Supraglottic Airway Devices

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SGA Basics - Gateway Guardians

  • Definition: Supraglottic Airway (SGA) devices seal above glottis; ventilate without tracheal intubation.
  • Purpose: Maintain airway, oxygenate, ventilate. Alternative/rescue to ETT. 📌 S.G.A.: Simple, Good for Anaesthesia.
  • Advantages:
    • Rapid, easier insertion vs. ETT.
    • ↓ Hemodynamic stress.
    • ↓ Laryngeal/tracheal trauma.
    • Key in difficult airway.
  • Disadvantages:
    • ⚠️ Lower seal pressure (↑ aspiration risk vs. ETT).
    • Not for high Peak Inspiratory Pressures (PIP).
    • Risk of gastric insufflation, malposition.
  • Indications:
    • Routine anaesthesia (spontaneous/controlled ventilation).
    • Difficult airway management (rescue).
    • Pre-hospital/resuscitation.
  • Contraindications (Absolute):
    • High aspiration risk (e.g., full stomach, pregnancy >14 wks).
    • Pharyngeal pathology (abscess, hematoma). Supraglottic Airway Device Insertion Illustration

⭐ SGAs are crucial in "can't intubate, can't oxygenate" (CICO) events, serving as a primary rescue oxygenation device.

SGA Types - The Airway Cast

LMA Classic and ProSeal Sizing by Patient Weight

  • 1st Generation (e.g., LMA Classic)
    • Features: Original, inflatable cuff, reusable.
    • Seal Pressure: ~15-20 cmH₂O.
    • Gastric Access: No.
    • Uses: Spontaneous ventilation, short procedures.
    • Sizes: 1 (infant) - 6 (large adult).
  • 2nd Generation (e.g., LMA ProSeal, LMA Supreme, i-gel)
    • Features: Enhanced: better seal, airway protection, ventilation.
    • Seal Pressure: Up to 25-30 cmH₂O.
    • Gastric Access: Yes (most), allows drainage.
    • Bite Block: Often integrated.
    • LMA ProSeal: Reusable, double cuff (airway & oesophageal), drain tube.
    • LMA Supreme: Disposable, pre-curved, reinforced tip, drain tube.
    • i-gel: Disposable, non-inflatable cuff (thermoplastic elastomer gel), anatomical seal, gastric channel.
  • Intubating LMAs (e.g., LMA Fastrach - ILMA)
    • Purpose: Facilitates ET intubation (blind/fiberoptic).
    • Features: Rigid, curved tube with handle. Reusable.
    • Sizes: 3 (small adult), 4 (medium adult), 5 (large adult).

⭐ The i-gel's cuff is made of a unique thermoplastic elastomer that softens at body temperature to create an anatomical seal without inflation, reducing compression trauma risk.

SGA Use & Woes - Smooth Sailing or Stormy?

SGA Use:

  • Insertion Techniques:
    • Standard: Lubricate posterior surface, glide along hard palate until resistance.
    • Rotational (e.g., LMA Classic): Insert 180° rotated, then correct orientation in pharynx.
    • Introducer tool: For some SGAs (e.g., LMA Fastrach).
    • Jaw thrust/chin lift facilitates passage.
  • Sizing (Adults, approx. guide):
    • LMA Classic/Unique: Size 3 (Small adult, 30-50kg), Size 4 (Normal adult, 50-70kg), Size 5 (Large adult, 70-100kg).
    • i-gel: Size 3 (30-60kg), Size 4 (50-90kg), Size 5 (>90kg).
  • Confirmation of Placement:
    • Gold Standard: Persistent ETCO₂ waveform (capnography).
    • Clinical: Bilateral chest rise, auscultation (chest clear, no epigastric gurgling), visible condensation in tube.

SGA Woes (Complications & Management):

  • Malposition/Leak: Commonest. Leads to ↓Vᴛ, hypoxia. Action: Reposition, check cuff, change size.
  • Airway Obstruction:
    • Tongue fall-back, epiglottic downfolding. Action: Jaw thrust, chin lift, head tilt.
    • Laryngospasm: Inspiratory stridor. Action: 100% O₂, deepen anesthesia, PPV, suxamethonium if severe.
  • Aspiration: Risk ↑ with inadequate NPO, GERD, obesity, pregnancy, peak airway pressure >20-25 cm H₂O.
  • Trauma: Sore throat (most common), hoarseness. Rare: nerve injury (lingual, hypoglossal).
  • Gastric Insufflation: Especially with high inflation pressures or partial obstruction.

⭐ Capnography is the gold standard for confirming SGA placement and continuous monitoring of ventilation.

High‑Yield Points - ⚡ Biggest Takeaways

  • Supraglottic Airway Devices (SADs) are essential for difficult airway management and as an alternative to endotracheal intubation.
  • LMA Classic is the original; ProSeal LMA allows gastric drainage and higher seal pressures.
  • i-gel is a second-generation SAD made of thermoplastic elastomer, requiring no cuff inflation.
  • Key contraindications include risk of aspiration (e.g., full stomach, GERD), restricted mouth opening, and pharyngeal pathology.
  • Common complications are sore throat, dysphagia, and rarely, nerve injury or aspiration.
  • Second-generation SADs generally offer improved airway seal and aspiration protection compared to first-generation devices.
  • Correct sizing and adequate lubrication are crucial for successful placement and minimizing trauma.
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Practice Questions: Supraglottic Airway Devices

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Patient with BMI 40 presents for emergency surgery. All are correct about airway management EXCEPT:

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Flashcards: Supraglottic Airway Devices

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Laryngeal mask airway and other supraglottic airway devices are part of advanced airway management, which comes under _____ guidelines

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Laryngeal mask airway and other supraglottic airway devices are part of advanced airway management, which comes under _____ guidelines

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