Download Alternative Design 2 - Biomedical Engineering

Figure 13. Pulsatile signals found in the intensity of detected light [15].
One pulse is one cardiac cycle. The microprocessor will count the pulses to determine
heart rate (beats per minute), which will be displayed on an LCD screen.
1.2.3 Non Invasive Blood Pressure
Blood pressure will be automatically measured through the oscillometric method
[14]. This is done by wrapping a blood pressure cuff around the upper arm and inflating
it until the pressure around the arm due to the cuff collapses (or occludes) the brachial
artery. The cuff is then slowly deflated. As the cuff deflates, blood starts pumping
through the brachial artery causing minute vibrations of .5 to 1 mmHg in the cuff [2].
The pressure at which these vibrations start is the systolic pressure, and the pressure at
which they stop is the diastolic pressure [3]. The block diagram in Fig. 16 illustrates how
this method will be used to measure blood pressure in the accessible vital signs
monitoring system. Each system in the flow chart is described in more detail in the
following paragraphs.
When the blood pressure “Start” button on the vital signs monitor is pressed, the
blood pressure cuff will be inflated to about 40mmHg above normal (160mmHg). The
blood pressure cuff used will be a DRE Adult single lumen cuff from DREMed.com at a
cost of $37.00, before shipping and tax (Fig. 14).
http://www.dremed.com/catalog/ product_info.php/cPath/56_121_241_242/products_id/194
Figure 14. DRE Adult Single Lumen Blood Pressure Cuff
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