Examination of the hypopharynx predicts ease of laryngoscopic visualization and subsequent intubation: a prospective study of 665 patients

STUDY OBJECTIVE: To determine (a) whether the ability to visualize a patient's airway preoperatively correlates with the ability to visualize his or her larynx during laryngoscopy and (b) whether the presence of certain anatomic characteristics allows anesthetists to predict difficult laryngoscopic visualization and intubation.

DESIGN: Observational. Patients were categorized into two groups: those who had one or more physical characteristics to alert an anesthetist to the possibility of difficult intubation (obesity, overbite, short neck, or decreased neck/jaw mobility) and those with none of these characteristics.

SETTING: University-affiliated hospital.

PATIENTS: Six hundred sixty-five patients scheduled for general anesthesia and requiring endotracheal intubation. Patients were between the ages of 18 and 88 years, with body weight ranging from 21 kg to 141 kg.

INTERVENTIONS: Preoperatively, the anesthetist obtained the best view of the hypopharynx by having the patient extend the tongue and phonate. The airway was then categorized into one of three classes by the ability to see the tonsillar pillars and uvula (Class A, best view--all four tonsillar pillars and uvula seen; Class B, part of the pillars and uvula seen; Class C, worst view--pillars not seen and uvula partially or not seen). After induction, the same anesthetist graded laryngeal visibility into one of four groups depending on his ability to see the patient's epiglottis and vocal cords.

MEASUREMENTS AND MAIN RESULTS: Patients with one or more clinical clues were more likely to have poor visualization of the hypopharynx and, in turn, poor laryngoscopic visualization of the glottis. Patients who had a Class A airway tended to have easy laryngoscopic visualization and were relatively easy to intubate. Conversely, patients with no clinical clues and a Class C airway had poor glottic exposure.

CONCLUSIONS: Our study confirms work showing that the ability to visualize structures of the hypopharynx is a good predictor of subsequent glottic visualization during laryngoscopy and of ease of intubation.