Fluke Biomedical 2MF Index - Manual (Page 19)

2-1
Chapter 2
Blood Oxygen and Pulse Oximeters
Blood Pressure
Blood pressure readings provide valuable information about the condition of our bodies,
indicating health or the lack of it. As the heart contracts (systole) and relaxes (diastole),
the volume of freshly-oxygenated blood increases and decreases measurably within the
artery walls. This action causes the artery walls to expand and contract in rhythm with the
heart. The force of the blood exerted upon the artery walls is what is called blood
pressure. Contraction produces the highest pressure, and relaxation the lowest.
A sphygmomanometer (shown in Figure 2-1) is one tool for measuring blood pressure.
When our blood pressure is taken, it is measured at the brachial artery in the forearm in
millimeters of mercury (mmHg). If our blood pressure reading is at or near 120 mmHg
(systolic) over 80 mmHg (diastolic), we are considered to be in peak health, all else being
normal.
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Figure 2-1. Sphygmomanometer
Gases in Blood
Blood pressure is not the whole story, however, since the exact concentration of gases
such as carbon dioxide and especially oxygen in your blood cannot be determined by a
simple blood pressure test.
To determine gas concentrations accurately, specifically saturated oxygen, a blood-gas
sensing device must be used, and must be capable of detecting the wide range of nominal
values for these gases. Gas concentrations in blood, specifically oxygen (O2) and carbon