Assessment of airway visualization: validation of the percentage of glottic opening (POGO) scale

Abstract

Objective: Research defining optimal methods of intubation has been limited by the lack of a validated outcome measure to assess airway visualization. The objective of this study was to develop a reliable scale for the assessment of airway visualization during endotracheal intubation.

Methods: This prospective study was performed to assess the intra- and interphysician reliabilities of emergency physicians (EPs) for estimating the percentage of glottic opening (POGO) that is visualized during direct laryngoscopy. Using video images of laryngeal views obtained from a commercially available videotape, still slide images were prepared representing glottic openings ranging from 0% to 100%. Five EPs, blinded to study objective, reviewed 25 pairs of airway slides (50 slides total). For each slide, the physicians recorded the POGO and their scores using a modified Cormack-Lehane (MCL) scale, where grade I is a view of the full glottic opening, MCL grade II is a partial view of the glottic opening, and MCL grade III is a view of the epiglottis only. Inter- and intraphysician reliabilities were assessed using the kappa statistic (K) for MCL grade and intraclass correlation coefficient for the POGO scores.

Results: For the POGO score, the degree of intrarater reliability was very good, with an intraphysician correlation of 0.85 and an interphysician correlation of 0.74. For the MCL score, the intraphysician concordance had a K of 0.71, and interphysician concordance was also good, with a kappa of 0.59.

Conclusion: Both the modified version of the Cormack-Lehane grading classification and the POGO score have good interphysician and intraphysician reliabilities. Because the POGO score can distinguish patients with large and small degrees of partial glottic visibility, it might provide a better outcome for assessing the difference between various intubation techniques.