Variability in cardiovascular and plasma norepinephrine responses to head-up tilt in healthy human subjects.
Eight healthy, young adult males underwent three separate, 10-min 70 degrees head-up tilts (HUT) over a period of nine days, in order to assess the intra- and inter-individual variability of cardiovascular and plasma norepinephrine (NE) responses to the manoeuvre. Cardiovascular parameters and plasma NE were measured in the basal state and at 2-min intervals during the HUT. The results indicate that: (1) the intra-individual variability is a smaller component of the total variability of both cardiovascular and plasma NE responses to HUT; (2) the variability in cardiovascular parameters is smaller than that in plasma NE levels, both basal and in response to postural stress; (3) there does not appear to be any difference in variability when expressed either as the maximal or the mean response to HUT; and (4) there does not appear to be an increase in the variability of the measured parameters over the duration of the HUT.
Vaz
M
M
Department of Physiology, St. John's Medical College, Bangalore, India.
Kumar
M V
MV
Rodrigues
D
D
Kulkarni
R N
RN
Shetty
P S
PS
D000328:Adult; D001794:Blood Pressure / Q000502:physiology; D002307:Cardiography, Impedance; D004562:Electrocardiography; D006339:Heart Rate / Q000502:physiology; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D008297:Male; D009638:Norepinephrine / Q000097:blood*; D011187:Posture / Q000502:physiology*
D009638:Norepinephrine