بسم اهللا الرحمن الرحيمبسم اهللا الرحمن الرحيمبسم اهللا الرحمن الرحيمبسم اهللا الرحمن الرحيم

اللهم علمنى بما ينفعنى اللهم علمنى بما ينفعنى اللهم علمنى بما ينفعنى اللهم علمنى بما ينفعنى وأنفعنى بما علمتنى وأنفعنى بما علمتنى وأنفعنى بما علمتنى وأنفعنى بما علمتنى

وذدنى علماوذدنى علماوذدنى علماوذدنى علما

BIO-SIGNALS

*The bio-signals potentials are generate at cellular level and the source of these

potentials is ionic in nature.

* cell consists of an ionic conductor separated from the outside environment by

a semi permeable membrane which acts as a selective ionic filter to the ions. This means that some ions can pass through the

membrane freely where as other cannot do so.

*All living matters are composed of cells different types.

* The bio-signals are EMG, EOG, ECG, or

EEG this signals can be analyzed and sensors.

*This signal can monitoring ,rehabilitation ,

feedback functions and control gain .

* EMG is electro mayo graph its detect contraction of the skeletal muscles result in generation of action potentials in the

individual muscle fibers.

* EOG is electro oculo graph its detect the potentials that generated by the movement of the

eye ball.

ELECTRICAL SYSTEM OF HEART

THE ECG WAVEFORM

ECG BASICS

*P wave: represents the depolarization impulse across the atria

*Q, R and S waves: all these three waves

represent the ventricular depolarization

*T wave: represents the repolarization of the ventricles

ECG Basics

*P wave : 0.25 mv

*R wave : 1.60 mv

*Q wave : 25% of R-wave

*T wave : 0.1 to 0.5 mv

ECG Basics

*P-R Interval : 0.12 to 0.20 s

*Q-T Interval : 0.35 to 0.44 s

*S-T Segment : 0.05 to 0.15 s

*P wave : 0.11 s

*QRS Interval : 0.09 s

Electro cardio graph

*ECG is an instrument which records the electrical activity of the heart.

Electrical signals from the heart characteristically precede the normal mechanical function and

monitoring of these signals has great

significance.

*ECG provides valuable information about wide range of cardiac disorders such as the presence

of an inactive part (infarctions) or an

enlargement (cardiac hypertrophy) of the heart muscle.

Block diagram

*The potentials pick up by electrodes are taken to

the lead selector switch. In the lead selector the electrodes are selected two by two according to

the lead program.

*The signal is connected symmetrically to the pair

deferential amplifier. The pre amplifier is usually a three or four stages the output signal pick to

power amplifier.

*Direct writing recorder is usually adequate since

the ESG signal of the interested has limited has bandwidth.

Frequency selective network is an R-C network. Which provides necessary damping of the pen

motor and is preset by the manufacture.

*The auxiliary circuit provide a 1mV calibration

signal and automatic blocking of the amplifier

during a change in the position of the lead switch.

*It may include a speed control circuit for the chart drive motor.

*Isolated preamplifier :

It had traditional for all ECG to have the right leg

(RL) electrode connected to the chassis . And from

there to the ground.

*this provided a ready path for any ground

seeking current through the patient and presented an electrical hazard.

ECG LEADS

*Two electrodes placed over different areas of the

heart and connected to the galvanometer will picket up the electrical current resulting from the

potentials difference between them.

*So that any two sides due to electrical activity of the heart is called (LEAD)

Bipolar lead:

ECG recording by using two electrodes such

that the final trace corresponds to the difference of electrical potentials existing between them. They

are called standard leads

* I lead the electrodes are placed on the

right and the left arm (RA&LA).

* II lead the electrodes are placed on the

right arm and left leg (RA&LL).

* III lead the electrodes are placed on the

left arm and left leg (LA & LL).

Unipolar limb leads:

*Also know as augmented limb leads, examine the

composite potentials from all three limbs simultaneously.

*in all three augmented leads, the signals from

two limbs are summed in resistor network and then applied to the amplifier’s inverting input.

*the signal from the remaining limb electrode is applied to the noninverting input.

*Lead aVR: RA is connected to the no inverting input while LA and LL are summed at the inverting

input

*Lead aVL: LA is connected to the no inverting input, while RA and LL are summed at the

inverting input.

*Lead aVF: LL is connected to the no inverting input while RA and LA are summed at the

inverting input.

Unipolar chest leads:

V1 through V6 are measured with the signals

from certain specified location on the chest applied to the amplifier no inverting input.

Leads Combination

* LEAD I :LA+RA

* LEAD II :LL+RA

* LEAD III :LL+LA

* AVR :RA & LA+LF

* AVF :LF & RA+LA

* AVL :LA & RA+LF

ELECTRODES :

*Bioelectric events have to be picked up from the surface of the body before they

can be put into the amplifier for subsequent record or display.

*This done by using electrodes.

*Electrodes make a transfer from the

ionic conduction in the tissue to the electronic conduction which is necessary for making measurements.

*They are two types of the electrodes are used in practice surface electrodes and the

deep seated electrodes.

*The surface electrodes pick up the potential difference from the tissue surface when placed

over it without damping the live tissue.

*Whereas the deep-seated electrodes indicate the electric potential difference arising inside the live tissue or cell.

Electrode-Tissue Interface:

*used electrodes in patient monitoring and related studies are surface electrodes.

*The notable examples are when they are used for recording ECG, EEG and respiratory activity by impedance pneumography.

*The characteristics of a surface electrodes of a metal electrode and attached to the surface body through electrolyte jell depend on the condition of metal-electrolyte interface .

Metal electrolyte interface :

* They are tendency for each electrodes to discharge ions to the solution and for ions

in the electrolyte to combine with each electrode.

*That creations a charge gradient

(difference- potentials)

Electrodes tissue interface

Tissue Electrolyte skin interface

Electrolyte Metal Electrolyte Interface

To Instruments

ECG electrodes:

1- Limb electrodes

* rectangular surface

* German silver

* impedance is 2 to 5 KΩ

* using in surgery

2- Floating electrodes:

* used without jell

* contact impedance 50K Ω

3- Pregelled Disposable Electrodes: * stress testing ,long term monitoring

* reducing possibility of artifacts and drift

Electrode Placement

Electrode Placement

* C1 - the fourth intercostals space on the right side of the sternum

* C2 - the fourth intercostals space on the

left edge of the sternum

* C3 half way between C2 and C4

Electrode Placement

* C4 - the fifth intercostals space in the left central clavicular line

* C5 - straight line from the C4 point

perpendicularly to the left front auxiliary line in the intersection point with this line.

* C6 - at the same level as C5, but in left

central auxiliary line

ECG Machine Block Diagram

Preamplifier

Operation Amplifier

Galvanometer: * A galvanometer is a permanent magnet moving coil (PMMC).

* The pen will at rest in the centre of its travel when no current flows in the coil. The movement of the pin is depend on the current supply to the coils.

they are also other types of writing:

* hot-tip (styles) heated by resistor wire.

* the thermal paper its turn black when its heat

* writing knife edge in the thermal recorder.

* Dot matrix printer used with the computer its 27 pin printer make good quality recording waveform

and numerical number like blood pressure,

temperature etc.

Motors :

*The motor is connected to the drive roller through either a drive a chain or a gear train.

*Most machines use ac motors, with tapped

windings to select drive speed.

*Some ac motors provide very accurate drive

speeds that are synchronized to the ac power main’s frequency 60 Hz in the united states.

*Only few models use dc motors, and those regulated speed by using a regulated dc power

supply.

* in some cases an alternator /tachometer on

the motor shaft to provide negative feedback.

Figure 239 small

ECG FAULTS AND TROUBLESHOOTING:-

Most common problem that occur in an ECG are:

PROBLEM 1:-

SYMPTOM: machine runs but the thermal tip stylus does not writes or writes very lightly.

POSSIBLE CAUSE:

(1) Too little heat on the stylus tip .

(2) Insufficient stylus pressure.

TROUBLESHOOTING: Use a screw driver or any isolated tool to gently press the stylus if a dark line appears on the paper the problem is pressure , but if no dark line appears the problem is heat.

ECG FAULTS AND TROUBLESHOOTING:-

SOLUTION:

(1) For no heat check the heater voltage at the stylus

,if voltage is correct change the stylus ,if voltage is

not correct refer the service manual for details on

stylus power drive.

(2) Adjust the stylus pressure , use a pressure gage

and refer to the service manual for the correct

value.on some models pressure must be made at a

specific heater voltage.

ECG FAULTS AND TROUBLESHOOTING:-

PROBLEM 2:-

SYMPTOM: Smeared trace.

POSSIBLE CAUSE:

Worn stylus or incorrectly loaded paper.

TROUBLESHOOTING:

Check paper loading and if proper ,check stylus for wear

,pitting and other irregularities.

Incorrect loading is one of the most common fault and

often results from bypassing the paper brake or tension

bar.

PROBLEM 3:-

SYMPTOMS: Poor recording.

POSSIBLE CAUSE: Electronic or mechanical problem , bad switch or patient cable.

TROUBLESHOOTING:

(1) Place lead selector switch in STD ,short all electrodes together and press 1- mv cal button.

(2) If normal calibration pulse appears then problem is connection to the patient.

(3) If problem persists then repeat step 1 using known good patient cable .

ECG FAULTS AND TROUBLESHOOTING:-

ECG FAULTS AND TROUBLESHOOTING:-

60 Hz INTERFERENCE:-

CAUSES: 60 Hz interference appears due to power

mains,another cause of 60 Hz interference if a broken

or loose cable or broken power main ground on the

ECG machine, additionally some dc supply also

cause these artifacts.

SOLUTION:

The problem can be isolated by shorting together all

electrodes of the patient cable and checking each

position of the lead selector switch.

ECG FAULTS AND TROUBLESHOOTING:-

(1) If the interference ceases , then the problem is a bad

electrode or no electrolytic gel.

(2) If the interference exists on all positions of the lead

selector switch then the problem is internal of the

machine.

(3) If the problem occurs in certain lead position of the

selector switch then suspect an open wire, use

ohmmeter for continuity.

Stress ECG

*Some potentials dangerous cardiac arrhythmia

and other anomalies shown up only under stress conditions.

*Physicians examine the stress condition by placing

the patient on the treadmill or stair stepper while

monitoring the patient's ECG waveform on both an oscilloscope monitor and a paper chart.

*Modern stress ECG machines are usually equipped with a microcomputer that analyzes the waveform .

*A common method is to perform the stress test, recording the ECG waveform, and then follow the

stress test with a thallium scan.

*The radioactive thallium is taken up by healthy

cardiac cells, so areas of the heart where blood

flow is sufficient appear darker on a gamma camera display then healthy areas.

*These two tests allow the physician to evaluate

the existence, location and extent of cardiac

disease.

Manual Controller

The optional manual controller

Allows personal treadmill operation, while

giving the user control of speed and

elevation functions without interfering

with

medical usage.

Drive Assembly

The low profile design and simplified layout of

drive assembly components provide easy accessibility for maintenance and provides a

high level of performance.

displays Body weight, Time, Distance ,Elevation

Total calories, Calories per minute

Pace (minutes/mile), Heart rate.

ECG PARAMETER

• ECG leads 12 standard • Record speed 5/25/50

• Sensitivity 2.5/5/10/20