title: [Effects of repeated low body negative pressure (LBNP) exposures on LBNP tolerance].
abstract: OBJECTIVE
  To investigate variation of low body negative pressure (LBNP) tolerance and the relationship with change of heart function after repeated LBNP exposures.
  
  
  METHODS
  Ten healthy subjects were exposed to eight min consecutive daily LBNP (-50 mmHg). Before and after this exposures, tolerance to LBNP was determined by a cumulative stress index (CSI) and duration of negative pressure (DNP).
  
  
  RESULTS
  The pre- and post repeated exposure values of CSI and DNP were 1058 +/- 216 s, 1354 +/- 233 s and 45833 +/- 12546 s mmHg, 63433 +/- 13458 s mmHg, respectively. It showed that both were increased significantly (P<0.05), and the heart function was showed to have a tendency of being enhanced.
  
  
  CONCLUSIONS
  It suggested that LBNP tolerance increased after repeated exposures, which might be achieved via strengthening of ventricular contractivity, decreasing the compliance of peripheral vascular, the hypotensive [correction of hypotentive] reflex compensatory mechanisms becoming more effective, and increasing arterial blood pressure on heart level.
authors.affiliation: Department of Aerospace Biodynamics, The Fourth Military Medical University, Xi'an, China.
authors.forename: C B
authors.initials: CB
authors.lastname: Yang
authors.forename: Y J
authors.initials: YJ
authors.lastname: Yao
authors.forename: Y B
authors.initials: YB
authors.lastname: Wei
authors.forename: Y H
authors.initials: YH
authors.lastname: Wu
authors.forename: X Q
authors.initials: XQ
authors.lastname: Sun
authors.forename: X Y
authors.initials: XY
authors.lastname: Wu
mesh_terms: D000222:Adaptation, Physiological; D000293:Adolescent; D000328:Adult; D002302:Cardiac Output / Q000502:physiology; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D008150:Lower Body Negative Pressure; D013312:Stress, Physiological / Q000503:physiopathology; D013318:Stroke Volume / Q000502:physiology; D014655:Vascular Resistance / Q000502:physiology