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POGO Score

Bath, UK

To the Editor:

The results of Ochroch and colleagues' comparing percentage of glottic opening (POGO) score vs Cormack and Lehane grading.¹confirm previous work by Cohen and colleagues, who showed that trained anesthesiologists are frequently unable to assign Cormack and Lehane grading correctly to a picture of laryngeal view.² Less than half of 120 British anesthetists correctly graded a picture of a difficult, grade 2 view.

Ochroch's study clearly identifies that greater sensitivity can be achieved using their POGO score. However providing some part of the glottis can be seen intubation difficulty is rare. The majority of difficult intubations occur when no part of the glottis can be seen. Rose studying more than 3000 patients found 84% of difficult intubations and all failed intubations were associated with inability to see the vocal cords.³ These cases are Cormack and Lehane grade 3 -4: POGO score will always be 0% and so will provide no discriminating information.

I have described⁴ and recently evaluated a new practical classification of laryngeal view.⁵ The laryngeal view is easy (E) if any part of the glottis is visible. It is restricted (R) if only the posterior glottic structures (arytenoids, posterior commisure) are visible or when only the epiglottis is visible and it can be lifted. It is difficult (D) if only the epiglottis is visible but it cannot be lifted or if no glottic structures can be seen. Studying 500 cases the ERD classification correlated significantly better than Cormack and Lehane's grading with increasing difficulty with intubation (time taken and intubation aids needed).

References

1 Ochroch EA, Hollander JE, Kush S, Shofer FS, Levitan RM. Assessment of laryngeal view: percentage of glottic opening score vs Cormack and Lehane grading. Can J Anesth 1999; 46: 987–90.[Abstract/Free Full Text]

2 Rose DK, Cohen MM. The incidence of airway problems depends on the definition used. Can J Anaesth 1996; 43: 30–4.[Abstract/Free Full Text]

3 Cohen AM, Fleming BG, Wace JR. Grading of direct laryngoscopy. A survey of current practice. Anaesthesia 1994; 49: 522–5.[Medline]

4 Cook TM, Tuckey JP. A comparison between the Macintosh and the McCoy laryngoscope blades. Anaesthesia 1996; 51: 977–80.[Medline]

5 Cook TM. A new practical classification of laryngeal view. Anaesthesia 1999; (in press).

Philadelphia, USA

Thank you for your letter.¹ Our research and that of Rose and Cohen, shows that Cormack and Lehane grading has poor inter-observer reliability for assessing laryngeal exposure.² The POGO score is about quantification of laryngeal exposure. It does not address the prediction of difficult intubation, nor the difficulty of passing a tracheal tube. Adnet et al. has proposed an intubation difficulty scale that addresses seven components of intubation difficulty, only one of which is laryngeal exposure.³ In his study, many of the more difficult intubations (higher IDS scores) occurred despite adequate laryngeal exposure, while many of the intubations with lower IDS scores occurred in the setting of CL grade 3 views. For this reason, we believe it is best to separate laryngeal exposure and intubation difficulty. Although your scale has a simplistic descriptive appeal, it confuses the two issues by using the terms "easy" and "difficult" to describe different amounts of laryngeal exposure. It appears as though you are really trying to characterize intubation difficulty.

We believe that percentage of glottic opening score is a useful research tool for quantifying laryngeal exposure, particularly when used in conjunction with videotaping of laryngeal view.⁴ This research methodology can be used to assess exposure with different blades, the effect of laryngeal manipulation, and other aspects of direct laryngoscopy. For describing intubation difficulty, we suggest that Adnet et al. have appropriately included many other variables, in addition to laryngeal exposure, that impact on intubation difficulty.⁵

References

1 Ochroch AE, Kush S, Stuart S, Hollander JE, Levitan RM. Assessment of laryngeal view in direct laryngoscopy: the percentage of glottic opening (POGO) score compared to Cormack and Lehane grading. Can J Anesth 1999; 46: 987–90.

2 Rose DK, Cohen MM. The incidence of airway problems depends on the definition used. Can J Anaesth 1996; 43: 30–4.

3 Adnet F, Borron SW, Racine SX, et al. The intubation difficulty scale (IDS): proposal and evaluation of a new score characterizing the complexity of endotracheal intubation. Anesthesiology 1997; 87: 1290–7.[Medline]

4 Levitan RM. Direct laryngoscopy imaging: teaching and research applications. Educational Synopses in Anesthesiology and Critical Care Medicine (June, 1998): The On-line Anesthesia Journal, http://gasnet.med.yale.edu/esia/1998/june/samart.html. Reprinted: American Journal of Anesthesiology 1999; 26: 39–42.

5 Benumof JL. Intubation difficulty scale: anticipated best use (Editorial). Anesthesiology 1997; 87: 1273–4.[Medline]

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