ELECTROCARDIOGRAPHY I

Physiology Lessons for use with the

Biopac Student Lab

Lesson 5

ELECTROCARDIOGRAPHY I Components of the ECG

PC running Windows®

98SE, Me, 2000 Pro, XP Pro/Home/Media

Manual Revision PL3.7.0 11.16.07

Richard Pflanzer, Ph.D. Associate Professor

Indiana University School of Medicine Purdue University School of Science

J.C. Uyehara, Ph.D.

Biologist BIOPAC Systems, Inc.

William McMullen

Vice President BIOPAC Systems, Inc.

BIOPAC Systems, Inc. 42 Aero Camino, Goleta, CA 93117 (805) 685-0066, Fax (805) 685-0067

Email: [email protected] Web Site: http://www.biopac.com

© BIOPAC Systems, Inc.

Page 2 Biopac Student Lab

I. INTRODUCTION

The main function of the heart is to pump blood through two circuits:

1. Pulmonary circuit: through the lungs to oxygenate the blood and remove carbon dioxide; and 2. Systemic circuit: to deliver oxygen and nutrients to tissues and remove carbon dioxide.

Because the heart moves blood through two separate circuits, it is sometimes described as a dual pump.

In order to beat, the heart needs three types of cells:

1. Rhythm generators, which produce an electrical signal (SA node or normal pacemaker); 2. Conductors to spread the pacemaker signal; and 3. Contractile cells (myocardium) to mechanically pump blood.

The Electrical and Mechanical Sequence of a Heartbeat

The heart has specialized pacemaker cells that start the electrical sequence of depolarization and repolarization. This property of cardiac tissue is called inherent rhythmicity or automaticity. The electrical signal is generated by the sinoatrial node (SA node) and spreads to the ventricular muscle via particular conducting pathways: internodal pathways and atrial fibers, the atrioventricular node (AV node), the bundle of His, the right and left bundle branches, and Purkinje fibers (Fig 5.1).

Fig. 5.1 The Heart

When the electrical signal of a depolarization reaches the contractile cells, they contract. When the repolarization signal reaches the myocardial cells, they relax. Thus, the electrical signals cause the mechanical pumping action of the heart.

The SA node is the normal pacemaker of the heart, initiating each electrical and mechanical cycle. When the SA node depolarizes, the electrical stimulus spreads through atrial muscle causing the muscle to contract. Thus, the SA node depolarization is followed by atrial contraction.

The SA node impulse also spreads to the atrioventricular node (AV node) via the internodal fibers. (The wave of depolarization does not spread to the ventricles right away because there is nonconducting tissue separating the atria and ventricles.) The electrical signal is delayed in the AV node for approximately 0.20 seconds when the atria contract, and then the signal is relayed to the ventricles via the bundle of His, right and left bundle branches, and Purkinje fibers. The Purkinje fibers relay the electrical impulse directly to ventricular muscle, stimulating the ventricles to contract (ventricular systole). Repolarization of the SA node is also spread throughout the atria, and then the ventricles, starting the relaxation phase (ventricular diastole).

Although the heart generates its own beat, the heart rate (beats per minute or BPM) and strength of contraction of the heart are modified by the sympathetic and parasympathetic divisions of the autonomic nervous system.

The sympathetic system acts as an accelerator, speeding up and increasing the contractile force of the heart. Whenever oxygen demands increase, e.g., during exercise or if blood pressure drops, the sympathetic input

Lesson 5: ECG I Page 3 increases, causing heart rate and strength of contraction to increase. Sympathetic influence increases during inhalation.

The parasympathetic input acts like a brake, slowing down the heart. When you relax, the parasympathetic input becomes dominant and the heart rate slows. Parasympathetic influence increases during exhalation.

The Electrocardiogram (ECG)

Just as the electrical activity of the pacemaker is communicated to the cardiac muscle, “echoes” of the depolarization and repolarization of the heart are sent through the rest of the body. By placing a pair of very sensitive receivers (electrodes) on other parts of the body, the echoes of the heart’s electrical activity can be detected. The record of the electrical signal is called an electrocardiogram (ECG). You can infer the heart’s mechanical activity from the ECG.

Components of the ECG

The electrical events of the heart are usually recorded on the ECG as a pattern of a baseline broken by a P wave, a QRS complex, and a T wave (Fig. 5.2).

Fig. 5.2 Components of the ECG

In addition to the wave components of the ECG, there are intervals and segments.

The baseline (isoelectric line) is a straight line on the ECG. It is a point of departure of the electrical activity of depolarizations and repolarizations of the cardiac cycles.

The P wave results from atrial depolarization.

QRS complex is a result of ventricular depolarization and initiates ventricular contraction.

The T wave results from ventricular repolarization.

An interval is part of the ECG containing at least one wave and a straight line. For example, the PR interval includes the P wave and the connecting line before the QRS complex.

A segment is the period of time from the end of one wave to the beginning of the next wave. For example, the PR segment represents the time of AV nodal delay and transmission to the ventricles.

Page 4 Biopac Student Lab Table 5.1 Components of the ECG

COMPONENTS OF THE ECG Segment Measurement points… Represents… P wave begin and end on the (baseline);

normally upright in standard limb leads depolarization of atrial muscle as negativity spreads from the SA node toward the ventricles

P-R Interval from start of P wave to start of QRS complex

time it takes for the impulse sent from the SA node to travel to the ventricles

P-R Segment from end of P wave to start of QRS complex

interval between atrial depolarization and ventricular polarization

QRS complex begin and end on the isoelectric line (baseline) from start of Q wave to end of S wave

spread of excitation through ventricular myocardium—results in depolarization of ventricular muscle. Repolarization is also part of this segment, but the electrical signal for atrial repolarization is masked by the larger QRS complex (see Fig 5.2)

S-T Segment interval between end of S wave and start of T wave

period during which ventricles are more or less uniformly excited

T wave begin and end on the isoelectric line (baseline)

beginning of ventricular relaxation (restoration of ventricular myocardium to resting or excitable state)

Q-T Interval start of QRS complex to end of T wave electrical systole (when ventricular beat is generated)

Electrical activity varies through the ECG cycle as shown below (Fig. 5.3):

Fig. 5.3 Electrical Activity (+ or -) during the ECG

Because the ECG reflects the electrical activity, it is a useful “picture” of heart activity. If there are interruptions of the electrical signal generation or transmission, the ECG changes. These changes can be useful in diagnosing changes within the heart. During exercise, however, the position of the heart itself changes, so you cannot standardize or quantify the voltage changes.

Leads

The particular arrangement of two electrodes (one positive, one negative) with respect to a third electrode (the ground) is called a lead. The electrode positions for the different leads have been standardized. For this lesson, you will record from Lead II, which has a positive electrode on the left ankle, a negative electrode on the right wrist, and the ground electrode on the right ankle. Typical Lead II values are shown in Table 5.2.

Lesson 5: ECG I Page 5

Table 5.2 Normal Lead II ECG Values (Wrist & Ankle Electrodes)*

PHASE

DURATION (second)

AMPLITUDE (millivolts)

P wave 0.06 – 0.11 < 0.25 P-R interval 0.12-0.20 P-R segment 0.08 QRS complex (R) < 0.12 0.8 - 1.2 S-T segment 0.12 Q-T interval 0.36-0.44 T wave 0.16 < 0.5

* Tabled values represent results from a typical Lead II setup (wrist and ankle electrode placement); values for torso placement would be different.

Proper electrode attachment to the subject will influence the quality of data collected. In addition, many factors—normal and abnormal—determine R wave amplitude.

Normal factors include body size (BSA) and distribution of body fat, heart size (ventricular mass), position of the heart in the chest relative to lead locations, metabolic rate, and others.

Abnormal factors include hyper- and hypothyroidism, ventricular hypertrophy (observed for example, in chronic valvular insufficiency), morbid obesity, essential hypertension and many other pathologic states.

Effects of the Resting Respiratory Cycle on Heart Rate

Temporary minor increases and decreases in heart rate associated with the resting respiratory cycle reflect heart rate adjustments made by systemic arterial and systemic venous pressure receptor (baroreceptor) reflexes in response to the cycling of intrathoracic pressure (Fig. 5.4).

When inspiratory muscles contract, pressure within the thorax (intrathoracic pressure) decreases, allowing thoracic veins to slightly expand. This causes a momentary drop in venous pressure, venous return, cardiac output, and systemic arterial blood pressure. The carotid sinus reflex normally decreases heart rate in response to a rise in carotid arterial blood pressure. However, the momentary drop in systemic arterial blood pressure during inspiration reduces the frequency of carotid baroreceptor firing, causing a momentary increase in heart rate.

When inspiratory muscles relax, resting expiration passively occurs. During early resting expiration, intrathoracic pressure increases causing compression of thoracic veins, momentarily increasing venous pressure and venous return. In response, systemic venous baroreceptors reflexively increase heart rate. However, the slight increase in heart rate is temporary because it increases cardiac output and systemic arterial blood pressure, which increases carotid baroreceptor firing causing heart rate to decrease.

The average resting heart rate for adults is approximately 70 beats/min. Slower heart rates are typically found in individuals who regularly exercise. Athletes are able to pump enough blood to meet the demands of the body with resting heart rates as low as 50 beats/min. Athletes tend to develop larger hearts, especially the muscle in the left ventricle—a condition known as “left ventricular hypertrophy.” Because athletes (usually) have larger and more efficient hearts, their ECGs may exhibit differences other than average resting heart rate. For instance, low heart rate and hypertrophy exhibited in sedentary individuals can be an indication of failing hearts but these changes are “normal” for well-trained athletes.

Page 6 Biopac Student Lab

Fig. 5.4 Effects of The Resting Respiratory Cycle on Heart Rate

In this lesson, you will record the ECG under four conditions.

Because ECGs are widely used, basic elements have been standardized to simplify reading ECGs.

ECGs have standardized grids of lighter, smaller squares and, superimposed on the first grid, a second grid of darker and larger squares (fig. 5.5). The smaller grid always has time units of 0.04 seconds on the x-axis and the darker vertical lines are spaced 0.2 seconds apart. The horizontal lines represent amplitude in mV. The lighter horizontal lines are 0.1 mV apart and the darker grid lines represent 0.5 mV.

Figure 5.5 standard ECG Grid

Lesson 5: ECG I Page 7

II. EXPERIMENTAL OBJECTIVES 1) To become familiar with the electrocardiograph as a primary tool for evaluating electrical events within the heart.

2) To correlate electrical events as displayed on the ECG with the mechanical events that occur during the cardiac cycle.

3) To observe rate and rhythm changes in the ECG associated with body position and breathing.

III. MATERIALS BIOPAC electrode lead set (SS2L)

BIOPAC disposable vinyl electrodes (EL503), 3 electrodes per subject

Cot or lab table and pillow

BIOPAC electrode gel (GEL1) and abrasive pad (ELPAD) or Skin cleanser or alcohol prep

Computer system

Biopac Student Lab 3.7 for PC running Windows

BIOPAC data acquisition unit (MP35/30)

BIOPAC wall transformer (AC100A)

BIOPAC serial cable (CBLSERA) or USB cable (USB1W) if using a USB port

IV. EXPERIMENTAL METHODS For further explanation, use the online support options under the Help Menu.

A. SET UP FAST TRACK Set Up DETAILED EXPLANATION OF SET UP STEPS

1. Turn the computer ON. The desktop should appear on the monitor. If it does not appear, ask the laboratory instructor for assistance.

2. Make sure the BIOPAC MP35/30 unit is turned OFF.

3. Plug the equipment in as follows:

Electrode lead (SS2L) — CH 2 Plugs into Channel 2

SS2L Electrode Lead Set Fig. 5.6

4. Turn the BIOPAC MP35/30 unit ON.

Set Up continues…

Page 8 Biopac Student Lab

5. Place three electrodes on the Subject as shown in Fig. 5.7.

left legRED lead

right legBLACK lead

(ground)

right forearmWHITE lead

Fig. 5.7

Place one electrode on the medial surface of each leg, just above the ankle. Place the third electrode on the right anterior forearm at the wrist (same side of arm as the palm of hand).

Note: For optimal electrode adhesion, the electrodes should be placed

on the skin at least 5 minutes before the start of the Calibration procedure.

6. Attach the electrode lead set SS2L to the electrodes following Fig. 5.7.

Each of the pinch connectors on the ends of the electrode lead cables needs to be attached to a specific electrode. The lead cables are each a different color, and you should follow Fig. 5.7 to ensure that you connect each cable to the proper electrode.

The pinch connectors work like a small clothespin, but will only latch onto the nipple of the electrode from one side of the connector.

When the electrode leads are connected properly, the LEAD II electrode configuration will be established.

7. Have the Subject lie down and relax. Position the electrode cables such that they are not pulling on the electrodes. Connect the electrode cable clip (where the cable meets the three individual colored wires) to a convenient location (can be on the Subject’s clothes). This will relieve cable strain.

The Subject should not be in contact with nearby metal objects (faucets, pipes, etc.), and should remove any wrist or ankle bracelets.

8. Start the BIOPAC Student Lab program.

9. Choose Lesson L05-ECG-1. 10. Type in your filename.

Type in a unique identifier.

11. Click OK.

12. Optional: Set Heart Rate display: a) Choose File > Preferences. b) Select “Heart Rate Data.” c) Select “Calculate and display

Heart Rate data” and click OK.

END OF SET UP

This ends the default Set Up procedure.

The default lesson will display ECG data only, but the lesson can be set up to calculate and display Heart Rate data as well. To calculate and display Heart Rate data, the lesson Preference must be established prior to Calibration.

When the Heart Rate Preference is established, Heart Rate data will be calculated and displayed on CH 40 during the Recording and Analysis modes (Heart Rate data is not displayed for Calibration).

Lesson 5: ECG I Page 9

B. CALIBRATION The calibration procedure establishes the hardware’s internal parameters (such as gain, offset, and scaling) and is critical for optimum performance. Pay close attention to the following calibration steps.

FAST TRACK Calibration DETAILED EXPLANATION OF CALIBRATION STEPS

1. Double check the electrodes, and make sure the Subject is relaxed.

Make sure the electrodes adhere securely to the skin. If they are being pulled up, you will not get a good ECG signal.

The Subject must be relaxed and as still as possible during the calibration procedure. The electrocardiograph is very sensitive to small changes in voltage caused by contraction of skeletal muscles, and the Subject’s arms and legs need to be relaxed so that the muscle (EMG) signal does not corrupt the ECG signal.

2. Click Calibrate. The Calibrate button is in the upper left corner of the Setup window. This will start the calibration recording.

The Subject needs to remain relaxed throughout calibration.

3. Wait for the calibration procedure to stop.

The calibration procedure will stop automatically after eight seconds.

4. Check the calibration data:

If correct, proceed to Data Recording

If incorrect, Redo Calibration.

END OF CALIBRATION

At the end of the 8-sec calibration recording, there should be a recognizable ECG waveform with no large baseline drifts.

Fig. 5.8

If your data resembles Fig. 5.8 (with allowance for any difference in vertical scaling), proceed to the Data Recording section.

If the data shows any large baseline drifts, you should check your electrodes for good contact and redo the calibration by clicking Redo Calibration and repeating the entire calibration sequence.

Page 10 Biopac Student Lab

C. RECORDING LESSON DATA FAST TRACK Recording DETAILED EXPLANATION OF RECORDING STEPS

1. Prepare for the recording and have the Subject lie down and relax.

You will record the Subject in four conditions: Lying down, After sitting, Breathing deeply, and After exercise. The Subject will perform tasks in the intervals between recordings.

In order to work efficiently, read this entire section so you will know what to do for each recording segment.

The Subject should remain in a supine position and continue to relax while you review the lesson.

Check the last line of the journal and note the total amount of time available for the recording. Stop each recording segment as soon as possible so you don’t use an excessive amount of time (time is memory).

Hints for obtaining optimal data: a) The Subject should not talk or laugh during any of the recording

segments. b) The Subject should be in a relaxed state for each recording segment

and in the position noted for each segment. c) When asked to sit up, the Subject should do so in a chair, with arms

relaxed on the armrest (if available). d) For Steps 6 and 7: Click Resume as soon as possible after the

Subject sits up in order to capture the heart rate variation, but not while the Subject is in the process of sitting up or there will be excessive motion artifact.

e) The Subject should be as still as possible during the recording segment. The electrocardiograph is very sensitive to small changes in voltage caused by contraction of skeletal muscles, and the Subject’s arms and legs need to be relaxed so that the muscle (EMG) signal does not corrupt the ECG signal.

Segment 1 — Lying down 2. Click Record. When you click Record, the recording will begin and an append marker

labeled “Lying down” will automatically be inserted.

3. Record for 20 seconds. Subject is lying down (seconds 0-20).

4. Click Suspend. The recording should halt, giving you time to review the data and prepare for the next recording segment.

5. Review the data on the screen.

If correct, go to Step 6.

Recording continues…

If all went well, your data should look similar to Fig. 5.9 and you can proceed to Step 6.

Fig. 5.9 Lying down

Lesson 5: ECG I Page 11

If incorrect, click Redo. The data would be incorrect if: a) The Suspend button was pressed prematurely. b) An electrode peeled up causing a large baseline drift, spike, or loss

of signal. c) The Subject has too much muscle (EMG) artifact.

In this case, you should redo the recording by clicking Redo and repeating Steps 2-5. Note that once you press Redo, the data you have just recorded will be erased.

Segment 2 — After sitting up

6. Have the Subject quickly get up and sit in a chair, with arms relaxed.

Subject should sit with arms relaxed, preferably in a chair with armrests.

In order to capture the heart rate variation, it is important that you resume recording as quickly as possible after the Subject sits. However, it is also important that you do not click Resume while the Subject is in the process of sitting or you will capture motion artifact.

7. Click Resume as soon as possible once the Subject sits and relaxes.

When you click Resume, the recording will continue and an append marker labeled “After sitting up” will be automatically inserted.

8. Record for 20 seconds and have Subject take in 5 deep breaths during recording.

Recorder should insert event markers at a corresponding inhale and exhale.

∇ “Inhale”

∇ “Exhale”.

Subject is seated (seconds 21-40).

During this time, the Recorder should insert an event marker at the beginning of an inhale and insert another event marker at the corresponding exhale. The Recorder should label these markers “Inhale” and “Exhale.”

These event markers will help you locate data to complete Table F in the Data Report.

9. Click Suspend. The recording should halt, giving you time to review the data and prepare for the next recording segment.

10. Review the data on the screen.

If correct, and more segments are required, go to Step 11.

If all went well, your data should look similar to Fig. 5.10 and you can proceed to Step 11.

Fig. 5.10 After Sitting Up

If incorrect, click Redo. The data would be incorrect for the reasons in Step 5.

If incorrect, you should redo the recording by clicking Redo and repeating Steps 6-10. Note that once you press Redo, the data you have just recorded will be erased.

Recording continues…

Page 12 Biopac Student Lab Segment 3— Seated, Deep Breathing

11. Click Resume. When you click Resume, the recording will continue and an append marker labeled “Deep breathing” will be automatically inserted.

12. Record for 20 seconds and have Subject take in 5 deep breaths during recording.

Recorder should insert event markers at a corresponding inhale and exhale.

∇ “Inhale”

∇ “Exhale”

Subject is seated (seconds 41-60).

After the recording begins, the Subject should start a series of slow, prolonged breaths, continuing for five cycles.

Note: It is important to breathe with long, slow, deep breaths in order to minimize the EMG artifact.

During this time, the Recorder should insert an event marker at the beginning of each inhale and insert another event marker at the corresponding exhale. The Recorder should label these markers “Inhale” and “Exhale.”

These event markers will help you locate data to complete Table F in the Data Report.

13. Click Suspend. The recording should halt, giving you time to prepare for the next recording segment.

14. Review the data on the screen.

If correct, go to Step 15.

If all went well, your data should look similar to the Fig. 5.11 and you can proceed to Step 15.

Fig. 5.11 Deep Breathing

If incorrect, click Redo. The data would be incorrect for the reasons in Step 5. Note: The Deep Breathing recording may have some baseline drift (as shown previously in Fig. 5.11). Baseline drift is fairly normal and unless it is excessive, it does not necessitate redoing the recording. If incorrect, you should redo the recording by clicking Redo and repeating Steps 11-14. Note that once you press Redo, the data you have just recorded will be erased.

Segment 4 — After exercise 15. Have the Subject perform an exercise

to elevate his/her heart rate. Subject should perform an exercise to elevate his/her heart rate fairly rapidly, such as push-ups or jumping-jacks.

Note: You may remove the electrode cable pinch connectors so that the Subject can move about freely, but do not remove the electrodes.

If you do remove the cable pinch connectors, you must reattach them following the precise color placement in Fig. 5.4 prior to clicking Resume.

In order to capture the heart rate variation, it is important that you resume recording as quickly as possible after the Subject has performed the exercise. However, it is also important that you do not click Resume while the Subject is exercising or you will capture motion artifact.

Recording continues…

Lesson 5: ECG I Page 13

16. Click Resume. When you click Resume, the recording will continue and an append marker labeled “After exercise” will be automatically inserted.

17. Record for 60 seconds. Subject is seated in a relaxed state, recovering from exercise (seconds 61-120).

18. Click Suspend. The recording should halt.

19. Review the data on the screen.

If correct, go to Step 20.

If all went well, your data should look similar to the Fig. 5.12 and you can proceed to Step 20.

Fig. 5.12 After Exercise

If incorrect; click Redo. The data would be incorrect for the reasons in Step 5.

Note: The “After exercise” recording may have some baseline drift (as shown in Fig. 5.12 above). Baseline drift is fairly normal and, unless excessive, does not necessitate redoing the recording.

If incorrect, you should redo the recording by clicking Redo and repeating Steps 15-19. Note that once you press Redo, the data you have just recorded will be erased.

20. Click Done. A pop-up window with options will appear. Make your choice, and continue as directed.

If choosing the “Record from another Subject” option:

a) Attach electrodes per Set Up Steps 5-7 and continue the entire lesson from Set Up Step 9.

b) Each person will need to use a unique file name.

21. Remove the electrodes. Remove the electrode cable pinch connectors, and peel off the electrodes. Throw out the electrodes (BIOPAC electrodes are not reusable). Wash the electrode gel residue from the skin, using soap and water. The electrodes may leave a slight ring on the skin for a few hours. This is normal, and does not indicate that anything is wrong.

END OF RECORDING

Page 14 Biopac Student Lab

V. DATA ANALYSIS In this section, you will examine ECG components of cardiac cycles and measure amplitudes (mV) and durations (msecs) of the ECG components.

Note: Interpreting ECGs is a skill that requires practice to distinguish between normal variation and those arising from medical conditions. Do not be alarmed if your ECG is different than the examples shown or from the tables and figures in the Introduction.

FAST TRACK Data Analysis DETAILED EXPLANATION OF DATA ANALYSIS STEPS

1. Enter the Review Saved Data mode. Enter the Review Saved Data mode from Lessons menu.

Note Channel Number (CH) designation:

CH 2 ECG Lead II

The data window should come up the same as Fig. 5.13.

Fig 5.13

2. Setup your display window for optimal viewing of four successive beats from Segment 1.

Data Analysis continues…

Fig. 5.14 Sample data from Segment 1

The following tools help you adjust the data window: Autoscale horizontal Horizontal (Time) Scroll Bar Autoscale waveforms Vertical (Amplitude) Scroll Bar Zoom Tool Zoom Previous

Turn Grids ON and OFF by choosing Display>Preferences from the File menu.

Adjust Baseline Button: Allows you to position the waveform up or down in small increments so that the baseline can be exactly zero. This is not needed to get accurate amplitude measurements, but may be desired before making a printout, or when using grids.

Once the Adjust Baseline button is pressed, two more buttons, Up and Down, will be displayed. Simply click on these to move the waveform up or down.

Lesson 5: ECG I Page 15

3. Set up the measurement boxes as follows:

Channel Measurement

CH 2 ΔT (Delta Time)

CH 2 BPM (Beats Per Minute)

CH 2 Δ (Delta Amplitude)

CH 2 max (Maximum Amplitude)

The measurement boxes are above the marker region in the data window. Each measurement has three sections: channel number, measurement type, and result. The first two sections are pull-down menus that are activated when you click on them.

Brief definition of measurements: ΔT: The Delta Time measurement is the difference in time between the end and beginning of the selected area. BPM: The Beats Per Minute measurement first calculates the difference in time between the end and beginning of the area selected by the I-Beam tool (same as ΔT), and divides this value into 60 seconds/minute. Δ: The Delta Amplitude measurement computes the difference in amplitude between the last point and the first point of the selected area. max: Finds the maximum amplitude value within the area selected by the I-Beam tool (including the endpoints).

Note: The “selected area” is the area selected by the I-beam tool (including the endpoints).

4. Using the I-Beam cursor, select the area between two successive R waves.

A

Try to go from R wave peak to R wave peak as precisely as possible. Fig. 5.15 shows an example of the selected area.

Fig. 5.15

5. Take measurements at two other intervals in the current waveform display.

A

6. Zoom in on a single cardiac cycle from Segment 1.

Be sure to stay in the first recorded segment when you select the cardiac cycle.

7. Use the I-Beam cursor and measurement box values (and refer to Fig. 5.2 as necessary) to record the following amplitudes and durations for 3 cycles.

Gather data for 3 cycles. You may paste the measurements into the Journal by using the Edit > Journal > Paste measurement option.

Data Analysis continues…

Page 16 Biopac Student Lab

Durations P wave QT interval PR interval ST segment QRS interval T wave

Amplitudes

P wave T wave QRS complex

Time Interval QT Interval (ventricular systole) End of T wave to subsequent R wave (ventricular diastole)

A

Fig. 5.16 shows a sample setup for measuring P wave amplitude. Note that the Δ measurement shows the amplitude difference between endpoints in the selected area.

Fig. 5.16

Note: See Fig. 5.2 in the Introduction for details of the components of the ECG.

8. Repeat measurements as required for the Data Report.

A, B, C, D

Follow the examples shown above to complete all the measurements required for your Data Report.

9. Save or print the data file. You may save the data to a drive, save notes that are in the journal, or print the data file.

10. Exit the program.

END OF DATA ANALYSIS

END OF LESSON 5 Complete the Lesson 5 Data Report that follows.

Lesson 5: ECG I Page 17

ELECTROCARDIOGRAPHY I ECG I

DATA REPORT

Student’s Name:

Lab Section:

Date: I. Data and Calculations

Subject Profile

Name Height

Age Weight

Gender: Male / Female

A. Supine, Resting, Regular Breathing (using Segment 1 data) Complete the following tables with the lesson data indicated, and calculate the Mean and Range as appropriate.

Table 5.3 From Cardiac Cycle

Measurement Channel 1 2 3 Mean Range ΔT CH 2

BPM CH 2

Table 5.4 ECG Duration Amplitude (mV)

Component Δ T [CH 2] Δ [CH 2] Cycle 1 Cycle 2 Cycle 3 Mean Cycle 1 Cycle 2 Cycle 3 Mean

P wave

PR interval

PR segment

QRS complex

QT interval

ST segment

T wave

Table 5.5 CH 2 Δ T

Ventricular Readings Cycle 1 Cycle 2 Cycle 3 Mean QT Interval (corresponds to Ventricular Systole)

End of T wave to subsequent R wave (corresponds to Ventricular Diastole)

Page 18 Biopac Student Lab

B. Seated, deep breathing Table 5.6

Rhythm CH # Cycle 1 Cycle 2 Cycle 3 Mean

Inspiration

Δ T CH 2

BPM CH 2

Expiration

Δ T CH 2

BPM CH 2

C. Sitting Table 5.7

Heart Rate CH # Cycle 1 Cycle 2 Cycle 3 Mean

Δ T CH 2

BPM CH 2

D. After Exercise Table 5.8

CH 2 Δ T

Ventricular Readings Cycle 1 Cycle 2 Cycle 3 Mean QT Interval (corresponds to Ventricular Systole)

End of T wave to subsequent R wave (corresponds to Ventricular Diastole)

II. Data Summary and Questions

E. Heart Rate (BPM)

Condition Mean Range

Supine, regular breathing

Seated, deep breathing, inhalation

Supine, deep breathing, exhalation

Sitting, regular breathing

After exercise – start of recording

After exercise – end of recording

Explain the changes in heart rate between conditions. Describe the physiological mechanisms causing these changes.

Lesson 5: ECG I Page 19

F. Duration (Δ T) Rhythm

Measurement Mean Range

Supine, regular breathing

Inhalation

Exhalation

Supine, deep breathing

Inhalation

Exhalation

Are there differences in the cardiac cycle with the respiratory cycle?

Measurement Mean Range

Supine, regular breathing

Ventricular systole

Ventricular diastole

After Exercise

Ventricular systole

Ventricular diastole

What changes occurred in the duration of systole and diastole between resting and post-exercise?

G. Review your Data 1. Is there always one P wave for every QRS complex? Yes No

2. Describe the P and T wave shapes:

3. Do the wave durations and amplitudes for all subjects fall within the normal ranges listed in Table 5.2? Yes No

4. Do the ST-segments mainly measure between –0.1 mV and 0.1 mV? Yes No

5. Is there baseline “drift” in the recording? Yes No

6. Is there baseline “noise” in the recording? Yes No

End of Lesson 5 Data Report