Laryngeal Mask Airways (LMAs)

Multiple airways devices exist that are used to help oxygenate and ventilate a patient in an emergency or a controlled setting. One set of products is called supraglottic airways devices (SAD). Supraglottic airways sit above or around the glottic opening and do not go any further into the airway. SADs are devices that keep the upper airway clear for unobstructed ventilation.⁸ The laryngeal mask airway (LMA) is an example of a supraglottic airway and has been in use since 1981. The development of the LMA has been hailed as one of the most significant advances in airway management since the endotracheal (ET) tube.⁹ A great deal of literature exists that reports the successful use of the LMA as a primary airway device and as a conduit for intubation of the trachea.⁶ SADs are now used in a wide variety of clinical indications and their versatility and ease of use make them particularly valuable to caregivers practicing anesthesia, resuscitation, and intensive care.⁸

The LMA has many advantages over an ET tube in that LMAs are less invasive, decrease airway trauma, decrease neck mobility requirements, and have a reduced risk of laryngospasm and bronchospasm.³

First-Generation LMAs

There are varied types and designs of LMAs, developed and used for specific purposes. First-generation devices are simple airway tubes that do not have specific design characteristics aimed at reducing the risk of pulmonary aspiration of gastric contents.⁸ The LMA Classic was the first product used and has been in place since the early 1980s. The LMA Classic received wide recognition in a short time and has had a major impact on anesthesia practice and airway management². Other variations include the Flexible, ProSeal, Supreme, and Fastrach models (all from Teleflex in Wayne, PA).

LMAs come in multiple sizes and the correct one is based on the patient’s weight. LMA insertion is usually accomplished using the classic technique, which involves placing a water-based lubricant on the posterior aspect and deflating the cuff. The practitioner inserts the LMA midline into the mouth with the posterior surface pressed flat against the palate of the mouth and then advances with the index finger along the palatopharyngeal curve.⁷ The LMA device can be aligned with anatomical landmarks such as the lips and mandible to ensure proper sizing and correct placement produces a leak-free seal against the glottis.¹⁰ Reports have indicated between an 88% and 95% success rate on the first attempt with an experienced provider.⁵

Second-generation LMAs

Second-generation SADs incorporate specific features to improve positive pressure ventilation (PPV) and reduce the risk of aspiration.⁸ Compared to original SAD designs, second-generation SADs are designed to do the following:

• attempt to reduce the risk of aspiration by incorporating a channel for gastric decompression and suctioning secretions;
• have reinforced tips that prevent folding;
• incorporate improved cuff designs to help create a better cuff seal with higher ventilation pressures; and
• are more rigid in their design to prevent rotation and to facilitate easier insertion.⁸

 

Van Esch reported that second-generation supraglottic airway devices have been introduced, enabling a higher positive pressure, reducing the risk of aspiration, and lowering the risk on respiratory complications.

Some examples of second-generation LMAs are the LMA ProSeal (PLMA) and LMA Supreme (Teleflex), i-gel (Intersurgical), and the AuraGain (Ambu).⁷ The King LTS-D (Ambu) is also considered a second-generation device and is traditionally used in the prehospital setting.

The early recognition of the value of the LMA in the management of difficult airway situations has influenced the widespread acceptance of SAD technology in clinical practice.⁸

The use of the LMA does not exclude potential risks and complications. Many complications – from airway injury, bleeding, edema, aspiration of gastric contents, failed placement, and more – are still possible. Nerves at risk for insult due to LMA placement include the recurrent laryngeal nerve, hypoglossal nerve, and lingual nerve.⁴ Potential factors responsible for lingual nerve injury include:

• difficult LMA insertion;
• operator inexperience;
• excessive balloon inflation;
• improper LMA sizing;
• prolonged anterior displacement of the mandible during jaw thrust;
• cricoid pressure during LMA placement;
• perioperative LMA manipulation;
• use of nitrous oxide;
• lubrication with lidocaine jelly;
• extreme head rotation during LMA placement or during the procedure;
• alternating insertion techniques;
• inadequate depth of anesthesia; and
• excessive intra-cuff pressure¹.

 

SADs continue to be an important mode of rescue ventilation in patients in whom mask ventilation or tracheal intubation is impossible.⁸ Despite these advances, specific concerns such as ventilatory failure, airway injury, and pulmonary aspiration of gastric contents remain, necessitating careful patient selection and appropriate techniques for the successful use of these devices.⁸

References

1. Brimacombe J, Clarke G, Keller C. Lingual nerve injury associated with the ProSeal laryngeal mask airway: a case report and review of the literature. British Journal of Anaesthesia. 2005;95:420-3.
2. Brodrick PM, Webster NR, Nunn JF. The laryngeal mask airway: a study of 100 patients during spontaneous breathing. 1989;44(3):238-241.
3. Butterworth JF, Mackey DC, Wasnick JD, eds. Morgan & Mikhail’s Clinical Anesthesiology. 5^th ed. New York, NY: McGraw-Hill Co; 2013.
4. Cardoso HE, Kraychete DC, Lima Filho JA, Garrido LS, Rocha AP. Temporary lingual nerve dysfunction following the use of the laryngeal mask airway: report. Brazilian Journal of Anesthesiology. 2007;57:410-3.
5. Deakin C, et al. Securing the prehospital airway: a comparison of laryngeal mask insertion and endotracheal intubation by UK paramedics. Emergency Medicine Journal. 2005;22:64-67.
6. Gerstein NS, et al. The fastrach intubating laryngeal mask airway: an overview and update. Canadian Journal of Anaesthesia. 2010;57(6):588-601.
7. Nagelhout JJ, Elisha S, Rieker M. (2018). Nurse Anesthesia. St. Louis, MO: Elsevier.
8. Ramachandran SK, Kumar AM. Supraglottic airway devices. Respiratory Care. 2014;59(6):920-932.
9. Tanaka A, et al. Laryngeal resistance before and after minor surgery: endotracheal tube versus laryngeal mask airway. Anesthesiology. 2003;99:252-258.
10. Teleflex Medical. Instructions for use – LMA Classic, LMA Flexible, LMA Flexible Single Use and LMA Unique. http://lmana.com/viewifu.php?ifu=18 Published, 2013. Accessed February 10, 2014.
11. Van Esch BF, Stegeman I, Smit AL. Comparison of laryngeal mask airway vs tracheal intubation: a systematic review on airway complications. Journal of Clinical Anesthesia. 2017;36:142-150.

Recommended Articles