250+ TOP MCQs on Ambulatory Monitoring Instruments and Answers

Biomedical Instrumentation Multiple Choice Questions on “Ambulatory Monitoring Instruments”.

1. Where are the electrodes placed for recording foetal electrocardiogram?
a) heart
b) abdomen
c) brain
d) veins
Answer: b
Clarification: Foetal electrocardiogram is recorded by suitably placing the electrodes on the mother’s abdomen and recording the combined maternal and foetal ECG. The maximum amplitude of FECG (R wave) recorded during pregnancy is about 100 to 300 mV. This magnitude is much smaller than in the typical adult ECG which is about 1 mV in the standard lead connection.

2. What is the maximum amplitude of FECG recorded during pregnancy?
a) 100 to 300 mV
b) 300 to 500 mV
c) 500 to 700 mV
d) 700 to 900 mV
Answer: a
Clarification: Foetal electrocardiogram is recorded by suitably placing the electrodes on the mother’s abdomen and recording the combined maternal and foetal ECG. The maximum amplitude of FECG (R wave) recorded during pregnancy is about 100 to 300 mV. This magnitude is much smaller than in the typical adult ECG which is about 1 mV in the standard lead connection.

3. The foetus heart rate is approximately _______ time/s of normal adult foetal heart rate.
a) one
b) two
c) three
d) four
Answer: b
Clarification: The foetal heart rate is computed from the foetal ECG by appropriately shaping the foetal QRS wave. The foetus heart rate is approximately twice that of the normal adult ranging approximately from 110 to 180 bpm. The main problem in processing the foetal heart signals is the poor SNR.

4. Which of the following is periodic noise source in the foetal ECG signal from the maternal abdomen?
a) Amplifier input noise
b) Maternal Muscle noise
c) Fluctuations in electrode polarization potential
d) Maternal ECG

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Answer: d
Clarification: The major sources of noise in the foetal ECG signal recorded from the maternal abdomen are (i) amplifier input noise, (ii) maternal muscle noise (EMG), (iii) fluctuations in electrode polarization potential, and (iv) maternal ECG. For practical purposes, the first three of these sources can be considered as random whereas the maternal ECG is a periodic noise source.

5. What is the magnitude of ECG for a typical adult in the standard lead connection?
a) 1 mV
b) 2 mV
c) 3 mV
d) 4 mV
Answer: a
Clarification: Foetal electrocardiogram is recorded by suitably placing the electrodes on the mother’s abdomen and recording the combined maternal and foetal ECG. The maximum amplitude of FECG (R wave) recorded during pregnancy is about 100 to 300 mV. This magnitude is much smaller than in the typical adult ECG which is about 1 mV in the standard lead connection.

6. Which of the following technique is used to measure foetal heart rate?
a) ECG
b) FECG
c) PCG
d) VCG
Answer: b
Clarification: Abdominal FECG processing circuit is used for computing foetal heart rate. After proper placement of the electrodes, the signals are amplified in a preamplifier which provides a very high input impedance (100 MW) and high sensitivity and good common mode rejection ratio (up to 120 dB).

7. What is the CMRR of Foetal electrocardiogram?
a) 0-150 dB
b) 0- 130 dB
c) 0-120 dB
d) 0-200 dB
Answer: c
Clarification: Abdominal FECG processing circuit is used for computing foetal heart rate. After proper placement of the electrodes, the signals are amplified in a preamplifier which provides a very high input impedance (100 MW) and high sensitivity and good common mode rejection ratio (up to 120 dB).

8. What is responsible for most of the common-mode interfering signal?
a) Preamplifier
b) Notch Filter
c) Power Line Hum
d) Band Pass Filter

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Answer: c
Clarification: A sizable common-mode signal manages to pass through the input amplifier, a circumstance to be expected whenever electrodes spaced a few centimetres apart are attached to the human body in a hospital environment. Power line hum is responsible for most of the common-mode interfering signal. This is suppressed by a notch filter following the input amplifier.

9. What is present in the processing circuit for signal separation?
a) Preamplifier
b) Power Line Hum
c) Notch Filter
d) Band Pass Filter
Answer: d
Clarification: The signal path then splits into two channels: the maternal ECG channel or Mchannel and the foetal or F channel. Since the frequency spectrum of the foetal ECG differs somewhat from the maternal ECG, some initial signal separation is achieved by using the appropriate bandpass filtering in each channel.

10. The F channel has a _______ ms pulse generator that is triggered by the foetal ECG.
a) 5
b) 10
c) 20
d) 30
Answer: d
Clarification: The F channel has a 30 ms pulse generator that is triggered by the foetal ECG. It is inhibited, however, by the blanking pulse from the M channel, so it will not generate a pulse in response to the maternal ECG signal feeding through to the F channel.

11. Foetal ECG signal detected via electrodes placed on mother’s abdomen is complex and requires accertion of maternal signals for obtaining FHR.
a) True
b) False
Answer: b
Clarification: False, Foetal ECG signal detected via electrodes placed on the mother’s abdomen is complex and requires attenuation of maternal signals for obtaining FHR. Also, due to the overlapping of the foetal ECG with the maternal ECG, about 20% to 50% of the expected pulses may be missing.

12. AECG technique fails in those rare cases where the amniotic fluid fails to provide adequate electrical coupling from foetus to mother.
a) True
b) False
Answer: a
Clarification: Clinical trials have shown that the AECG technique is usually effective in most cases except in those rare cases where the amniotic fluid fails to provide adequate electrical coupling from foetus to mother. However, during labour, the uterine and abdominal wall electromyogram signals tend to obliterate the FECG signal, making FHR counting quite difficult. At present, the abdominal FECG, therefore, does not seem to offer a practical reliable means of FHR monitoring during labour and delivery.

13. What is delay time to establish a missing foetal trigger pulse by substitution logic?
a) 150 ms
b) 200 ms
c) 250 ms
d) 270 ms
Answer: d
Clarification: The substitution logic requires a delay time to establish a missing foetal trigger pulse. On the one hand, this delay has to be longer than the maximum permissible change in heart period (14 bpm change from 50–64 bpm = 262 ms) and on the other hand, it has to be shorter than the shortest period duration (216 bpm = 285.7 ms). It is thus kept as 270 ms.

14. What is the range of FHR measurement due to substitution logic?
a) 0-200 bpm
b) 40-240 bpm
c) 20-220 bpm
d) 60-260 bpm
Answer: b
Clarification: The substitution logic requires a delay time to establish a missing foetal trigger pulse. It is thus kept as 270 ms. The range of FHR measurement is limited to 40–240 bpm because of the substitution logic. Thereafter, the output of logic circuits goes to standard heart rate computing circuits.

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