Transcript الشريحة 1

Electromyography (EMG)
Electromyogram
A tracing made with an electromyograph 
Electromyograph
Electromyography (EMG) is a medical technique
for measuring muscle response to nervous
stimulation. An electromyograph detects the
electrical potential generated by muscle cells
when these cells contract.
EMGSignal
Signal
Characteristics
is generated in the muscle cells 
Amplitude range: 50 mV to 30 mV 
Frequency range: 7 to 20 Hz depending on the size 
of the muscle
To perform EMG, a needle electrode is inserted 
through the skin into the muscle tissue
Because of the needle electrodes, EMG may be 
somewhat painful or extremely painful to the
patient, and the muscle may feel tender for a few
days, surface electrodes are used→
That gives much less accurate results with a higher level 
of disturbance from the surrounding environment.
EMG
Signal
To perform
EMG,
a needleperforming

electrode is inserted through
the skin into the muscle tissue
Because of the needle 
electrodes, EMG may be
somewhat painful or extremely
painful to the patient, and the
muscle may feel tender for a
few days, surface electrodes
are used
That gives much less accurate 
results with a higher level of
disturbance from the
surrounding environment.
Electromyogram (EMG) (cont.)
Blood Pressure
Blood Pressure Measurements
Pressure is force per unit area
1. Non-invasive measurement
Palpatory Method
Auscultatory Method
Oscillometric Method
2. Invasive measurement
Auscultatory Method
systolic pressure
diastolic pressure
systolic pressure
diastolic pressure
Auscultatory Method
Pulse waves that 
propagate through the
brachial artery, generate
Korotkoff sounds.
There are 5 distinct 
phases in the Korotkoff
sounds, which define SP
and DP
The Korotkoff sounds are 
ausculted with a
stethoscope or
microphone (automatic
measurement)
The frequency range is 
20-300 Hz and the
accuracy is +/- 2mmHg
(SP) and +/- 4mmHg
(DP)
Also with this method, several
measurements should be done.
Auscultatory Method (cont.)
ADVANTAGES
+) Auscultatory technique is simple and does not require much
equipment
DISADVANTAGES
-) Auscultatory tecnique cannot be used in noisy environment
-) The observations differ from observer to another
-) A mechanical error might be introduced into the system e.g.
Mercury leakage, air leakage, obstruction in the cuff etc.
-) The observations do not always correspond with intra-arterial
pressure
-) The technique does not give accurate results for infants and
hypotensive patients
Oscillometric Method
The intra-arterial pulsation is
transmitted via cuff to
transducer (e.g. piezo-electric)
The cuff pressure is deflated
either linearly or stepwise
The arterial pressure oscillations
(which can be detected throughout
the measurement i.e. when Pcuff > SP
and Pcuff< DP) are superimposed on
the cuff pressure
SP and DP are estimated from the amplitudes of the
oscillation by using a (proprietary) empirical algorithm.
Oscillometric Method (cont.)
ADVANTAGES
+) In the recent years,
oscillometric methods
have become popular for
their simplicity of use
and reliability.
+) MP can be measured
reliably even in the case
of hypotension
DISADVANTAGE
-) Many devices use fixed algorithms leading to large
variance in blood pressures
Measurment disply
Electroencephalography (EEG)
EEG measurement
EEG is a representation (writing on paper or display on CRT, 
PC) of the electrical activity of brain
The electroencephalograph is an apparatus uses electrodes 
placed on a patient’s scalp to measure (detect), amplify,
display in graphic form, and record the weak electrical
signals generated by the brain
The technique involves the following: 
Biopotential pickup: cranial or cerebral surface transducer electrode
EEG signal conditioning: transducer output amplification and filtering
(0.1 to 100 Hz)
EEG signal recording: signal displayed on graphic recorder, CRT or
PC
EEG signal analysis: visual or computer interpretation of resulting
EEG




EEG measurement
Current due to 
voltage drops along
the path of the axon
 lead to scalp
potentials (EEG).
EEG characteristic
Signal is generated in the brain 
Voltage amplitude range is from 1 to 100 mV peak-to-peak at low 
frequencies (o.5 to 100 Hz)
EEG frequency bands: 
Delta 0.5 - 4 Hz
deep sleep, lucid dreaming, increased immune
functions, hypnosis
Theta
4 - 8 Hz
deep relaxation, meditation, increased memory, focus,
creativity, lucid dreaming, hyponagogic state
Alpha
8 - 13
Hz
light relaxation, "super learning", positive
thinking
Beta
13 - 22
Hz
relaxed focus, improved attentive abilities
Gamma
22-30 Hz
and
higher
associated with information-rich task processing and
high-level information processing
EEG
electrode
placement
Standard
electrode placement
known as 10-20 system 
10-20 system drives from the spacing of electrodes at intervals of 10% 
and 20% of the distance between particular points on the scalp
An asymmetry of 1 cm can alter an EEG reading 
The 10-20 EEG electrode placement system
EEG
recording
modes
Unipolar: Composed of a number of scalp leads connected
to a common indifference point (one electrode is common
to all channels such as an earlobe )
Unipolar

EEG recording modes (cont.)
Unipolar average: Composed of a number of scalp leads 
connected to a common indifference point (summation of
scalp electrodes is common to all channels)
Unipolar average
EEG
recording
modes
(cont.)
Bipolar:
Achieved by the
interconnection
of scalp
electrodes
Bipolar
