Question

Classify supraglottic airway devices (SADs). What are the modifications done in 3rd generation SADs? Enumerate the possible complications associated with use of SADs. [3+4+3]

Hint:

Supraglottic airway devices are classified based on their generation, with the third generation offering better sealing, aspiration protection, and easier ventilation.
Third-generation SADs offer enhanced features like esophageal drainage, improved sealing, and cuff pressure monitoring to improve patient safety and device performance.
While SADs offer several advantages, careful insertion, monitoring, and proper fitting are essential to avoid complications like aspiration, airway obstruction, and trauma.

Answer 1

Step 1: Classification of Supraglottic Airway Devices (SADs).
Supraglottic airway devices (SADs) are used to maintain an open airway in patients during anaesthesia or in emergency settings when endotracheal intubation is difficult or contraindicated. SADs are designed to sit above the glottis, providing a secure airway while minimizing trauma to the vocal cords. SADs can be classified based on their design and the generation to which they belong:
(1) First Generation SADs:
- Laryngeal Mask Airway (LM: The LMA consists of a cuffed tube that fits over the laryngeal inlet to form a seal, with no need for tracheal intubation. It is commonly used for general anaesthesia and in emergency settings.
- Combitube: A dual-lumen airway device, one lumen is placed in the esophagus and the other in the trachea, providing a means of ventilation if the first lumen fails.
(2) Second Generation SADs:
- LMA ProSeal: A modification of the standard LMA that includes a more secure gas-tight seal and an esophageal drain tube, reducing the risk of gastric aspiration.
- I-gel: A non-inflatable device that forms a seal against the pharyngeal and laryngeal structures. It is typically used in difficult airway management.
(3) Third Generation SADs:
- LMA Supreme: A modification of the ProSeal LMA that improves the seal and allows for better positive pressure ventilation. It includes an integrated bite block and esophageal drainage port.
- Air-Q: A newer design that features a soft, non-inflatable cuff, with an integrated bite block and gas-tight seal, providing better protection against aspiration.
- Cuff Pressure Monitored Devices: Devices with built-in mechanisms to monitor and adjust cuff pressure to prevent complications associated with excessive cuff inflation.
Step 2: Modifications Done in 3rd Generation SADs.
Third generation SADs incorporate several modifications designed to improve airway security, reduce complications, and provide better performance during ventilation. These modifications include:
(1) Improved Sealing Mechanism:
- Devices like the LMA Supreme and Air-Q have enhanced designs that ensure a more secure, gas-tight seal, which is important for positive pressure ventilation. This reduces the risk of air leaks, especially when high ventilatory pressures are used.
(2) Esophageal Drainage Port:
- Many third-generation devices, such as the LMA Supreme, have an esophageal drainage port to reduce the risk of gastric aspiration by allowing the drainage of stomach contents. This provides better protection against aspiration, which is a significant risk during anaesthesia.
(3) Integrated Bite Block:
- Devices like the LMA Supreme incorporate an integrated bite block, which prevents the patient from biting the device and potentially obstructing the airway or causing damage to the device.
(4) Cuff Pressure Monitoring and Adjustment:
- Modern third-generation SADs often come with built-in mechanisms for cuff pressure monitoring. This feature helps maintain optimal cuff inflation, preventing high cuff pressures, which can lead to mucosal injury or nerve damage.
(5) Improved Ease of Insertion:
- Devices like the Air-Q have a more anatomically conforming shape that facilitates easy insertion and minimizes trauma to the airway structures.
Step 3: Possible Complications Associated with the Use of SADs.
Despite their advantages, the use of supraglottic airway devices (SADs) is associated with potential complications, which include:
(1) Aspiration:
- Aspiration of gastric contents is one of the major risks associated with SADs. Even with devices like the LMA ProSeal and Air-Q that have esophageal drainage ports, there is still a risk of gastroesophageal reflux during anaesthesia, leading to pulmonary aspiration.
(2) Airway Obstruction:
- Improper positioning or poor-fitting SADs can cause partial or complete airway obstruction, resulting in hypoxia. This can occur due to inadequate seal or device displacement, especially when positive pressure ventilation is used.
(3) Trauma to Airway Structures:
- Insertion of SADs can cause oral or pharyngeal trauma, including teeth damage, lacerations to the oropharynx, or injury to the epiglottis. While the risk is lower than that associated with endotracheal intubation, it still exists, particularly in patients with difficult airways.
- Pressure necrosis from prolonged use or high cuff pressures can lead to mucosal damage or nerve injury.