Transcript Marek OCHOCKI, Slawomir LATOS Institute of Medical

Marek OCHOCKI, Slawomir LATOS
Institute of Medical Technology and Equipment
ITAM,
118, Roosevelt Str., Zabrze, Poland
INFLUENCE OF DEFIBRILLATION
TREATMENT ON SOME ELECTRICAL
PARAMETERS AND APPLICATION
SAFETY OF ECG ELECTRODES
Presentation scheme
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The subject of presentation
Introduction
Examination procedure
Examination results
Conclusions
Wider context
The subject of presentation
• A contribution to determination of safety of disposable
ECG electrodes use in conditions of defibrillation
treatment in monitored patients for risk stratification
and referential purposes
ECG electrodes available on the Polish market
4 European manufacturers including Polish one
•
Illustration of relations between patient’s safety,
standards, market considerations, compliance to
standards and regulations as well as research activity
Introduction
Fig. 1 ECG electrode filled with gel
Introduction
Fig. 2 Schematic representation of electrodegel-patient’s skin structure and its equivalent
circuit model according to [3]
Introduction
• ECG recording or monitoring
• The use of cardiac defibrillation treatment
– Defibrillation voltages transposed up to 200 V
between ECG electrodes on patient’s body
• Hazards to ECG electrodes and patients
– Up to 2% of defibrillation current absorbed by
electrodes, mostly in sensor Ag/AgCl structure
– Degradation of sensor layer - impairment of electrode
characteristics [3]
– Electrodes polarization (publication [6])
– Rise of electrodes impedance – next slide:
Increase of ECG electrodes
impedance may cause:
• unwanted decrease of common mode
rejection ratio (CMRR) of ECG amplifier
channel.
• raise of disturbing interference of alternative
current on ECG waveform [5].
• augmentation of exuded energy during
defibrillation or even electrosurgical operation
involving possible heating up of electrodes
and the patient's burns [3].
Procedure of ECG electrodes
examination
• Selection of electrodes
• Tests distribution in years
• Gluing electrodes in gel-to-gel mode into pairs –
correspondence to impedance measurement on abraded patient’s skin [4]
• Measurement of polarization potential of electrodes
60÷90 s after gluing
• Measurement of impedance with the 10 Hz current
• Fourfold defibrillation recovery test − according to
schematic diagram in Fig. 4
• Measurement impedance with the 10 Hz current after
defibrillation
Testing according to globally
recognized standard:
American National Standard
ANSI/AAMI EC12:2000/(R)2010
Disposable ECG electrodes
AAMI Association for the
Advancement of Medical
Instrumentation
The photo of measuring equipment set for ECG
electrodes testing
tested
electrode pair
measuring
amplifier
oscilloscope
sinusoidal current
source of
efficiency
80µA/10Hz
Ka=12,5V/V
Fig. 3 Measurement circuit for testing the
electrodes impedance with 10 Hz current
Fig. 4 Instrumentation system for defibrillation
recovery testing of ECG electrodes according to
standard [1]
Fig. 5 Electric scheme for defibrillation recovery
testing of ECG electrodes according to [1]
Results
• Initial self-polarization potential („DC
offset voltage”), measured in simple circuit
after 60÷90 s stabilization period of glued
electrode pairs did not exceed 6 mV in all
the measurements of 2012 year.
• In previous years indicated, these voltages
were also far below 100 mV upper
allowable limit according to [1]
Polarization recovery from defibrillation
induced overload in 2012 tests
• Measurements 5 secs after each of four
discharges of 200 V did not exceed 21 mV in all
tests of 2012 year. The upper permissible limit
being 100 mV [1]
• Rate of decrease of induced polarization
potential during 30 secs following each ‘5 secs’
measurement did not exceed 0,5 mV/s
(permissible maximum 1 mV/s [1])
Polarization potential [mV]
30
25
20
15
10
5
0
00:00 00:15 00:30 00:45 01:00 01:15 01:30 01:45 02:00 02:15 02:30 02:45 03:00 03:15 03:30
Time [min:s]
Fig. 6 Example of recovery polarization potential in
time after a series of four defibrillation-like
expositions impacting the electrode pair chosen
Table 1. Results of impedance measurements for electrode pairs
examined, in four selected years
Years of examinations conducted
Measured
Impedance
Parameters
Impedance
interval
before
defibrilla
-tion k
2006
2007
2011
Each year
one electrode type
from one producer,
and quantity of
12 electrode pairs tested
0,29÷
0,38
0,41÷
0,48
0,04÷
0,06
2012
Electrode types of one producer and
quantity of electrode pairs tested
A
7 pairs
0,21÷
0,41
B
C
D
12 pairs 12 pairs 12 pairs
0,23÷
0,46
0,18÷
0,29
0,16÷
0,34
Mean
impedan
ce value
before
defibrillation
k
0,34
0,44
0,05
0,27
0,34
0,22
0,22
Impedance
interval
after
defibrilla
-tion k
0,28÷
0,32
0,30÷
0,37
0,03÷
0,04
0,17÷
0,37
0,08÷
0,22
0,07÷
0,13
0,12÷
0,16
Mean
Impedan
-ce value
after
defibrillation
k
0,30
0,34
0,04
0,23
0,15
0,10
0,15
Interval
of
impedance
drop %
0,0÷
23,7
9,9÷
31,4
17,2÷
29,5
2,2÷
21,9
46,9÷
71,7
51,1÷
69,6
12,1÷
55,4
Mean
value of
impedance
drop %
10,8
21,8
22,3
13,8
56,3
57,0
31,2
End of Table 1.
Changes of electrode impedance
In result of fourfold defibrillatory exposition the
impedance drop in all examined electrode pairs
has occurred.
Mean value of this drop for each electrode lot
falls into 10,8% do 57% interval.
Checked ECG electrodes comply with the
American standard [1], to not exceed 2 kΩ by
the mean impedance value for each production
lot of 12 electrode pairs, and individually be
below 3 kΩ.
Conclusions
• All tests have been complied to globally recognized
American standard [1] with considerable safety margin.
• The results of conducted examinations generally have
put in a good light the quality of tested ECG
electrodes of four selected European manufacturers,
including Polish one,
• This made possible safe use of these electrodes on
patients undergone the serious treatment as cardiac
defibrillation.
• In that important was (or is) to allow the physician
obtaining quickly information for assessment of
effectiveness of this defibrillation procedure.
Conclusions
• Referential meaning of these examinations - wider
analyses, risk stratifications…
• On today market more and more medical devices
appears from outside Europe. their quality is not stable.
• Periodic checking of accessible sample lots of such
products - advisable
• Special care for long-term and little controlled
transport and storage periods as well as rough
conditions
• Particular care for semi-liquid materials like the gels.
• Essential performance – new kind of safety in
standards for electromedical equipment – here
represented
For further analysis
two other low intensity
parameters also positively tested
meaningful phenomena, required
by the American standard [1] :
1. Combined offset instability and internal
noise
After a 1-min stabilization period, a pair of
electrodes connected gel-to-gel shall not
generate a voltage greater than 150
microvolts (μV) p-p in the passband of 0.15 to
100 Hz, for a period of 5 min following the
stabilization period.
Fig. 7 Test circuit for offset instability and
internal noise measurement [1]
2. Bias current tolerance:
Observed DC voltage offset change
across a glued pair of electrodes
required to not exceed 100 mV
when the pair is subjec-ted to a
continuous 200 nano-ampere DC
current during
at least 8 hours.
BIBLIOGRAPHY
[1] ANSI/AAMI EC 12:2000/(R)2010 Disposable ECG electrodes.
[2] EN 60601-1:2006 Medical electrical equipment. Part 1: General
requirements for basic safety and essential performance.
[3] HOI-JUN YOO, VAN HOOF CH. Bio-Medical CMOS ICs
(Integrated Circuits and Systems) 2011, pp 31-124, Springer, New
York
[4] KLINGLER DR, SCHOENBERG AA, WORTH NP, EGLESTON CF,
BURKART JA. A comparison of gel-to-gel and skin measurements
of electrode impedance. Med. Instrum. 1979 Sep-Oct;13(5):266-8.
[5] OLSON WH, SCHMINCKE DR, HENLEY BL. Time and frequency
dependence of disposable ECG electrode-skin impedance. Med.
Instrum. 1979 Sep-Oct;13(5):269-72.
[6] PATTERSON RP. The electrical characteristics of some
commercial ECG electrodes. J Electrocardiol. 1978 Jan;11(1):236
[7] SCHOENBERG AA, BOOTH HE, LYON PC. Development of
standard test methods for evaluating defibrillation recovery
characteristics of disposable ECG electrodes. Med. Instrum. 1979
Sep-Oct;13(5):259-65