Measuring Blood Pressure
Blood pressure is a measurement of the force of blood pushing against arterial walls. Blood pressure is highest when the heart contracts or pumps blood and lowest when the heart relaxes or pauses between beats. The measure of blood pressure during the point in the cardiac cycle when the heart contracts is called systolic pressure, and the measure of blood pressure when the heart relaxes is called diastolic pressure. Blood pressure is typically recorded using a sphygmomanometer, which relies on the height of a column of mercury to represent arterial pressure in millimeters of mercury (mmHg) or kilopascals (kPa). For example, adult blood pressure of 110/70 mmHg would be considered within normal values, and blood pressure of 120/90 mmHg would be considered as high blood pressure or hypertension.
Common factors that influence blood pressure are as follows:
- Age, gender, and body type
- Time of day
- Body position
- Activity and exercise
- Emotional status
- Medication
- Medical and family history
- Social habits (i.e., smoking and alcohol consumption)
- Disease (i.e., kidney, metabolic, or congestive heart failure)
- Pain
- Blood volume
- Blood thickness/viscosity
- Vessel resistance and size
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