Purpose: The objective of this lab is to teach you how to effectively measure blood pressure at rest and during exercise.

1. Measurement of blood pressure at rest.

2. Measurement of blood pressure during exercise.

3. Proper placement and usage of blood pressure equipment.

Blood pressure is defined as an outward force that distends blood vessel walls. The magnitude of blood pressure depends primarily on the volume of blood and the size of the vessel. The unit for expressing blood pressure is typically millimeters of mercury (mm Hg).

Blood pressure, from a health and fitness standpoint, is most commonly measured within the arteries. The standard site of blood pressure determination is the brachial artery (see figure). Selecting the brachial artery as the standard site of measurement is due to convenience, accessibility, and its position at heart level.

In the laboratory setting, blood pressure is determined indirectly by listening to Korotkoff sounds, which are sounds made from vibrations along the vascular walls. The equipment needed to detect these sounds are a stethoscope and cuff manometer (sphygommanometer pronounced sfig-mo-ma-nom-e-ter). The manometer (gauge used to quantify blood pressure can be either aneroid or mercury.

Korotkoff sounds are only present when the vascular wall is deformed in some way. If the vessel wall is round and symmetrical, no vibrations or sounds can be detected. The blood pressure cuff is used to change the shape of the vessel wall and facilitate Kortkoff sounds. By inflating the air bladder in the cuff, the walls of the brachial artery become compressed. As blood attempts to flow past the compressed area, turbulent blood flow causes the arterial wall to vibrate and sounds are detected with the stethoscope. There are five different Korotkoff sounds or phases that are used to define blood pressure. However, we will concern ourselves primarily with the first, fourth and fifth phases (see figure).

Systolic blood pressure (SBP), the pressure exerted against the brachial artery as the heart muscle contracts, is indicated by the first Korotkoff sound. The first step in measuring blood pressure is inflating the cuff so that the blood flow through the brachial artery is completely occluded. At this point no vibration sounds can be heard. As the bladder of the cuff is slowly deflated, the blood pressure within the vessel overcomes the cuff pressure and a bolus of blood flows through the brachial artery. This initial blood flow produces a Korotkoff sound (Phase 1) and indirectly represents the peak blood pressure or systolic blood pressure.

Diastolic blood pressure (DBP), the pressure exerted against the brachial artery when the heart is relaxed, is indicated by the fourth and fifth Korotkoff sounds. As the cuff pressure is continuously released, blood pressure within the vessel increases and eventually exceeds the cuff pressure. At this point the vessel wall returns to its original shape and the Korotkoff sounds will fade (phase 4) then disappear (phase 5).

An effort should be made to minimize the following sources of measurement error when taking blood pressure:

Back ground noise

Experience of test administrator

Improper cuff width or length

Improper stethoscope placement and pressure

Inaccurate sphygmomanometer

Rate of inflation or deflation of the cuff pressure

Reaction time of the test administrator

Allowing the patient to hold to the treadmill rails or the cycle handles

Some physiological abnormalities, e.g. a damaged brachial artery

Blood pressure is measured at rest ( in the supine, sitting, and standing positions) and during exercise. At rest, blood pressure is used to screen for hyper- or hypo- tension. In addition, resting blood pressure is sued to evaluate the influence medications may have on the cardiovascular system.

Normal resting blood pressure is considered to be 120/80 ( numerator = systolic blood pressure; denominator = diastolic blood pressure). Some individuals have higher than normal blood pressure levels, which result in the condition known as hypertension. The National Heart and Blood Institute has classified normal and hypertensive levels of blood pressure as follows:

Normal < 90 mm Hg

Mild hypertension 90-104 mm Hg

Moderate hypertension 105-114 mm Hg

Severe hypertension > 114 mm Hg

Normal < 140 mm Hg

Borderline hypertension 140-159 mm Hg

Isolated hypertension >159 mm Hg

The same principle of blood pressure measurement applies during exercise. Testing protocols often dictate how often BP should be measured. In general, measurements should be taken with each increase in workload or every three minutes. For consistency in this class, all exercise BP measures will be taken in the leftt arm.

Do not allow the subject’s arm or hand to be on the exercise machine.

During exercise, measuring blood pressure is routinely used to determine the normality of blood pressure responses and assess the influence medications have on functional capacity. As a result of exercise, systolic blood pressure is expected to rise due to an increase in cardiac output. Diastolic blood pressure, on the other hand, is expected to remain equivalent to resting levels or decrease during exercise due to increased vasodilation and opening of capillary beds.

Individuals who have cardiovascular disease may have abnormal blood pressure responses to exercise. Exercise or exercise testing is usually terminated if blood pressure responses are abnormal.

Contraindicated exercise blood pressure responses include:

A rise in diastolic blood pressure to 120 mm Hg or more.

brachial artery and below the lower cuff edge.

Record blood pressure SBP/4thDBP/5thDBP

Repeat this procedure in the right arm.

Position the stethoscope over the brachial artery in the antecubital fossa.