For patients with compromised airways who struggle to breathe independently, intubation is often a necessary intervention. Intubation involves the insertion of a tube through the mouth and into the trachea of the patient to create a clear airway. Between 13 and 20 million intubations are performed in ERs across the U.S. annually, according to commercial estimates; however, the recent Covid-19 pandemic has resulted in a surge of necessary intubations in hospitals across the U.S. as well as globally.(1) One risk of intubation is vocal cord paralysis.
Though intubation is not considered a high-risk procedure, there have been adverse outcomes associated with invasive endotracheal intervention. One particularly devastating risk is intubation-related vocal cord paralysis. One study found that the risk of vocal cord paralysis following intubation is less than 0.1 percent;(2) however, give the number of intubations performed annually across all contexts, as many as 2 million Americans may be affected by partial or complete vocal cold paralysis each year.
The cause of intubation-related vocal cord paralysis can be traced back to peripheral nerve damage. More specifically, it is thought that pressure exerted by either the inflated endotracheal tube cuff or the tube itself compresses adjacent thyroid cartilage, causing neuropraxia and resulting in paralysis.(3) Prolonged acute ischemia of the recurrent laryngeal nerve may also play a role in lasting immobility.(4) A 1985 study performed by John Cavo, MD, suggested that the specific site of injury in cases of vocal cord paralysis is approximately 6-10mm inferior to the cord itself, at the junction of the arytenoid cartilage and the membranous vocal cord.(5) Interestingly, unilateral paralysis is more common than bilateral paralysis, which would suggest that asymmetric placement of the endotracheal tube could be a contributing factor.(3)
In order to ensure that vocal cord paralysis does not result from intubation, a number of preventative measures may be taken. Primarily, appropriate endotracheal tube size and cuff pressure must be evaluated for each patient to avoid unnecessary laryngeal damage. Patients who have hypotension, peripheral vascular disease, or coronary artery disease are at greater risk for ischemia-related vocal cord immobility; therefore, these factors should be taken into consideration prior to elective intubation. For higher-risk patients, noninvasive ventilation – such as a face mask ventilator – may be a preferable option.
If proper preventative measures are taken and vocal cord paralysis still occurs, several treatment options are available. If both vocal cords are paralyzed, they may inhibit airflow, in which case a tracheotomy may be necessary. An explorative test, such as a laryngoscopy or a laryngeal electromyography, may be performed in order to evaluate the damage. Depending on the severity of the paralysis, either voice therapy or surgery may be recommended. Surgical interventions include bulk injections, structural implants, reinnervation, or vocal cord repositioning, which can be done in the case of unilateral paralysis and involves moving the functioning vocal cord towards the middle of the voice box where it can better vibrate against its nonfunctional partner. Currently, researchers are working to develop an electronic stimulating device to galvanize paralyzed vocal cords, similar to a pacemaker; however, this type of technology remains in development.
References
1. Lovett, P. B., Flaxman, A., Stürmann, K. M., & Bijur, P. (2006). The insecure airway: a comparison of knots and commercial devices for securing endotracheal tubes. BMC emergency medicine, 6, 7. https://doi.org/10.1186/1471-227X-6-7
2. Kikura, M., Suzuki, K., Itagaki, T., Takada, T., & Sato, S. (2007). Age and comorbidity as risk factors for vocal cord paralysis associated with tracheal intubation. British journal of anaesthesia, 98(4), 524–530. https://doi.org/10.1093/bja/aem005
3. Evman, M. D., & Selcuk, A. A. (2020). Vocal Cord Paralysis as a Complication of Endotracheal Intubation. The Journal of craniofacial surgery, 31(2), e119–e120. https://doi.org/10.1097/SCS.0000000000005959
4. Campbell, B. R., Shinn, J. R., Kimura, K. S., Lowery, A. S., Casey, J. D., Ely, E. W., & Gelbard, A. (2020). Unilateral Vocal Fold Immobility After Prolonged Endotracheal Intubation. JAMA otolaryngology– head & neck surgery, 146(2), 160–167. https://doi.org/10.1001/jamaoto.2019.3969
5. Cavo J. W., Jr (1985). True vocal cord paralysis following intubation. The Laryngoscope, 95(11), 1352–1359. https://doi.org/10.1288/00005537-198511000-00012