title: [Hemodynamic changes of pulmonary circulation during HDT -30 degrees].
abstract: OBJECTIVE
  To study the hemodynamic changes of pulmonary circulation during simulated weightlessness.
  
  
  METHODS
  12 subjects were studied using echocardiography and electrocardiography during head-down tilt (HDT) of -30 degrees lasting for 45 min.
  
  
  RESULTS
  Right ventricular ejection time increased significantly (P<0.05); peak velocity of pulmonary arterial blood flow decreased significantly (P<0.05); acceleration time of pulmonary arterial blood flow did not change significantly; significant decrease of right ventricular output occurred at the 10th minute and the 30th minute (P<0.05); pre-ejection period significantly decreased at the 30th minute and recovery. Heart rate, mean velocity of pulmonary arterial blood flow, and acceleration of pulmonary arterial blood flow did not change significantly; left ventricular cardiac output, stroke volume and blood pressure remained constant throughout the experiment.
  
  
  CONCLUSIONS
  Changes of the parameters of pulmonary circulation suggested that pulmonary resistance increased, and the increase of pulmonary resistance maybe be the direct cause of the increase of pulmonary arterial pressure.
authors.affiliation: Institute of Space Medico-Engineering, Beijing, China.
authors.forename: C F
authors.initials: CF
authors.lastname: Zhong
authors.forename: L L
authors.initials: LL
authors.lastname: Lu
authors.forename: J S
authors.initials: JS
authors.lastname: Yang
authors.forename: G X
authors.initials: GX
authors.lastname: Zhao
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity; D001794:Blood Pressure / Q000502:physiology; D018475:Head-Down Tilt; D006339:Heart Rate / Q000502:physiology; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D011651:Pulmonary Artery / Q000502:physiology; D011652:Pulmonary Circulation / Q000502:physiology*; D013318:Stroke Volume / Q000502:physiology; D014655:Vascular Resistance / Q000502:physiology; D016278:Ventricular Function, Right / Q000502:physiology; D018474:Weightlessness Simulation