title: Paced breathing can prevent vasovagal syncope during head-up tilt testing.
abstract: BACKGROUND
  Clinical experience suggests that, through the control of heart rate, paced breathing may prevent syncope.
  
  
  OBJECTIVE
  To assess the effect of metronome-paced breathing (0.2 Hz) on the outcome of head-up tilt test (HUT) in patients with vasovagal syncope.
  
  
  METHODS
  Ten patients (two men), mean +/- SD age 18.4 +/- 5.1 years, with a positive HUT with spontaneous breathing and no evidence of cardiovascular or neurological disease, were exposed to a second HUT under metronome-paced breathing (0.2 Hz). Continuous electrocardiographic recordings were obtained during the two tests, and heart rate variability was analyzed off-line.
  
  
  RESULTS
  During HUT with metronome-paced breathing, only one of the 10 patients developed bradycardia, hypotension and syncope (P<0.01, Wilcoxon). Compared with HUT with spontaneous breathing, HUT with paced breathing induced a larger increase in the heart rate in the first minute of tilt (4 +/- 6 beats/min versus 16 +/- 12 beats/min, P<0.05).
  
  
  CONCLUSIONS
  The results show that paced breathing can prevent vasovagal syncope induced by HUT. This finding suggests that respiratory training could be useful to prevent vasovagal syncope.
authors.affiliation: Unidad de Investigación Médica, HG Centro Médico Nacional La Raza IMSS, Mexico City, Mexico.
authors.forename: Kathrine
authors.initials: K
authors.lastname: Jáuregui-Renaud
authors.forename: Manlio F
authors.initials: MF
authors.lastname: Márquez
authors.forename: Antonio G
authors.initials: AG
authors.lastname: Hermosillo
authors.forename: Ayax
authors.initials: A
authors.lastname: Sobrino
authors.forename: José Luis
authors.initials: JL
authors.lastname: Lara
authors.forename: Andrei
authors.initials: A
authors.lastname: Kostine
authors.forename: Manuel
authors.initials: M
authors.lastname: Cárdenas
mesh_terms: D000293:Adolescent; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D012119:Respiration; D019462:Syncope, Vasovagal / Q000517:prevention & control*; D018667:Tilt-Table Test