Biomedical Instrumentation Questions and Answers – Recording Electrodes

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This set of Biomedical Instrumentation Multiple Choice Questions & Answers (MCQs) focuses on “Recording Electrodes”.

1. Electrodes make a transfer from the __________ in the tissue to the electronic conduction which is necessary to make measurements.
a) electronic conduction
b) ionic conduction
c) electric conduction
d) impulsive conduction
View Answer

Answer: b
Explanation: Electrodes make an exchange from the ionic conduction in the tissue to the electronic conduction which is important to make measurements. An electrolytic paste is applied between the electrodes and the skin to reduce skin contact impedance. The electrolyte also facilitates ionic conduction from the skin to the electrodes.
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2. Surface electrodes damage the living tissues.
a) True
b) False
View Answer

Answer: b
Explanation: The surface electrodes pick up the potential difference from the tissue surface when placed over it without damaging the living tissues. They are placed above the skin and cause no harm to the living tissues. They capture the electrical activities of bunch of tissues together.

3. Deep-seated electrodes indicates the electric potential difference arising ________ the living tissues or cells.
a) inside
b) outside
c) around
d) adjacent
View Answer

Answer: a
Explanation: Deep-seated electrodes indicate the electric potential difference arising inside the living tissues or cells. Surface electrodes indicates the electric potentials arising outside the living tissues that is on the surface of the skin. Needle electrodes are example of deep seated electrodes.
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4. Impedance pneumography is a commonly-used technique to monitor a person’s _______
a) respiration rate
b) heart rate
c) pulse rate
d) skin impedance
View Answer

Answer: a
Explanation: Impedance pneumography is a commonly-used technique to monitor a person’s respiration rate, or breathing rate. It is implemented by using two electrodes or four electrodes. Skin impedance is the resistance between the skin and the electrode. Heart rate measurement is called ECG.

5. Electrode paste ____________
a) increases contact impedance
b) equates contact impedance
c) reduces contact impedance
d) absorbs contact impedance
View Answer

Answer: c
Explanation: In order to obtain a clearly established contact (low contact impedance) an electrolyte or electrode paste is usually employed as an interface between the electrode and the surface of the source of the event. It is placed between the skin and the electrode. It helps to get better signal acquisition.
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6. All electrode potentials are measured with respect to which reference electrode?
a) hydrogen electrode
b) platinum electrode
c) calomel electrode
d) hydrogen absorbed on platinum electrode
View Answer

Answer: d
Explanation: All electrode potentials are measured with respect to a reference electrode, usually that of hydrogen absorbed on platinum black. Thus, considering potential of hydrogen absorbed on platinum electrode to be zero, other all have positive of negative potentials.

7. What is the frequency range of ECG?
a) 70-120 Hz
b) 0.05-120 Hz
c) 5-120 Hz
d) 12-120 Hz
View Answer

Answer: b
Explanation: Primary signal characteristics of ECG are:
Frequency range: 0.05-120 Hz.
Signal amplitude: 0.1-5 mV.
Typical signal: 1mV.
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8. What is the signal amplitude of EEG?
a) 2-200 µV
b) 2-200mV
c) 2-2000 µV
d) 2-2000mV
View Answer

Answer: a
Explanation: The signal amplitude of EEG is between 2-200 µV. It is very small and requires special type of electrodes namely scalp electrodes. EEGs are difficult to capture because its signal range in very small and motion artifacts are much greater.

9. Needle electrode is used to measure ____________
a) EKG
b) EEG
c) EOG
d) EMG
View Answer

Answer: d
Explanation: EMG stands of Electromyogram. For recording action potential for individual motor units of muscle fiber, needle electrodes are used for better diagnostic information. These electrodes fall in the category of deep seated electrodes.
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10. From equipment point of view, the respiratory system in the human body is a _________ system.
a) hydraulic
b) pneumatic
c) mechanical
d) electrical
View Answer

Answer: b
Explanation: Respiratory system is a pneumatic system in which an air pump (diaphragm) alternately creates negative and positive pressures in a sealed chamber (thoracic cavity) and causes air to be sucked into and forced out of a pair of elastic bags (lungs). Blood circulatory system is related to hydraulic system.

11. Off-set potential is _____________
a) difference in half-cell potentials between two electrodes
b) sum of half-cell potentials between two electrodes
c) average of half-cell potentials between two electrodes
d) complement of half-cell potentials between two electrodes
View Answer

Answer: a
Explanation: The difference in half cell potential that exists between two electrodes is called off-set potential. The differential amplifies used to measure potentials between two electrodes are generally designed to cancel the electrode offset potential so that only the signals of interest are recorded.

12. Which of the following is not preferred for electrode making?
a) Ag-AgCl
b) Copper
c) Stainless-steel
d) Gold
View Answer

Answer: c
Explanation: Stainless steel in contact with a saline electrolyte produce a potential difference of 10 mV between the electrodes which is much more than the limit (i.e 2.5 mV). Ad-AgCl electrodes give almost noise free characteristics. They are also found to be acceptable from the point of view of long term drift.

13. Which of the following statement is false about polarizable electrodes?
a) they are made using stainless steel
b) used for recording resting ECG
c) retain a residual charge when exposed to large pulse of energy
d) can transmit small bioelectric signals even after getting exposed to large pulse of energy
View Answer

Answer: d
Explanation: Polarizable electrodes usually employ stainless steel and are used for resting ECG or other situations where there is small likelihood that the electrode would be exposed to a large pulse of energy (such as defibrillation discharge) in which case they would retain a residual charge, become polarized, and will no longer transmit the relatively small bioelectric signals, thus become useless.

14. Which electrodes can work even after being induced to large electric discharge such as defibrillation?
a) polarizing electrodes
b) magnetic electrodes
c) non-polarizing electrodes
d) electrolytic electrodes
View Answer

Answer: c
Explanation: Non-polarizing electrodes are designed to rapidly dissipate any charge imbalance induced by powerful electric discharges such as a defibrillation procedure. Rapid depolarization enables the immediate reappearance of bioelectric signals on the monitor after defibrillation. For this reason, non-polarizing electrodes have become the electrodes of choice for monitoring in the intensive care units and stress testing procedures.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn | Youtube | Instagram | Facebook | Twitter