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• The intubating laryngeal mask airway: What is there not to like?
  Andrew M. Mason
  Published on: 29 April 2016

• Published on: 29 April 2016

  The intubating laryngeal mask airway: What is there not to like?

  • Andrew M. Mason, Hon. President

  I was interested to read the paper by Castle & Naguran describing use of the intubating laryngeal mask airway (iLMA) in an entrapped patient [1]. The authors might be interested to know that I have also used the iLMA in the treatment of trapped trauma patients [2][3], and their case bears striking similarities to the ones that I encountered. Their report provides further evidence of the efficacy of the iLMA in trapped...

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  I was interested to read the paper by Castle & Naguran describing use of the intubating laryngeal mask airway (iLMA) in an entrapped patient [1]. The authors might be interested to know that I have also used the iLMA in the treatment of trapped trauma patients [2][3], and their case bears striking similarities to the ones that I encountered. Their report provides further evidence of the efficacy of the iLMA in trapped trauma situations, both as a primary airway rescue device and as a bridge to tracheal intubation. Their report was encouraging, but I felt that there were a number of important questions left unanswered, and I would like to draw attention to these and offer some observations of my own.

  The first important issue concerns the use of drugs. The authors failed to say if an anaesthetic or sedative agent was used to assist with insertion of the iLMA, and whether or not a neuro-muscular blocking agent (NMBA) was used to facilitate intubation via the device. In my own small case series involving five hypoxaemic trapped trauma patients, four of the patients who went on to survive to discharge from hospital required the administration of a dose of midazolam to facilitate insertion of the iLMA, and the single patient who accepted the iLMA without the need for medication was the only non-survivor. Although it has been shown that there is no statistical difference in the success rates for intubation via the iLMA between chemically paralysed and non-paralysed patients [4], the incidence of reflex coughing is likely to be higher in non-paralysed individuals, and the possible implications of coughing in the presence of brain injury and raised intracranial pressure clearly need to be borne in mind. Consequently, I would be interested to know if any drugs were used.

  Secondly, although the SpO2 and EtCO2 readings suggested that there was a significant improvement in the casualty's condition after insertion of the device, we were not told if the patient went on to survive to discharge from hospital - an important test of the efficacy and safety of any prehospital intervention.

  Finally, the authors omitted to mention the size and type of ET tube that they used, and it would be interesting to know if the iLMA's dedicated atraumatic wire-reinforced tube was employed, or simply a standard ETT rotated through 180-degrees, as some authors have recommended [5].

  I agree with the authors that it is probably wise to leave the iLMA in situ during transportation to hospital, even when tracheal intubation via the iLMA has been undertaken in the prehospital phase, since manipulation to remove the device from around the tracheal tube could cause the tube to become accidentally dislodged. It should be noted, however, that when the iLMA is left in situ after intubation, the manufacturer recommends reducing the volume of air in the cuff of the iLMA by 50%. This reduces pressure on the hypopharyngeal mucosa with the aim of preventing possible ischaemic damage to tissues.

  Castle & Naguran report that the first attempt to intubate via the iLMA was unsuccessful, with resistance felt at the point where the ETT should have entered the larynx, but that a second attempt at intubation was successful after the iLMA was repositioned and forward traction applied. Early studies suggested that a learning curve of approximately twenty cases existed for proficiency in tracheal intubation via the iLMA [6]. However, subsequent refinements to the recommended insertion technique have managed to improve first-time intubation success rates significantly [7].

  The recommended technique for intubation via the iLMA is sometimes called the 'Chandy' manoeuvre, named after the UK anaesthetist, Dr Chandy Verghese. The first part of the Chandy manoeuvre involves grasping the iLMA by its handle and moving it back-and-forth in the sagittal plane while noting the rise-and-fall of the chest (tidal volume) together with the resistance to manual ventilation. This optimises ventilation through the device which occurs when the distal airway aperture in bowl of the mask is directly opposite the laryngeal inlet. The second part of the manoeuvre involves lifting the handle of the iLMA at 45% to the horizontal plane of the patient's chest. This helps to align the angled ramp at the distal end of the airway aperture with the longitudinal axis of the upper trachea, so facilitating direct and unhindered passage of the tip of the tube into the upper trachea. Use of the Chandy manoeuvre can be expected to improve first-time intubation rates with the iLMA to levels approaching 100%.

  Castle and Maguran's case report shows the potential value of the iLMA as a device for rapid control of the airway in the prehospital setting, particularly when there is restricted access to a trapped casualty. They also show the value of the device as a bridge to blind intubation of the trachea.

  I believe that the iLMA is a much underrated and underused supraglottic airway device which is particularly suitable in a trapped trauma situation where there is limited access to the casualty. Its benefits include:

  1. Insertion and ventilation can be achieved easily by persons with minimal training [8][9][10][11][12]

  2. Functions as an initial rescue airway device in its own right

  3. Laryngoscopy unnecessary

  4. Neutral alignment of head & neck is a pre-requisite for insertion, rendering manipulation of a potentially injured cervical spine unnecessary

  5. Insertion requires an interdental gap of only 20mm

  6. Neuromuscular blockade not essential for insertion of the iLMA or subsequent intubation via the device

  7. Can be introduced blindly with one hand from any position

  8. No need to insert a finger into patient's mouth

  9. Rigid airway tube resists occlusion by biting

  10. When the cuff is inflated, this provides protection of the airway from bleeding arising above

  11. Facilitates seamless progression to tracheal intubation

  12. Permits ventilation between and even during intubation attempts

  13. Available as a disposable single-use device.

  With regard to the iLMA as a suitable rescue ventilation device for prehospital trauma care, one is tempted to ask, 'What is there not to like?'

  Dr Andrew M Mason

  (Hon. President, Suffolk Accident Rescue Service, Ipswich, UK)

  REFERENCES:

  [1] Castle N, Naguran S. Reflection: on the use of the ILMA in an entrapped patient. Emerg Med J 2014; 31(12): 1014-1015

  [2] Mason AM. Use of the intubating laryngeal mask airway in pre- hospital care: a case report. Resuscitation 2001 Oct; 51(1): 91-5

  [3] Mason AM. Prehospital use of the intubating laryngeal mask airway in patients with severe polytrauma: a case series. Case Rep Med 2009; 2009:938531. doi: 10.1155/2009/938531. Available for free download at: http://www.hindawi.com/journals/crim/2009/938531/

  [4] Ambulkar R, Tan AYH, Chia NCH, Low TC. Comparison between use of neuromuscular blocking agent and placebo with the intubating laryngeal mask airway. Singapore Med J. 2008; 49(6): 462-465

  [5] Shah VR, Bhosale GP, Mehta T, Parikh GP. A comparison of conventional endotracheal tube with silicone wire-reinforced tracheal tube for intubation through intubating laryngeal mask airway. Saudi J Anaesth 2014; doi:10.4103/1658-354X.130702

  [6] Baskett PJF, Parr MJA, Nolan JP, et al. The intubating laryngeal mask. Results of a multicentre trial with experience of 500 cases. Anaesthesia 1998; 53(12): 1174-1179

  [7] Ferson DZ, Rosenblatt WH, Johansen MJ, Osborn I, Ovassapian A. Use of the intubating LMA-Fastrach in 254 patients with difficult-to- manage airways. Anesthesiology 2001; 95(5): 1175-1181

  [8] Levitan RM, Ochroch EA, Stuart S, Hollander JE. Use of the intubating laryngeal mask airway by medical and nonmedical personnel. Am J Emerg Med 2000; 18(1): 12-16

  [9] Reeves MD, Skinner MW, Ginifer CJ. Evaluation of the intubating laryngeal mask airway used by occasional intubators in simulated trauma. Anaesth Intens Care 2004; 32(1): 73-76

  [10] Menzies R, Manj H. The intubating laryngeal mask: is there a role for paramedics. Emerg Med J 2007; 24(3): 198-199

  [11] Timmermann A, Russo SG, Crozier TA, et al. Laryngoscopic versus intubating LMA guided tracheal intubation by novice users - a manikin study. Resuscitation 2007; 73(3): 412-416

  [12] McCall MJ, Reeves M, Skinner M, Ginifer C, Myles P, Dalwood N. Paramedic tracheal intubation using the intubating laryngeal mask airway. Prehosp Emerg Care 2008; 12(1): 30-34.

  Conflict of Interest:

  AMM is a former adviser in prehospital care to both Intavent Direct and the Laryngeal Mask Company, former distributors of the iLMA. Opinions expressed are purely those of AMM who has no connection with the current distributor(s) and no financial interest in sales of the iLMA.

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  Conflict of Interest:
  None declared.

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