Background: The prediction of the probability of difficult intubation and the associated problems before Induction of anesthesia could be lifesaving. The aim of this study was the investigation of association between the stage of thyroid cartilage prominency and laryngoscopic view for predicting the difficult intubation.
Methods: Five hundred and thirty five patients aged 18-60 years old, with prominent thyroid cartilage, "Adam's apple", enrolled in a cross -sectional study based on the stage of "Adam's apple" and the relationship with laryngoscopic view. After induction of anesthesia, laryngoscopy performed and laryngoscopic view of larynx was recorded, and analyzed according to Modified Cormackand Lehane's Scoring.
Results: No significant association between laryngoscopic view and thyroid cartilage prominency staging was observed. There was no significant relationship in females and aged under 50 y.o. The relationship in males with poor correlation coefficient was significant. The results are as follows: [male :(p=0.028, r=-0.096), Female: (p=0.821, r=0.082), <50 yrs: (p=0.87, r=0.007) no significant association for age decades and thyroid cartilage prominency stages, were observed. In ages above 50 y.o, difference was significant. Thirty patients had a laryngoscopic view in which the tracheal rings were visible just bellow the vocal cords.
Conclusions: As the increased age was related to laryngoscopic view and thyroid cartilage prominency stage it seems that there is relationship between ages over 50 y.o and difficulty of laryngoscopic view or intubation. With the observation of a view different from the grade I Cormack and Lehane's scoring, we named it the "stage Ia" that the tracheal rings are visible bellow the vocal cords during laryngoscopy.