Lidocaine for airway topicalisation

We read with interest the study on airway topicalisation in morbidly obese patients by Wieczorck et al. using atomised lidocaine [1]. They state in their method that the lidocaine was delivered via an atomiser but did not include a schematic diagram or photograph to illustrate this equipment or show how it was used. The atomiser was used to deliver 40 ml of lidocaine 2% to one group of patients and 40 ml of 4% to the other. The latter group received a total dose of 1600 mg of lidocaine. The mean body weight of this group was 151.8 kg, who received, therefore, 10.54 mg.kg−1 of lidocaine. The British Thoracic Society guidelines for flexible bronchoscopy recommend a total dose of topical lidocaine of no more than 8.2 mg.kg−1 [2]. The authors clearly describe how they measured the plasma lidocaine concentrations by means of arterial blood sampling. They report the peak plasma lidocaine level as 6.5 μg.ml−1 in the 4% group. At this level, other studies have reported features of lidocaine toxicity, with some early symptoms being seen at 4 μg.ml−1 [3]. We would be interested to know more precisely the method of administration and the origin of the dose of lidocaine administered to patients in this study.