Airway anatomy

  nerves or their branches can selectively be blocked for an awake bronchoscopic intubation:

1. Trigeminal nerve (CN V) (nasal cavity, mouth)

   The nasal cavity is entirely innervated by the trigeminal nerve.

   • Anterior ethmoidal nerve (from V1) – septum
   • Greater and lesser palatine nerves, from sphenopalatine ganglion in pterygopalatine fossa (V2)
   • Nasopalatine nerve, from sphenopalatine ganglion (V2) – septum
2. Glossopharyngeal nerve (CN IX) (posterior 1/3 tongue, pharynx, valleculae, lingual surface of epiglottis and gag reflex)

   Gag reflex:

   • Elicited by stimulation of the glossopharyngeal nerve, efferent from vagus nerve
   • Abolished by bilateral block of glossopharyngeal nerve
3. Vagus nerve (X) (larynx, trachea)

   The superior laryngeal nerve divides into internal and external branches.

   • Internal branch: sensation from epiglottis to above vocal cords
   • External branch: cricothyroid muscle
   
   

   Recurrent laryngeal nerve:

   • Given off the vagus nerve during it's intra-thoracic course (loops around ligamentum arteriosum on left and around subclavian artery on right)
   • Provides sensation of larynx below and including vocal cords and trachea. Motor to all intrinsic muscles of the larynx except cricothyroid muscle
   • Glottic closure reflex (exaggeration of this reflex = laryngospasm) – this is caused by stimulation of superior laryngeal nerve, efferent from recurrent laryngeal nerve

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Nerve blocks

Superior laryngeal nerve (sensation to larynx above vocal cords)

• Blocked between hyoid bone and thyroid cartilage where it penetrates the thyrohyoid membrane
• Place patient supine with maximal neck extension
• Grab the hyoid between the thumb and index finger and firmly displace it towards the side to be blocked
• Advance a 25g needle to the greater cornu then walk it off inferiorly and advance it a further 2 – 3mm
• Inject 2 – 3ml and an additional 1ml as the needle is withdrawn (to block the external branch)

Glossopharyngeal nerve: (gag reflex and sensation from the oropharynx to the lingual surface of the epiglottis)

• Usually blocked by the local anesthetic applied to the back of the tongue and throat
• Can also be blocked by holding a local anesthetic soaked swab bilaterally at the palato-glossal arch (the rim of tissue than runs from the uvula to the base of the tongue)

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Continue to: Module 5: Procedure