From the Guidelines
Direct laryngoscopy (DL) is generally indicated for routine intubations in patients with normal airway anatomy, while indirect laryngoscopy (IL) is preferred for difficult airways or when neck manipulation is limited. The choice between DL and IL should be based on patient factors, clinical scenario, provider experience, and equipment availability.
Indications for Direct Laryngoscopy
- Routine intubations in patients with normal airway anatomy
- Emergency situations requiring rapid intubation
- Situations where blood or secretions might obscure video views
- Limited equipment availability
Indications for Indirect Laryngoscopy
- Difficult airways
- Limited mouth opening
- Restricted neck mobility
- Obesity
- Anatomical variations that make glottic visualization difficult
- Anticipated difficult intubations, where video laryngoscopy often serves as the first-line approach 1
Some key points to consider when choosing between DL and IL include:
- The performance of videolaryngoscopes depends on the type of device, the expertise of the operator, and the patient’s characteristics 1
- Videolaryngoscopes should be used in patients with difficult intubation criteria by trained practitioners 1
- A videolaryngoscope should be immediately available for all obstetric general anaesthetics 1
- The use of a stylet or bougie can facilitate tracheal intubation, especially in patients with difficult airways or cervical spine immobilization 1
Overall, the decision to use DL or IL should be based on a thorough assessment of the patient's airway and the clinical scenario, with consideration of the provider's experience and equipment availability. Providers should maintain proficiency in both techniques, as equipment failure may necessitate switching approaches.
From the Research
Indications for Direct vs Indirect Laryngoscopes
The choice between direct and indirect laryngoscopes for intubation depends on various factors, including the patient's airway anatomy, the predicted difficulty of intubation, and the operator's experience.
- Direct laryngoscopy is typically used for patients with a normal airway anatomy and when the operator is experienced in its use 2.
- Indirect laryngoscopy, on the other hand, is often preferred for patients with a predicted difficult airway or when the operator is less experienced 3, 4.
Advantages of Indirect Laryngoscopes
Indirect laryngoscopes, such as videolaryngoscopes, have several advantages over direct laryngoscopes, including:
- Improved visualization of the glottis, particularly in patients with a difficult airway 3, 5
- Reduced risk of failed intubation, especially in patients with a predicted difficult airway 5
- Easier to use, even for less experienced operators 4, 5
- Potential reduction in laryngeal and airway trauma 5
Disadvantages of Indirect Laryngoscopes
However, indirect laryngoscopes also have some disadvantages, including:
- Higher cost compared to direct laryngoscopes 6
- Potential for impaired visualization due to blood, vomit, or other debris 6
- Steeper learning curve for some devices, such as the Airtraq laryngoscope 6
Specific Devices
Different indirect laryngoscopes have varying characteristics and advantages. For example:
- The C-MAC video laryngoscope has been shown to improve intubation success rates and reduce the need for external laryngeal manipulation 3
- The Airtraq laryngoscope has been found to have a higher failure rate in the prehospital setting, particularly for less experienced operators 6
- The AirwayScope AWS has been shown to perform well in both normal and difficult airway scenarios, with a short intubation time and low rate of failed intubation 4