title: The effect of rigid cervical collars on internal jugular vein dimensions.
abstract: OBJECTIVE
  Prior research has demonstrated that rigid cervical collars cause an increase in intracranial pressure (ICP). The mechanism for this effect is unclear and one proposed mechanism involves obstruction of venous outflow in the neck. Ultrasound (US) allows assessment of internal jugular vein dimensions and may yield information regarding the mechanism for the increase in ICP seen with rigid collar application.
  
  
  METHODS
  Forty-two healthy volunteers underwent US examination of the internal jugular vein before and after cervical collar application. Internal jugular vein cross-sectional areas were compared with and without the cervical collar in place.
  
  
  RESULTS
  The cross-sectional area of the internal jugular vein increased significantly (p < 0.0001) after application of the cervical collar. The mean percentage increase in cross-sectional area was 37% (95% confidence interval [CI] = 20% to 53%).
  
  
  CONCLUSIONS
  Internal jugular vein cross-sectional area increases after application of a rigid cervical collar. This supports the hypothesis that venous obstruction in the neck may contribute to the increase in ICP seen after rigid collar application.
authors.affiliation: Department of Emergency Medicine, SUNY Downstate/Kings County Hospital Center, Brooklyn, NY, USA. drmikestone@gmail.com
authors.forename: Michael B
authors.initials: MB
authors.lastname: Stone
authors.forename: Catherine M
authors.initials: CM
authors.lastname: Tubridy
authors.forename: Robert
authors.initials: R
authors.lastname: Curran
mesh_terms: D000328:Adult; D006259:Craniocerebral Trauma / Q000503:physiopathology / Q000628:therapy*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007103:Immobilization / Q000009:adverse effects*; D007427:Intracranial Pressure / Q000502:physiology*; D007601:Jugular Veins / Q000000981:diagnostic imaging / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D014463:Ultrasonography; D055815:Young Adult