Direct Laryngoscope

Aka: Direct Laryngoscope, Laryngoscope, Laryngoscope Handle, Laryngoscope Blade, Straight Laryngoscope Blade, Miller Laryngoscope Blade, Curved Laryngoscope Blade, Macintosh Laryngoscope Blade

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II. Types: Laryngoscope Blade

  1. Macintosh Curved Laryngoscope Blade
    1. Named for Sir Robert Reynolds Macintosh, who invented the Macintosh blade (1941)
    2. Tip of Laryngoscope Blade is placed in the vallecula, indirectly elevating the epiglottis
    3. Preferred Laryngoscope Blade in older children and adults (or hyperangulated blade)
    4. Available for both Direct Laryngoscopy and Video Laryngoscopy
  2. Miller Laryngoscope Blade
    1. Named for Robert Arden Miller, who modified older straight blades to be thinner and with a curved end (1941)
    2. Laryngoscope Blade directly lifts the epiglottis
    3. Preferred Laryngoscope Blade in younger children
    4. Primarily available for Direct Laryngoscopy (although Video Laryngoscopy straight blades are available)
  3. Video Laryngoscopy Hyperangulated Blade (e.g. glidescope)
    1. Hyperangulated blade follows the neutral airway curvature, and does not require direct line of sight
    2. Relies on a hyperangulated Endotracheal Tube Stylet to follow the airway
    3. Easiest blade for airway visualization, but Endotracheal Tube passage may be more difficult
    4. Only available for Video Laryngoscopy

III. Preparation: Estimated blade size selection

  1. With Laryngoscope Blade held next to patient's face
    1. Blade should reach between lips and Larynx (or lips to angle of jaw)
    2. Similar distance as with sizing Oral Airway
  2. Better to choose a blade too long than too short
    1. Estimate 1 cm longer than needed
    2. However, shorter Macintosh blades are easier to lift (shorter lever arm)
  3. Video Laryngoscopy Hyperangulated Blade (e.g. Glidescope)
    1. Size 3 Glidescope disposable blade fits most adults (even large adults)
    2. Size 4 Glidescope disposable blade is typically difficult to fit inside the mouth

IV. Preparation: Blade size guidelines by age

  1. Adult: #3 to #4 Macintosh Blade (curved)
    1. Video Laryngoscope blade sizes vary widely (e.g. Glidescope #3 fits most patients, including large males)
    2. Direct Laryngoscope #3 blades fit most adults and are easier to lift (shorter) than #4 blades
  2. Child
    1. Consider a wider Laryngoscope Blade in syndromic children (e.g. Macroglossia)
    2. Miller blade (straight blade) used most often in infants and young children
      1. Keeps the large floppy epiglottis out of the way
    3. Miller blade #0
      1. Premature Infant
    4. Miller blade #1
      1. Term infant
    5. Miller blade #2
      1. Age 2 years old
    6. Miller blade #3
      1. Third grade (age 9 years old)
    7. Macintosh Blade #2 (curved)
      1. Child at age 8

V. Preparation: Pearls

  1. Airway needs repositioning (e.g. BURP Technique) in 80% of cases
    1. De Jong (2014) Intensive Care Med 40(5): 629-39 [PubMed]
  2. High intensity light sources on Laryngoscopes are critical to adequate visualization
    1. Best sources approach 10,000 LUX
    2. LED light sources are preferred
  3. Disposable Direct Laryngoscope Blade and Handle
    1. Consider as back-up in Emergency Kit

VI. References

  1. Levitan (2013) Practical Airway Management Course, Baltimore

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