Why is a grade 1 view not ideal for Vaginal Labor (VL)?

Why Grade 1 View is Not Ideal for Video Laryngoscopy

A grade 1 view during video laryngoscopy is paradoxically not ideal because it often indicates the blade is inserted too deeply, which can make tube passage more difficult despite excellent glottic visualization. 1

Understanding the Issue with Grade 1 View in Video Laryngoscopy

• Video laryngoscopes (VLs) function differently from direct laryngoscopes, changing the relationship between optimal view and successful intubation 1
• With VLs, especially those with hyperangulated blades, the best glottic view may not correspond with the best chance of passing the tracheal tube easily 1
• When the blade is inserted too deeply to achieve a perfect Grade 1 view, the angle for tube insertion becomes more acute and difficult to navigate 1

The "Two Curves" Concept Explains the Problem

• Traditional direct laryngoscopy relies on aligning oral, pharyngeal, and tracheal axes 1
• Video laryngoscopy works differently - Greenland suggested considering two curves (oro-pharyngeal and pharyngo-glotto-tracheal) with VLs serving to move the eye along the primary curve 1
• With VLs, particularly those with hyper-angulated blades, a 60° curve is often needed on the stylet to navigate these curves 1

Practical Solutions for Optimal VL Use

• When using VLs, withdrawing the blade slightly from a Grade 1 view may be beneficial for tube passage 1
• Operators should adopt a "patient-screen-patient" approach rather than fixating solely on the screen 1
• The stylet should be shaped to match the curvature of the specific VL blade being used 1

Evidence Supporting VL Effectiveness Despite This Paradox

• VLs optimize laryngoscopic view and have their place either initially or after failure of direct laryngoscopy in difficult intubation algorithms 1
• The C-Mac VL performed significantly better than Macintosh direct laryngoscopy, increasing first-attempt success from 55% to 79% 1
• The McGrath Mac appears to be the best validated VL, showing superiority to Macintosh in laryngoscopy quality and success rates 1

Common Pitfalls to Avoid

• Becoming fixated on achieving a perfect Grade 1 view can paradoxically make tube passage more difficult 1
• Failing to shape the stylet appropriately to match the blade curvature can lead to failed intubation despite good visualization 1
• Not recognizing when to withdraw the blade slightly from a perfect view to facilitate tube passage 1

Clinical Implications

• For difficult airways, hyperangulated VLs are more likely to reduce failed intubation (RR 0.29,95% CI 0.17 to 0.48) compared to direct laryngoscopy 2
• Metal blades should be used for direct laryngoscopy in ICU settings to improve endotracheal intubation success rates 1
• Proficiency with any VL device requires training and regular practice to understand its optimal positioning 1