title: Orthostatic responses in adolescent chronic fatigue syndrome: contributions from expectancies as well as gravity.
abstract: BACKGROUND
  Orthostatic intolerance is common in chronic fatigue syndrome (CFS), and several studies have documented an abnormal sympathetic predominance in the autonomic cardiovascular response to gravitational stimuli. The aim of this study was to explore whether the expectancies towards standing are contributors to autonomic responses in addition to the gravitational stimulus itself.
  
  
  METHODS
  A total of 30 CFS patients (12-18 years of age) and 39 healthy controls underwent 20° head-up tilt test and a motor imagery protocol of standing upright. Beat-to-beat cardiovascular variables were recorded.
  
  
  RESULTS
  At supine rest, CFS patients had significantly higher heart rate, diastolic blood pressure, and mean arterial blood pressure, and lower stroke index and heart rate variability (HRV) indices. The response to 20° head-up tilt was identical in the two groups. The response to imaginary upright position was characterized by a stronger increase of HRV indices of sympathetic predominance (power in the low-frequency range as well as the ratio low-frequency: high-frequency power) among CFS patients.
  
  
  CONCLUSIONS
  These results suggest that in CFS patients expectancies towards orthostatic challenge might be additional determinants of autonomic cardiovascular modulation along with the gravitational stimulus per se.
authors.affiliation: Department of Pediatrics, Oslo University Hospital, N-1478 Oslo, Norway ; Division of Medicine and Laboratory Sciences, Medical Faculty, University of Oslo, Oslo, Norway ; Department of Pediatrics, Akershus University Hospital, Nordbyhagen, Norway.
authors.forename: Vegard Bruun
authors.initials: VB
authors.lastname: Wyller
authors.affiliation: Institute of Clinical Medicine, Medical Faculty, University of Oslo, Oslo, Norway ; Department of Anesthesiology and Critical Care, Oslo University Hospital, Oslo, Norway.
authors.forename: Even
authors.initials: E
authors.lastname: Fagermoen
authors.affiliation: Department of Pediatrics, Oslo University Hospital, N-1478 Oslo, Norway ; Department of Pediatrics, Lillehammer County Hospital, Lillehammer, Norway.
authors.forename: Dag
authors.initials: D
authors.lastname: Sulheim
authors.affiliation: Institute of Nursing Sciences, Oslo and Akershus University College of Applied Sciences, Oslo, Norway ; Institute of Clinical Medicine, Medical Faculty, University of Oslo, Oslo, Norway.
authors.forename: Anette
authors.initials: A
authors.lastname: Winger
authors.affiliation: School of Pharmacy, University of Oslo, Oslo, Norway ; Norwegian Institute of Public Health, Oslo, Norway.
authors.forename: Eva
authors.initials: E
authors.lastname: Skovlund
authors.affiliation: Department of Pediatrics, Medical University of South Carolina, Charleston, USA.
authors.forename: Jerome Philip
authors.initials: JP
authors.lastname: Saul
keywords: Adolescence; Autonomic nervous system; Chronic fatigue syndrome; Expectancies; Orthostatic intolerance