Supraglottic Airway Devices

Introduction

• SADs are ventilation devices placed above the glottis, providing airway support without entering the trachea.¹
• The devices include a variety of single-use and reusable options used in both elective and emergency airway management.^1,2,3
• SADs have been recommended as non-invasive tools for both anticipated and unanticipated difficult airway management, including use as primary devices and as rescue options when face mask ventilation or tracheal intubation fails.^1,2,3
• SADs are a key component of modern airway management. The development of these devices began in the early 1980s with the laryngeal mask airway created by Dr. Archie Brain.²
• These devices have undergone rapid development and have been widely adopted in the clinical setting.²
• Compared to ETTs, SADs have several advantages, including easier insertion and reduced need for neuromuscular blocking agents.²
• SADs have been shown to eliminate the need for translaryngeal placement, thereby reducing associated cardiovascular responses and contact with the vocal cords.²

Classification of Supraglottic Airways and Their Features

• First-generation SADs are characterized by a simple breathing tube that is equipped with a mask or an opening positioned at the laryngeal inlet.^1,2
• Relative to first-generation SADs, second-generation SADs have an overall reduced airway morbidity. A lower incidence of sore throat, dysphagia, and hoarseness is also observed.^2,5-7
• Improved hemodynamic stability and higher oropharyngeal leak pressures have been reported with second-generation SADs, along with shorter recovery periods and reduced overall hospital stay.^2,5,7
• Third-generation SADs are characterized by self-pressurizing and dynamic sealing properties, which allow for an improved ease of intubation through the device and greater stability under varying airway pressures.^2,4

• Important features to consider include the integrity of the esophageal seal, the angle of curvature in devices with rigid shafts, the presence of a gastric channel, and the thickness and shape of the cuff.³
  • A secure esophageal seal and cuff is considered essential for minimizing aspiration risk and enabling ventilation with higher peak airway pressures.³
  • The angle of curvature is evaluated because it influences the ease of insertion. Inappropriate curvature may be associated with mechanical injury and compromise of the protective barrier.³
  • The inclusion of a gastric channel is recognized as a means of reducing the likelihood of regurgitation.³
• The material used for SAD construction (silicone, polyvinyl chloride, or elastomere) and the presence of an integrated bite block should also be noted.³
  • A reduced risk of airway compromise has been demonstrated when an integrated bite block is incorporated, as it protects against device occlusion or rupture if the patient bites down.¹
• The 2nd- and 3rd-generation SAD designs have incorporated channels to direct gastric contents away from the airway and integrated cuff pressure measurement.^6,7

Indications

Airway Rescue

• SADs are employed in “cannot intubate, cannot oxygenate” situations.^1-3
• SADs have been shown to prevent the need for emergency surgical airway and are recommended by multiple difficult airway guidelines.³
• Complex cases have utilized second-generation SADs which include obese patients, laparoscopic surgery, and obstetric patients.^1,3,5-7
  • SADs have demonstrated similar efficacy to ETTs with fewer postoperative complications during laparoscopic surgery.^3,6,7
  • Access for endotracheal Intubation:
    • Some SADs are specifically designed to facilitate ETT intubation. Examples include: i-gel®, LMA® Fastrach™, air-Q®, and Ambu AuraGain™.^2,3,5,6
    • These devices allow visualized intubation using fiberoptic bronchoscopy.⁶
    • Blind intubation can also be accomplished in select devices.²

Primary Airway Management

• SADs can be used for primary airway management, which include ambulatory anesthesia and short-duration procedures with spontaneous ventilation.³
  • Compared with ETTs, SADs have a lower incidence of postoperative cough, hoarseness, and nausea when used as primary airway management.⁸
• Emergency and pre-hospital airway management:
  • SADs are used in out-of-hospital airway management, particularly by paramedics with limited experience in endotracheal intubation.³
  • As supported by international resuscitation guidelines, SADs have been used during cardiac arrest resuscitation.²

Special Considerations

Obesity/Obstructive Airway Disease

• Device failure due to inadequate ventilation is more likely in obese patients with obstructive airways disease.^1-3

Patients with a High Risk of Aspiration and Regurgitation

• Obstructive sleep apnea, gastroesophageal reflux, nausea/vomiting, and obesity should be considered.^1,3

Pediatric Anesthesia

• The use of SADs has reduced the incidence of perioperative respiratory adverse events in infants compared to ETTs.³
• SADs can be used for neonatal resuscitation as an alternative to mask ventilation or ETT in term or near-term infants.^2,3

Use During Extubation

• SADs have facilitated controlled extubation by minimizing hemodynamic stimulation and coughing and have allowed post-extubation airway assessment with flexible bronchoscopy.^1,2,4,7

Use During Percutaneous Dilatational Tracheostomy (PDT)

• SADs may be used during PDT as an alternative to ETT for ventilation in ICU patients.³

Perioperative Use

• Although caution is required, SADs may be used in Trendelenburg, Lithotomy, prone positioning, and rescue ventilation after accidental prone extubation.³

Technique

Standard Technique of SAD Insertion

• First, the appropriate device size should be selected.^4,10
• The posterior surface should then be lubricated, and the patient’s head should be positioned in the sniffing position.^4,10
• The mouth should be opened, and the device should be advanced along the hard palate until resistance is encountered.^4,10
• The cuff should then be inflated, and correct placement of the device should be confirmed.^4,10

Optimal Airway Seal

• Two seals should be produced to ensure a functional fit: one for the gastrointestinal tract and one for the respiratory tract, which seals the glottic ^entrance.4
• The esophageal seal serves as a functional barrier that prevents contamination of the airway by secretions, blood, or pus, while also reducing gastric inflation and the risk of aspiration.⁴
• The epiglottis should be rested outside of the airway device, and the ideal intracuff pressure should range between 40–60 cm H₂O.⁴
  • An optimal seal should produce a normal capnogram, adequate air entry, and excellent gas exchange. This is indicated by an Oropharyngeal Leak Pressure greater than 25 cm H₂O, and peripheral oxygen saturation (SpO₂) levels greater than 95%.⁴

Optimal Anatomical Position

• A properly positioned SAD should have its tip resting against the upper esophageal sphincter, with the cuff filling the hypopharynx and sitting behind the cricoid cartilage.⁴
• The device’s opening should directly oppose the glottis, while the cuff’s sides rest in the pyriform fossae.⁴
• The epiglottis should be located externally to the device and aligned with the proximal portion of the mask.⁴
• When correctly placed, the SAD forms two effective seals for both the respiratory and digestive tracts.⁴

Complications

Trauma and Local Injury

• Complications related to SAD placement are more likely to be encountered in patients with traumatic airway injuries.¹
• Complications include worsening of airway trauma, inadequate oxygenation, and nerve injury.^1,9

Device-Related Problems

• Some classifications of SADs are not given protection against aspiration as a cuffed endotracheal tube.⁷
• Mispositioning of the device has resulted in clinical malfunction and interference with gas exchange, loss-of-airway, and gastric inflation.⁴
• If a difficult intubation is expected, SADs should be used cautiously.
  • Poor outcomes can occur when an SAD is used to avoid an anticipated difficult airway without a proper backup plan.⁴

Airway and Ventilation Issues

• Situations with expected difficulty inserting or ventilating with an SAD has suggested a reduced efficacy of the device.³
  • Examples include reduced mouth opening, fixation of the cervical spine or the use of manual in-line stabilization, abnormal or absent dentition, airway pathology or edema at the glottic, supraglottic, or subglottic levels, elevated intra-abdominal pressure, and restricted airway access due to surgical positioning.³
• When patients are placed in lithotomy, Trendelenburg positions, there may be elevated intraabdominal pressure leading to ventilation issues, as well as increased aspiration risk.³
• When patients are in the prone position, there will be restricted airway access.³

Cardiopulmonary Effects

• SADs can be less suitable due to inadequate anesthetic depth or inexperienced operators which can lead to increased risk of laryngospasm, loss of airway, or improper placement.³
• Elevated airway pressures such as poor lung compliance and pneumoperitoneum can exceed the seal capability of some SADs, resulting in an increased leak or aspiration risk.^3,4