Modern airway management relies increasingly on indirect visual technology to secure access to the lungs. However, achieving an optimal view does not guarantee that tube passage will proceed smoothly. Clinical evidence indicates that videolaryngoscopic tracheal intubation frequently involves a distinct mechanical dissociation between laryngeal visualisation and actual procedural execution. In many emergency departments and intensive care units, anaesthesiologists observe perfect vocal cord exposure yet encounter significant resistance when passing the endotracheal tube. Consequently, clinical documentation that records only the glottic view fails to reflect true technical difficulty. A prospective multicentre study by Fernández-Vaquero and colleagues across 44 hospitals now clarifies this relationship. By evaluating over 5,000 intubation encounters, the investigators demonstrated that visual grading alone cannot predict tube delivery success.

The Visualisation Paradox in Videolaryngoscopic Tracheal Intubation

Historically, direct laryngoscopy tied vocal cord visualization directly to procedural ease. If an airway operator achieved an unobstructed line of sight, the tube almost always passed without incident. Conversely, poor visualisation universally predicted technical failure. The wide implementation of videolaryngoscopy fundamentally disrupted this traditional correlation. Cameras positioned at the distal tip of the blade create an indirect optical axis that looks around the tongue base. Consequently, operators can visualize the glottis with minimal neck extension or tissue displacement. However, delivering the endotracheal tube into the trachea requires traversing an acute angle from the oral cavity. Therefore, a pristine camera angle does not guarantee an unobstructed path for the endotracheal tube. This phenomenon, colloquially termed "can see, cannot intubate," represents a persistent source of procedural frustration. In addition, attempting to force a tube around an acute geometric curve can cause pharyngeal trauma or arytenoid injury. Airway experts therefore recognize that assessing videolaryngoscopy requires evaluating both visual clarity and mechanical navigation. As a result, relying solely on historical scales like Cormack-Lehane documentation creates substantial communication gaps between clinicians.

Methodology of the VCISpain Multicentre Airway Study

To resolve these documentation discrepancies, clinical researchers launched the VCISpain collaborative project across 44 academic and community hospital centres. This prospective observational study systematically investigated whether a novel, three-domain classification could capture the nuances of modern airway management. The research protocol mandated simultaneous, independent evaluations performed by both the primary airway operator and an unblinded bedside observer. Together, these paired evaluators examined 5,302 adult videolaryngoscopic tracheal intubations conducted across diverse operating rooms, intensive care units, and emergency suites. For every encounter, the observers recorded three discrete operational domains. First, they documented blade geometry, noting whether the practitioner selected a standard Macintosh-style curve or a hyperangulated device. Second, they quantified the glottic view using the objective Percentage of Glottic Opening (POGO) score. Third, they classified the ease or complexity of tracheal tube delivery, documenting any need for adjuncts such as bougies, rigid stylets, or external laryngeal manipulation. Furthermore, the protocol evaluated inter-rater reliability between the active airway operator and the external observer. By examining these paired observations across predefined POGO categories, the investigators successfully created a robust evidence base reflecting real-world clinical performance.

Inter-Rater Reliability and the Three-Domain Framework

A major clinical objective of the investigation focused on whether independent clinicians could reproduce this three-domain airway evaluation consistently. Traditional visual scoring tools often suffer from significant inter-observer variability, which degrades their utility in electronic medical records. In contrast, this prospective investigation revealed outstanding concordance across all participating medical centres. The overall inter-rater agreement for the three-domain classification reached a Krippendorff's alpha of 0.86, with narrow 95% confidence intervals between 0.85 and 0.87. This high statistical coefficient confirms that both the active operator and the bedside observer perceived blade geometry, glottic view, and tube passage identically. Furthermore, agreement remained robust across varying clinician experience levels, ranging from novice trainees to seasoned consultant anaesthesiologists. Standardizing documentation across three distinct components eliminates subjective ambiguity. Clinicians no longer describe an intubation simply as "easy" or "difficult" based solely on visual quality. Instead, the framework distinguishes whether procedural challenges arose from inadequate blade seating, limited laryngeal exposure, or mechanical resistance during catheter advancement. Consequently, this multi-component framework offers an objective common language that enhances handover communications, quality improvement initiatives, and multicentre scientific investigations.

Clinical Realities of Glottic View Versus Tube Delivery

The study produced illuminating findings regarding the association between percentage of glottic opening and actual tube delivery. As expected, higher POGO scores generally correlated with a greater likelihood of straightforward, first-pass tube insertion. However, the data revealed surprising operational nuances at the lower end of the visualization spectrum. Remarkably, lower POGO scores of 0% to 25% were not uniformly associated with failed tube delivery. In fact, even when operators obtained a restricted glottic inlet view of 25% POGO, independent observer pairs still rated 50% of these intubations as technically easy. Moreover, the absolute incidence of complete tube delivery failure remained low despite compromised laryngeal views. Conversely, achieving a full 100% POGO view did not guarantee effortless tube delivery. A notable subset of patients with pristine visual exposure still required secondary adjuncts, rigid stylet adjustments, or multiple manipulation attempts to advance the tube past the vocal cords. Therefore, these findings demonstrate that glottic visualization and mechanical tube delivery operate as linked, yet clinically distinct, procedural dimensions. Clinicians cannot assume an intubation will succeed simply because the monitor display shows the vocal cords clearly.

Optimising Practice for Anaesthesiologists and Intensivists

These findings carry critical tactical implications for anaesthesiologists, emergency physicians, and critical care specialists managing airways in high-acuity environments. Healthcare institutions across India and internationally increasingly deploy videolaryngoscopes as first-line tools in emergency wards and intensive care units. Consequently, training curricula must shift away from prioritizing monitor views above all else. Educators must teach junior trainees that achieving a panoramic view can paradoxically narrow the space available for tube delivery. When an operator places a hyperangulated blade too close to the larynx, the blade tip can impede the tube pathway. In such scenarios, deliberately backing the blade out slightly may widen the optical field and create essential room for tube maneuverability. Furthermore, clinical teams must prepare pre-curved stylets, bougies, and flexible video endoscopes before initiating induction. Practitioners should also implement structured recording tools within institutional airway registries. Replacing outdated Cormack-Lehane grades with multi-domain frameworks ensures that medical documentation accurately reflects mechanical complexity. Ultimately, mastering tube delivery techniques ensures patient safety when visual scores fail to predict procedural success.

Frequently Asked Questions

What causes the dissociation between glottic view and tube delivery during intubation?

The dissociation occurs because modern videolaryngoscopes use camera optics to look around anatomical curves without requiring a direct visual line of sight. While the distal camera easily visualizes the glottis, the endotracheal tube must still navigate an acute geometrical angle from the mouth to the larynx. Consequently, optimal visualization can paradoxically crowd the airway entrance, obstructing the tube pathway and requiring specialized stylets or bougies to achieve successful tracheal placement.

How does the three-domain classification improve videolaryngoscopy documentation?

Traditional airway documentation relies almost exclusively on Cormack-Lehane visual grades, which do not reflect modern videolaryngoscopy performance. In contrast, the three-domain classification captures blade geometry, objective percentage of glottic opening, and the specific mechanics of tracheal tube delivery. This structured method provides a reproducible, comprehensive record that distinguishes visual clarity from technical manipulation, thereby improving clinical communication, training assessments, and future airway management planning.

Why is standardising videolaryngoscopic tracheal intubation reporting crucial in clinical practice?

Standardising airway documentation ensures consistent clinical communication across operating theatres, intensive care units, and emergency wards. When clinicians document blade design, laryngeal exposure, and delivery adjuncts systematically, subsequent airway teams can prepare appropriate equipment for future interventions. Furthermore, standardised registries provide reliable data for clinical audit, quality improvement initiatives, and multicentre research, ultimately reducing airway-related morbidity and improving overall patient outcomes across diverse healthcare settings.

Disclaimer: This content is for informational and educational purposes only and should not be taken as medical advice. Refer to the latest local and national guidelines for clinical practice.

References

1. Fernández-Vaquero MÁ et al. Association between glottic view and tracheal intubation during videolaryngoscopy: a prospective observational study. Anaesthesia. 2026 Oct 02. doi: 10.1111/anae.70417. PMID: 42823939.


2. Fernández-Vaquero MÁ, Charco-Mora P, Sastre-Rincón JA, et al. VCISpain: Protocol for a prospective multicenter observational study to validate a standardized classification tool for tracheal intubation using videolaryngoscopy. Rev Esp Anestesiol Reanim. 2025;72(5):844653.


3. Hansel J, Rogers AM, Lewis SR, Cook TM, Smith AF. Videolaryngoscopy versus direct laryngoscopy for adults undergoing tracheal intubation: a Cochrane systematic review and meta-analysis update. Br J Anaesth. 2022;129(4):612-623.