Jordan University of Science & Technology Faculty of Engineering … · 2011-02-20 · Cardiovascular Physiology and Correlation ECG to Peripheral Circulation 1. Cardiovascular Physiology

Jordan University of Science & Technology

Faculty of Engineering

Department of Biomedical Engineering

Experiment Title Page

PART ONE: Bench Experiments Experiment # 1: BioBench I .. 2 Experiment # 2: BioBench II

Experiment # 3: BioBench III

11 16

Experiment # 4: Safety Analyzer .. 22 Experiment # 5: Pulmonary Function Test. ... ... 30 Experiment # 6: Audiometry

36 Experiment # 7: Gait Analysis .............................. 43 PART TWO: Lab view Experiments

Prepared and Edited by: Dr.Naser Hamdi, Dr.Khaldon Saleh, Eng. Shereen Haddad and Eng. Roba Alomari

Jordan University of Science and Technology

Faculty of Engineering Biomedical Engineering Department

Page

Experiment # 1

BioBench I Cardiovascular Physiology and Correlation ECG to Peripheral Circulation

1. Cardiovascular Physiology

Objectives:

To become familiar with the BioBench system.

To record ECG signals during rest and exercise in order to achieve the environmental effects, and patient status on the signal itself.

To understand the ECG signal characteristics in order to relate it to pulse volume as well as pressure.

Equipment Required:

Computer.

Data Acquisition unit.

ETH

256 (Signal Conditioning)

ECG Leads.

Discussion:

Electrocardiogram (ECG)

An electrocardiogram (ECG or EKG) is one of the simplest and fastest procedures used to evaluate the heart. Electrodes (small, plastic patches) are placed at certain locations on your chest, arms, and legs. When the electrodes are connected to the ECG machine by lead wires, the electrical activity of your heart is measured, interpreted, and printed out for the physician's information and further interpretation. It is a non-invasive technique that is commonly used by researchers as a measure of cardiac function. Specific waveforms within the ECG represent the electrical activity associated with mechanical events such as ventricular contraction and relaxation (systole and diastole). These bioelectrical signals are typically very small in amplitude (mV) and an amplifier is required to accurately record, display and analyze the ECG depending on the hardware and software used.

The ECG has a wide array of uses:

Determine whether the heart is performing normally or suffering from abnormalities (e.g. extra or skipped heartbeats - cardiac arrhythmia).

May indicate acute or previous damage to heart muscle (heart attacks) or ischemia of heart muscle (angina).



Page

Can be used for detecting potassium, calcium, magnesium and other electrolyte disturbances.

Allow the detection of conduction abnormalities (heart blocks and in bundle branch blocks).

As a screening tool for ischaemic heart disease during an exercise tolerance test.

Can provide information on the physical condition of the heart (e.g.: left ventricular hypertrophy, mitral stenosis).

Can suggest non-cardiac disease (e.g. pulmonary embolism, hypothermia)

ECG Leads:

An ECG is constructed by measuring electrical potential between various points of the body using a galvanometer. Leads I, II and III are measured over the limbs: I is from the right to the left arm, II is from the right arm to the left leg and III is from the left arm to the left leg. From this, the imaginary point V is constructed, which is located centrally in the chest above the heart. The other nine leads are derived from potential between this point and the three limb leads (aVR, aVL and aVF) and the six precordial leads (V1-6).

Therefore, there are twelve leads in total. Each, by their nature, record information from particular parts of the heart:

The inferior leads (leads II, III and aVF) look at electrical activity from the vantage point of the inferior region (wall) of the heart. This is the apex of the left ventricle.

The lateral leads (I, aVL, V5 and V6) look at the electrical activity from the vantage point of the lateral wall of the heart, which is the lateral wall of the left ventricle.

The anterior leads, V1 through V6, and represent the anterior wall of the heart, or the frontal wall of the left ventricle.

aVR is rarely used for diagnostic information, but indicates if the ECG leads were placed correctly on the patient.

Understanding the usual and abnormal directions, or vectors, of depolarization and repolarization yields important diagnostic information.



Page

The right ventricle has very little muscle mass. It leaves only a small imprint on the ECG, making it more difficult to diagnose than changes in the left ventricle.

The leads measure the average electrical activity generated by the summation of the action potentials of the heart at a particular moment in time. For instance, during normal atrial systole, the summation of the electrical activity produces an electrical vector that is directed from the SA node towards the AV node, and spreads from the right atrium to the left atrium (since the SA node resides in the right atrium). This turns into the P wave on the EKG, which is upright in II, III, and aVF (since the general electrical activity is going towards those leads), and inverted in aVR (since it is going away from that lead).

The normal ECG:

P wave

The P wave is the electrical signature of the current that causes atrial contraction. Both the left and right atria contract simultaneously. Its relationship to QRS complexes determines the presence of a heart block. Irregular or absent P waves may indicate arrhythmia. The shape of the P waves may indicate atrial problems.

QRS

The QRS complex corresponds to the current that causes contraction of the left and right ventricles, which is much more forceful than that of the atria and involves more muscle mass, thus resulting in a greater ECG deflection. The Q wave, when present, represents the small horizontal (left to right) current as the action potential travels through the interventricular septum. Very wide and deep Q waves do not have a septal origin, but indicate myocardial infarction that involves the full depth of the myocardium and has left a scar. The R and S waves indicate contraction of the myocardium itself. Abnormalities in the QRS complex may indicate bundle branch block (when wide), ventricular origin of tachycardia, ventricular hypertrophy or other ventricular abnormalities. The complexes are often small in pericarditis or pericardial effusion.

T wave

The T wave represents the repolarization of the ventricles. The QRS complex usually obscures the atrial repolarization wave so that it is not usually seen. Electrically, the cardiac muscle cells are like loaded springs. A small impulse sets them off, they depolarize and contract. Setting the spring up again is repolarization (more at action potential). In most leads, the T wave is positive. Negative T waves can be signs of disease, although an inverted T wave is normal in V1 (and V2-V3 in African-Americans/Afro-Caribbeans). T wave abnormalities may indicate electrolyte disturbance, such as hyperkalemia and hypokalemia. The ST segment connects the QRS complex and the T wave. It can be depressed in ischemia and elevated in myocardial infarction, and upslopes in digoxin use.



Page

QT interval

The QT interval is measured from the beginning of the QRS complex to the end of the T wave. A normal QT interval is usually about 0.40 seconds. The QT interval as well as the corrected QT interval are important in the diagnosis of long QT syndrome and short QT syndrome. The QT interval varies based on the heart rate.

PR interval

The PR interval is measured from the P wave to the QRS complex. It is usually 0.12 to 0.20 seconds. A prolonged PR indicates a first degree heart block, while a shorting may indicate an accessory bundle, such as seen in Wolff-Parkinson-White syndrome

Procedure:

Recoding ECG on resting state:

1. Connect ETH

256 to the computer, and then turn the computer on.

2. Connect the ECG cable to ETH

256. Be sure to connect it correctly.

3. Attach Electrodes to the left and right wrists of the volunteer. The ground electrode should be connected to one of the volunteer s ankles.

4. The subject should sit quietly with their hands on the table.

5. Configure The ETH

256 as following:

a. The gain Knob for channel 1 should be set to X100. (You can change the gain in order to obtain a clear signal)

b. The filter should be set to 50Hz. c. Offset should be zero.

6. Start the BioBench application.

7. On the (View Menu) option choose 2 Graph Acquisition .

8. Click on the GO button to begin BioBench and to examine the ECG. To make the ECG signal as large as possible, click on the auto scale button. (Note: During recording the ECG signal, any movement of the hands will distort the signal).

9. Click on (logging) to save the ECG signal. Save it in the BioBench /Data folder.(you must change the folder's name)



Page

10. Measure the following parameters on the recorded ECG signal:

* In the acquisition view:

1- Minimum Value of ECG signal. 2- Measure the amplitude of the R wave of the ECG signal.

* In the analysis view:

Select a region of data with three or four heart beat cycles then measure:

a. The amplitude of three P Waves. b. The amplitude of three R Waves. c. The amplitude of three T waves. d. The time interval (in second) between three adjacent R waves.

Measurements are done by placing the first measurement line on the first point to be measured and the second line on the other point. Changes in the X value (dx) can be read from the screen and corresponds to change of time.

e. P-R time interval. f. R-T interval. g. T-P interval.

Acquiring and distinguishing a clean ECG (P-QRS-T) from a student in a lab is a very difficult process (several noise sources interfere with the signal, can you list a few?).

11. Try to open a demonstration/teaching data file (Open ECG#2 60BPM file)

and measure the above mentioned parameters. 12. Calculate the average value for the amplitude of the P wave, QRS wave, and

the T wave. 13. Is the amplitude of the different waves the same in different cardiac cycles?

14. Which wave has the largest amplitude?

15. What is the heart rate?

2. Electrocardiogram & Peripheral Circulation

Objectives:

To measure and correlate the ECG and rate of blood flow in a resting individual.

To study the time sequence between ECG signal and pulse signal.



Page

Equipment Required:

Computer

Data acquisition unit & cable

ETH-256

ECG leads

Plethysmograph

Discussion:

The heart is a hollow, muscular organ in vertebrates that pumps blood through the blood vessels by repeated, rhythmic contractions. The term cardiac means "related to the heart", from the Greek kardia for "heart".

Structure

In the human body, the heart is normally situated slightly to the left of the middle of the thorax, underneath the sternum (breastbone). It is enclosed by a sac known as the pericardium and is surrounded by the lungs. The apex is the blunt point at the base of the heart. A stethoscope can be placed directly over the apex and count the beats. In normal adults, its mass is 250-350 g, but extremely diseased hearts can be up to 1000 g in mass. It consists of four chambers, the two upper atria (singular: atrium) and the two lower ventricles.

A septum divides the right atrium and ventricle from the left atrium and ventricle, preventing blood from passing between them. Valves between the atria and ventricles (atrioventricular valves) maintain coordinated unidirectional flow of blood from the atria to the ventricles.The ventricular systole consists of the contraction of the ventricles and flow of blood into the circulatory system. Again, once all the blood empties from the ventricles, the pulmonary and aortic semilunar valves close. Finally complete cardiac diastole involves relaxation of the atria and ventricles in preparation for refilling with circulating blood.

The function of the right side of the heart is to collect deoxygenated blood from the body and pump it into the lungs so that carbon dioxide can be dropped off and oxygen picked up. This happens through a process called diffusion. The left side collects oxygenated blood from the lungs and pumps it out to the body. On both sides, the lower ventricles are thicker than the upper atria.

Oxygen-depleted or deoxygenated blood from the body enters the right atrium through two great veins, the superior vena cava which drains the upper part of the body and the inferior vena cava that drains the lower part. The blood then passes through the tricuspid valve to the right ventricle. The right ventricle pumps the deoxygenated blood to the lungs, through the



Page

pulmonary artery. In the lungs gaseous exchange takes places and the blood releases carbon dioxide into the lung cavity and picks up oxygen. The oxygenated blood then flows through pulmonary veins to the left atrium. From the left atrium this newly oxygenated blood passes through the mitral valve to enter the left ventricle. The left ventricle then pumps the blood through the aorta to the entire body. Even the lungs take some of the blood supply from the aorta via bronchial arteries.

The left ventricle is much more muscular (1.3 - 1.5 cm thick) than the right (0.3 - 0.5 cm thick) as it has to pump blood around the entire body, which involves exerting a considerable force to overcome the vascular pressure. As the right ventricle needs to pump blood only to the lungs, it requires less muscle.

Even though the ventricles lie below the atria, the two vessels through which the blood exits the heart (the pulmonary artery and the aorta) leave the heart at its top side.

The Cardiac Cycle

The function of the heart is to pump blood around the body. Every single beat of the heart involves a sequence of events known as the cardiac cycle, which consists of three major stages: atrial systole, ventricular systole and complete cardiac diastole. The atrial systole consists of the contraction of the atria and the corresponding influx of blood into the ventricles. Once the blood has fully left the atria, the atrioventricular valves, which are situated between the atria and ventricular chambers, close. This prevents any backflow into the atria. It is the closing of the valves that produces the familiar beating sounds of the heart, commonly referred to as the "lub-dub" sound due to the closing of the semilunar and atrioventricular valves.

The ventricular systole consists of the contraction of the ventricles and flow of blood into the circulatory system. Again, once all the blood empties from the ventricles, the pulmonary and aortic semilunar valves close. Finally complete cardiac diastole involves relaxation of the atria and ventricles in preparation for refilling with circulating blood.

Regulation of the cardiac cycle

Cardiac muscle is self-exciting. This is in contrast with skeletal muscle, which requires either conscious or reflex nervous stimuli. The heart's rhythmic contractions occur spontaneously, although the frequency or heart rate can be changed by nervous or hormonal influences such as exercise or the perception of danger.

The rhythmic sequence of contractions is coordinated by the sinoatrial and atrioventricular nodes. The sinoatrial node, often known as the cardiac pacemaker, is located in the upper wall of the right atrium and is responsible for the wave of electrical stimulation that initiates atria contraction. Once the wave reaches the atrioventricular node, situated in the lower right atrium, it is conducted through the bundles of His and causes contraction of the ventricles. The time taken for the wave to reach this node from the sinoatrial nerve creates a delay between contractions of the two chambers and ensures that each contraction is coordinated



Page

simultaneously throughout all of the heart. In the event of severe pathology, the Purkinje fibers can also act as a pacemaker; this is usually not the case because their rate of spontaneous firing is considerably lower than that of the other pacemakers and hence is overridden.

In this part; the aim is to measure the volume pulse signal; which indicates the pulsatile flow of blood through the finger (peripheral circulation); and correlate it to the recorded ECG signal. The peak of the pulse signal occur from the flow of blood through the finger (peripheral flow) and is detected by a pressure sensor using a strain gauge that detects the pressure exerted due to the flow of blood in the finger. The shift between the peak of QRS complex and the peak of the pulse signal indicates the time needed for the blood to reach the finger; so that there is a small shift in time between the peaks...that is logical; because the QRS complex occurs from the contraction of the ventricles (systole), and the pulse occur when the blood reaches the finger.

Procedure:

ECG and rate of blood flow in a resting volunteer

1. With the computer and all equipment shut down, connect the ETH-256 unit to the computer and restart the computer.

2. Volunteers should remove all jewelry from their wrists and ankles.

3. Plug the ECG cable into Channel 1 on the front panel of the ETH-256 unit .

4. Place the plethysmograph on the distal segment of the middle finger and wrap the Velcro to attach the unit firmly to the end of the finger .

5. Locate the BNC plug on the other end of the cable; push it into Channel 2.

6. The volunteer should sit quietly.

7. The ETH-256 unit should be configured with the following settings:

A. The Gain knob for Channel 1 should be set to X100 and XI on Channel 2. B. The ETH-256 Filter should be set to 50Hz for both Channels 1 & 2. C. Both Channels 1 and 2 should be offset to zero.


9. Under the <View> menu, choose "2 Graph Acquisition".



Page

10. Click on the <GO> button to begin BioBench and examine the ECG. If the

ECG is too small or too large click the Auto scale button to adjust it.

11. Click the <Logging> button, you will be prompted to title and save the data file.

12. Record for about 10 seconds

13. In the Analysis mode, place the first marker on the peak of the R wave.

14. Move the cursor to the peak of the following blood flow trace (pressure) .

15. Read off the time difference (dx).

16. Measure the number of beats per minute of the pressure signal.

17. Open a demonstration/teaching data file (Open ECG#2 60BPM file)

and measure the above mentioned parameters.

Questions

1. What produces the R wave in the ECG?

2. What does the peak of the blood flow trace represent?

3. What processes, therefore, take place between these two events?

4. What, therefore, does this time value represent?

5. Does the falling phase of the blood flow pulse have a small, transient plateau or upward deflection? This is called the dicrotic notch.

6. Would you expect a transient increase in blood pressure as the elastic arteries recoil after being stretched by blood entering from the ventricles?

7. What effect does cooling and warming on the amplitude of the pulse signal?

8. Through what mechanism does cooling and warming affect the peripheral circulation?



Page

Experiment # 2

BioBench II Electromyograms (EMGs)

Objectives:

1. Students measure the bioactivity accompanying muscular activity 2. To study the relation between EMG signal and Hand grip signal. 3. To learn how to achieve and record EMG signal. 4. To determine the relationship between EMG intensity and force contraction in

the subject s dominant and non-dominant arm 5. To examine the relationship between tetanus and movement. 6. To determine the rate of fatigue in the dominant and non-dominant forearms

Equipment Required:

Computer

Data acquisition unit & cable ETH-256.

EMG leads and Hand dynamometer

Discussion:

Small electrical currents are generated by muscle fibers prior to the production of muscle force. These currents are generated by the exchange of ions across muscle fibers to membranes, apart of the signaling process for the muscle fibers to contract. The signal called the electromyogram (EMG) can be measured by applying conductive elements or electrodes to the skin surface or invasively within the muscle. Surface EMG is the more common method of measurement, since it is non-invasive and can be conducted by personnel other than medical doctors, with minimal risk to the subject.

Measurement of surface EMG is dependent on a number of factors and the amplitude of the surface EMG signal (sEMG) varies from the V to low mV range.

The amplitude, time and frequency domain properties of the sEMG signal are dependent on factors such as:

The timing and intensity of muscle contraction.

The distance of the electrode from the active muscle area.

The properties of the overlying tissue (e.g. thickness of overlying skin and adipose tissue.

The electrode and amplifiers properties.



Page

The quality of contact between the electrode and the skin.

An EMG is a test that is used to record the electrical activity of muscle, when muscles are active, they produce an electrical current. This current is usually proportional to the level of muscle activity.

An EMG is also referred to as amyogram, there are two types of EMG:

Intra muscular EMG .

Surface EMG (sEMG).

Intra muscular EMG (The most commonly used type) involves inserting a needle electrode through the skin in to the muscle whose electrical activity is to be measured. Surface EMG (sEMG) involves placing the electrodes on (not into) the skin overlying the muscle to detect the electrical activity of the muscle.

Why is an EMG test done? An EMG is most often performed when patients have unexplained muscle weakness. The EMG helps to distinguish between muscle contractions, in which the problem begins in the muscle and muscle weakness due to nerve disorders, the EMG can also be used to detect true weakness as opposed to weakness from reduced use because of pain or lack of motivation.

What does the EMG signal actually indicate?

When EMG is acquired from electrodes mounted directly on the skin, the signal is a composite of all the muscle fiber action potentials occurring in the muscle(s) underlying the skin. These action potentials occur at somewhat random intervals so at any one moment, the EMG signal may be either positive or negative voltage. Individual muscle fiber action potentials are sometimes acquired using wire or needle electrodes placed directly in the muscle.

What are some of the applications for which EMG might be used?

There are many applications for the use of EMG. EMG is used clinically for the diagnosis of neurological and neuromuscular problems. It is used diagnostically by gait laboratories and by clinicians trained in the use of biofeedback or ergonomic assessment. EMG is also used in many types of research laboratories, including those involved in biomechanics, motor control, neuromuscular physiology, movement disorders, postural control, physical therapy, and many others.

How is the signal processed?

First, the signal is picked up at the electrode and amplified. Typically, a differential amplifier is used as a first stage amplifier. Additional amplification stages may follow. Before being displayed or stored, the signal can be processed to eliminate low-frequency or high-frequency noise, or other possible artifacts. Frequently, the user is interested in the amplitude of the



Page

signal. Consequently, the signal is frequently rectified and averaged in some format to indicate EMG amplitude. However, there are many types of EMG analysis schemes. Procedure:

Exercise 1: EMG Intensity and Force in Dominant Arm

1. With the computer and external devices powered down, connect the ETH-255.

2. The volunteer should remove all jewelry from their wrists and hands.

3. Place a small amount of gel on each electrode. Attach the + and - to the inner right forearm, under the elbow (ask the instructor for the best place).

4. Place the third electrode (ground) on the right wrist

5. Locate the DIN plug on the end of the dynamometer cable; push it into CHANNEL 2.

9. The volunteer should hold the fluid-filled dynamometer ball in the right hand and sit quietly.

10. The ETH-256 unit should be configured with the following settings:

A. The Gain knob for Channel 1 should be set to X1 and X100 on

Channel 2. B. The Filter on Channel 1 should be -set to 50Hz and on Channel

2 it should be 2000. C. Both Channels should be offset to zero.


12. Under the <View> menu, choose "2 Graph Acquisition".

13. Click the <Go> button to begin BioBench. The volunteer should squeeze the ball using single, brief contractions (twitches) of the fingers.

Notice the trace deflection as the ball is squeezed. If the deflection goes off screen when a maximum contraction is produced click <Auto scale> to adjust the range.



Page

14. Start recording by clicking on the <logging> button; the volunteer should

squeeze fist around the hand dynamometer four times, each contraction is two seconds long followed by two seconds of relaxation. Each successive contraction should be approximately two, three, and four times stronger than the first contraction and this is called (twitches).

15. Stop recording after the relaxation period of last contraction.

16. In Analysis mode, scroll back through your data.

17. On the EMG trace, place the two measurement lines immediately at the beginning and the end of the first contraction and read the amplitude.

18. On the dynamometer trace, place the two measurement lines immediately at the beginning and the end of the first contraction and read the amplitude.

19. Repeat steps 17 and 18 for the other three muscle contraction recorded.

20. Use a piece of string and a metric ruler to measure the circumference of the dominant forearm at approximately 3 centimeters below the elbow.

Questions

1. Plot the absolute area of muscle contraction as a function of the absolute area of the EMG signals for each muscle clinch.

2. Is there a correlation between the amplitude of the EMG signal and the force of contraction?

3. Do muscle fibers have a refractory period like nerve fibers?

4. How do you explain the increase in the amplitude of the EMG signal with an increase in contraction?

Hint: if a contraction involves a single twitch of the contracting muscle fibers, how can contraction be increased without making muscle fibers contract more than once?

Exercise 2: EMG Intensity and Force in non-Dominant Arm

Follow the same steps used in Exercise 1.



Page

Exercise 3: EMG Intensity and Fatigue in Dominant arm

1. The volunteer should sit quietly with his or her dominant forearm on the table

top.

2. The subject will squeeze the bulb of the hand dynamometer as tightly and as long as possible in an attempt to fatigue the muscles of the forearm.

3. As time passes, the subject s muscle force will decrease, but at a rate that is dependent on the fitness of the subject.

4. When the subject s muscle strength drops to a level that is below half of the subject s maximum muscle force at the beginning of the recording, the recording will be stopped. This could take as little as 20 or as long as a few minutes.

5. In Analysis mode, place the first marker just before the contraction in the EMG trace and the second to the peak of the contraction and read the amplitude.

6. In the dynamometer trace, place the first marker just before the muscle contraction and the second to the peak muscle force and read the amplitude. (Maximum muscle force).

7. Place one measurement line immediately before the contraction and the second immediately after the contraction and read off the duration (time) of the contraction.

Exercise 4: EMG Intensity and Fatigue in non-Dominant arm

Follow the same steps used in Exercise 3.

Questions

1. Using the EMG data, compare the amplitude of the maximum squeeze with the maximum single twitch contraction. Which is larger? Does this fit with your measurements from the hand dynamometer?



Page

2. If all fibers were contracting in both instances (maximum squeeze and single

twitches) explain why the maximum squeeze produced a more forceful contraction.

3. Compare the duration of this maximum squeeze contraction with the maximum contraction produced by a single twitch -which is longer?



Page

Experiment # 3

BioBench III Breathing Parameters

Objectives:

To achieve and record clean breathing signal.

To study the breathing parameters Vc, RV, .Etc while sitting and standing

Equipment Required:

Computer

A disposable flow head.

Sp-100 Spiro meter.

A cable to connect the Spiro meter unit to the ETH-256

Discussion:

Theory:

When a breath is taken, air passes in through the nostrils, through the nasal passages, into the pharynx, through the larynx, down the trachea, into one of the main bronchi, then into smaller bronchial tubules, through even smaller bronchioles, and into a microscopic air sac called an alveolus. It is here that external respiration occurs. Simply put, it is the exchange of oxygen and carbon dioxide between the air and the blood in the lungs. Blood enters the lungs via the pulmonary arteries. It then proceeds through arterioles and into the alveolar capillaries. Oxygen and carbon dioxide are exchanged between blood and the air. This blood then flows

out of the alveolar capillaries, through venuoles, and back to the heart via the pulmonary veins. For an explanation as to why gasses are exchanged here, see partial pressure.

Respiratory System:

Primary function is to obtain oxygen for use by body's cells & eliminate carbon dioxide that cells produce

Includes respiratory airways leading into (& out of) lungs plus the lungs themselves

Pathway of air: nasal cavities (or oral cavity) > pharynx > trachea > primary bronchi (right & left) > secondary bronchi > tertiary bronchi > bronchioles > alveoli (site of gas exchange)

Respiration occurs at TWO DIFFERENT LEVELS:



Page

A. The level of the CELL

B. The level of the ORGANISM

EXTERNAL RESPIRATION INVOLVES THE RESPIRATORY SYSTEM

Inspiration:

Contraction of external intercostals muscles > elevation of ribs & sternum > increased front- to-back dimension of thoracic cavity > lowers air pressure in lungs > air moves into lungs

Contraction of diaphragm

> diaphragm moves downward > increases vertical dimension of thoracic cavity > lowers air pressure in lungs > air moves into lungs:

Expiration:

Relaxation of external intercostals muscles & diaphragm > return of diaphragm, ribs, & sternum to resting position > restores thoracic cavity to preinspiratory volume > increases pressure in lungs > air is exhaled .

Respiratory Air Volumes

Respiratory air volumes during rest and exercise are of physical and clinical interest and they can be measured using a spirometer. The main volumes of interest are:

Functional Residual Capacity (FRC )

Residual Volume (RV )



Page

Tidal Volume (TV) = amount of air breathed in and out during quiet breathing

Expiratory Reserve Volume (ERV) = amount of air forced out of the lungs in a maximal expiration, over and above that expired in normal breathing

Inspiratory Reserve Volume (IRV) = amount of air inhaled in a maximal inspiration, over and above that inhaled in normal breathing

Vital Capacity (VC) = TV+ERV+IRV

Residual Volume (RV) = volume of air that remains in the lungs at all times (can't be measured by spirometry)

Total Lung Capacity (TLC) = VC+RV

Important definitions:

Spirometer = Instrument used to measure lung volumes

Tidal volume = Volume of air entering or leaving the lungs in a single breath. Normal TV = 500 ml.

Respiratory rate = Number of breaths per minute. Normal RR = 12 - 20 breaths/min.

Dead space = Volume of air in each breath which does not reach the alveoli. This is approximately the volume of the conducting system. Normal dead space = 150 ml

Minute ventilation = Total volume of air breathed per minute. MV = TV x RR.

Spirometry

1. The maneuver is performed rather slowly

The vital capacity is assessed during an inspiratory maneuver. Starting from end-tidal volume the subject expires maximally and subsequently makes a full inspiration. This is the inspiratory vital capacity (IVC).

The vital capacity is assessed during an expiratory maneuver. Starting from end-tidal volume the subjects makes a full expiration and subsequently exhales maximally. This represents the expiratory vital capacity (EVC), or slow vital capacity in the Anglo-American literature.

2. The maneuver is performed with maximal force

If the subject first fills the lung to the fullest (i.e. to total lung capacity), and then exhales forcefully and completely to residual volume, the volume change of the lung is the forced vital capacity (FVC); it would be more correct to speak of forced expiratory vital capacity (FEVC).



Page

If the subject first exhales fully to residual volume, and then inhales forcefully and fully to total lung capacity, the volume change of the lung is the forced inspiratory vital capacity (FIVC).

Procedure:

1. The ETH-256 unit should be configured with the following settings

a. The Gain knob for Channel 1 should be set to 10X

b. The Filter should be set to 50Hz for Channel l.

c. Offset Channel 1 to zero

2. Start the Bio Bench application

Before starting: Breathing will be recorded from a volunteer. It is important that the volunteer is healthy and has no history of respiratory or cardiovascular problems

3. The Spiro meter box should be placed on a flat surface and held firmly in place either using tape or a heavy book

4. The tubes on the flow head should always be in the upright position, to avoid problems with condensation

Breathing in a resting sitting volunteer

1. The volunteer should hold the Spiro meter head with the air flow tubes up. Breath normally -this is difficult when you think about it! The volunteer should sit quietly and become accustomed to breathing through the Spiro meter

2. Ask the volunteer to inhale as much as possible and then exhale as much as possible. The trace should not go off screen and should produce a deflection of at least 50% of the window -if not, adjust the range and repeat if necessary. The volunteer should return to normal breathing through the Spiro meter

3. When ready to begin recording, click on the <Logging> button to begin saving data.

4. After about 5 breathing cycles ask the volunteer to inhale as much as possible.

5. For each of the 5 breathing cycles (prior to the forced inhale and exhale use the marker and the cursor to measure



Page

a. Tidal volume (TV): amplitude average of each of the 5

breathing cycles. b. The duration of each of the 5 breathing cycles (period). c. Measure IR, ER and VC.

Breathing in a resting standing volunteer

Repeat the previous steps while the volunteer is standing

Calculations:

1. Use the mean duration of the breathing cycles to measure breathing rate

Breathing rate = 60 (breaths/minute)/mean time interval.

2. Multiply the mean tidal volume by the breathing rate to calculate the volume of air passing in and out of the resting volunteer's lungs each minute



Page

Experiment # 4 Safety Analyzer

Objectives:

To understand the principles involved in performing electrical safety measurements on medical devices.

To perform acceptance tests on medical devices using an electrical safety analyzer that include main voltage, dual lead voltage, current consumption, insulation resistance, protective earth resistance, earth leakage current, enclosure leakage current , patient leakage current, etc.

Equipment Required:

International safety analyzer

Oscilloscope

Lead selector

ECG cable

Medical Kit (ECG)

Discussion:

Commercially available instruments called Electrical-Safety Analyzers are available for testing both medical-facility power systems and medical appliances. These analyzers range in complexity from simple conversion boxes used with any voltage-ohmmeter to computerized automatic measurement systems. The features to consider are accuracy, ease of use, testing time, and cost. The analyzers also reduce errors caused by incorrect test setups and reduce the risk of shock to person performing tests such as applying line voltage to patient leads to test isolations.

Adequate electrical safety in health-care facilities can be achieved at moderate cost by combining a good power-distribution system, careful selection of well-designed equipment, periodic testing of power systems and equipment, and a modest training program for medical personnel.

For an electrical accident to occur, current of sufficient magnitude must flow through the body of the victim in such a way that it impairs the functioning of vital organs.

The Physiological effect of electrical current:

The physiological effect of the current depends not only on their magnitude



Page

but also on the current pathway through the body, which in turn depend on the location of the contact.

The effect of small current applied directly to the heart is often referred to as microshock

Electric current can affect the tissue in two different ways:

1. The electrical energy dissipated in the tissue resistance can cause a temperature increase, if high enough, tissue damage can occur.

2. An extraneous electric current of sufficient magnitude can cause local voltages that can trigger action potential and stimulate nerves, the stimulation of motor nerves or muscles causes contraction of muscle fiber In the muscles or muscle group

There are three methods of accident prevention:

1. Reliable Grounding design: The design and construction of equipment, excluding self-powered equipment, should insure that all external parts, surfaces, and shields, exclusive of antenna and transmission line terminals, are at ground potential at all times during normal operation. A point on the electrically conductive chassis or equipment frame should serve as the common tie point for static and safety grounding.

2. Reduction of Leakage current: Leakage current is that current which flows through the equipment conductive paths to a solidly grounded source. The equipment leakage current should not exceed 3.5 milliamperes dc or rms.

3. Double insulation of equipment.

Front Panel A Applied Part Terminal: The jacks allow direct connection to banana jacks, or 4mm-to- alligator adapters provided B Red Input Terminal : Single test lead connection



Page

C Black Input Terminal: Used for dual lead testing in combination with red test lead. D Green Input Terminal: Protective Earth of Device Under Test E Power Outlet: Allows standard power plug connection of the Device Under Test. 120V @ 15A or 240V @ 15A maximum F On-Off Switch

Comparable Terminology: International and United States

INTERNATIONAL/IEC U.S./AAMI

L1 Neutral L2 Hot Earth Ground Mains Line Voltage

Applied Parts Patient Leads Enclosure/Case Chassis Protective Earth Ground Wire Earth Leakage Current Leakage in Ground Wire Enclosure Leakage Chassis Leakage Patient Leakage Lead Leakage Patient Auxiliary Leakage between Patient Leads Mains on Applied Parts Lead Isolation Insulation Resistance Dielectric Strength or Insulation Resistance between Hot and Neutral to Ground Earth Resistance Ground Wire Resistance

Keys Used to Enter Device Control Numbers

0 Volts: In single lead mode, displays mains voltage. In dual lead mode, displays voltage between RED and BLACK test leads. 1 Current: Measures the current consumption (in amperes) flowing in the L2 of the device under test. 2 Insulation: Tests insulation resistance (mains to case or applied parts to case). 3 Protective Earth Resistance: Measures the earth resistance using a 1A test current (unless 10A or 25A is selected) using the RED test lead attached to the DUT Protective Earth terminal or enclosure. The front panel outlet power is turned off for this test. * Note: Calibrate the test leads if performing a protective earth resistance test for the first time with a unit or when using a new set of leads. Also calibrate the leads if the unit does not read zero when the test lead is connected between the RED and GREEN input jacks and a measurement is taken. 4 Earth Leakage: easured between the DUT Protective Earth terminal and the Protective Earth

terminal of the 601PRO. 5 Enclosure Leakage: In single-lead mode, measures the enclosure leakage (RED test lead to DUT protective earth on the 601PRO). 6 Patient Leakage: Measures the patient leakage current (applied part to earth).



Page

7 Mains on Applied Part Leakage: Applies 110% mains voltage to selected applied part and measures leakage to earth in both normal and reverse polarity. Does not apply to patient auxiliary selections. 8 Patient Auxiliary Current: Measures the leakage and biasing current between applied parts.

Procedure:

Part 1:

1. Connect the power cable of oscilloscope to the safety analyzer machine. At this time make sure that safety machine in OFF status.

2. Turn ON the safety test machine. Wait until the safety analyzer tests itself. When the test is successfully completed, "Main Menu" appears on the screen.

3. Select (System Setup) Key, Select (setup function). Then select test standard key The select test standard option allows you to choose among IEC 601-1,VDE 701-1, VDE 751-1, HEL 95, IEC 1010, AAMI, AS/NZS 3551.

4. At this part choose IEC 601-1. Note : To enable /disable the test standards that appear at the Main Menu, press Utilities at the Main menu , then More then Enable standards. Press Yes

5. At the enable test standard once the selection is made, the system will automatically return to the main menu where the selected standard is displayed.

6. In order to record the testing times do the following.

7. From the main menu press system setup to access the Select setup Function menu. Press More until time format appear on the screen, choose it, and enter the time of the test.

Selecting the class/Type:

The class /Type selection sets the type of equipment that is being tested. This affects the limits for the protective earth resistance, insulation resistance, and earth leakage.

The class / type should be set to the instrument classification and type before testing.

What is the class and the type of the oscilloscope?

1. On the main menu under class/type menu enter the type and the class of the oscilloscope.

2. Press view present setting key. View present setting allows you to inspect all the entered data. If the entered data are true continue with the following.



Page

3. Press (0) key, main voltage test and lead voltage test.

a. The main voltage test measures and displays the mains voltages from L1 to Earth, L2 to Earth, and L1 to L2.

b. The main voltage test appears on the display L1-Earth =

L2-Earth =

L1-L2 = .

4. Press key (1),Current Consumption Test. The current consumption test is displayed and the test begins immediately.

Current consumption = ..

5. Press on soft key 1 toggle the device polarity from normal to off to reverse. Current consumption = .. 6. Toggle the device outlet from Earth to No Earth by pressing on key (2) Current consumption = ..

7. Toggle the device out let from L2 to No L2. Current consumption = ..

Did the current value change, why?

8. The insulation Resistance tests measure (in Megohms) the resistance from the device outlet L1 and L2 to device earth .The measurement is taken with a test voltage of 500 Volts Dc. The test will not begin until start test is pressed

Insulation resistance =

Do we need very high input resistance, why?

9. Attach the red lead for the safety machine to any conductive part of the oscilloscope.

10. Press shortcut key 3. The protective earth resistance test is displayed.

11. Press soft key 3 to select a test current (1 AMP), the selected test current is displayed in the upper right corner of the display

Protective earth resistance for 1 AMP =

12. In order to measure earth leakage current, from the main menu press short key (4), the

earth leakage test appears on the display and the test begins immediately:

a. soft key 1 toggles the device polarity from normal to off to reverse. b. soft key 2 toggles the device outlet from Earth to no Earth.



Page

c. soft key 3 toggles the device from L2 to no L2.

13. Now, record the output for all the conditions above.

14. To measure the Enclosure leakage current connect the red lead terminal to the safety analyzer machine (on the red front point) and attach it to any metal part in the oscilloscope.

15. Press key (5) on the main menu

a. Soft key 1 toggles the device outlet polarity from normal to off to reverse, or reverse to off to normal.

b. Soft key 2 toggles the device outlet from Earth to no Earth. c. Soft key 3 toggles the device outlet from L2 to no L2.

16. Now , record the data for all above conditions

Are all values the same? Why?

17. Shutdown safety analyzer machine by pressing (Off) key, then remove the power cable for the oscilloscope.

Part 2:

18. Connect the power cable for the medical kit to the safety analyzer, then power on the machine.

19. Repeat steps from 1 to 7.

20. Press key (2). Record the insulation resistance as in step 8. Attach the ECG applied parts to safety analyzer machine then press soft key (2) to change the test to AP insulation resistance. The unit will beep repeatedly as long as the test is active. Press soft key (4) to toggle between all applied parts .

a. ALL

CASE . b. RA

CASE

c. RL - CASE

d. LA - CASE . e. LL

CASE .

Is their any deference between the measured values? if yes, why?

21. Repeat step (10), then record the data.

22. Repeat step (12), then toggle soft key (4) in order to change from AP to earth and from No AP to earth. Record all the results.



Page

23. Repeat step (14), also toggle soft key from AP to No AP, then record all the outputs.

24. Patient leakage current is measured between a selected applied part and main earth. The following outlet conditions apply when performing this test:

a. Normal polarity, earth open, Outlet ON b. Normal polarity, L2 Open, Outlet ON c. Reversed Polarity, Outlet ON d. Reversed Polarity, Earth Open, Outlet ON e. Reversed Polarity, L2 Open, outlet ON.

25. To perform patient leakage current test , from the main menu press short cut Key (6). The patient leakage test is displayed, and the test begins immediately. Record the output for the following cases:

a. All To Earth (RMS) = b. RA To Earth (RMS) = .. c. RL To Earth (RMS) =

d. LA To Earth (RMS) = .. e. LL To Earth (RMS) = ..

26. Mains on applied part test applies a test voltage, which is 110 of the mains voltage, through a limiting resistance, to selected applied part terminal. Current measurements are then taken between the selected part and earth .measurements are taken with test voltage (110 of mains) to applied parts in the normal and reverse polarity conditions as indicated on the display. The following outlet conditions apply when performing the Mains on applied part test:

Normal polarity Reversed Polarity

27. Attach the red terminal lead to a conductive part on the device enclosure. Press short key (7). The Mains applied Part test is displayed .then select the desired outlet configuration and applied part to test using the following Keys: Soft key (1) takes one pair of readings and displays the result, Soft Key (3) toggles the device outlet polarity from Normal To device OFF to Reverse Polarity, or refers to device OFF to normal Polarity.

28. Now, record the following: a. All To Earth = . b. Ra To Earth = .. c. Rl To Earth = .. d. La to Earth =

e. LL To Earth = . (Note : on each item press start key to begin the test )



Page

29. Patient auxiliary Current Tests are measured between any selected ECG jack and the

remaining Selected ECG jack. The following outlet conditions apply when performing this test

a. Normal Polarity, earth open, outlet ON b. Normal Polarity, L2 Open, Outlet ON c. Reverse Polarity, outlet ON d. Reverse Polarity, earth open, Outlet ON e. Reversed Polarity, L2 open, Outlet ON

30. From the Main menu press shortcut Key (8), the Patient auxiliary Current test is displayed, and the test begins immediately. The display is updated until another test is selected.

31. Toggle between soft keys (1,2,3,4) and record all data. Including the following:

a. Ra to All (RMs) = b. Rl to All (RMS) = c. LL to All (RMS) = d. La to All (RMS) =



Page

Experiment #5

Pulmonary Function Test

Objectives:

To understand and analyze different respiratory parameters VC, FVC, and MVV.

Understand how to prepare PFT patient data.

To study the effect of exercise on respiratory parameters.

Equipment Required:

Computer interface signal converter

Spirobank unit s601

Computer

Spirobank cable

Mouthpiece tubes

Nose clip

Discussion:

Background:

Pulmonary function testing (PFT) is one of the basic tools for evaluating patient s respiratory status. Pulmonary function tests are tests performed to make measurements of how your lungs and airways function. Results from pulmonary function tests enable your physician to evaluate your breathing, make diagnosis, recommend treatment and follow your progress.

PFT is used for the following reason:

1. Screening for the presence of obstructive and restrictive diseases 2. Evaluating the patient's condition for weaning from a ventilator. If the patient

on a ventilator can demonstrate a vital capacity (VC) of 10 - 15 ml/Kg of body weight, it is generally thought that there is enough ventilatory reserve to permit (try) weaning and extubation.

3. Documenting the progression of pulmonary disease - restrictive or obstructive 4. Documenting the effectiveness of therapeutic intervention

Terminology and Definitions:

Total Lung Capacity (TLC): the volume of air in lungs during a maximal effort of inhalation.

Functional Residual Capacity (FRC): the volume of air in lungs when the respiratory muscles are inactive and relaxed.



Page

Residual Volume (RV): the volume of air remaining in lungs after a maximal effort of exhalation.

Vital capacity (VC): the maximum volume of air that can be expired slowly after a full inspiratory effort.

Forced Vital Capacity (FVC): measured by taking the deepest possible breath, this is the volume of air which can be forcibly and maximally exhaled out of the lungs until no more can be expired. This value is critically important in the diagnosis of obstructive and restrictive diseases.

Forced Expiratory Volume in One Second (FEV1): the volume of air which can be forcibly exhaled from the lungs in the first second of a forced expiratory maneuver. This PFT value is critically important in the diagnosis of obstructive and restrictive diseases.

FEV1/FVC - FEV1 Percent (FEV1%): - This number is the ratio of FEV1 to FVC - it indicates what percentage of the total FVC was expelled from the lungs during the first second of forced exhalation - this number is called FEV1%, %FEV1 or FEV1/FVC ratio. This PFT value is critically important in the diagnosis of obstructive and restrictive diseases.

Maximal Voluntary Ventilation (MVV): - this value is determined by breath in and out as rapidly and fully as possible for 12 -15 seconds. This test parameter reflects the status of the respiratory muscles, compliance of the thorax-lung complex, and airway resistance.

Dynamic Lung Volumes and Flow Rates: Dynamic lung volumes reflect the caliber and integrity of the airways. Spirometry records lung volume against time during an FVC maneuver. It's mainly expressed by (FEV1) (%FVC), (MVV).

Flow-Volume Loop: The flow-volume loop is generated by continuously recording flow and volume with an electronic spirometer during a forced inspiratory and expiratory VC maneuver. The shape of the loop reflects the status of the lung volumes and airways throughout the respiratory cycle. Characteristic changes occur in restrictive and in obstructive disorders. The loop is especially helpful in detecting laryngeal and tracheal lesions. It can distinguish between fixed obstruction (e.g., tracheal stenosis) and variable obstruction (e.g., tracheomalacia, vocal cord paralysis) of the upper airway. The figure below illustrates some characteristic flow-volume loop abnormalities.

Obstructive lung disorders

The most common disorders are: asthma, chronic obstructive bronchitis, emphysema, and cystic fibrosis.

These disorders are all characterized by low expiratory airflow as measured by low FEV1. The low FEV1 is due to narrowing of the airways with increased airflow resistance.



Page

The patient with obstructive lung disease has a smaller flow-volume-loop than that of a normal subject - performed as a forced vital capacity maneuver The RV of the patient is 2.4 l or twice as high as that of the healthy individual, because of air trapping (a large volume of trapped air).

Flow through the tubular passageways of the lung can be reduced for a number of reasons:

Narrowing of the airways due to bronchial smooth muscle contraction as is the case in asthma

Narrowing of the airways due to inflammation and swelling of bronchial mucosa as is the case in bronchitis

Material inside the bronchial passageways physically obstructing the flow of air as is the case in excessive mucus plugging, inhalation of foreign objects or the presence of pushing and invasive tumors

Destruction of lung tissue with the loss of elasticity and hence the loss of the external support of the airways as is the case in emphysema

External compression of the airways by tumors and trauma

Procedure:

Spirobank measurement (FVC, VC and MVV)

1. Insert a mouthpiece into the sensor opening; it must go in by at least ¼ in so that it s held securely.

2. Fit the nose clip to the nose in order to ensure that no air can escape from the nostrils.

3. Hold Spiro bank at either end using both hands.

4. Switch on Spiro bank and use keyboard to arrive at the required phase of testing.

5. Put the free end of the mouthpiece well into the mouth, so that at least ¼ in of the mouthpiece is inside the mouths in order that air cannot escape

close the side of the mouth tights around the mouthpiece. It is recommended carrying out testing in standing position, and during an expiration to lean forward.

6. Start the test by breathing at rest for few moments.

7. Inspire slowly as much air as possible.

8. Make complete expiration as fast as possible. Then with the mouthpiece always held firmly in the mouth, complete the cycle by inspiring again as quickly as possible.

9. Measure FVC.

10. Repeat the measurement three times and choose the beast one.



Page

11. Carry out several complete breaths at rest. After three breathes (which should be

similar in terms of depth and speed) a beep will sound to confirm that the ventilator profile has been measured and now you can proceed to carry out the VC.

12. After the beep inspire slowly as much air as possible and then expire slowly as much air as possible.

13. Record VC.


15. Breathe in and out as rapidly and fully as possible for 12-15 seconds.

16. Measure MVV.


Using Computer Pulmonary Function Test Software and the Recording of VC ,FVC and MVV

After completing this part, the student should be able to:

Understand how to prepare PFT patient data.

Explain how to use the software interface to conduct PFT tests.

Learn how to measure VC, FVC and MVV.

1. Use the computer software to control the Spirobank Spirometer.

2. Double-click on the red lunges icon; a display will open with a series of icons across the top of the screen.

3. To start filling a new table, click on the white-page-marked icon.

4. Insert all of the data required in this table. When you have completed the table, note the green arrow located in the upper-right hand corner. Click on this arrow to open another display giving the address information and possible lung disease.

5. When you have completed the table, click on the OK button at the bottom of the display, and then close the first window.

6. Click on the Configure button and then move to the general-configuration window. Fill the blank spaces with the data required.

7. Move to the green line at the upper bar, an indication measure VC will appear. By clicking on it, a graph showing the parameter volume on the vertical axis and time on the horizontal axis is obtained.



Page

8. Put the bacterial filter between the mouthpiece tubes and the Spirobank. Apply the

nose clip during the test.

9. Press the ON button of the Spirobank, and wait. Enter the Age, height, gender and record them into the table given below.

10. Measure the VC.

11. Repeat the procedure three times each for different student and select the best of them test three times.

The FVC may be calculated as:

0.058 0.025 4.24 for male

0.0453 0.024 2.852 for female

FVC Hc A

FVC Hc A

Where Hc and A stand for the height and age, respectively

12. Put the cursor on FVC icon, then turn the Spirobank on (you will be required to inspire slowly, fully and rapidly) with the filter and nose clip fixed in the predetermined place, inhale slowly, fully and then bellow, as long as you can, into the tube. (It is possible to start the test by breathing normally at rest, for a few minutes to make your measurements more accurate. When ready to start, inspire slowly as much air as possible and then make a complete expiration as quickly as possible).

13. After performing the function record the obtained results, and plot the diagram. Repeat the measurement three times and choose the best one.

Name

Age Height cm Gender VC

measured FVC measured

FVC calculated

Percentage

%

Name Age Height cm Gender

VC measured

FVC measured

FVC calculated

Percentage %



Page

Measurement of MVV

When participating in sports such as running, one is often required to use maximum voluntary ventilation (MVV). The individual is inhaling and exhaling more deeply and at more rapid rate. Normal respiratory rate is in the order of 11-18 times/min. During MVV activity the respiratory rate is likely to be 30 or more times/min. MVV value depends directly on gender and height and indirectly on age, for people in their twenties with average height and weight, males produce an MVV value of 160-170 L/min and females average 120 L/min. MVV may be estimated according to the following equation:

malesfor 9.37816.019.1 AHc

1.004 0.685 48.7 for femalesHc A

Also, it s possible to estimate its value from FEV1 MVV =135 FEV (l/m).

14. After clicking on the red lung icon a menu will appear, click on the red ripple icon or go to the test spirometry MVV to plot the volume vs. time graph.

15. Click on start trial icon.

16. Insert the filter to your mouth, breath rapidly in and out, and then return to the normal breathing rate until the end of tracing.

17. Record the results and plot the graph.

18. Repeat the measurement three times.

Patient name Weight

Age Height

Gender

Calculated MVV

Measured

MVV



Page

Experiment #6

Audiometry

Objectives:

To evaluate the audibility threshold by using an electronic audiometer.

To compile an audiometric graph

Equipment Required:

Oscilloscope

Digital Multimeter

Electronic Audiometer

Power Supply base unit

Headphones.

Discussion:

Hearing Process:

Hearing occurs when sound waves are conducted to the nerves of the inner ear and from there to the brain. Sound waves can travel to the inner ear by air conduction (through the ear canal, eardrum, and bones of the middle ear) or bone conduction (through the bones around and behind the ear).

Definition:

An audiology exam tests your ability to hear sounds. Sounds vary according to the intensity (volume or loudness) and the tone (the speed of sound wave vibrations).

Audiometry is the testing of hearing ability. Typically, audiometric tests determine a subject s hearing levels, but may also measure ability to discriminate between different sound intensities, recognize pitch, or distinguish speech from background noise. Acoustic reflex and otoacoustic emissions may also be measured. Results of audiometric tests are used to diagnose hearing loss or diseases of the ear.

An equal-loudness contour is a measure of sound pressure (dB SPL), over the frequency spectrum, for which a listener perceives a constant loudness. The unit of measurement for loudness levels is the phon, and by definition two sine waves that have equal phons are equally loud.

The human s auditory system is sensitive to frequencies from 20 Hz to a maximum of around 20,000 Hz, although the hearing range decreases with age. Within this range, the human ear



Page

is most sensitive between 1 and 5 kHz, largely due to the resonance of the ear canal and the transfer function of the ossicles of the middle ear.

Threshold of Hearing:

INTENSITY of sound is measured in decibels (dB):

A whisper is about 20 dB

Loud music (some concerts) is around 80 to 120 dB

A jet engine is about 140 to 180 dB

Usually, sounds greater than 85 dB can cause hearing loss in a few hours. Louder sounds can cause immediate pain, and hearing loss can develop in a very short time.

TONE of sound is measured in cycles per second (cps) or Hertz:

Low bass tones range around 50 to 60 Hz

Shrill, high-pitched tones range around 10,000 Hz or higher

The normal range of human hearing is about 20 Hz to 20,000 Hz, and some animals can hear up to about 50,000 Hz.

The measured threshold of hearing curve shows that the sound intensity required to be heard is quite different for different frequencies. The standard threshold of hearing at 1000 Hz is nominally taken to be 0 dB, but the actual curves show the measured threshold at 1000 Hz to be about 4 dB. There is marked discrimination against low frequencies so that about 60 dB is required to be heard at 30 Hz. The maximum sensitivity at about 3500 to 4000 Hz is related to the resonance of the auditory canal.

Pure Tone Audiometry:

It is typical to do this testing with pure tones by providing calibrated tones to a person via earphones, allowing that person to increase the level until it can just be heard. Various strategies are used, but pure tone audiometry with tones starting at about 125 Hz and increasing by octaves, half-octaves, or third-octaves to about 8000 Hz is typical. Hearing tests of right and left ears are generally done independently. The results of such tests are summarized in audiograms.

Audiogram Showing Presbycusis:

The progressive loss of high frequency sensitivity with aging is typical, and is called presbycusis. The loss of the high frequencies can make it difficult to understand speech, since the intelligible differences in speech sounds are often in the range above 2000 Hz.



Page

Audiograms Showing Hearing Loss:

Audiograms can help with the diagnosis of various types of hearing disorders. Specific geometries of curves are found to be typical of presbycusis, and a characteristic notch in the hearing curve may be the signature of damage by a sudden loud sound like a gunshot or a firecracker explosion close to the ear.

In this experiment, an electronic audiometer will be used. It is made up of the following blocks:

1. Low frequency signal generator

To carry out the audiometer we need a low frequency generator able to provide in output a perfectly sinusoidal wave with a very low distortion and a constant amplitude on the whole audio range about from 20 to 25,000 Hz. The generator has to allow to vary the output frequency by tuning on reference frequencies, for example 100

200

400

800

1,000

2,000

4,000

6,000

8,000 Hz.

Sinusoidal waveform generator

This selection is made through the knob of selector S1 and a finer regulation is carried out through trimmer R3.The oscillator is made up of three stages of operational amplifiers at very low noise (N1A-N1B-N2A); to trigger this oscillator it is necessary to pick up the LF signal from the output of the third stage (N2A) and apply it to the input of switch S1.The output of the first operation N1A is connected to switch S1 which allows us to get with the second operational N1B and the double potentiometer R3 all the acoustic frequencies required by the audiometer.



Page

The capacitors present on the five positions of the switch S1 block 1 are the same as the ones present on switch S1 block 2 as well as the resistance of the double potentiometer R3 is the same (22k ).

The frequency of the output sinusoidal wave is determined by the product of the capacity and of the resistance respectively selected through switch S1 and trimmer R3.

The frequency is calculated by using the following formula:

F= 1/6.28 R C

2. Variable gain output amplifier

The generator is connected to an output stage which has the purpose of piloting the earphones; such an output stage is made up of a manual amplitude regulator, an operational and a deviator.

3. Measure block and logarithmic display of the emitted sound level

To measure and display the intensity of the emitted sound signal, it is necessary to use a logarithmic meter. This meter behaves as a comparator which compares a fixed voltage level in input with a scale of logarithmic levels. Since the signal emitted by the generator is sinusoidal, to measure its intensity it is necessary to rectify the signal itself. The block which deals with rectifying the signal, is made up of the double half-wave rectifying stage composed by the two operational amplifiers N4 and N5.The direct voltage present on terminal 26 of N5A is applied to the non-inverting terminal 29 of the operational N5B and picked up by terminal 30 to be applied to the Audio Level at LED diodes. The audio level is the most complex part of the whole circuit; it is made up of five integrated circuits LM324 containing each one four operational amplifiers. By connecting all the non-inverting inputs to a resistive divider of 36 resistances, we get a comparator of 19 levels at discrete components. The comparator outputs pilot 19 LED diodes, each one of which lights up with a variation of the input voltage of 1 dB.The criticality of this logarithmic comparator is due to the fact that an error of the lighting up level of the first LED diode (0 dB) reflects in an error of logarithmic type as to the lighting up level of the other LED diodes.

4. Stereo earphones with selector

It transforms the electric signal in acoustic signal by allowing to select the ear under test.

Procedure:

1. Supply the circuit. 2. Turn trimmer R17 fully counter clockwise 3. Set switch S1 to 2



Page

4. Turn trimmer R3 fully clockwise (minimum frequency) 5. Insert the jack of the stereo headphones in the AUDIO OUT connector. 6. Set selector S2 to LEFT (L). 7. Connect the digital multimeter between terminal 10 and ground. 8. Adjust trimmer R3 until getting a frequency of about 100 Hz. 9. Adjust the volume (R17) until the student (patient under test) can hear the sound in

the headphones. 10. Write down in Table 1 the corresponding Audio Level in dB. 11. Turn trimmer R17 fully counter clockwise. 12. Set switch S1 to 2. 13. Turn trimmer R3 until getting an output frequency of about 200 Hz. 14. Adjust the volume until the student (patient under test) can hear the sound in the

headphones. 15. Write down in table 1 the corresponding Audio Level in dB . 16. Repeat from step 19 to step 23 for all the frequencies shown in table 1. 17. By using the values shown in the table, draw on logarithmic panel the audiometric

graph relative to the left ear of the student (patient under test). 18. Move switch S2 to RIGHT (R). 19. Repeat the procedure you have already carried out for the left ear. 20. Graph the left audio level and the right audio level versus the frequency. 21. Compare the obtained graphs. 22. Comment such results as to the studied theory. 23. Turn off the circuit.

Table 1

Sound Frequency

[Hz]

Selector S1 position

Left Audio Level [dB]

Right Audio Level

[dB]

20 1 50 1

100 2 200 2 500 3

1000 3 2000 4 3000 4 4000 4 5000 4 6000 4 7000 5 8000 5 9000 5

10000 5



Page

11000 5 12000 5 13000 5 14000 5 15000 5 16000 5 17000 5 18000 5 19000 5 20000 5

Air Conduction Threshold Measurement by PC-based Audiometer

MA 33 is a small and PC-based audiometer that offers fast and reliable tone audiometric screening for children and adults.

Standard Accessories

1. Air conduction headphone (Red plug and blue one) 2. Patient response key 3. USB connector 4. LEDs: The right one indicates the operating state and the left shows the starting

sequence. Before performing the test, the following steps should be recognized to prepare the patient:

1. The patient should sit at a distance from the device.

2. Ensure that the headphones are positioned correctly (red on the right and blue on the left).

3. Adjust the headband of the headphones so the earphones are positioned at the correct height (the sound output grid exactly facing the ear canal)

4. Explain to the patient that he/she needs to press the patient response key as soon as he/she just hears the test tone.

Default Settings: 1. Right Channel is set to air conduction pure tone and the left channel is in active.

2. The frequency is set to 1KHz.

3. Select the ear to be tested either by mouse or by pressing R / L on the keyboard.

4. The volume can be changed using

the cursor or the mouse which is displayed as markers in the audiogram.



Page

5. The measuring frequency can be adjusted using

cursor or mouse.

6. Test through the frequencies: start at 1 KHz, set the higher frequencies then the lower ones.

7. Select the next frequency, increase the level again and proceed with presenting the test signal.

8. Once a threshold has been established, record and confirm the measured value by pressing Enter key, the appropriate symbol will be plotted on the audiogram ( O for the right ear and X for the left one).

9. Compare between this audiogram and the previous plotted one from the table.



Page

Experiment #7 Gait Analysis

Objectives:

Learn how to collect and analyze the gait signals

Discuss the relation between the different parameters.

Equipment Required:

Computer.

Biopac System

Heel and toe sensor

Discussion:

Gait analysis is a process of quantification and interpretation of human locomotion. The study of gait analysis allows diagnosis processes to be made, as well as permitting future developments in rehabilitation engineering. Gait analysis is widely used in professional sports training to optimize and improve athletic performance.

Gait analysis provides the patient with what gait experts refer to as 'Dynamic Testing' - testing during movement, thus allowing the dysfunction to occur in a near natural state, while under controlled testing conditions. By studying the motion of the lower extremities, combined with the forces exerted upon those extremities, gait experts are usually able to identify the source of pain and thus the real cause of the pain and/or dysfunction. Very often, treatment using other methods means treating symptoms of the dysfunction and lengthy trial end error because identification of the true source of the problem cannot occur without continuous movement or exertion of the lower extremity. Gait Analysis allows for such movement and exertion of the lower extremities, and thus the source of the dysfunction/pain can usually be identified.

Walking is the most convenient way to travel short distances. Free joint mobility and appropriate muscle force increases walking efficiency. As the body moves forward, one limb typically provides support while the other limb is advanced in preparation for its role as the support limb. The gait cycle in its simplest form is comprised of stance and swing phases. The stance phase further is subdivided into 3 segments, including initial double stance, single limb stance, and terminal double limb stance.

Each double stance period accounts for 10% of the gait cycle, while each single stance typically represents 40%, thus the stance phase of each limb represents 60% of the limbs gait cycle. The swing phase for the same limb is the remaining 40% of the gait cycle.



Page

A stride is the equivalent of a gait cycle. The duration of a stride is the interval between sequential initial floor contacts by the same limb. A step is recognized as the interval between sequential floor contacts by the two limbs. Two steps make up each gait cycle, which is roughly symmetric in normal individuals.

Gait Cycle Phases:

Stance phase 60%

Heel Strike (HS)

Foot Flat (FF)

MidStance (MS)

Heel Off (HO)

Toe Off (TO)

Swing Phase 40%

Initial Swing

MidSwing

Late Swing

A consistent sequence of motions is performed at each of the lower extremity joints during locomotion. Stance is comprised of 5 gait phases (Heel strike, Foot flat, MidStance, Heel off, and Toe-off), with the remaining 3 phases occurring during swing. Figure (1) shows the five gait phases of the stance phase.

The first two phases of the Stance phase occur during initial double support. These phases include initial contact and the loading response. Initial contact often is referred to as heel strike. The joint motion during this phase allows the transfer of weight onto the new stance phase leg while attenuating shock, preserving gait velocity, and maintaining stability.

Figure (1): Heel strike, Foot flat, MidStance, Heel off, and Toe-off



Page

Procedure: Normal Walking

1. Choose the Setup Channels item from the MP150 menu. You will see three columns of boxes next to rows of text boxes that describe different types of sample data.

If you would like to collect and plot sample data for a given channel, check the boxes that correspond to the Acquire and Plot columns for that channel.

For instance, you could select the Plot boxes for one or all of the Analog channels, which are normally checked for plotting at startup in the sample file.

The next time you press the button, data will be collected on these channels, but that data will not be plotted on the screen as it is being acquired. During a recording, when the data plot reaches the right edge of the window, the waveforms continuously scroll from right to left. For long recordings, it may be desirable to view the data collected earlier in the acquisition while new data is coming in. To demonstrate this, go up to the MP150 menu and uncheck Scroll and Auto Plot (the checkmarks will disappear).

2. Start the acquisition again.

3. When the data plot reaches the right limit, the screen will not be re-written. At this point you can use the horizontal scroll bar to look back through the data.

Note that the scroll bar position indicator is changing while the data collection is taking place. This indicates that the record is getting longer as new data is being acquired. You can re-select Auto Plot to again view the new data as it is acquired, and Scroll as desired.

During long recordings, you may wish to do other things with your computer, such as word processing. By minimizing or resizing the window, the MP System can be easily collecting data in the background while you're using another program. You can even reposition the windows to watch the data coming in while you are typing away in your word processing program. In addition to the ability to collect data in the background, Acknowledge also gives you total control over the channel acquisition parameters



Page

4. To illustrate this, choose Setup Channels from the MP menu. To the left of

each channel, the Acquire checkbox enables acquisition and the Plot checkbox enables plotting. If Acquire is on but Plot is off, data from that channel will be recorded, but not plotted on the screen.

5. The Values checkbox will cause the channel s current value to be numerically displayed in the Input Values window. Select a Channel to setup by clicking in the circle next to the channel numbers, and edit the Label as desired. Calculation Channel Presets offer an easy way to get

started.

6. When you choose Calc in the Setup Channels dialog, the Presets menu is activated. Click on the (arrow icon) to generate a list of preset options. Use an existing preset, or modify it to create a new one, and then organize the channel presets (via the MP 150 menu) to suit your needs. Calculation Presets can only work in conjunction with Analog input presets, or with other calculation channels that are ultimately pointing to an Analog source channel You must set the appropriate Source Channel via Scaling..." (PC) or "Settings..." (Mac) in the Setup Channels dialog for Calc channels.

7. To instantaneously view the input channel values in numerical and/or bar chart format, choose Show Input Values from the MP menu. This is useful for displaying data as it is being acquired, and can be especially useful for biofeedback procedures. Click on the Options button to generate controls for the size, precision and format of the values in the Input values window.

8. To further control the acquisition, select Setup Acquisition from the MP 150

menu to generate the Acquisition Setup window. This is where you will set up parameters controlling data collection. The basic options are Sample rate and Total Acquisition Length. Sample rate is analogous to the mm/sec setting on a chart recorder.

9. To change it, simply type the desired value in the Sample rate box or make a selection from the pop-up menu. To set the amount of data to record, either adjust the Total Acquisition Length scroll box or enter the length value directly. The units for the length can be set to samples, msec, seconds, minutes or hours by clicking on the pop-up menu to the right of the Total Acquisition Length value. Beginning the acquisition again (clicking on the Start button) will cause these new settings to go into effect (the demo is locked to an acquisition sample rate of 1000 samples/second ).

The storage device can be set to store data to memory, disk, or MP1 150, or, for more sophisticated acquisitions using signal averaging, Averaging (the demo is locked to Memory). Any storage medium that



Page

you can copy a file to can be used (including removable hard disks and optical disks).

All acquisition parameters and window positions are saved along with the data when the Save command is chosen. This way you can open a data file and is chosen. This way you can open a data file and is chosen. This way you can open a data file and parameters. The Save dialog box is not available in the demo but is shown here for reference. Saving the data as an ACQ file saves data in a binary file format that uses minimal disk space. Text is a standard ASCII format that can easily be read by other programs. PICT (Mac) and WMF (PC) files can be read by most drawing and word processing programs The powerful Graph Template feature lets you save predefined experiment parameters then you just open a Graph Template and click Start to recreate the protocol and acquire

10. Choose channel and label it Heel and Toe. The label of the selected channel appears to the right of the channel boxes. The vertical scroll bar adjusts the vertical offset of the selected channel. You may use it to slide the selected waveform s scale up or down. To adjust the vertical scale of the selected channel, click the mouse on the vertical scale region. The vertical scale dialog box will be generated. Type in a value that is about half the current value and click on the OK button. The selected waveform's screen amplitude should now be twice as large as it was before. You have complete independent control over each channel. To display the optimal vertical scale for all channels choose Auto scale waveforms from the Display menu.

11. Connect heel and toe sensor to MP150 then choose on of the selected channels then walk 10 steps then record the measured signal.

12. For different students fill the following table :

Weight Heel frequency Toe frequency Toe amplitude Heel amplitude

Walking with limp

Repeat steps 11 and 12 while walking with limp



Page

Questions

1. What are the relation between weight and the above parameters? 2. Plot heel and toe signal for the two cases and explain if there is difference between

Heel and toe durations. 3. If the sensors places were changed, what are the expected results? 4. Is there a difference in the gait signal during normal walking and walking with

limp?

This document was created with Win2PDF available at http://www.daneprairie.com.The unregistered version of Win2PDF is for evaluation or non-commercial use only.

http://www.daneprairie.com

Documents

Jordan University of Science & Technology Faculty of Engineering … · 2011-02-20 · Cardiovascular Physiology and Correlation ECG to Peripheral Circulation 1. Cardiovascular Physiology