Lecture Clinical procedures for medical assisting (4/e): Chapter 21 – Booth, Whicker, Wyman

CHAPTER

21
Electrocardiography
and Pulmonary
Function Testing
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21­2

Learning Outcomes
21.1 Describe the anatomy and physiology of the
heart.
21.2 Explain the conduction system of the heart.
21.3 Describe the basic patterns of an
electrocardiogram (ECG).
21.4 Identify the components of an
electrocardiograph and what each does.
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21­3

Learning Outcomes (cont.)
21.5 Explain how to position the limb and
precordial electrodes correctly.
21.6 Describe in detail how to obtain an ECG.
21.7 Identify the various types of artifacts and
potential equipment problems and how to
correct them.

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21­4

Learning Outcomes (cont.)
21.8 Identify how the ECG is interpreted.
21.9 Identify common arrhythmias.
21.10 Summarize exercise electrocardiography.
21.11 Explain the procedure of Holter
monitoring.
21.12 Describe forced vital capacity.
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21­5

Learning Outcomes (cont.)
21.13 Describe the procedure of performing
spirometry.
21.14 Describe the procedure for obtaining a
performing peak expiratory flow rate.
21.15 Describe the procedure for performing pulse
oximetry testing.

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21­6

Introduction
• Patients often have cardiovascular
or respiratory problems
• Medical assistant
–

–

Perform screening and/or diagnostic
testing
Understand the anatomy and physiology of
the heart and respiratory system

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21­7

The Medical Assistant’s Role
• Electrocardiography
– Graphic recording of the
electrical impulses of the
heart
– Uses
• Evaluate symptoms of heart
disease
• Check effectiveness or side
effects of medications
• General examination

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21­8

The Medical Assistant’s Role (cont.)
• Pulmonary function tests
– Measure and evaluate a
patient’s lung capacity and
volume
– Uses
• Help detect and diagnose
pulmonary problems
• Monitor respiratory
disorders
• Evaluate effectiveness of
treatments
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21­9

Anatomy of the Heart
• Muscular double pump
– Right – receives blood from the body, sends it
to the lungs
– Left – receives blood from the lungs, sends it
out to all parts of the body

• Four chambers

– Two atria
– Two ventricles

• Valves
• Septum
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21­10

Physiology of the Heart
• Systole – contraction phase
• Diastole – relaxation phase
• Cardiac cycle – sequence of contraction
and relaxation
• Cardiac muscle fibers are interconnected
so when one is stimulated to contract, all
fibers in the group contract.

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21­11

Conduction System of the Heart
• Cardiac cycle
– Controlled by
specialized tissues
in the heart wall
that transmit

electrical impulses
– Impulses cause
muscle to contract
and relax

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21­12

Conduction System of the Heart (cont.)
SA Node
Pacemaker of
the heart
Sets rhythm of
contractions

AV Node
Bottom of right
atrium
Impulse delayed
slightly

Bundle of His
Located in septum
between ventricles

Bundle Branches
Relay impulse to
Purkinje fibers

Purkinje Fibers
Located in
ventricle walls
Contraction of
ventricles

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21­13

Conduction System of the Heart (cont.)
•

Electrocardiography
–

Transmission, magnitude,
and duration of electrical
impulses of the heart

•

Polarity
–
–

Having a positive and
negative pole

Resting cell
• Positive outside
• Negative inside

• Depolarization
– Impulse that initiates a
contraction

• Repolarization
– Period of electrical
recovery following
depolarization
– Prior to polarized (resting)
state

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21­14

Conduction System of the Heart (cont.)
• Basic pattern of the ECG
– Waves (deflections) are labeled P, Q, R, S,
T, U

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21­15

Apply Your Knowledge
True or False

ANSWER:

F The AV node is the heart’s pacemaker. SA
___
F The medical assistant does not perform ECGs or PFTs.
___

may

T The bundle branches relay impulses to the Purkinje fibers in
___
the ventricles.
T The heart is resting in the polarized state.
___
T Depolarization initiates contractions of atria and ventricles.
___
F Repolarization occurs before depolarization.
___

following

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21­16

The Electrocardiograph

• Electrical impulses
are detected
through the skin
– Measures
– Amplifies – signal
is increased
– Records using the
stylus

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21­17

The Electrocardiograph (cont.)
• Types of
electrocardiographs
– Standard machine –
12-lead, which records
12 different views at
once
– Single channel –
one lead and records
only one view

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21­18

The Electrocardiograph (cont.)
• Electrodes and
electrolyte products
– Electrolyte – enhances
transmissions of
electric
current
– Electrodes
• Ten areas of the body
– Right and left arms
– Right and left legs
– Six locations on the
chest

• Enables physician to
pinpoint origin of
problems

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21­19

The Electrocardiograph (cont.)
• Leads
– Provide different images of electrical activity
– Marked automatically on the ECG
– Limb leads
• Three standard – I, II, III
• Three augmented – AVF, AVR, AVL

– Precordial leads – V1 through V6

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21­20

The Electrocardiograph (cont.)
• ECG paper
– Single or multichannel
available

0.04 sec

0.2 sec

– Heat- and pressuresensitive

1 mm
(0.1 mV)

– Standardized to permit
uniform interpretation
– Vertical axis – strength

5 mm
(0.5 mV)

5 mm

1 mm

of impulse (millivolt)
– Horizontal axis – time
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21­21

The Electrocardiograph (cont.)
• Controls
– Standardization
control
– Speed selector –
25mm/sec standard
– Sensitivity control –
adjusts height of
tracing

– Centering control –
adjusts position of
stylus
– Line control – adjusts
darkness of line
– On/Off switch

– Lead selector –
enables selection of a
single lead

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21­22

Apply Your Knowledge
Matching: ANSWER:
G Adjusts position of stylus
___

A. Vertical axis

B Adjusts height of tracing
___

B. Sensitivity control

H Adjusts darkness of tracing
___

C. Precordial leads

A Measures strength of impulse
___

D. Horizontal axis

D Measures time
___

E. Limb leads

E AVF, AVR, AVL
___

F. Amplification

C V1 through V6
___

G. Centering control

F Increases signal
___

H. Stylus temperature control

Superbly
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21­23

Preparing to Obtain an ECG
• Proper technique essential
• Preparing the room and equipment
– Other electrical equipment turned off
– Quiet room, comfortable temperature
– Check machine
• Warm up

• Adequate paper

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21­24

Preparing to Obtain an ECG (cont.)
• Preparing the patient
– Introduce yourself
– Explain the procedure
– Answer questions
– Ensure patient comfort
– Perform ECG procedure

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Applying the Electrodes and the Connecting
Wires

21­25

• Electrodes –
disposable are most
common
• Positioning electrodes
– Use consistent
technique
– Limb electrodes –

place at same level
– Precordial electrodes –
specific intercostal
spaces

Precordial Lead
Placement

© 2011 The McGraw-Hill Companies, Inc. All rights reserved.