title: Cardiovascular and pulmonary adaptations during short-term 15° and 30° head-down posture in healthy male volunteers.
abstract: BACKGROUND
  Healthy male volunteers were investigated for cardiopulmonary adaptations to a head-down posture (HDT).
  
  
  METHODS
  Thirty-three volunteers were enrolled in this study. Their changes in cardiopulmonary parameters at 15° and 30° HDT, for 7.5 minutes in each posture, were studied using echocardiography. Spirometric measurements of pulmonary function were performed during sitting and supine positions, and 15° and 30° HDT, while measurements of blood pressure, carotid blood flow, and electrocardiographic (ECG) and echocardiographic examinations were performed in the supine position and under 15° and 30° HDT.
  
  
  RESULTS
  A significant increase (p<0.05) in mean, systolic, and diastolic pressure, and a decrease in heart rate (p<0.05) were observed during the HDT postures. Right ventricular diameter increased (p<0.05) from supine to 15° and 30° HDT. Forced vital capacity, forced expiratory volume in 1 s, and peak flow rate decreased significantly from supine to 15° and 30° HDT. Maximum ventilatory volume decreased significantly only from the sitting to the supine posture and then remained steady in the HDT postures.
  
  
  CONCLUSIONS
  During short-term HDT, the cardiovascular system maintains a stable ejection fraction, with a significant in heart rate, and a decrease in pulmonary ventilation.
authors.affiliation: Laboratory of Physiology, Department of Chest Medicine, Medical School, University of Ioannina, Ioannina, Greece.
authors.forename: Dimitris S
authors.initials: DS
authors.lastname: Galanis
authors.forename: Katerina K
authors.initials: KK
authors.lastname: Naka
authors.forename: Patrona
authors.initials: P
authors.lastname: Veziraki
authors.forename: Yannis V
authors.initials: YV
authors.lastname: Simos
authors.forename: Vicky
authors.initials: V
authors.lastname: Kalfakakou
authors.forename: Angelos M
authors.initials: AM
authors.lastname: Evangelou
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000328:Adult; D001794:Blood Pressure / Q000502:physiology*; D004452:Echocardiography; D018475:Head-Down Tilt / Q000502:physiology*; D006321:Heart / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D011652:Pulmonary Circulation / Q000502:physiology*; D012016:Reference Values; D055815:Young Adult