In response to the issues about our study raised by Hassani and Kessell,1 our study included lean as well as obese patients.2 We agree that a limitation of our study was the lack of blinding. However, it is difficult to assess difficult intubation using a validated score (intubation difficulty scale),3 with blinded anesthesiologists. Moreover, the aim of our study was not known to the anesthesiologist who intubated the tracheas of either lean or obese patients. The anesthesiologists were only aware of classical bedside tests and not of neck circumstance (NC). We choose intubation difficulty scale because it is an objective score that is more accurate than “difficult” or “easy.”
The preponderance of females in our study represented the sex ratio in our obese surgical population and sex was not a predictive factor of difficult intubation.
Finally, when searching for factors predicting difficult intubation, we need to define both specificity as well as sensitivity of the test. Neck circumference alone is a sensitive test (92%) meaning that NC <43 tracheal intubation will probably be uneventful. In combination with Mallampati's score, it becomes more specific (92%) meaning that, if both NC >43 and Mallampati >3, tracheal intubation will probably be difficult. In other words, although not a perfect predictor of difficult intubation, NC is a useful and easily performed bedside test that helps the anesthesiologist in the matter of airway assessment. However, we agree with Hassani and Kessell,1 that this cutoff value has to be assessed prospectively.
Vincent Minville, MD
Department of Anesthesiology and Intensive Care
University Hospital of Toulouse
1. Hassani A, Kessell G. Neck circumference and difficult intubation. Anesth Analg 2008;1756–7
2. Gonzalez H, Minville V, Delanoue K, Mazerolles M, Concina D, Fourcade O. The importance of increased neck circumference to intubation difficulties in obese patients. Anesth Analg 2008;106:1132–6
3. Adnet F, Borron SW, Racine SX, Clemessy JL, Fournier JL, Plaisance P, Lapandry C. The intubation difficulty scale (IDS): proposal and evaluation of a new score characterizing the complexity of endotracheal intubation. Anesthesiology 1997;87:1290–7