Assessment of Upper Airway Anatomy in Awake, Sedated and Anaesthetised Patients Using Magnetic Resonance Imaging

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Abstract
Magnetic Resonance Imaging was used to quantify the effects of 1. sedation and 2. general anaesthesia with a laryngeal mask airway (LMA) in place on the minimum antero-posterior (A-P) diameters of the naso-, oro- and hypopharynx and on the angle of the epiglottis relative to the adjacent posterior pharyngeal wall. Median saggital T1-weighted images of the pharynx were obtained in 46 patients (16 awake, 14 sedated, 16 under general anaesthesia). In sedated patients, the A-P diameters of the pharynx were less than in awake patients, in particular at the levels of the epiglottis and soft palate. General anaesthesia and placement of a LMA was also associated with a reduced A-P diameter at the level of the soft palate, but with increased diameters at the levels of the tongue and epiglottis. Placement of a LMA caused abnormal downfolding of the epiglottis in most cases but this did not cause clinically significant airway obstruction.