Acute effect of 30 degrees, 60 degrees and 80 degrees head-down tilt on blood pressure in young healthy human subjects.
There are very few reports on the acute cardiovascular responses to head-down tilt of more than 30 degrees on blood pressure (BP) and heart rate (HR) in human subjects. The aim of the present study was to determine the BP and HR response to five minutes of 30 degrees, 60 degrees and 80 degrees head-down tilt in healthy human subjects. The study was conducted on 20 healthy male volunteers aged 18-20 years. In this study, 30 degrees head-down tilt produced no significant change in BP and HR. With 60 degrees and 80 degrees head-down tilt, there was a significant graded increase in diastolic pressure and a decrease in pulse pressure (P<0.01 for both). This pressor response is most likely due to raised intracranial tension and/or hypoxemia in this condition. The decrease in pulse pressure is possibly due to excessive cardiopulmonary blood volume resulting in a decreased stroke volume. Our study confirms earlier findings that acute 30 degrees head-down tilt produces no significant changes in BP and HR. However, the mechanisms leading to increases in BP that occurred with 60 degrees and 80 degrees acute head-down tilt need to be investigated.
Vijayalakshmi
P
P
Department of Physiology, Jawaharlal Institute of Postgraduate Medical Education and Research, Pondicherry 605 006.
Madanmohan
D000293:Adolescent; D000328:Adult; D001794:Blood Pressure / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D011674:Pulse / Q000379:methods; D018667:Tilt-Table Test / Q000379:methods; D014893:Weightlessness