A novel method for measuring blood pressure

Blood pressure is the pressure generated by the heart to push blood around the circulation to supply vital organs like the brain and the kidneys. Measurement of blood pressure is important in many situations: high blood pressure puts a strain on the heart and can lead to heart attacks and strokes; low blood pressure can cause vital organs to fail; during pregnancy high blood pressure is often the sign that pre-eclampsia , a potentially serious problem, is developing. An old fashioned method for measuring blood pressure involves inflating a rubber cuff around the upper arm, measuring the pressure in the cuff with a column of mercury and listening to sounds over the artery in the arm with a stethoscope. Although probably the most accurate method, it is being phased out because it is difficult to perform accurately and mercury is potentially hazardous. Existing automatic electronic methods are less accurate than the mercury method especially in pregnancy and during exercise (another situation in which accurate measurement of blood pressure is important). Neither method works well in seriously ill patients. We have developed a new method based upon detecting changes in pressure or movement of the artery in the lower arm while a blood pressure cuff is inflated around the upper arm. When pressure in the cuff becomes greater than blood pressure in the artery, the artery wall becomes squashed and this changes the movement of the artery further down the arm. The purpose of this research is to develop software that will make this method work automatically and to check that it works well in certain situations such as during exercise, in pregnancy and in critically ill patients.