I. A. Introduction

This lab experience is designed to demonstrate:

1. how blood pressure is internally regulated.

2. how external factors can affect our blood pressure

3. how blood pressure responds to various postures, gender and exercise

4. how to measure and record resting and exercise blood pressures.

The body has a complex system of regulators to control blood pressure. Baroreceptors, located in the walls of the aorta and carotid arteries, are one of the major short-term regulators of blood pressure. Baroreceptors monitor cardiac output, and cardiac output parallels blood pressure: as cardiac output increases, blood pressure increases and vice versa.

Sympathetic and Parasympathetic nervous systems also play an important role in the regulation of blood pressure. Sympathetic nerves stimulate the adrenal medulla to release catecholamines; epinephrine and norepinephrine which increase heart rate. This system also causes constriction of arteries and vessels which decreases the diameter of the vessel, thus causing more resistance (total peripheral resistance) to blood flow. This process will result in an increase in blood pressure.

The parasympathetic system, regulated by the catecholamine acetylcholine, is responsible for slowing down the activity of the heart, thereby decreasing heart rate.

While performing this lab today and when writing your discussion questions, think about what is happening physiologically as you see pressure changes with posture, exercise, etc.

B. Definitions:

1. Blood pressure - refers to the pressure exerted by the arterial blood on the

walls of the vessels.

2. Systolic BP (the first sound heard) - is the result of the arterial pressure being

greater than the cuff pressure. The blood goes through the artery

intermittently, and a fairly strong "thud...thud" is heard.

3. Diastolic BP (when sound disappears) - it is a result of the pressure of the

C. Blood Pressure Sounds (Karotkoff Sounds)

These sounds change in intensity and character during the procedure, providing

important circulatory and diagnostic information. The examiner is looking at a

pressure dial or mercury column as he correlates the pressure cuff which is being deflated. These sounds consist of a tapping sound and a murmur. On the basis of the character of the tapping sound and the presence or absence of the murmur, the sounds have been divided into five phases.

1. First Phase: Onset of tapping sound which gradually increases in pitch and intensity. Keep in mind that the forearm and hand are cut off from the general circulation by the inflated cuff. As the cuff pressure is gradually released, the first spurt of blood passing through the artery beneath the cuff exceeds critical velocity in the partially constricted artery and produces turbulent blood flow which results in sound. This is considered to be systolic pressure. The tapping sound is probably produced by the sudden distention of the walls of the collapsed artery. The intensity of the tap appears to be related to the forcefulness of the distending stream of blood which, in turn, depends on the speed of rise of the arterial pressure and amount of blood flow.

2. Second Phase: The tap is followed by a murmur. Normally the second phase usually starts 10 to 15mm. below the onset of the first phase and lasts for 14 to 20 mm. The murmur is probably produced by the flow of blood from the narrowed artery underneath the cuff into the wider artery distal to the cuff. The change in artery size from the narrow to a wider caliber creates eddies which set the blood and the vessel wall into vibration and produces the murmur.

3. Third Phase: Consists of the tapping sound alone which now is comparatively loud and high pitched. There is no murmur. (The addition of a murmur made the tap less evident in the second phase).

4. Fourth Phase: The third phase ends when the tap rather suddenly becomes lower-pitched and less intense. This lower-pitched, or so-called muffled sound constitutes the fourth phase. From a physiological standpoint, the beginning of the fourth phase, or muffling, should be the event related to diastolic pressure. When the cuff pressure is just below the arterial diastolic pressure, the artery is still constricted, but the turbulent flow of blood is continuous. Continuous sounds have a muffled quality.

5. Fifth Phase: Disappearance of sound. Indicates the artery is opened continuously and the flow of blood is streamlined. The best index of diastolic pressure, at least for the novice, is the point at which the heart sounds completely disappear. It is recommended however, that both the onset of the fourth and fifth phases be recorded.

An understanding of the theory and technique of measuring blood pressure should be important to anyone responsible for designing or administering any type of fitness program. Thus, most physical educators should find this information helpful.

Methods: (Groups two of alternate responsibilities and participation)

A. Procedures for taking BP at rest

1. Locate the brachial artery with fingers and mark the location with a pen.

2. Compression bag should be placed with the middle,approximately over the brachial artery. (2-3 cm above fold of the elbow)

3. The compression bag should be long enough to go at least halfway around arm.

4. Place stethoscope on pen mark.

5. While supporting arm at heart level inflate the cuff to 150 mg. Listen to see if you hear a pulse through the bell of the stethoscope. If you hear a pulse inflate the cuff to 180. (It is helpful to ask if they know their current blood pressure before inflation)

6. Deflate the cuff at a rate of 2-3 mm/Hg/sec. (this process should take 30-60 seconds - GO SLOWLY!)

7. While deflating listen for the systolic and diastolic BP and note the pressure on the dial.

8. As soon as the sound disappears, rapidly deflate cuff.

9. Record values on class data sheet.

B. BP during various postures

1. Supine BP (all subjects)

a. Place cuff as designated above.

b. Take one reading after 3 minutes in the supine position.

2. Standing BP (all subjects)

a. Place cuff as above.

b. Sit or stand and be still without flexing leg muscles.

c. Take one reading after 3 minutes of standing.

3. Isometric Exercise (all subjects)

a. Place cuff as above.

b. While BP is being taken, isometrically contract the opposite forearm

by continually squeezing a tennis ball.

c Take only one recording while contracting.

A. Sub-maximal Treadmill Test

a. Place cuff as above, before exercising.

b. Have the subject begin walking on the treadmill

c. Subject warms up at 2 mph at 0% grade

d. The exercise test will follow the Bruce Protocol

e. BP will be taken during the last 45 seconds of each stage (2:15)

f. BP will also be taken during the recovery.

B. Sub-maximal Bicycle Test

a. Place cuff as above, before exercising.

b. Have subject pedal at 60 rpm,

c. Subject warms up at 1 Kp for 1 minute.

d. Increase workload to 1.5 Kp for two minutes.

e. Follow bike protocol that was used in HR lab

f. Take blood pressure the last 45 seconds of each stage.

Keep arm at heart level!

During exercise, systolic pressure increases to a greater degree than diastolic pressure. This is due to the enhanced stroke volume with exercise. Diastolic pressure may decrease at first because of dilation of the vessels of the skeletal muscles during exercise. Generally, diastolic pressure will remain the same or increase very slightly with exercise.

* It is important to keep noise to a minimum, so you can hear sounds without extra disturbances.

* Keep the testing arm consistent throughout lab because some people have a higher BP in one arm as compared to the other. (Typically, the right arm will produce lower readings).

1. List the raw scores for each class member and calculate the average for the class for the following measurements. Calculate the averages for males and females separately. (6 points)

a) supine BP

b) standing BP

c) isometric BP

2. Graph blood pressure results from the bike test. Let time be the "x" axis, and pressure (mm/Hg) be the "y" axis. (5 points)