title: Vocal cord collapse during phrenic nerve-paced respiration in congenital central hypoventilation syndrome.
abstract: OBJECTIVE
  Phrenic nerve pacing can be used to treat congenital central hypoventilation syndrome (CCHS). We report how the lack of normal vocal cord tone during phrenic paced respiration can result in passive vocal cord collapse and produce obstructive symptoms.
  
  
  METHODS
  We describe a case of passive vocal cord collapse during phrenic nerve paced respiration in a patient with CCHS. As far as we know, this is the first report of this etiology of airway obstruction. The patient, a 7-year-old with CCHS and normal waking vocal cord movement, continued to require nightly continuous positive airway pressure (CPAP) despite successful utilization of phrenic nerve pacers. On direct laryngoscopy, the patient's larynx was observed while the diaphragmatic pacers were sequentially engaged.
  
  
  RESULTS
  No abnormal vocal cord stimulation was witnessed during engaging of either phrenic nerve stimulator. However, the lack of normal inspiratory vocal cord abduction during phrenic nerve-paced respiration resulted in vocal cord collapse and partial obstruction due to passive adduction of the vocal cords through the Bernoulli effect. Bilateral phrenic nerve stimulation resulted in more vocal cord collapse than unilateral stimulation.
  
  
  CONCLUSIONS
  The lack of vocal cord abduction on inspiration presents a limit to phrenic nerve pacers.
authors.affiliation: Department of Surgery, University of Mississippi, Jackson, MS, 39216, USA.
authors.forename: Mark C
authors.initials: MC
authors.lastname: Domanski
authors.affiliation: Department of Otolaryngology, Children's National Medical Center, Washington, D.C., 20010-2970, USA.
authors.forename: Diego A
authors.initials: DA
authors.lastname: Preciado