(taken by Bishop & Guitterez)
Developing of automatic controlled inflating thigh cuffs for patients with orthostatic intolerance
In about 500,000 Americans the adjustments to upright posture for some reason fail and is known as orthostatic intolerance. After tachycardia (high heart rate) the most consistent cardiovascular feature of orthostatic intolerance has been hypovolemia. It is now recognized that about 15% of plasma volume seems to leave the vasculature and enter the interstitial tissue within about twenty minutes of standing (relative or dynamic orthostatic plasma loss). In a group of patient of orthostatic intolerance could shown that the plasma loss during standing was twice as in the controls. Also the patient had 5-20% reduction in supine blood volume. Patient with orthostatic intolerance have a less risk to faint at the end of the day rather than in the morning time. One possible mechanism could be the fluid load to the tissue in the leg, which will prevent fast and extended extravasation (fluid shift from the vessel to tissue) of plasma during standing. At night the patients extravascular fluid will be restored into the vascular compartment. The unloaded tissue" and loss of fluid during night by diuresis can increase the risk of fainting during standing in the morning.
The concept of cuff occlusion of extremities was studied many years ago. Tourniquests has been applied to improve the orthostatic tolerance during tilt table testing and after bedrest. The Russian space program has employed a device called braselyet". The braselyet" is a cuff worn at the level of the thigh which is designed to increase venous pressure 10-40 mmHg. This device has been used for many years by Russian cosmonauts, to reduce the headwards fluid shift during early phases of space flights and to improve the orthostatic tolerance during longterm flights.
The aim of this project is to develop a thigh compression apparatus to prevent fluid unloading of the tissue during night or to induce a fluid loading in supine position in the morning. This apparatus will be applied in patient with orthostatic intolerance to prevent fainting.
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