Direct versus indirect laryngoscopy using a Macintosh video laryngoscope: a mannequin study comparing applied forces

Area of Science:

• Anesthesiology
• Airway Management
• Medical Device Technology

Background:

• Laryngoscopy, a common procedure, can cause upper airway injury and sympathetic activation due to applied forces.
• Direct laryngoscopy and indirect video laryngoscopy are two methods used for visualizing the glottis.
• Understanding the forces exerted during these procedures is crucial for patient safety.

Purpose of the Study:

• To compare the forces applied during laryngoscopy using direct versus indirect visualization techniques.
• To investigate the relationship between visualization quality and applied forces in a standardized mannequin model.

Main Methods:

• Force transducers were attached to a GlideScope T-MAC video laryngoscope, usable for both direct and indirect views.
• Thirty-four anesthesiologists performed randomized direct and indirect laryngoscopies on a mannequin.
• Participants aimed for >80% and 50% glottic opening views, with peak and impulse forces measured.

Main Results:

• Achieving a 50% glottic opening view required significantly higher peak and impulse forces with direct laryngoscopy compared to indirect.
• Similarly, obtaining a >80% glottic opening view also resulted in higher peak and impulse forces using direct laryngoscopy.
• The differences in forces were statistically significant, with specific newton and newton-second values reported.

Conclusions:

• Lower forces were applied during indirect laryngoscopy compared to direct laryngoscopy in this mannequin study.
• Video laryngoscopy may offer an advantage in reducing applied forces during airway procedures.
• Further clinical studies in patients are necessary to validate these findings and their implications.