250+ TOP MCQs on Oximeters and Answers

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Biomedical Instrumentation Multiple Choice Questions on “Oximeters”.

1. Blood flow detectors based on Doppler shift start detecting foetal pulses as early as in which week of pregnancy?
a) tenth
b) eleventh
c) twelfth
d) ninth
Answer: b
Clarification: Blood flow detectors based on ultrasonic Doppler shift can detect foetal pulse as early as the tenth week of pregnancy and in nearly all cases by the twelfth week. At about 20 weeks it is possible to detect multiple pregnancies especially if two instruments are used together and the pulse rates compared. Intrauterine death of the foetus can also be diagnosed.

2. When it is possible to detect multiple pregnancies?
a) 10th week
b) 12th week
c) 15th week
d) 20th week
Answer: d
Clarification: Blood flow detectors based on ultrasonic Doppler shift can detect foetal pulse as early as the tenth week of pregnancy and in nearly all cases by the twelfth week. At about 20 weeks it is possible to detect multiple pregnancies especially if two instruments are used together and the pulse rates compared. Intrauterine death of the foetus can also be diagnosed.

3. Which of the following is the most reliable method for detecting FHR pattern?
a) Abdominal foetal electrocardiogram
b) Foetal phonocardiogram
c) Ultrasound technique
d) Foetal ECG with scalp electrode
Answer: c
Clarification: We can hear the signal through a loudspeaker with a scarce chance of failing to recognize any beat, but a simple electronic circuit may fail to trigger from this signal. Still, the ultrasound Doppler shift method is more practical and easy to use during labour. It is currently the most reliable method for detecting the FHR pattern that is interpretable.

4. Signal processing for FHR determination can be based either on detecting the foetal heart valve motion or on detecting the heart wall motion in Abdominal foetal electrocardiogram technique.
a) True
b) False

Answer: b
Clarification: False, Signal processing for FHR determination can be based either on detecting the foetal heart valve motion or on detecting the heart wall motion in Ultrasound technique as The heart valve motion detection technique is based on the distinct ultrasound frequency shift produced by the fast opening and closing of the heart valves. The technique, however, requires that the ultrasound beam must be directed against the relatively small heart valves involving a longer search period and frequent repositioning of the transducer. Therefore, it is not preferred for continuous monitoring applications.

5. What is maximum ultrasound intensity of narrow beam transducer?
a) 15 mW/cm2
b) 20 mW/cm2
c) 25 mW/cm2
d) 30 mW/cm2
Answer: c
Clarification: The narrow beam transducer uses a single ultrasound transmitter/receiver piezo-electric crystal pair. The maximum ultrasound intensity is generally kept below 25 mW/cm2. The typical transducer diameter is 25 mm. The narrow beam transducer is very sensitive and produces a good trigger signal for instantaneous heart rate determination.

6. What is the diameter of a narrow beam transducer?
a) 15 mm
b) 20 mm
c) 25 mm
d) 30 mm
Answer: c
Clarification: The narrow beam transducer uses a single ultrasound transmitter/receiver piezo-electric crystal pair. The maximum ultrasound intensity is generally kept below 25 mW/cm2. The typical transducer diameter is 25 mm. The narrow beam transducer is very sensitive and produces a good trigger signal for instantaneous heart rate determination.

7. What is used to detect foetal heart movements in broad beam transducer?
a) Quartz crystal
b) Piezo electric crystal
c) Topaz crystal
d) Berlinite crystal
Answer: b
Clarification: The broad beam transducers are available in many configurations. The transducers comprise a number of piezo-electric crystals mounted in such a way as to be able to detect foetal heart movements over a wider area.

8. The narrow beam transducer is very sensitive and produces a good trigger signal for instantaneous heart rate determination.
a) True
b) False

Answer: a
Clarification: True, The narrow beam transducer is very sensitive and produces a good trigger signal for instantaneous heart rate determination because it takes time to detect a good signal and, therefore, frequent transducer repositioning is necessary.

9. Which of the following transducer is used to detect foetal heart movements over a wider area?
a) piezo-electric
b) ultrasonic
c) array
d) pressure
Answer: a
Clarification: The broad beam transducers are available in many configurations. The transducers comprise a number of piezo-electric crystals mounted in such a way as to be able to detect foetal heart movements over a wider area.

10. Which transducer is arranged in the shape of a clover leaf so that it provides a large area of illumination?
a) piezo-electric
b) ultrasonic
c) array
d) pressure
Answer: b
Clarification: The ultrasonic transducer is arranged in the shape of a clover-leaf so that it provides a large area of ultrasonic illumination which allows the monitoring considerable lateral and descending foetal motion before requiring repositioning. The transducer housing is flexible to permit it to follow the contour of the abdomen regardless of shape changes with contractions.

11. The array transducer housing is flexible to permit it to follow the contour of the abdomen regardless of shape changes with contractions.
a) True
b) False
Answer: b
Clarification: False, the ultrasonic transducer is arranged in the shape of a clover-leaf so that it provides a large area of ultrasonic illumination which allows the monitoring considerable lateral and descending foetal motion before requiring repositioning. The ultrasonic transducer housing is flexible to permit it to follow the contour of the abdomen regardless of shape changes with contractions.

12. At what angle divergent beam is transmitted by a crystal in array transducer?
a) 10°
b) 20°
c) 30°
d) 40°

Answer: d
Clarification: An alternative arrangement is the array transducer which has one transmitter and six peripheral ceramic receiving crystals. The transmitting crystal emits a 40° divergent beam so that at 10 cm from the skin surface the beam covers an area of approximately 10 cm diameter.

13. The transmitting crystal emits 40° divergent beam so that the beam covers an area of approximately _____ cm diameter.
a) 10
b) 20
c) 30
d) 40
Answer: a
Clarification: An alternative arrangement is the array transducer which has one transmitter and six peripheral ceramic receiving crystals. The transmitting crystal emits a 40° divergent beam so that at 10 cm from the skin surface the beam covers an area of approximately 10 cm diameter.

14. What is the diameter of an array transducer?
a) 2
b) 4
c) 6
d) 8
Answer: c
Clarification: The transmitting crystal emits a 40° divergent beam so that at 10 cm from the skin surface the beam covers an area of approximately 10 cm diameter. This construction ensures continuous recording of the foetal heart activity without the need to reposition the transducer which is otherwise necessitated due to normal foetal movement. The transducer has a diameter of 6 cm and can be held in place either by a simple buckle or a stretch belt.

15. The array transducer can be held in place by a simple buckle.
a) True
b) False
Answer: a
Clarification: True, the transmitting crystal emits a 40° divergent beam so that at 10 cm from the skin surface the beam covers an area of approximately 10 cm diameter. This construction ensures continuous recording of the foetal heart activity without the need to reposition the transducer which is otherwise necessitated due to normal foetal movement. The transducer has a diameter of 6 cm and can be held in place either by a simple buckle or a stretch belt.

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