In their unit, the investigators are experienced in this kind of study, as they recently published (Pediatric Anesthesia 2008) an MRI study demonstrating that in children, head extension improves the alignment of the visualisation axis on the laryngeal axis, but worsens the alignment of the pharyngeal axis on the laryngeal axis. However, patients included in their study were in major part infants, so the influence of the age could not be properly analyzed. Morevover, this study suffered of two main limitations, the lack of standardisation of head postures, and that a laryngeal mask the children, who were on general anesthesia (required for the MRI examination) were made using a laryngeal mask (as it was at this time the standard in their institution).