Download CV LAB Circulation in Human Subjects Part I: Measurement of Blood

CV LAB
Circulation in Human Subjects
Part I: Measurement of Blood Pressure
1. Introduction: Form teams of two and take each other’s blood pressure. Enter the data
in the Table Page. Measurement of human blood pressure is usually made by the
indirect method in which the blood pressure is estimated from the influence of
externally applied pressure on the blood flow through a limb. Wrap the blood pressure
measuring cuff (approx. 12 cm breadth) around the upper arm of the subject. Place the
stethoscope head gently in the antecubital fossa over the brachia artery (identified by
sensing the pulse). Can you hear any sound without inflating the cuff? By squeezing
the bulb (with the side vent valve closed), which is attached to the cuff and the
manometer, raise the cuff pressure to approximately 160mmHg. Lower the cuff
pressure gradually (2-4 mm Hg per sec) by opening slightly the vent valve; watch the
mercury level in the manometer while listening through the stethoscope. The pressure
at which the sound first appears (sharp, tapping sound) is the systolic pressure. With
progressive decreases of cuff pressure, the sound first becomes louder, and the
thudding sounds gradually fade and become muffled. The pressure at which this
muffling occurs is taken as the diastolic pressure. Usually the sound disappears a few
mm Hg below the point of muffling. Release the cuff pressure completely and wait for
10 seconds before making another measurement. What would be the effect of using a
cuff that is too large or too small? Should one use a cuff of different size for the obese
subject or for a small child?
2. Comparison of Methods of Blood Pressure Measurement. With the subject sitting,
determine the blood pressure by using the auscultatory method described above. In
addition, also determine the pressure at which the radial pulse begins during gradual
deflation of the cuff (palpation method). Take three readings for each method of
determination, alternating one with the other. Before beginning the palpation
measurement, count the pulse for 15 seconds and record the pulse rate per minute.
During each blood pressure measurement, also note the pressure at which the mercury
column begins to oscillate. Compare the systolic pressure determined by auscultation
with the readings obtained by palpation and visual observation of oscillation. Explain
the differences. Can you determine the diastolic pressure by palpation?
3. Effects of Body Position on Blood Pressure and Pulse Rate. Allow the subject to lie
flat for 3 minutes, then make three blood pressure measurements by auscultation and
take the pulse rate three times. Let the subject stand up, and take four blood pressure
and pulse rate measurements in quick succession (approx. 1 minute intervals).
Compare the systolic pressure, diastolic pressure, pulse pressure (PP = systolic pressure
- diastolic pressure) and pulse rate in different positions. Explain the differences.
Blood Pressure Measurements
Systolic/Diastolic
Pressures
(mm Hg)
Pulse
Rate
(per min)
Pressure at
which oscillation
begins (mm Hg)
Auscultatory 1
Auscultatory 2
Auscultatory 3
_____/_____
_____/_____
_____/_____
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Mean
_____/_____
_______
______
Palpatory 1
Palpatory 2
Palpatory 3
Mean
___________
___________
___________
___________
______
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Comparison of methods
Body positions
Supine 1
Supine 2
Supine 3
_____/_____
_____/_____
_____/_____
______
______
______
Mean
_____/_____
______
Standing 1
Standing 2
Standing 3
Standing 4
_____/_____
_____/_____
_____/_____
_____/_____
______
______
______
______
Mean (2,3,4) _____/_____
______
4. Effects of Exercise on Blood Pressure and Pulse Rate: (One subject per table). After
measurement of blood pressure and pulse rate in the control state (quiet standing), the
subject performs 30 deep knee bends in 30 seconds, with the blood pressure cuff
wrapped around his upper arm but disconnected from the manometer. Immediately at
the end of the exercise, connect the cuff to the manometer, and determine blood
pressure and pulse rate as soon as possible. Repeat these measurements (Note the
time of measurement) until the values return to control levels.
Using the control data and the first measurement obtained immediately after
exercise, calculate the effects of exercise on stroke volume, cardiac output and total
peripheral resistance by using the following assumptions: (a) the control cardiac index
(cardiac output per unit body surface area) is 3.3 L/min/m2, (b) the effect of exercise on
stroke volume is proportional to its effect on pulse pressure, and (c) the mean arterial
pressure equals [diastolic pressure + (pulse pressure/3)].
Calculation of Cardiac Output, Stroke Volume and Total Peripheral Resistance
Control
Exercise
Measured Data
Systolic pressure (SP, mm Hg)
Diastolic pressure (DP, mm Hg)
Pulse rate (HR, per min)
Body surface area1 (SA,M2: estimate from hgt./wt.)
______
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Calculated results
Pulse pressure (PP = SP-DP, mm HG)
Control cardiac output (COc = 3.3 SA, L/min)
Control stroke volume (SVc = COc/HRc, ml)
Exercise Stroke volume (SVE = SVc x PPE/PPc, ml)
Exercise Cardiac output (COE = SVE x HRE, L/min)
Mean Arterial Pressure [MAP = DP + (PP/3), mm Hg]
Total peripheral resistance (TPR=MAP/CO, mm Hg-sec/ml)
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Hemodynamic Effects of Exercise (percent of control):
100 HRE/HRc
100 SVE/SVc
100 COE/COc
100 MAPE/MAPc
100 TPRE/TPRc
1
=
=
=
=
=
______%
______%
______%
______%
______%
Surface Area (cm2) = Wt0.425 X Ht0.725 X 71.84. Weight (Wt) is in kilograms, and
height (Ht) is in centimeters. From DuBois and DuBois. Arch. Internal. Med. 17:865, 1916
Part II: Cold pressor test: Record blood pressure and pulse rate from right arm to 1
min intervals until a stable reading is obtained. Continue the recording and perform the
cold pressure test by placing left hand and lower forearm in a basin containing equal
parts of water and ice for 2 min. After removal of the hand from the basin, continue the
recording for 3 more min. What is the effect of cold pressure test on blood pressure
and heart rate?
Control
Blood Pressure
(systolic/diastolic
)
Pulse
Rate
(/min)
1 min (in ice)
2 min (in ice)
3 min
4 min
5 min
Part III: Study of Skin
1.The Red Reaction. Draw a blunt instrument firmly across the forearm. The lighter
flush of an arteriolar flare may be seen peripheral to the red reaction.
2.The Triple Response. Draw a blunt instrument 6 to 7 times over the same area of the
skin. Look for local vasodilation, the flare, and local edema.
3.Veins. Examine the veins of the hand and then allow the hands to hang at the side.
Note the size of the veins. What is the effect on the veins of opening and closing the
fist several times? Raise the hand slowly from the subject’s side. At what level do the
veins collapse? What is the effect on the veins of the forearm and hand of applying a
blood pressure cuff to the arm inflated to a pressure of 40 mm Hg for 3 to 5 minutes?
PART IV: Electrocardiography: Each electrocardiographic lead is labeled with the
initials of the extremity to which it must be attached. The chest lead is designated
similarly. In order to record the standard leads I, II and III, and leads aVR, aV1 and
aVF, it is only necessary to turn the dial to the leads desired. When recording the chest
leads, the dial is turned to V, and electrocardiographic recordings are obtained by
moving the chest lead to each of the standard sites, V1-6, as follows:
V1 - Fourth intercostal space at right sternal border
V2 - Fourth intercostal space at left sternal border
V3 - Halfway between V2 and V4
V4 - Fifth intercostal space at mid clavicular line
V5 - Anterior axillary line at the same level as lead V4
V6 - Mid axillary line at the same level as leads V4 and V5
1. Identify P, QRS and T in each lead.
2. Use a stethoscope to listen to the heart sound at the apex. What is the relationship
between electrocardiographic waves and the heart sounds?
3. With the use of Einthoven’s triangle, determine the direction of the QRS axis from
the mean QRS amplitudes in leads I and III.
4. Measure and calculate the following parameters from lead II:
Chart speed
R-R interval
PR interval
QRS duration
QT interval
Ventricular rate
=
=
=
=
= 25 mm/sec; 1mm = 0.04 sec
mm
sec.
sec.
sec.
= (25•60)/R-R
= ?/min
This formula is derived from the following:
time between beats (sec)
the number of beats (per min)
= (R-R interval)/(chart speed)
= 60 seconds/time between beats