=18), all of which were related to incorrect positioning. In these cases, the ILMA was not situated above the larynx (verified by bronchoscopy). Despite carrying out manipulations similar to the ‘Chandy manoeuvre’, with four patients, sufficient ventilation could not be established. In trials with LMA-classic, we achieved better results: in all cases, a correct positioning above the glottis was verified by bronchoscopy. The advantages of the ProSeal-LMA are easy to understand; clearly, it is a suitable airway during PDT. Nevertheless, we do not use ProSeal-LMA for two reasons:
- The risk of aspiration seems to be not as high as they presumed. It has never occurred in any of >250 procedures in our institutions. (Routine procedures before PDT include abstaining from feeding for 6 h and suctioning before removing the gastric tube.)
- The main advantage for us, in using the LMA-classic, is that its lumen is much larger than that of the ProSeal-LMA. As a result, there is substantially less airway resistance with the bronchoscope inside.
References
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2 Verghese C, Rangasami J, Kapila A, Parke T. Airway control during percutaneous dilatational tracheostomy: pilot study with the intubating laryngeal mask airway. Br J Anaesth (1998) 81:608–9.
3 Agrò F, Carassiti M, Magnani C, Alfery D. Airway control via the CobraPLA during percutaneous dilatational tracheotomy in five patients. Can J Anaesth (2005) 52:418–20.[Web of Science][Medline]
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6 Cook TM, Lee G, Nolan JP. The ProSealTM laryngeal mask airway: a review of the literature. Can J Anaesth (2005) 52:739–60.[Web of Science][Medline]
7 Brimacombe J, Keller C, Judd DV. Gum elastic bougie-guided insertion of the ProSealTM laryngeal mask airway is superior to the digital and introducer tool techniques. Anesthesiology (2004) 100:25–9.[CrossRef][Web of Science][Medline]
8 Craven RM, Laver SR, Cook TM, Nolan JP. Use of the Pro-Seal LMA facilitates percutaneous dilatational tracheostomy. Can J Anaesth (2003) 50:718–20.[Web of Science][Medline]
9 Dob DP, Shannon CN, Bailey PM. Efficacy and safety of the laryngeal mask airway vs Guedel airway following tracheal extubation. Can J Anaesth (1999) 46:179–81.[Web of Science][Medline]
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