INDIRECT METHOD OF BLOOD PRESSURE MEASUREMENTRHEOGRAPHIC TECHNIQUE GROUP

INDIRECT METHOD OF BLOOD PRESSURE MEASUREMENTRHEOGRAPHIC TECHNIQUE GROUP MEMBER MATRICES NUMBER GOH WEN JUN 091150278 TAN KAE MENG 091151414 REENA A/P THRIUMANI 091151230 MANGGAI YARKARASI A/P BELUTHAM 091150498 YALLINI A/P SELVA 091151528

INDIRECT MEASUREMENT OF BLOOD PRESSURE �Definition: an attempt to measure intra-arterial pressures noninvasively. �Most commons methods: �Rheographic techniques �Sphyngmomanometry �Ultrasonic Doppler Shift Method

Rheographic method �Generally, rheographic method is used to record the fluctuation of electrical impedance caused by the blood flow. �It is measured between electrodes placed on opposites of a part of the body.

�As shown above, three electrodes are attached to the cuff and placed in contact with skin. �Electrode B- acts as a common electrode, placed in between electrodes A and C, with certain distance. �A high frequency current source operating at 100 k. Hz is connected to electrode A and C. �When measure impedance between any 2 electrodes before pressurizing the cuffs, it shows modulation according with the blood flow pulsation in the artery. �Thus, arterial pulse can be detected by the demodulation and amplification of this modulation.

Working principles �No pulse will be detected by electrode A when the cuff is inflated above systolic pressure. �Detection of the first arterial pulse will generate an electrical signal, which then trigger the systolic pressure indicator pointer to show the systolic pressure value. �When cuff pressure is between systolic and diastolic pressure, differential value will always exist.

�This indicates that the blood flow is impeded by the cuff and the pulse appearing at electrode A is time delay from pulse at electrode C. �Arterial blood pressure no longer impeded as cuff pressure reaches diastolic pressure. �Therefore, differential signal disappeared, diastolic pressure will be shown on the diastolic pressure indicator.

ADVANTAGES �The cuff does not have to be positioned right above an artery as Korotkoff microphone. �The reading is not affected by environmental sounds.