cardiovascular physiology lab

8/16/2019 Cardiovascular Physiology Lab

1/13

Exercise

ardiovascular Physiology

l bor tory Objectives

On

completion of the activities

in

this exercise, you will be able

to

Locate the auscultation areas for the heart.

• Use a stethoscope

to

listen to the heart

sounds

at the aus-

cultation areas.

• Measure blood pressure at rest,

during

exercise, and

during

the recovery period after exercise.

• Calculate the pulse pressure

and

mean arterial

pressure (MAP).

• Measure the pulse rate at rest ,

during

exercise, and

during

the recovery period after exercise.

Describe the function

of

the cardiac

conducting

system.

Measure and evaluate the electrical activity of the heart (ECG).

aterials

Stethoscopes

Alcohol swabs

Sphygmomanometers

Stopwatch

or

clock with a

se

c

ond

hand

Stationary cycle

• Biopac Student Lab system

T

he

cardiac

cycle refers to the series of events

that

occurs

during one

heartbeat.

During one

cycle, the two atria

will

contract

at the same time.

As

the atria relax, the two

ventricles will

contract

simultaneously. A period

of contraction

in a heart

chamber

is called

systole atrial

systole, ventricular

systole)

,

and

a period

of

relaxation is called

diastole

atrial

diastole,

ventricular

diastole) .

[n clinical use, these

terms

typically refer

to

events in the ventricles, because they are the

larger

and more powerful

chambers that

pump blood into the

grea t arteries.

The events of the cardiac cycle are illustrated and described

in Figure 22.1. During the cycle , changes in blood pressure in-

side the chambers and great arteries cause the heart valves

to

open and close. These events regulate the flow

of

blood through

the heart and into the systemic and pulmonary circuits. During

this laboratory exercise you will investigate some of the physio-

logical

events-heart

valve function, pulse, blood

pressure-that

characterize the cardiac cycle.

You

will also record measurements

of

the electrical activity of the heart (an electrocardiogram or

ECG) and evaluate the results.

(f)

Ventricular diastole-late:

All chambers are relaxed.

Ventricles fill passively.

(e) Ventricular

diastole-

early: .

As

ventricles relax, pressure

in ventricles drops; blood

flows back against cusps of

semilunar valves and forces

them closed. Blood flows

into the relaxed atria.

(a) Atrial

systole

begins:

Atrial contraction forces

a small amount of additional

blood into relaxed ventricles .

(b)

Atrial systole ends;

atrial

diastole

begins

(c) Ventricul ar

systole

first phase: Ventricular

contraction pushes AV

valves closed but does

not create enough pressure

to open semilunar valves.

(d)

Ventricular

systole

second phase: As

ventricular pressure rises

and exceeds pressure in

the arteries, the semilunar

valves open and blood

is ejected.

Figure 22.1 The cardiac cycle.

The illustrated steps describe the

events that occur during one heart-

beat. During each cycle, the atria con-

tract together and the ventricles

contract together.

393


2/13

EXERCISE

TWENTY- TWO

Heart

Sounds

During the cardiac cycle,

when

blood passes from the atria to the

ventricles

and

from the ventricles to the great vessels, the heart

valves open

and

close. The closing of the values produces two dis-

tinctive heart sounds. The sounds can be heard, with the aid of a

stethoscope,

as Iub-dup

vibrations. The cardiac cycle begins

when a small volume of blood

is pumped

into each ventricle dur-

ing atrial systole (Figure

n.la).

The first "lub"

sound is

caused

by vibrations that follow the closing of the atrioventricular AV )

valves (Figure n.2b . This occurs at the end of atrial systole

(Figure n.lb). This point in the cardiac cycle also marks the be-

ginning of ventricular systole (Figure 22.1c), known as isovolu

metric contraction,

when all heart valves are closed. As the

pressure in the ventricles increases, the semilunar valves open

and blood

is pumped

into the great vessels. This

is

the second

phase of ventricular systole (Figure n ld , known as

ventricular

ejection. The closing of the semilunar valves occurs at the begin-

ning of ventricular diastole (Figure n le ) . Vibrations , generated

by the closing of these valves, creates the second "dup" sound

(Figure

n.2b

At

this time, pressure in the ventricles is decreas-

ing and falls below the pressure in the great arteries. At the end of

the cycle, ventricular pressnre falls below the atrial pressure.

As

a

result, the

AV

valves open and passive filling of the ventricles be-

gins. A new cycle begins with the initiation of atrial systole.

CLINICAL

CORRELATION

Incomplete

closure

of the

AV

valves can

cause regurgitation or

backflow of blood into the atria. This can cause an abnormal gur-

gling sound known as a heart murmur.

On

the left side of the

heart, incomplete closure of the biscuspid (mitral) valve is called

a

mitral valve prolapse.

Minor

prolapses are fairly

common

and most people

live

with them and do not experience adverse

effects. However, a major prolapse, possibly caused

by

rupturing

of the

chordae

tendinae

or severe damage to the cusps,

can

nave serious if not life-threatening

consequences.

ACTIVITY 11.1 listening

for Heart Sounds

1.

The best locations to hear heart sounds are the

auscultation areas for the heart

(Figure

n.2a) on

the

anterior thoracic wall. These areas are named after the

heart valve that can best be heard. locate the following

auscultation areas on yourself or your lab partner.

• The

biscupid area

is

located in the left fifth inter-

costal space, where

the apex

of

the

heart

is located . To

find this region, locate the inferior end

of

the sternum

by finger palpation.

From

this point, move

your

finger

approximately

7 em (2.75 in) to the left, where you

120

Valve location

1

Pulmonary

Sounds heardf valve

Semilunar

90

Pressure

(mmHg)

60

30

Sounds heard AV (bicuspid)

Orta

( eft

ventricle

Left

atrium

S,

AV valves

close

AV

valves

open

}

Left

Valve location valve

Valve location

1

Right

Sounds heard f AV (tricuspid)

S2

8

4

i

~ 8 3 . _

8

4

Heart

---A ...'_---lI,

r .

sounds r , r-

"Lub"

"Dup"

(a) (b)

Figure

22

.2 Auscultation

areas

for the heart. a)

Diagram that illustrates the locations

of

the heart valves

(oval areas) and the auscultation areas (circular areas), where heart sounds can best be detected with a stetho

scope.

b)

Graph

sh

owing the relationship

of

the heart sounds with events

in

the cardiac cycle. The two primary

heart sounds, 51and 52 ("Iub-dup"), are caused by the closing of heart valves. Two minor sounds, 53and 54, are

not related to valve

fund

ion and are difficult to hear.


3/13

can feel thefifthintercostalspace

between

the fifth

andsixth ribs.

•

To

locatethe

tricuspid area,

palpatetheinferior

end

of

the

sternum and

place

your

stethoscope

just to

theleft

of

tharpoint.

• The

aortic

semilunar

area is

locatedinthesecondin-

tercostalspace,just to the rightof thesternum.Thesec-

ond

intercostalspacecanbe locatedbyfirstpalpating

thesuperiormarginofthemanubrium.

Fromthismar-

gin,moveyourfingerinferiorlyuntilyoucan feel the

junction

betweenthe

manubrium

andthebodyof the

sternum

.

f

youmoveyourfingerlaterally

to

the right

of

the

sternum,

youcanfeel thecostalcartilageofthesec-

ondrib. Thesecondintercostalspace

is just

inferior

to

thisrib.Place

your

stethoscopein thisspace,

just

lateral

to

thesternum.

• Thepulmonary

semilunar

area is locatedin thesec-

ond

intercostalspace,

just

to theleftofthesternum.

Followthesameprocedurefor locatingtheaorticseml-

lunararea,

but

this time,move to theleftsideofthe

sternum.

WHAT S IN

WOIlD

The term

uscult tion is

derivedfrom the

Latinword

auswlto

whichmeans"tolisten

."

Auscultation

is

an

importantdiagnostictoolused

by

doctorsand

other

healthcare

providers.

t

involveslistening

to

the

sounds

madebyvariousor-

gansinthethoracic

or

abdominalcavities,

such

astheclosing

of

heartvalves.

2. Obtainastethoscopeandsterilize theearpieceswith

an

al-

coholswab.

3. Place the

stethoscope on

thebicuspid areaand listen

lor

theheart

sounds. f

thebackgTOundnoiseis too

highandyouare

experiencing

dirficultyin

detecting

thesounds ,move to a

quieter

area in

the

laboratory

or toanother room.Can you hear

both

heart

sounds

("

lub-dub

")

when

the

stethoscope

is placedover the

biscuspid area? Canyou

hear

one sound better

than

the other?

4.

Listento theheart

sounds

at the

other

auscultationareas.

Howdo the

sounds

compareateacharea? Answerthe

same twoquestionsthat,v e

re

asked forthebiscuspidarea

in thepreviousstep.

an

you hear

an

you hear one

both heart sound better than

sounds?

the other?

• Tricuspid area

• Aortic semilunar area

• Pulmonary

semilunar area

CARDIOVASC ULAR PHYSI OLOG Y

Duringaphysicalexamination,

wh

ydoes the

doctor

listento theheart

sounds

atallfouraus-

cultationareas

7

lood

Pressure

Bloodpressure is theforceexertedbyblood

on

thewallsof blood

vessels .

It

is a function of the

pumping

action ofthe heart and

theresistanceto flowasbloodmovesthrough thebloodvessels.

Bloodflows

throughout

theCirculatorypathways

due

totheex-

istence

of

apressuregradientthat allowsblood

to

movefromar-

eas of high pressure to areas

of

low pressure. Blood flow in

arteriesandveinsbeginswithventricularejection intothegreat

arteries

and

endswithvenous return

to

theatria.

In

thesystemic

circulation ,bloodpressureishighest intheaortadue

to

theforce

of ejection by the left ventricle. Pressure gradually declines

throughout the Circulatory pathway,

and

is close to zero when

bloodentersthe rightatrium.

In large elastic arteries, the blood pressure fluctuates be-

tweenamaximum

and

minimum value,whichcorrespond tothe

cardiac cycle.

For

example,

during

ventricularsystole ,bloodis

ejectedintotheaortafrom theleftventricle.Theforce

of

ejection

causes theelasticwallsofthe aorta to stretch,and the pressure

insidetheaortareachesapeak.This

maximum

pressure

is

called

the

systolic pressure.

During ventricular diastole, the aortic

semilunarvalvecloses ,

and

the elastic fibers in thewall ofthe

aortarecoil to forceblood forward.At this time ,theaorticpres-

suredeclines to a

minimum

level, referred

to

as the diastolic

pressure.

Thus

, bloodpressure in the aorta

is

not

smooth

or

constant,

but

pulsatileinnature. Thischaracteristic is also true

forother elasticarteries,

but

itdiminishesinthesmallerarteries

andarteriolesas the

number

ofelastic fibers inthe vesselwalls

diminishes.Blood, flowingthroughcapillaries

and

veins ,travels

under

relativelylowpressurewith little

or

nofluctuation.

Blood pressure

is

measured in units called millimeters of

mercury

(mm

Hg).Ifthepressureinabloodvessel

is

95

mm

Hg,

itmeansthattheforceexertedbythebloodwillcausea

column

of

mercurytorise95 millimeters.When bloodpressureismea-

sured,it is thearterial blood

pressure

inthe systemiccircula-

tion that is recorded. Usually, the

brachial artery

is used

to

measurearterialbloodpressure(Figure22.3),becauseit is atthe

same level as the heart, so the effects

of

gravity are negligible.

Thus,bloodpressuremeasurementstakenfrom thebrachialar-

teryare fairly close to thebloodpressurein theaorta.

Sincethe

pr

essureinarteriesis pulsatile,bothsystolicand di-

astolic pressures are measured.

f

a person's blood pressure

is

120/80

itmeansthalthesystolicpressure

is

120

mm

Hgandthe

diastolicpressureis

80 mm

Hg. Thesystolicpressurerepresents

the force exertedbythe leftventriclewhenit

pumps

bloodinto

theaorta.Thediastolicpressuremeasurestheresistancetoblood

flow inthearteries.


4/13


5/13

this by listening to the brachial artery as you squeeze the

culT.

vVhen you hear no sound, compression is complete.

4. Slowly deBate

the

cuff while listening to the brachial

artery with the s tethoscope.

The

cuff can be deBated by

turning the knob

at

the

base

of

the hand bulb. Try to de

!late

the

cuff at a rate

of

2

to

3 mm Hg per second.

5.

As

the cuff pressure slowly decreases, it will eventually be

come less

than

the arterial pressure. At this

point

, the ar

tery is partially

open

and blood will begin to pass

through

(Figure

n.3c .

Because the blood Bow is

turbul

ent at this

time,

thumping sounds

will be heard. These sounds,

known

as

Korotkoff s sounds,

correspond to the systolic

blood pressure. Make a mental note of the pressure read

ing at the time that you begin to hear KorotkolT's so unds.

6. Continue

to

slowly de!late the cuff. As you do so, the

constriction in the artery is reduced

and

blood !low

becomes less

turbulent. As

a

consequence,

the

thumping

sounds will become faint and eventually disappear.

-r he pressure at the time

when

the thumping sounds stop

corresponds

to the diastolic pressure (Figure n.3d .

Make a

mental

note

of

the

pressure

readi

ng

at this time.

7.

Record your partner's blood pressure in Table 22 .1. Calcu

late your partners' pulse pressure and mean arterial pres

sure and record these values in Table n l

8.

With

your lab partner's assistance, repeat steps 2 through

6 to determine your own blood pressur

e.

Record this value

in Table 22.l. Calculate your pulse pressure and mean ar

terial pressure and record these values in Table 22.l.

The pulse pressure is a good diagnostic tool for

predicting the condition of the arteries. For exam

ple,

arteriosclerosis

causes a decrease in the elasticity of arterial

walls

and

an increase in the resistance to blood

!lmv.

Under these

conditions, how ,vould you expect the pulse pressure to change

so that normal blood flow

is

maintained? Explain.

CARDIOVASCCLAR PHYS10LOGY

ACTIVITY 11 3 Examining the

Effect

of

Exercise

on

Blood Pressure

1.

Using the instructions from Activity 22.2, measure

your partner's blood pressure after he or she sits quietly for

2 to 3

minute£. Record these results in Table

n.2.

Form iJ

Hypothesis

Before

you

begin,

predict

what ef

fect,

if

any, a

period of

exercise will

have on blood pres·

sure,

pulse pressure, and

mean

arterial

pressure

(MAP).

a. Effect on

blood

pressure

b. Effect on pulse pressure _

c. Effect on MAP

2.

Have your partner exercise for 10

to

15 minutes on a sta

tionary bicycle . If a bicycle is not available, another form

of exercise, such as

running

in place, can be substiruted.

Ke

ep the sphygmomanometer an d stethoscope in position

during the exercise period.

Warning:

Anyone who

is

ph

ysically

or

medically unable

to

perJorm

physical eXCI c

ise

should

not

participate

in

this

por-

tion oj the laboratory activity

3. At 3-minute intervals during the exe rcise period, and im

mediately aft

er

exercise ends (i5 minutes), measure yo

ur

lab partner's blood pressure. Calculate the pulse pressure

and MAP Record the results in Table 22.2.

4.

Measure your lab partner 's blood pressure 1 minute after

the exercise period. Take additional measurements at

3-minute intervals until the return to resting blood pres

sure. For each measurement , calculate the pulse pressu re

and

MAP Record the results in Table

22.2.

Assess

the

Outcome Did

your actual results

agree

with

the prediction you

made

earlier?

Explain.

Table 22.1 Blood Pressure Readings

Subject Blood pressure mm

Hg)

1. Population

average

*

120/80

2.

3

Pulse pressure mm Hg) Mean arterial pressure mm Hg)

40

93

.3

• Keep in

mind

that

these readings

are on ly average va lu

es.

You should expect variatio n

In

the population.


6/13

EXE RC I

SE n

NT Y-T W O

Table 22_2 Effect

of

Exercise on

Blood

Pressure

Time

Blood pressure (mm Hg Pulse pressure (mm Hg

Mean arterial pressure (mm Hg

1. Preexercise:

At rest

2. Exercise period:

3 minutes

I

6 minutes

9 minutes

12 minutes

15 minutes

3 Postexercise:

1 minute

4 minutes

7 minutes

10 minutes

I

13

minutes

Pulse

Rate

In the systemic Circulation , waves of pressure are initiated

wh en the left ventricle pumps blood into the aorta . Th e pul se

pressure generates these pressure waves. The waves then

travel alon g other elastic arteries whose walls ex pand and re

co

il

at a frequ ency th at corresponds to the heartbeat. Th e

rhythmi

c

exp

ansion a

nd

reco il of the arteri es is

kn

own as th e

pulse . Pulses can b e felt at various lo

cation

s,

such

as th e radial

artery in

th

e wri st

and

th e femoral

art

ery in

th

e thi gh. They

tend to

dimini

sh in smaller arteries

and

are absent in capillar-

ies and veins.

CTIVITY

22 4 Measuring the

Pulse

Rate

Using your index and middle fingers , appl y

li

ght pressure to the

pulse points a t the following lo cati ons.

l . Temporal artery

pulse

on the side of the head in the tem

poral area

2. Carotid artery pulse in the neck , about 1 cm inferome

dial to the angle of th e jaw

3. Radial artery

pulse

on the

ant

erior su rface of the lateral

wrist

4. Popliteal artery pulse in the popliteal fossa, pos terior to

the

kn

ee

1 Vlhile measuring the pulse, you were in

structed to apply light pressure to the various

pulse points. Exerting too much pressure will stimulate the va

gus nerve. How will this affect y

our

pulse measurement?

2.

The average res ting pulse is b etween 70

and 80

beats per

minute

, but there

is

considerable va

ri

ation in the popula

ti

on.

For example,

it

is not

unu

sual for w ell-trained athletes to ha

ve

pulse rates as low as 40

to

50 beats per

minut

e. (The pulse

rates of some world-class marathon runners are 35

to 40

beats

per minute!)

Wh

y do a thletes tend to have slower pulses?

CTIVITY 22 5

xamining the

ffect of xercise

on

Pulse Rate

l. Have yo

ur

lab pa

rtn

er sit quietly for abo

ut

3

minut

es.

Af-

ter this period, tak e his or her resting pulse. The mos t ac

curate measurement would be to count the number of

beats for 1 full minute; how ever, a resting pulse can usu

ally be measured accurately by counting for 15 seco nds

and multiplying by 4. Reco

rd

your results in Table 22.3.

2.

Ha

ve

yo

ur partn

er exercise for 10 to 15

minut

es

on

a s ta

tionary bicycle. If a b icycle is

not

available, s ubstitute an

other form of exercise (running in place or running up

and down stairs) .


7/13

Table 22.3

easuring

Pulse Rates

Subject

Yourself

I

Lab partner

Resting pulse:

Pulse immediately after exercise:

Pulse rate at various times after exercise:

2 minutes:

4 minutes:

6 minutes:

8 minutes:

10 minutes:

12

minutes:

14

minutes:

16

minutes:

Warning

Anyone who

is

physically

or

medically unable

to

peljonn physical exercise should not participate n this por-

tion o the laborat01J activity

3. Immediately after the exercise period , measure

your

lab

panner s pulse by counting beats for lO seconds and mul-

tiplying by 6. Record the results in Table 22.3.

4. Measure

your

panner s pulse every 2 minutes after exer-

cise until she

or

he returns

to

the resting pulse. Record the

results in Table 22.3. How long does it take for the resting

pulse to return?

5.

Repeat steps 1 through 4 for yourself and record the re-

sults in Table 22.3.

1.

After a period of exercise , counting the pulse

for 10 seconds and multiplying by 6 is more ac-

curate than

counting

for a full minute. Explain why.

2. The length of time it rakes for your pulse to recover

to

a rest-

ing level is an indication

of your

physical fitness and cardiovas-

cular efficiency. As a general rule ,

the

shorter the recovery time,

the better your fitness. How do you compare with your lab

partner

and

with

other

members of the class)

CARDIOVASCULAR PHYSIOLOGY

Sinoatrial

(SA)

node

i AV bundle

k ;rlb

Bund e

branches

Purkinje

fiber

Figure 22.4 The cardiac conduction system. Action potentials

are

spon-

taneous

ly

generated

at

the sinoatrial

SA)

node.

The

other components of

the conduction

sy

stem sp r

ead

depolarizing electric impulses along the

atrial

and

ventricular walls, and

thus,

regulate the heart s pumping action.

lectrocardiography

The heart contains a network of specialized cardiac muscle cells,

known

as the

cardiac conduction system

(Figure 22.4) , which

is able to generate and conduct action potentials without neural

or hormonal stimulation. The sinoatrial (SA)

node

is located in

the posterior wall of the right atrium, adjacent to the opening for

the superior vena cava. Cells in the SA node serve as the heart's

pacemaker

by

spontaneously

generating electrical impulses.

These depo larizing impulses spread across the walls of the atria,

resulting in atrial contraction (systole). As the impulse reaches

the atrioventricular (AV) node in the floor of the right atrium,

the atrial muscle cells repolarize and relax. From the

AV

node,

impulses spread along the AV

bundle,

left

and

right bundle

branches, and Purkinje fibers, resulting in ventricular contrac-

tion. In this manner, these waves of electrical impulses cause the

mechanical

pumping

activity of the heart. Faint traces of these

electric impulses spread through the rest

of

the body

and

create

changes in the electrical potential of the skin. These electrical

changes can be detected by electrodes on the skin and recorded

in a procedure known as electrocardiography. From the resulting

electrocardiogram

(ECG)

it is possible to

examine

the heart's

mechanical activity. If a medical condition causes disruptions in

the electrical activity of the heart, these may be reflected in the

ECG

and

useful for diagnosis.

The normal ECG tracing is a flal baseline interrupted by a

series of waves (Figure 22.5). In a single cardiac cycle,

the

P

wave

indicates the depolarization of the atria

just

prior to the

beginning of atrial contraction or systole.

The

QRS

complex

(QRS interval) represents the depolarization

of

the ventricles,

which precedes ventricular systole. The T

wave

results from


8/13

EXERCISE

TWENTY TWO

• t

:

and other

metal objects.Ask

your

partner

tolie

down

and relax.

ingdeeply,

and

after exercise. In each case, itis

important that

the actual recordingbe done while

your

partner is physically

800

msec

1

I'

-I

R R

P R

S T

+0.5

segmen

egment

S

l

I I

0

0

I I

I

I

S T

I I

I I

I

P-R I

I

interval

1 1

0.5

interval:

ORS interval

O T

(ventricles depolarize)

interval

I I I I

b)

Figure 22.5 Components of the

ECG.

Intervals, such

as

the

P-R

interval,

are

measured from the beginning of the fi

rst

wave to the beginning of the

second wave. Segments. such as the SoT segment, are measured from the

end of the first wave to the beginning of the second wave.

ventricular

repolarization,

which

occurs before

ventricular

re-

laxation

or

diastole.

The

waveassociated

with

repolarizationof

the atriaishidden by the much largerQRScomplex.

Inthefollowingactivity,youwill recordtheECGofyour lab

partner under

varying conditions, correlate electrical

and

me-

chanicaleventsof the heart,and observe the changes inheart

rateassociatedwithbody position

and

breathing pattern.

CLINICAL CORRELATION

Variations

in

the

size

and length

of

the various waves and wave

segments

in

an ECG

are useful in detecting abnormalities in the

heart.

For

example,

a higher

than

normal P

wave may

indicate an

enlarged atrium, and an increase in the height

of the R

wave

(part of the

QRS

complex)

suggests

that

the ventricles

are

en

larged.

The

position of

the ST

segment

(Figure

22.5) can identify

the previous occurrence of a heart attack (myocardial infarction).

If the segment

is

above its normal horizontal position, a heart at

tack likely occurred.

CTIVITY 21 6

Using

the

Biopac Student Lab

System to

Measure

and Evaluate

~ ~

the

Electrical Adivity of

the

Heart

Setup and alibration

1.

Instruct your

lab

partner

to removealljewelry,watches ,

Right forearm,

white lead

Figure 22 ,6 Proper electrode placement and connection

for Lead II ECG.

2.

Attachelectrodeleads(SS2L)to

Channel

2

of

theAcquisi-

tionUnitand then turn theunit on.

3. Use Figure22.6asaguide toattachthreeelectrodes to

your labpartner. Placeone electrodeon themedialaspect

ofeach

Leg just

above theankle

and

athirdelectrode

on

the

anterior

wristof therightforearm. Attach thewhite

electrode lead to therightforearm, theredleadtotheleft

ankle,

and

theblackleadto the rightankle.

4. StarttheBiopac

Student

LabSystem,chooseLesson5

(L05-ECG-l), and

clickOK.

When prompted, enter

a

unique filenameand clickOK.

5. Clickon theCalibrate

button

and waitwhilethecom-

puter

adjusts for optimal recording.The calibrationproce-

dure

willautomatically

stop

after8seconds.

6.

If

thereisasmallECGwaveformwitha relativelyflat

baseline,then calibrationwassuccessful. Ifnot ,clickon

theRedo

Calibration button

,check allconnections,

and

repeatstep 5.

Recording Data

Inthisactivity, youwill recordthe ECG from your lab partner

under

fourconditions: lying

down

,aftersitting

up

,whilebreath-


9/13

CARDIOVASCU LAR

PHYSIOLOGY

still. Electrical actIvit)' from muscular movements, like that

B.OpdCSludent I ~ b

flJ - TaJ·lOS

recordedinanEMG,can corrupt the ECG signal.

Fie Edit Transform Display lessons Help

1. With your labpartner lyingcomfortably, click

on

the

Recordbutton.

2. Wait20

seconds

and th enclickon theSuspend button.If

thedatadonotappearcorrector havesignificantbaseline

drift, thenclickontheRedobutton and repeatthis

recordingsegment.

3. Instruct yourlabpartner toqUicklysitupright.Immedi

atelyclickon theResumebutton assoon as

he or

she

is

sittingfullyupright. AmarkerlabeledAftersitting

up

will

beautomaticallyins ertedinto the recording.

4.

Recordfor 20seconds and thenclick

on

theSuspend but

ton

.

I f

thedatadonot appearco rrect,thenclickon the

Redo

button

and repeatthis reco rdingsegment.

5. With yourpartner remainingsea ted,clickon theResume

button.AmarkerlabeledDeep

breathing

will beautomat

icallyinsertedintotherecording.

6.

Recordfor 20secondsand thenhave

your

lab

partner

take

five long,slow,deepbreaths.

You

should

insertmarkersat

thebeginningof eachinhaleand at thesubsequent exhale.

Markersare insertedbypressing theEsckey (Mac)

or

F9

key (PC).

7. Clickon theSuspend buttonand inspectthedata.Deep

breathingmaycausesome baselinedrift.As longasit is

not excessive,youdo notneed to redotherecording.If

thedatacia not appear correct,thenclickon theRedobut

ton,checktheelectrodesandcon nections ,andrepeatthis

recordingsegment.

8. Have

your

labpartner perform anexercise,such aspush-

ups ,jumping jacks ,or running in place to raise theheart

rate. The exerciseperiod

should

lastfor

about

3minutes.

Be careful that theelectrode leadsare not pulled loose

and

are

not obstructing

your partner'smovements. If

necessary,youmayremove theleads,but do not remove

theelectrodes.If

you

do

removethe

le

ads,youmust re

connect th emproperlyimmediatel ya fter theexe rcise is

complete.

Waming Anyone who is phys ically or medically unable to

pe

rform phYSical

exercise should

not

participate

in

this

por-

Iion o th e laboratory activity

9. Onceyourlabpartner

is

seated,

imm

ediatelyclickon the

Resume

button

tocapturetheECGwhile heor she is re

coveringfromexercise.

10. Recordfor 60secondsandclickon the

Suspend

button.

Inspectthedata.Somebaselinedriftisnorma

l. As

long as

it is notexcessive,clicktheDone

button

.i f thedatado

not appearcorrect,clicktheRedo

button

,check theelec

trodesandconnections ,and repeatthissegment.

Data

Analysis

1.

Enterth eReviewSavedData

mode

andselecttheappro

priatedata fil eforLesson5, whichends in-LOS.

E l ~ ~ i l c £ ] ~ D D ~ [ J [ i l l J ~ ~ [ E [ f j J

m

I max I 0.13342mV [TI I none

CG

1.50

1.00

>

5

0.00

-0.50

2716.70 2903.70 31 00.70 3292.70

3484.70

rnliSecondS

Figure22.7 Measuringamplitude

of

the Pwave.

Amplitude

is

mea

su

r

ed by

computingthedifference

in

values between the

last and

firstpoin

ts

of

th

eselected

area

2. Setthreechannelmeasurementboxesas follows:

Ch 2deltaT

Ch2delta

Ch 2

BPM

3. Measure theduration andamplitudeofvariouscompo

nentsofanECG.Thedurationiscalculatedusingthe

delta T measurement.Thismeasurem entcomputes the

differencein timebetween theending andbeginning

pointsof theareaselectedbytheI-beam cursor tool.The

amplitude(mV)ofanECG

component iscalculatedusing

the

delta

measurement.

a. Whenyo uusetheI-beamcursor tool toselectthepeak

andadjacentbaselineofanECG component,themea

surementcomputesthedifferenceinvaluesbetweenthe

lasta

nd

firstpointsoftheselectedarea (Figure22.7).

b. Inorder toaccuratelyselect theproper regionsofthe

ECG,youwillneed tousethemagnifyingglass toolto

zoominonthedesiredheartcycl es. Then ,ifnecessa

ry,

from the

Display

menu,useAutoscale

waveforms

to

scaleandpositiontheECGforoptimalanalysis.

c.

Referto Figure22.5andusetheI-beamcursortoolto

select theappropriateregionsfrom threedifferentcom

pleteheartcycles inSegmentI (atrest ,lyingdown).

Calculatethemean

and recordtheresultsinTable22.4.

tNM wi Do thewavedurations and amplitudes

fall

• h

within normalranges? If anyareabnormal,what

mechanicalor elect ri caleventsareoccurring in theheartat

thistime?

Note Accurately interpreting EeGs

requires significant

training

and practice AIrail ed hea lth care

profeSSional

is best able to


10/13

EXERCI E

TWENTY-TWO

Table 22.4 Components

of

the ECG at Rest Segment 1

Component

Normal

range Cycle 1

Duration of P wave delta T 0.06-0

.12

s

Amplitude

of

P wave delta)

0.1-0.3 mV

Duration of PR interval delta

T

0.12-0.20

s

Duration of

PR

segment delta T

0.06-0

.12

s

Duration of QR5 complex delta

T)

0.06-0.10 S

Amplitude of QR5 complex delta)

0.8-1.2 mV

Duration of the

QT

interval delta

T

0.36-0.44

S

Duration of the

5T

segment delta

T

0.12 s

Duration of the T wave delta

T

0.12-0.16 s

Amplitude of the T wave delta)

0.3 mV

- -

Cycle 2 Cycle 1

Mean

determine what abnonnalUies are due

to

/lonnal variation experi-

mental noise and med

ical

cone/itions.

Do

not be alarmed ifyour

ECC is different from those illustrated or from th e nonnal values

in

the tabl e.

4. Measure

the duration delta

T

of the

cardiac cycle. This

measurem

e

nt

reflects

the amount

of time

between

heart

beats.

Th

e

computer can automatically convert

this mea

surement

to beats per

minute

(BPM ) by

dividing

the delta

T value by 60 seconds. BPM will be displayed in the ap

propriate channel measurement

box.

a. In Segment

1, use the

l-b

eam cursor tool to select a

single cardiac cycle from R wave

peak

to R wave peak

(Figure 22.8). Record

the

duration (delta

T and heart

rat e (BPM) in Table 22.5. Repeat for two additional cy

cles

in Segment

1

and

calculate

the mean

.

b. Repeat step (a) for

each of the

remaining three rec

or

d

ing segments and record

your

results in Table 22 .5. In

Segment 3, Deep Breathing, select three cycles that oc

curred during inspirations and then

repeat

on

three cy

cles that occurred

during expirations.

1.

How does

the

heart

rate (BPM)

change dur

ing ea

ch

of the fOllr experimental conditions?

Describe the

ph

ysiological mec

hanisms causing

these changes.

..ta

_

...

...

.. 1

,,1WlII

2J j-oQ

3

__

V )l

..w

I: _

jJ.

u

Figure 22.8

Measuring

beats

per minute.

Heart

rate

is measured by

computing

the

change in time between the last and first points of the se-

lected a

re

a.

2. How does

the duration

(delta T) of

the

cardiac cycle change

during inspiration and expiration?

What

causes

thi s change?

5. Measure changes in the

duration of

ventricular systole and

diastole that. occur

during

exercise.

The

QT interval

is

de

fined as the. period from the Q wave to the e

nd of

the T

wave.

It

corresponds

to

ventricular

systole. Ventricular di

astole, th en , is measured from

the end

of

the

T wave to the

subsequent

R wave.

a. Transfer the

data you

recorded in Table 22.4 for

the

QT interval into the appropriate cells

of

Table 22.6 for

Segment 1.


11/13

CARDIOVASC ULAR PHYSIOLOGY

Table 22.5 Changes in eart Rate and Duration

of

Cardiac Cycle

Segment

Measurement

Cardiac cycle Mean

Range

1 2 3

I-Resting lying down Delta T

BPM

2-Sitting

up Delta T

BPM

3-Seated, inspiration Delta T

BPM

3-Seated, expiration

erta

T

BPM

4-After

exercise Delta T

BPM

Table 22 6 Changes in Duration delta T of Ventricular Systole and Diastole

Segment

Measurement

Cardiac

cycle Mean

1 2

3

I-Resting lying down QT interval ventricular systole)

End

of T to subsequent R ventricular diastole)

4-After

exercise QT interval ventricular systole)

End

of T to subsequent R ventricular diastole)

b.

Scroll to the ECC waveform from Segment

1.

Using

How does the

duration

(delta T) of ventricular

the I-beam cursor tool, select the region corresponding

ff WrlNj'j

systole and diastole change from resting to after

to ventricular diastole (from the

end of

T to next

R)

exercise?

and record the delta T measurement. Repeat for two

additional cycles.

c. Scroll to Segment 4, After Exercise,

and

measure the

duration of

ventricular diastole an d systole from three

cardiac cycles. Record the results in Table 22.6 and cal

culate the means.


12/13

Name

______________________________________

Exercise Review Sheet

LabSection ____ __________________________

__

ardiovascular

hysiology

Date

______________________________________

1 Describe the physical basis for the first ( lub ) and second

( dup )

heart sounds.

2 Why

is it important for the walls

of

large arteries

to

have an

abundant

supply of elastic

fibers?

3.

What

is

meant

by systolic pressure

and

diastolic pressure?

4

What

is

the pulse pressure? How

is

this value used as a diagnostic tool?

5

Calculate the mean arterial pressure of an individual with a blood pressure of 115170

Questions 6-11: Define the following terms:

6

Cardiac cycle

7

Hypertension

8. Pulse

9

AuscultaLion areas for the

heart


13/13

EXERCISE TWENTY TWO

10. Sphygmomanometer

11. Korotkoff s

sounds

12. Identi fy the

components

of the cardiac conduct ion system

and

describe their function .

13.

What

s an electrocardiogram (ECG)? Correlate the various wave patterns on a

normal

ECG with events that occur

during

the cardiac cycle.

cardiovascular physiology lab

Documents