Preoperative Endoscopic Airway Evaluation
Ralph L. Slepian
1 Describe in detail the device or technique.
The American Society of Anesthesiologists’ difficult Airway Practice Guidelines recommend a three-component approach to airway evaluation including history, physical examination, and additional evaluation as needed. When patients present with upper airway lesions or for airway surgery, preoperative endoscopic airway evaluation (PEAE) can provide information not available on routine history and external physical examination.
Upper airway lesions can severely disrupt the airway anatomy and function and render tracheal intubation, and mask or SGA ventilation difficult. Their location (frequently the base of tongue, the posterior pharynx, and the laryngeal structures) makes them difficult to appreciate by conventional airway assessment techniques. Symptoms related to respiration and swallowing can be misleading. PEAE allows for the close examination of these airway lesions and can aid the clinician in airway management decisions, such as the necessity of an awake intubation (AI) versus a standard induction technique.
Prior to PEAE, a routine preoperative airway assessment is performed. This incorporates an airway history including the review of previous intubation records, symptoms of airway compromise, recent food intake, and risk factors for aspiration. The external physical examination assesses predictors of difficult intubation and difficult mask or SGA ventilation and any medical conditions that may impact airway management such as obstructive sleep apnea, lung diseases, congenital diseases, and their associated anatomic abnormalities.
When planning for nasopharyngoscopic endoscopic examination, the patient should be screened for nasal pathology such as chronic epistaxis, nasal polyps, and obstructed passages. In addition, previous imaging studies should be reviewed. If the patient has undergone prior endoscopic examination in the surgeon’s office, it may be helpful to review their previous experience, including their level of discomfort with the procedure.
PEAE is performed with the patient in a semirecumbent, or sitting position. A vasoconstrictor (e.g., oxymetazoine) is applied to both nostrils, which is followed by application of topical analgesia. Three to four milliliters of lidocaine 4% solution, dispensed via a mucosal atomizer device, should provide effective analgesia for the airway.
A small flexible scope (e.g., 2.5-3.5 mm FIS) is inserted into one nare, advanced below the inferior turbinate until the epiglottis is visualized. The FIS is then used to examine the vallecula and the base of the tongue. The laryngeal apparatus is inspected, including the true and false vocal cords and the arytenoids. Direct contact with the epiglottis is avoided. The patient may be asked to phonate in order to assess movement of the vocal cords and the size of the laryngeal inlet. Lateral movement of the FIS allows for examination of pyriform sinuses.
The site of lesions, degree of vascularity, and any anatomic disruption of the airway should be noted. The clinician performing the examination assesses whether a single-plane optical path leads to the laryngeal inlet. Multiplane paths to the laryngeal inlet may portend difficulty with FIS-aided intubation and consideration should be given to an AI technique. Moorthy et al. suggest a grading system to aid the decision process. Patients with lower grade lesions (grades 0-1), characterized by clearly visible vocal folds and normal vocal function, are intubated using a standard induction technique. Intermediate lesions (grade 2a, b), characterized by partially visible vocal folds and hoarse voice on examination, may require AI depending on the clinician’s assessment of difficulty visualizing the laryngeal inlet. High-grade lesions (grades 3-4), characterized by a significantly obscured laryngeal inlet and difficulty breathing on examination, are typically subject to AI.