title: [Changes of cardiovascular indices during head up tilt plus lower body negative pressure].
abstract: OBJECTIVE
  To understand the change of the cardiovascular function and to evaluate the usefulness of sphygmography and heart rate variability (HRV) spectrum techniques on estimating cardiovascular function during HUP + LBNP.
  
  
  METHODS
  Blood pressure, ECG, cerebral oxygen saturation and sphygmogram of 16 subjects were studied during 75 degrees head up tilt plus lower body negative pressure (HUP + LBNP).
  
  
  RESULTS
  (1) During HUP + LBNP, heart rate, blood pressure, normalized low frequency component (LFn), LFn/HFn increased significantly, the cerebral blood oxygen saturation, T wave (ECG), HFn decreased significantly; (2) Blood pressure, heart rate and cerebral blood oxygen saturation decreased significantly in presyncopal state; (3) The heart rate in low tolerance group was higher than that in high tolerance group during the initial stage of HUT + LBNP; (4) The shape of pulse wave changed enormously during HUP + LBNP, so that no analysis could be made.
  
  
  CONCLUSIONS
  HUP + LBNP was an effective approach to examine the regulatory function of cardiovascular system, and the sphygmogram could not be used in studying the regulatory function of cardiovascular system during HUP + LBNP.
authors.affiliation: Institute of Space Medico-Engineering, Beijing, China.
authors.forename: X Y
authors.initials: XY
authors.lastname: Shen
authors.forename: J R
authors.initials: JR
authors.lastname: Meng
authors.forename: B
authors.initials: B
authors.lastname: Wu
authors.forename: J J
authors.initials: JJ
authors.lastname: Li
authors.forename: Q
authors.initials: Q
authors.lastname: Dong
authors.forename: Q L
authors.initials: QL
authors.lastname: Xiang
mesh_terms: D000328:Adult; D001794:Blood Pressure / Q000502:physiology; D002320:Cardiovascular Physiological Phenomena; D002560:Cerebrovascular Circulation / Q000502:physiology; D004562:Electrocardiography; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008150:Lower Body Negative Pressure; D011187:Posture / Q000502:physiology*; D011674:Pulse; D019722:Sphygmomanometers; D018667:Tilt-Table Test