title: Mechanisms of airway protection during chin-down swallowing.
abstract: OBJECTIVE
  This study examined the effects of chin-down swallowing on laryngeal vestibule closure. It also investigated the technique's rehabilitative impact, by assessing the stability of effects across multiple trials and aftereffects in neutral swallows on cessation of the technique.
  
  
  METHODS
  Duration of laryngeal vestibule closure (dLVC) was measured with videofluoroscopy in 16 healthy participants (mean = 33.2 years, 9 men). Participants swallowed 40 times: 5 head-neutral swallows (N1), then 30 chin-down swallows, followed by 5 head-neutral swallows (N2). The first 5 chin-down swallows were categorized as early posture swallows (P1) and the last 5 as late posture swallows (P2). Within-participant comparisons determined the effects of the maneuver on dLVC during and after execution.
  
  
  RESULTS
  The study found that dLVC increased during chin-down swallows (N1 to P1, p = .018). This increase remained stable throughout 30 repetitions (P1 to P2, p = .994). On return to neutral, dLVC returned to baseline (N1 to N2, p = .875).
  
  
  CONCLUSIONS
  This study demonstrated increased dLVC during chin-down swallowing, offering a possible mechanism responsible for previously reported reduced aspiration during the technique. As aftereffects were not evident after multiple chin-down swallows, the maneuver appears to offer more compensatory benefit than rehabilitative value for patients with dysphagia.
authors.forename: Phoebe
authors.initials: P
authors.lastname: Macrae
authors.forename: Cheryl
authors.initials: C
authors.lastname: Anderson
authors.forename: Ianessa
authors.initials: I
authors.lastname: Humbert
mesh_terms: D000328:Adult; D002680:Chin; D003679:Deglutition / Q000502:physiology*; D005260:Female; D006257:Head / Q000502:physiology; D064368:Healthy Volunteers; D006801:Humans; D007830:Larynx / Q000000981:diagnostic imaging* / Q000502:physiology; D008297:Male; D010779:Photofluorography / Q000379:methods*; D011187:Posture / Q000502:physiology*; D014741:Video Recording