The ability to predict a difficult airway is the cornerstone of avoiding its dreaded
complication. To standardize the task of airway assessment, multiple scores have been
developed and subsequently validated, such as the Wilson risk sum score, El-ghanzouri
risk index, Arne risk index...Despite utilizing these tools, there are situations in
which subjects classified as easy airways surprisingly present with challenging airways.
This has raised the need for developing and validating newer airway assessment scores,
that include quantitative ultrasound measurements. This study aims to develop a
comprehensive airway assessment score including traditional bedside clinical tests and
ultrasound measurements with high accuracy in predicting difficult airway, and to
validate it through testing it on a large population sample. After obtaining the consent
from patients to participate in the study, the day before the surgery in the PAU or
patients' rooms, a member of the research team with experience in ultrasound, will
collect the required data either in the preoperative unit or in the patient room the day
before the surgery (for admitted patients). The traditional metrics collected are:
Modified Mallampati score, inter-incisor distance, upper lip bite test, the maximum range
of head and neck movement, neck circumference, thyromental distance, receding mandible,
buck teeth, edentulousness, presence of beard, and sternomental distance and the
ultrasound measurements collected are a distance from skin to epiglottis (DSE), hyomental
distance (HMD), the ratio of hyomental distance in maximal head extension to hyomental
distance in neutral position (HMDR), tongue thickness (TT), the ratio of pre-epiglottic
distance to the epiglottic distance at the midpoint of the VC (Pre-E/E-VC), distance from
skin to the hyoid bone (DSHB), and distance from skin to vocal cords (DSVC). After
induction, the level of difficulty of laryngoscopy will be collected by a member of the
research team. For clinical and sonographic criteria with statistical significance, the
investigators will calculate their sensitivity, specificity, and positive and negative
predictive values. To determine the quantitative variable cut-off, the investigators will
establish the ROC (Receiver Operating Characteristics). After checking that the area
under the curve (AUC) is significantly >0.7, the investigators will choose as the
cut-off, the value of the variable that corresponds to the best "sensitivity-specificity"
pair. Finally, to identify independent criteria associated with difficult laryngoscopy,
the investigators will perform multivariable analysis by logistic regression. These
independent predictive criteria are the score parameters defined by values corresponding
to their respective odd ratios. Then the investigators establish the cutoff value of the
score from its ROC curve. As the patients in this study are almost all Lebanese or Arab,
potential bias and influencing factors must be considered when the models are used for
patients in other countries. Also, this is a single institution study, a multicenter and
multiracial study is needed to develop a score that can be widely used internationally.