What is the history and development of laryngeal mask airway (LMA) modifications, its placement technique, ventilation guidelines, and associated complications?

Laryngeal Mask Airway: History, Placement, Ventilation, and Complications

History and Development

The laryngeal mask airway (LMA) was invented by Dr. Archie Brain in 1981 at the London Hospital, Whitechapel, with the primary objective of providing superior airway maintenance compared to face mask ventilation while avoiding the hemodynamic stress of endotracheal intubation. 1, 2

• The device evolved through a complex series of prototypes from 1981-1988, beginning with home-made models built from the Goldman Dental Mask and progressing through one-off latex models to a primitive factory-made silicone cuff in 1986 1
• By early 1988, Dr. Brain had tested the final version in more than 7,500 patients undergoing routine surgery, establishing the foundational safety and efficacy data 1
• The LMA consists of a silicone rubber tube connected to a miniature silicone mask with an inflatable elliptical cuff that forms a low-pressure seal around the laryngeal inlet 2, 3
• Aperture bars in the dome of the mask lift the epiglottis away to maintain an unobstructed lumen 2

Placement Technique

For LMA insertion, limit attempts to a maximum of three; after three failures, switch to an alternative oxygenation strategy such as face mask or alternative supraglottic device. 4

Standard Insertion Sequence

• Administer 100% oxygen before insertion 5
• Ensure adequate depth of anesthesia before attempting insertion to improve first-pass success and reduce airway irritation 4
• Insert the deflated LMA without requiring muscle relaxants or laryngoscopy 3
• Ensure LMA placement with the tip in its correct position before inflating the cuff 5
• Inflate the cuff to create a low-pressure seal around the larynx 5
• Insert a bite block to prevent occlusion 5
• Confirm adequate ventilation and oxygenation 5

LMA Exchange Technique (Bailey Manoeuvre) for At-Risk Extubation

This advanced technique involves replacing a tracheal tube with an LMA to maintain a patent, unstimulated airway with stable physiological observations, particularly useful for patients with irritable airways, smokers, asthmatics, or those at risk of surgical repair disruption from cardiovascular stimulation. 5

• Administer 100% oxygen 5
• Avoid airway stimulation: either deep anaesthesia or neuromuscular blockade is essential 5
• Perform laryngoscopy and suction under direct vision 5
• Insert deflated LMA behind the tracheal tube 5
• Ensure LMA placement with the tip in its correct position 5
• Inflate cuff of LMA 5
• Deflate tracheal tube cuff and remove tube whilst maintaining positive pressure 5
• Continue oxygen delivery via LMA 5
• Insert a bite block 5
• Sit the patient upright 5
• Allow undisturbed emergence from anaesthesia 5

Critical Pitfalls to Avoid

• Do not exceed three insertion attempts; transition to alternative airway management after three failures 4
• The tracheal tube splints the epiglottis during Bailey manoeuvre insertion, preventing downfolding of the epiglottis and favoring correct LMA positioning 5
• When ventilation is inadequate after initial LMA placement, up-size to the next larger device before abandoning the technique 4

Ventilation Guidelines

For short-duration elective superficial surgery with low aspiration risk, the LMA is recommended over tracheal intubation to reduce perioperative respiratory complications, particularly laryngospasm (five-fold reduction) and hypoxemia. 4

Ventilation Strategy

• The LMA can facilitate both spontaneous and controlled ventilation in adults and children 3
• Continue oxygen delivery via LMA throughout the procedure 5
• Provide 100% oxygen with an anaesthetic breathing system and confirm airway patency and adequacy of breathing 5
• The device is best suited for short procedures, especially when light general anesthetic is combined with regional technique 3

Contraindications to LMA Use

• The LMA is contraindicated in any situation where the patient is at risk for pulmonary aspiration 2, 3
• For tonsillectomy, a cuffed endotracheal tube is required rather than an LMA (Grade 1+ recommendation) 4
• The LMA is inappropriate in patients where re-intubation would be difficult or if there is risk of regurgitation 5
• Avoid using an LMA in patients with high aspiration risk (e.g., full stomach) 4

Positive Pressure Ventilation Considerations

• Controversy exists regarding positive-pressure ventilation (PPV) through the LMA due to concern that gases under pressure may be forced into the stomach and predispose to regurgitation 3
• Despite this theoretical concern, the device has been used successfully for controlled ventilation when appropriately selected 3

Removal Timing

No definitive evidence favors removing the LMA under deep anesthesia versus when the patient is fully awake; either approach is acceptable, though each carries distinct risks. 5, 4

Deep Anesthesia Removal

• Removal under deep anesthesia is associated with higher risk of upper-airway obstruction, which can usually be managed with jaw thrust or oropharyngeal airway 5, 4
• Adequate depth of anesthesia is critical to avoid laryngospasm when removing under deep anesthesia 5
• Clinicians should anticipate and be prepared for possible upper-airway obstruction when using this technique 4
• Maintain airway patency with simple airway manoeuvres or oro-/nasopharyngeal airway until the patient is fully awake 5
• Anaesthetic supervision is needed until the patient is awake and maintaining their own airway 5

Awake Removal

• Removal while awake carries increased risk of cough after device extraction 5, 4
• There is no difference in serious complications (laryngospasm, desaturation) between deep-anesthesia and awake removal techniques 5, 4

Complications

Respiratory Complications

• The relative risk of any perioperative respiratory adverse event is 2.94 times higher with tracheal intubation compared to LMA use 4
• LMA use reduces the risk of laryngospasm by approximately five-fold compared to endotracheal intubation 4
• LMA use reduces the risk of bronchospasm by approximately five-fold compared to endotracheal intubation 4
• LMA use lowers the incidence of hypoxemia during device removal relative to tracheal tubes 4
• Patients with an LMA experience fewer postoperative cough episodes than those intubated 4
• Upper airway obstruction may occur with deep removal but is typically easily managed 5, 4

Aspiration Risk

• The LMA does not protect against aspiration of stomach contents and should not be used when aspiration is a risk 2, 3
• The device forms a low-pressure seal around the larynx, not a high-pressure seal like a cuffed endotracheal tube 2, 3

Placement-Related Complications

• Misplacement can occur, including downfolding of the epiglottis if insertion technique is suboptimal 5
• Monitor cuff pressure to maintain adequate seal while preventing excessive pressure that could cause mucosal injury 4
• Changes in intra-cuff pressure can occur during anesthesia 6

Role in Difficult Airway Management

In a "cannot-intubate/cannot-ventilate" scenario, the LMA is recommended as a rescue device to ensure oxygenation (Grade 1+ recommendation). 4

• The American Society of Anesthesiologists' difficult airway algorithm recommends LMA insertion when ventilation and/or intubation are difficult 2
• The LMA is incorporated as the second-step intervention in difficult-airway algorithms after failed direct laryngoscopy 4
• In unanticipated difficult intubation and ventilation, use a supraglottic airway to try to ensure the child's oxygenation (Grade 1+ recommendation) 5
• The distal aperture of the LMA is in close approximation to the vocal cords, allowing passage of a 6.0-mm internal diameter endotracheal tube over an intubating stylet or pediatric fiberoptic bronchoscope 2
• Flexible fiberoptic bronchoscopy can be performed through the LMA stem to confirm correct position and observe vocal cord motion, particularly useful after thyroid/parathyroid surgery 5