Considerations Related to Measurement of Blood Pressure
Blood Pressure
Blood pressure (BP) refers to the force of the blood against arterial walls.
Systolic pressure is the highest point of pressure on arterial walls when the ventricles contract and push blood through the arteries at the beginning of systole. When the heart rests between beats during diastole, the pressure drops. The lowest pressure present on arterial walls during diastole is the diastolic pressure (Taylor et al., 2023).
BP is measured in millimeters of mercury (mm Hg) and recorded as a fraction. The numerator is the systolic pressure; the denominator is the diastolic pressure.
The difference between the systolic and diastolic pressures is called the pulse pressure.
BP readings can be within a wide range and still be normal. It is important to know the normal blood pressure range of a particular person. A rise or fall of 20 to 30 mm Hg in a person's blood pressure is significant, even if it is within the generally accepted normal range.
Accurate Assessment of Blood Pressure
Ensure use of validated and calibrated devices
Obtain BP measurements
In a quiet environment, the patient should not talk or move during measurement
After the patient relaxes
After the patient has not consumed caffeine, exercised, or smoked for 30 minutes
With the patient in a supine or sitting position
(Sitting) with the patient's arm supported on a table at heart level or held up by the health care provider (midpoint of the sternum). The patient's feet and back should be supported as well (Whelton et al., 2018).
(Supine) with the patient's arm supported with a pillow at heart level (Muntner et al., 2019).
With the patient's legs uncrossed (Liu et al., 2016, as cited in Muntner et al., 2019).
Measuring BP Related to the Diagnosis/Management of Hypertension
BP measurements should be obtained ≥2 readings on ≥2 occasions and the measurements averaged to estimate the person's level of blood pressure (Whelton et al., 2018).