Instrumentation of the airway is among the most noxious procedures physicians perform. Laryngoscopy and tracheal intubation require 1.3–2.8 times more inhalation anesthesia than does surgical incision. Physiologic responses to bronchoscopy include hypertension, tachycardia, increased cardiac output, laryngospasm, bronchospasm, retching, and vomiting. These hemodynamic and respiratory changes may be well tolerated by healthy individuals, but can lead to myocardial ischemia or respiratory compromise in others. To safely and effectively perform bronchoscopy and other airway procedures, pulmonary specialists must be able to adequately anesthetize the upper airway with local anesthetics, and safely administer moderate (conscious) sedation. This chapter will describe the methods used to anesthetize the oropharynx and upper airway, and the safe use of sedative hypnotics to minimize the frequency and severity of these complications.
Neuroanatomy of the Airway
Branches of the Vth, IXth, and Xth cranial nerves provide sensation to the airway. The nasal mucosa is innervated by the sphenopalatine plexus, composed of branches of the maxillary branch of the trigeminal nerve. These fibers lie just below the mucosa along the lateral wall of the nares, posterior to the middle turbinate. Sensation to the anterior 2/3 of the tongue is provided by fibers of the mandibular branch of cranial nerve V. The posterior 1/3 of the tongue and the pharyngeal mucosa to the vocal cords are innervated by the glossopharyngeal nerve through the pharyngeal plexus. The superior laryngeal and recurrent laryngeal branches of the vagus innervate the vocal cords, trachea, and bronchi.