The Venous Distension Reflex and Orthostatic Hypertension
Milton S. Hershey Medical Center
Summary
This research is being done to find out whether distension of veins in legs will cause a rise in blood pressure (orthostatic hypertension).
Description
In humans, two-thirds of the blood volume is contained within the venous vasculature. Because of this, changes in peripheral blood volume and alterations in the mechanical properties of peripheral veins can greatly impact cardiac filling, cardiac output and blood pressure (BP) responses to physiologic stress. Work from our laboratory over the past seven years has shown that local upper limb venous distension via volume infusion into an occluded arm (i.e. volume infusion model) or applying negative pressure to an occluded leg (limb suction experimental model) leads to an acute and dramatic incr…
Eligibility
- Age range
- 18+ years
- Sex
- All
- Healthy volunteers
- Yes
Inclusion Criteria: * Are capable of giving informed consent * Are of any race or ethnicity * Are fluent in written and spoken English * Whose history and physical exam did not uncover any exclusion criteria * Are 18 years of age For subjects with elevated standing BP * Systolic BP (SBP) during standing is at least 10 mmHg \> the supine SBP * Patients with a diagnosis of stage I hypertension without other chronic diseases may be INCLUDED For normal subjects without elevated standing BP * The change in SBP by standing is within ± 5 mmHg from the supine SBP * Matched gender, similar age and…
Interventions
- OtherTilt + external pressure
In Visit 1, the anti-shock trousers will be inflated to 20, 40, or 60 mmHg. BP will be measured 3 times from the brachial artery. Then the table will be tilted head up to a maximum of 70o for up to 10 min, while BP will be measured from the brachial artery at 1 min intervals. The tilt table is returned to 0o and the resting supine baseline BP will be collected. Then, the anti-shock trousers will be inflated to a different pressure (20, 40, or 60 mmHg) and the head up tilt will be repeated. Repetitions at the various pressures will be performed in a random order with suitable resting intervals in between the tilting bouts.
- OtherTilt + no external pressure.
In Visit 1, the anti-shock trousers will NOT be inflated. Auscultatory BP will be measured 3 times from the brachial artery. Thereafter, the table will be tilted head up to a maximum of 70o for up to 10 min, while BP will be measured from the brachial artery at 1 min intervals.
- OtherLimb occlusion + negative pressure
In Visit 2, a cuff will be placed on the thigh of a leg that is sealed in an airtight pressure tank. After the cuff is inflated to 250 mmHg, the pressure in the tank will be reduced to -100mmHg for 2 minutes. The application of negative pressure creates a suction effect on the leg, and leads to an overall increase in pressure gradient across the blood vessel wall and induces vascular distension.
- OtherLimb occlusion + no negative pressure
Location
- Penn State Milton S. Hershey Medical CenterHershey, Pennsylvania