What are the different types of LMA airways?

Invented in the 1980s, the Laryngeal Mask Airway (LMA) revolutionized anesthesia and emergency medicine as an alternative to facemasks and endotracheal tubes. These supraglottic airway devices, or SADs, have since evolved into numerous designs, each with specific features for different clinical situations. Understanding what are the different types of LMA airways is crucial for medical professionals.

Quick Summary

LMA airways come in various types, including first-generation reusable (Classic) and disposable (Unique) models, and more advanced second-generation devices designed with enhanced safety features. These include devices with gastric drainage channels (ProSeal, Supreme), models specifically for intubation (Fastrach, CTrach), and gel-cuffed options (i-gel), each suited for different clinical needs and patient risks.

Key Points

• First vs. Second-Generation LMA: First-generation LMAs, like the Classic and Unique, are simple with basic inflatable cuffs, while second-generation devices, such as the ProSeal and Supreme, offer advanced safety features like a gastric drain channel for managing stomach contents.

• Intubating LMAs: Specialized devices like the LMA Fastrach and CTrach are designed to act as a conduit for inserting an endotracheal tube, particularly useful in difficult airway scenarios.

• I-gel Advantage: The i-gel is a unique LMA because it features a non-inflatable, gel-like cuff that molds to the patient's anatomy, simplifying insertion and potentially reducing trauma.

• Enhanced Safety with Second-Generation: Second-generation LMAs provide a higher oropharyngeal leak pressure, making them safer for procedures requiring positive pressure ventilation and for patients with an increased risk of aspiration.

• Choosing the Right Device: LMA selection depends on factors such as patient risk (e.g., aspiration), ventilation needs, the potential need for intubation, and the clinical setting (e.g., emergency vs. elective surgery).

The LMA: A Brief Overview

The LMA, or Laryngeal Mask Airway, is a medical device used to provide a clear airway for a patient during anesthesia, resuscitation, or in emergency situations. Positioned in the hypopharynx, it forms a low-pressure seal around the laryngeal inlet, allowing for ventilation without requiring full endotracheal intubation. The evolution of the LMA has led to a variety of designs, which can generally be categorized into first- and second-generation devices based on their features and advancements.

First-Generation LMA Devices

First-generation LMAs represent the original designs and are simpler in construction. They are effective for routine use but lack some of the advanced features found in newer models. The primary drawback is a lower seal pressure, which can increase the risk of gastric insufflation and aspiration, especially during positive pressure ventilation.

• LMA Classic: The original LMA, it is a reusable device made of silicone. Known for its soft, pliable cuff and straightforward design, it is a reliable choice for spontaneous breathing in fasted patients undergoing routine, short-duration procedures.
• LMA Unique: This is a disposable version of the LMA Classic. Its single-use design eliminates the risk of cross-contamination and is often used in emergency or prehospital settings where sterilization is not immediately possible.
• LMA Flexible: Featuring softer, more flexible tubing, this type is not suitable for emergency use. Its flexibility allows for better positioning during surgery involving the head and neck, as the tube can be bent and secured away from the surgical field.

Second-Generation LMA Devices

Second-generation LMAs incorporate new features aimed at enhancing safety and expanding clinical use. Key improvements include higher seal pressures and a dedicated gastric drain tube to manage regurgitated stomach contents.

• LMA ProSeal: An enhanced version of the Classic, the ProSeal features a separate channel for gastric drainage. This allows a suction tube to be passed into the stomach, reducing the risk of aspiration and enabling higher ventilation pressures. It typically uses a softer, silicone cuff for an improved seal.
• LMA Supreme: This single-use device combines the features of the ProSeal with a built-in bite block and an anatomically curved, semi-rigid airway tube for easier insertion. It offers an effective airway seal and provides gastric access, making it a popular choice for routine and some laparoscopic procedures.
• i-gel: A unique second-generation device, the i-gel uses a non-inflatable, gel-like cuff made of a thermoplastic elastomer. This cuff is anatomically pre-shaped to mold to the periglottic structures without requiring cuff inflation, which can reduce the risk of compression trauma. It also includes a gastric channel.

Intubating and Fiberoptic-Guided LMAs

Some LMAs are specifically designed for more complex airway management, including acting as a conduit for an endotracheal tube (ETT).

• LMA Fastrach: A rigid-tube intubating LMA (ILMA), it is designed with a specialized handle and an epiglottic elevating bar to facilitate the blind passage of an ETT through the device and into the trachea. It provides a higher success rate for intubation compared to standard LMAs in certain situations.
• LMA CTrach: An evolution of the Fastrach, the CTrach incorporates built-in fiberoptics and a video screen, allowing for direct visualization during intubation. This reduces reliance on the blind technique and improves intubation success rates.

First-Generation vs. Second-Generation LMA Comparison

Feature	First-Generation (e.g., Classic, Unique)	Second-Generation (e.g., ProSeal, Supreme, i-gel)
Key Feature	Simpler design; focuses on basic airway patency.	Enhanced safety features; often includes gastric drain channel.
Cuff Type	Inflatable silicone or PVC cuff.	Inflatable or non-inflatable (i-gel) cuff with improved sealing.
Gastric Access	No dedicated channel for stomach drainage.	Dedicated channel for gastric suction, reducing aspiration risk.
Seal Pressure	Lower seal pressures, less effective for high-pressure ventilation.	Higher oropharyngeal leak pressures (OLP), safer for positive pressure ventilation (PPV).
Insertion	Traditional insertion methods.	Anatomically curved tubes and bite blocks (Supreme) for easier insertion.
Intubation	Can be used, but success rate is lower; smaller ETT size limited.	Some types (e.g., Fastrach, CTrach) are specifically designed for intubation.
Main Use	Routine anesthesia for spontaneously breathing patients.	A wider range of uses, including positive pressure ventilation and procedures with aspiration risk.
Cost/Use	Often reusable (Classic) or low-cost disposable (Unique).	Often single-use and can be more costly due to added features.

How to Select the Correct LMA

Choosing the right LMA depends on several factors, including the clinical setting, patient characteristics, and procedural needs.

1. Patient Risk Factors: Patients with a higher risk of aspiration (e.g., obesity, pregnancy beyond 14 weeks) may benefit from second-generation LMAs with gastric drainage.
2. Ventilation Needs: Procedures requiring high positive pressure ventilation, such as laparoscopy, are safer with a second-generation LMA that provides a higher seal pressure.
3. Intubation Requirement: For cases where intubation might be necessary, an intubating LMA like the Fastrach is the appropriate choice.
4. Clinical Setting: In emergency or prehospital settings, a disposable LMA Unique is practical, whereas for elective surgery in a hospital, a reusable Classic or advanced single-use device like the Supreme might be used.
5. Patient Size: LMA size selection is primarily based on patient weight according to manufacturer recommendations, although newer studies also suggest considering pharyngeal anatomy or alternative sizing methods.

Conclusion

The array of LMA airways available today is a testament to the continuous innovation in airway management. From the reliable and simple first-generation devices to the enhanced safety features of second-generation models and specialized intubating options, the right choice of LMA is a critical decision in clinical practice. Healthcare professionals must understand the differences in design and function to match the appropriate device to the patient's needs and procedural requirements, ensuring effective and safe ventilation. For more information on the history and development of LMA devices, professionals can consult resources from the Anesthesia Patient Safety Foundation.

Disclaimer: This information is for informational purposes only and does not constitute medical advice. Consult a healthcare professional for diagnosis and treatment.

Frequently Asked Questions

What does LMA stand for?

LMA is an acronym for Laryngeal Mask Airway, which is a type of supraglottic airway device used in medical settings.

What is the primary difference between a first- and second-generation LMA?

The main difference lies in the features. Second-generation LMAs, such as the ProSeal and Supreme, typically include a gastric drain tube and provide a higher airway seal pressure, offering better protection against aspiration compared to simpler first-generation models like the Classic or Unique.

Which LMA is best for emergency situations?

For emergency or prehospital settings, the LMA Unique, a disposable version of the original LMA, is often preferred due to its simplicity and the elimination of cross-contamination risks.

When would a healthcare provider use an intubating LMA?

An intubating LMA, such as the LMA Fastrach, is used when a patient needs an endotracheal tube but standard intubation methods are difficult or have failed. It provides a reliable pathway to facilitate tracheal intubation.

Is an LMA suitable for a patient at risk of aspiration?

An LMA is not as protective against aspiration as an endotracheal tube. However, second-generation LMAs with gastric drainage channels (like the ProSeal or Supreme) are safer for these patients than first-generation devices, as they allow for the removal of stomach contents.

How is the correct size of an LMA determined?

The size of an LMA is primarily selected based on the patient's body weight, following manufacturer recommendations. However, experienced providers may also consider other anatomical factors.

Can an LMA be used for patients undergoing laparoscopic surgery?

Yes, second-generation LMAs like the Supreme and ProSeal are often used for laparoscopic procedures because they can accommodate the higher airway pressures associated with peritoneal insufflation and offer gastric access.