UNIT19: Cardiovascular Response to
- total heart volume and total blood volume
- want to know: amount of blood pumped out from the right ventricle to the lungs, and from the left ventricle
around the rest of the body, with each beat or stroke of the heart
o stroke volume (SV) of blood
active in absorbing oxygen from the lungs while unloading carbon dioxide to the air, and
carrying absorbed oxygen and food around the body
effectiveness of system
- depends on degree of dimensions (volumes)
- greater dependence on power of system (rate of circulation of volumes of blood)
- DETERMINING GOOD ENDURANCE PERFORMANCE = SIZE OF CARDIACOUTPUT (Q)
o Rate that heart pumps blood per min – given in product of stroke volume (SV) or blood pumped per min
of heart, and HR (bpm)
Q = SV × HR
Typically, for a male at rest, SV is 80 millilitres and HR is 70 beats per minute. Thus, at rest:
80 ml/b × 70 ml/min = 5,600 ml/min = 5.60 L/min
*can be 35 litres per minutes during maximal aerobic exercise in a world-class, male, endurance athlete.
- Set of adjustable tubes
flow of blood causes pressure to increase (depending on Q + FLEX OF TUBES)
Flow (Q) = Mean Arterial Blood Pressure / TPR
- Heart muscle contracts from electrical signal from right atrium (SINOATRIAL NODE ( PACEMAKER))
- 3 positions used to produce ecg
o Left wrist, right wrist, left ankle (EINTHOVEN LEADS)
o Right ankle = reference electrode
o Fifth electrode (exploring) used to p/u signals @ various points over chest
- Use conducting gel rubbed over area of skin to make good contact
- Held in place by being on adhesive patch
1 - LEAD 1.
o The negative terminal of the ECG machine is connected to the electrode on the right arm, the positive
terminal to the left arm electrode. Accordingly, when the right arm is negative with respect to the left
arm there is a positive or upward deflection of the recording pen
- LEAD II.
o The negative terminal is connected to the right arm electrode, the positive terminal to the left leg
- LEAD III
o The negative terminal is connected to the left arm electrode, the positive terminal to the left leg
12 Lead system used in medicine
- Can examine HR, rhythm, waveform @ rest
As the wave of depolarization moves across the atria and ventricles, the magnitude and direction of the ionic current
flow periodically changes
- Left fibre bundle diseased
o Conduction cannot take place
o Left ventricular contraction delayed
o Abnormal ECG waveform
- Cardiac impulse blocked @ AV Node
o Ventricles beat at own rate, abnormal wave
2 Exercise electrocardiography is used to determine:
if the oxygen demands of the working heart are > than the oxygen supply to it
an accurate measure of the heart rate (esp during exercise)
Other methods = palpation of the carotid (neck) or radial (wrist) pulse OR auscultation with a stethoscope over the
chest wall [both inaccurate though]
Blood Pressure Measurement
- high + low pressure in major artery due to contraction/relaxation of heart
- measured using blood pressure cuff, pressure reading manometer, stethoscope
o blood pressure cuff + recording manometer = SPHYGMOMANOMETER
Pulse Pressure (PP) = SBP – DBP mm Hg
Mean Arterial Pressure (MAP) = [(SBP – DBP) / 3] + DBP mm Hg
Equipment for Indirect Measurement of Blood Pressure
- DIRECT method = putting catheter into artery + recording pressure using pressure transducer
o Compression bag enclosed in a cuff, inflating bulb, pump
o Manometer = app pressure read
o Controlled exhaust to deflate system
- Bag and Cuff
o Inflatable bag surrounded by cuff
o Inflatable bag should be 20% wider than diameter of limb used
o MERCURY GRAVITY MANOMETER
o ANEROID MANOMETER *
Determination of Blood Pressure
- Comfortably seated in chair in quiet room with legs uncrossed
- Recognize biological factors: anxiety, emotional turmoil, meals, tobacco, bladder distension, climate variation,
- Avoid exertion, exposure to cold, eating smoking HALF HOUR BEFORE
- No postural change for 5 min before
1. Choose appropriate cuff
o <25cm use small adult or child size cuff
o 25-35 cm use adult cuff
3 2. Position cuff
o Wrap deflated cuff around upper arm
o Lower margin 2.5 cm above elbow
o Arrow placed over brachial artery of arm
o Put stethoscope directly over brachial artery
Medial and underneath biceps tendon (middle of elbow joint on anterior surface)
o Listen to korotkoff sounds
3. Position stethoscope
4. Listen to korotkoff sounds
o Turbulent blood flow
o Locate and be familiar with the sounds
o Pump bag go 100 mm hg pressure
6. Determine systolic pressure
o With the stethoscope in place, the pressure in the bag is raised approximately 30 mm Hg above the
point at which the radial pulse disappears, and then released at a rate of two to three mm Hg per
second. Faster or slower deflation will cause systematic errors. As the pressure falls, the Korotkoff
sounds become audible over the artery below the cuff. These sounds pass through four phases as the
pressure declines, until the sounds disappear:
Phase I— That period marked by the first appearance of faint, clear tapping sounds which
gradually increase in intensity.
Phase II— The period during which a murmur of swishing quality is heard.
Phase III— The period during which sounds are deeper and increase in intensity.
Phase IV — The period marked by the distinct, abrupt muffling of sound so that a soft, blowing
quality is heard.
Phase V — The point at which sounds disappear. The muffling and disappearance are commonly
referred to as the fourth and fifth points.
Sometimes, particularly in some hypertensive patients, the usual sounds heard over the brachial artery (when the cuff
pressure is high), disappear as the pressure is reduced, and then reappear at a lower level. This early, temporary
disappearance of sound is called the auscultatory gap and occurs during the latter parts of phase 1 and phase II. Because
this gap may cover a range of 40 mm Hg, one can seriously underestimate the systolic pressure or overestimate the
diastolic, unless its presence is excluded by first palpating for disappearance of the radial pulse as the cuff pressure is
raised. When all sounds have disappeared, the cuff should be deflated rapidly and completely. One to two minutes
should elapse for the release of blood trapped in the veins before further determinations are made.
7. Determine diastolic pressure— There is some controversy as to whether to make the fourth phase or the fifth
phase the true diastolic pressure point. We will use the fifth phase (the point at which the Korotokoff sounds
disappear), as the true diastolic pressure point.
Submaximum Tests of Cardiorespiratory Fitness—Astrand Test
Variety of step, bicycle ergometer + treadmill tests used to access cardioresp fitness (predicts VO2max)
Calculate size of work rate stimulus + heart rate response to it
Submaximal effort = 65-85% of max HR
4 Prediction of VO2max from Submaximum Bicycle Ergometry Using the Astrand Test
Astrand test predicts maximal aerobic power (VO2max) from HR measured @ end of 6 min submaximal work
rate on bicycle ergometer
Monarch bicycle ergometer
An electrocardiograph, or heart rate monitor
Pre-gelled disposable electrodes.
Stopwatch for recording exercise duration.
Ruler for measuring ECG intervals.
About the Monarch Bicycle Ergometer:
Work rates expressed in kilopond-meters/mi
o Kilopond = force of gravity acting on 1 kg (watts)
One watt = 6.12 kp·m·min-1
General subjects = 60revs/min
Trained cyclists = 90-100revs/min
Given a pedaling frequency of 50 rev/min, and 6.0 m/rev, work rate may be determined simply by the tension setting.
For example, a tension setting of 2.0 kiloponds will produce a work rate of (50 rev/min) x (6.0 m/rev) x (2.0 kp) = 600
1. The subject should refrain from energetic physical activity for two hours before the test, and not smoke for one hour
before the test. The test should not be performed earlier than about one hour after a light meal or earlier than about 2-
3 hours after a heavier meal.
2. Adjust the cycle seat height so the subject's leg is almost fully extended at the knee when the ball of the foot is
applied to the pedal at its lowest position.
3. Prepare the subject for heart rate measurement using either an electrocardiograph or a heart rate monitor.
4. Record and measure the resting HR of a subject after he/she has sat quietly for three minutes.
5. Astrand and Ryhming do not specify any warmup. However, 3 minutes of unloaded pedalling may minimize the risk of
injury, and should not affect the accuracy of the prediction of VO2max.
6. Start the subject pedalling at 50 rpm on a bicycle ergometer with no brake resistance. Continue this baseline work
rate for 3 minutes. Then immediately increase the work rate to 450, 600, 750, or 900 kp·m·min-1 for females and 600,
900 or 1200 kp·m·min-1 for males depending on the size and probable aerobic fitness level of the subject. Record the
heart rate during the last t en seconds of each minute.
7. Maintain the steady work rate chosen for 6 minutes.
5 8. If after one or two minutes it is apparent that a heart rate of less than 120 beats per minute is going to be the steady
state heart rate, increase the work rate to achieve a heart rate of 140 – 150 beats per minute and continue the work for
the full 6 minute period. Record the steady state heart rate. Average the heart rates for the 5th and 6th minutes.
9. If heart rate varies more than 5 b/min between the 5th and 6th minutes, the subject should continue exercising at
the same work rate until the difference between heart rate measured at 2 consecutive minutes is less than or equal to 5
b/min. Allow the subject to recover for 5 – 10 minutes.
10. Estimate the VO2max of the subject from the Astrand Tables (Tables 19-2 and 19-3) and correct the value with the
age adjustment factor (Table 19-1).
11. Use your subject's predicted VO2max in ml·kg-1·min-1 in Table 19-4 to get a rating of your subject's aerobic fitness
level. Note that these Swedish norms were created from a population with a more optimal level of aerobic fitness than
the typical North American population.
- ECG machine plus electrodes and alcohol
- Blood pressure cuffs and stethoscopes
- Monarch bicycle ergometers
- Heart rate monitors
1. Practice measuring blood pressure - Get a partner, and then choose the correct size blood pressure cuff for you and
your partner. Follow the procedures described for measuring blood pressure at rest when sitting. Record data for you
and your partner in Table 19-5.
2. Watch the demonstration of one subject being attached to the electrocardiograph. Obtain one piece of the resultant
trace each. Calculate the heart rate of the subject from your piece of trace – Table 19-6.
3. Perform the Astrand test. Use either an electrocardiograph or a heart rate monitor to measure the subject's heart
4. Put a blood pressure cuff around the subject's arm.
5. Measure blood pressure and resting heart rate while the subject is seated at rest on cycle ergometer.
6. Start the subject pedaling at 50 rpm with no brake resistance. Continue for 3 minutes.
7. Monitor heart rate in the last ten seconds of each minute of rest and exercise.
6 8. Increase the work rate to either 450, 600, 750 or 900 kp·m·min-1 for females and 600, 900 or 1200 kp·m·min-1 for
males depending on size and probable aerobic fitness. Maintain the steady state work rate chosen for 6 minutes. Follow
all of the Astrand Test procedures described with the first procedure.
9. Monitor blood pressure immediately at the end of the six minutes of exercise. It is very difficult to measure blood
pressure while a subject is exercising. Pump the blood pressure cuff up to 190 mm Hg 10 seconds before the end of the
six minutes of exercise. At the end of six minutes of exercise, the subject should stop pedaling. The measurer should
drop the pressure in the cuff until the first Korotkoff sounds are heard, indicating systolic pressure. Then drop the
pressure in the cuff very rapidly down to approximately 90 mm Hg and start searching for the pressure where the
Korotkoff sounds disappear, indicating diastolic pressure. Heart rate and blood pressure recover quickly when a subject
stops exercising so speed of measurement is essential if accurate data is to be obtained.
10. Take off the brake resistance and have the subject cool down at 50 rpm for 3 minutes. Monitor heart rate at the end
of each minute, and blood pressure at the end of the three minute cool down period.