A method and apparatus for ensuring accurate measurement of blood pressure regardless of the position of the sensing transducer relative to the position of the patient's heart. The method and apparatus provides a hydrostatic balancing system in which a column of fluid is used to offset the hydrostatic pressure created by the corresponding column of blood contained in the blood vessel in the limb upon which the measurement is being taken. A flexible tube is routed along the patient's limb with one end being positioned at heart level and the other end terminating at the occlusion cuff which supports the pressure sensing transducer. The tube is filled with fluid and is connected to a fluid reservoir chamber located at approximately the same level as the patient's heart. The hydrostatic pressure created by the fluid in the tube effectively balances the corresponding hydrostatic pressure created by the blood in the blood vessel. At the cuff end of the tube, a differential pressure transducer senses the difference between the cuff pressure and that generated by the fluid column of the pressure compensation system. This signal, after appropriate scaling, can be used in conjunction with oscillometric signal processing software to provide an accurate representation of the patient's actual blood pressure.
Harry H. Peel; James M. Burkes