This set of Biomedical Instrumentation Multiple Choice Questions & Answers (MCQs) focuses on “Electrocardiography”.
1. The frequency range of ECG is ____________
a) 0.05-150 HZ
b) 500-1500 Hz
c) 5-500 kHz
d) 0.5-150 MHz
Explanation: The diagnostically useful frequency range is usually accepted as 0.05 to 150 Hz. Although the electric field generated by the heart can be best characterized by vector quantities, it is generally convenient to directly measure only scalar quantities, i.e. a voltage difference of mV order between the given points of the body.
2. Which of the following amplifier circulatory is employed to reduce the hum noise generated by the power supply in the ECG circuit?
a) band pass filters
b) high pass filters
c) notch filters
d) low pass filters
Explanation: A notch filter is employed to suppress the hum noise generated by the power supply in the ECG circuit. CMRR of the order of 100–120 dB with 5 kW unbalance in the leads is a desirable feature of ECG machines. The instability of the baseline, originating from the changes of the contact impedance, demands the application of the automatic baseline stabilizing circuit.
3. The branch of medicine that deals with the provision and use of artificial devices such as splints and braces is _________
d) augmentative communication
Explanation: The branch of medicine that deals with the provision and use of artificial devices such as splints and braces are orthotics. A modality-specific appliance that aids the performance of a function or movement by augmenting or assisting the residual capabilities of that function or movement. An orthopaedic brace is an orthosis.
4. The sensitivity of an electrocardiograph is typically set at 10 mm/mV.
Explanation: It is true. The sensitivity of an electrocardiograph is typically set at 10 mm/mV. For routine work, the paper recording speed is 25 mm/s. Amplitude measurements are made vertically in millivolts. Time measurements and heart rate measurements are made horizontally on the electrocardiogram.
5. The volume of blood within the dialyzer is known as ___________
a) secondary volume
b) quarterly volume
c) priming volume
d) residual volume
Explanation: The volume of blood within the dialyzer is known as priming volume. It is desirable that this should be minimal. Priming volume of present day dialyzers ranges from 75 to 200 ml, depending on the membrane area geometry and operating conditions.
6. The ideal membrane should possess ___________ to water.
a) low permeability to water
b) high permeability to water
c) medium permeability to water
d) high permeability to waste
Explanation: The ideal membrane should possess high permeability to water, organic metabolites and ions, and the capability of retaining plasma proteins. The membrane should be of sufficient wet strength to resist tearing or bursting and non-toxic to blood and all body cells.
7. To achieve optimum performance and to enable the relationship of change in resistance with the volume of the cell to hold good, it is recommended that the ratio of the aperture length to the diameter of the aperture should be __________
Explanation: To achieve optimum performance and to enable the relationship of change in resistance with volume of the cell to hold good, it is recommended that the ratio of the aperture length to the diameter of the aperture should be 0.75:1, i.e. for an orifice of 100 m diameter the length should be 75 m. The instrument based on the Coulter principle works most satisfactorily when the average diameter of the particles ranges between 2 to 40% of the diameter of the measuring hole.
8. The blood is a poor conductor of electricity.
Explanation: It is true. Blood is a poor conductor of electricity. This principle is used in Coulter counters to count the number of RBCs in the blood.
9. In floating electrodes metal electrode does not make direct contact with the skin.
Explanation: In a floating electrode, the metal electrode does not make direct contact with the skin. The electrode consists of a light weighted metalled screen or plate held away from the subject by a flat washer which is connected to the skin. Floating electrodes can be recharged, i.e. the jelly in the electrodes can be replenished if desired.
Sanfoundry Global Education & Learning Series – Biomedical Instrumentation.
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