subject: You should be responsible for your health [print this page] A typical automatic oscillometric blood pressure monitor manufacturers also include a pump which first inflates a pressure cuff around the upper arm of the subject to occlude the brachial cuff about the upper arm of the subject to occlude the brachial arteryand then decreases the pressure in increments. However, instead of using an audio transducer on the arm, the oscillometric monitor uses a pressure transducer located in the monitor and connected to the cuff by a conduit. Even when the cuff has occludedthe artery, the pumping of the heart of the subject causes the artery to flex or oscillate, resulting in pressure pulses that are received in the cuff and the transducer. As the pressure is decreased, the amplitude of the pulses increases to a maximumand then decreases again. The cuff pressure when the pulse amplitudes are at a maximum is known as "mean arterial pressure" (MAP). Also, the cuff pressures above and below MAP where the pulse amplitudes are predetermined fractions of the amplitude atMAP, represent the systolic and diastolic pressures, respectively.
The testing of automatic blood pressure monitor manufacturers are typically very difficult because living subjects on which it may be tested may have different pressure levels at different times, and different subjects will have different pressure levels. Thus, the accuracy of the monitor with respect to its intended purpose can only be determined on a statistical basis by time consuming population studies. Since this is not possible on a production basis, typically only the electronics of the monitorare tested and a mercury manometer is used to test the accuracy with which the pressure transducer measures the cuff pressure. Then if the machine produces a correct reading for a single test subject known to have a stable blood pressure, it is assumedto be functioning properly. Obviously, the problem with this method of testing monitors is that there is no assurance that the monitor will operate to detect and measure pressure pulses in addition to the cuff pressure, or to measure blood pressures andpulse rates which are remote from those of the test subject. Also, a properly functioning monitor may be rejected if the test subject should have an unusual blood pressure level during the test.
It is known in the art to test automated ausculatory monitors by creating an artifical arm in the form of an inner cylinder filled with water in which sound waves approximating K-sounds are generated by a transducer. An outer layer of water in aflexible bag transmits the sound to the pressure cuff and microphone of the ausculatory monitor, and also simulates the compliance of a real arm. At present, however, there is no known method of simulating the arm of a test subject so that the pressurepulses of the oscillometric method can be generated for testing of a blood pressure monitor manufacturers of that type.
