Clinical Science Questions and Answers – Measuring Blood Pressure & Pulse Oximetry

This set of Clinical Science Quiz focuses on “Measuring Blood Pressure & Pulse Oximetry”.

1. Blood pressure measurement can be classified in _____ major way(s).
a) 2
b) 5
c) 7
d) 10d
View Answer

Answer: a
Explanation: Blood pressure can be measured in non invasive and invasive methods. Non invasive is when the method of measuring is completely outside the body, i.e. with the help of light or pressure detectors. Invasive is when some tube or measuring device is inserted into the body.

2. The regular BP cuff is a non – invasive method of measuring blood pressure.
a) True
b) False
View Answer

Answer: a
Explanation: BP cuff is a non invasive method of measuring blood pressure. The measuring is done by checking the pressure being applied to the mercury column due to the inflated cuff. When the cuff is inflated, it is in close contact with the arteries. Thus, the flowing blood in the arteries puts pressure on the inflated cuff which is recorded and represented by the mercury column.

3. How is the oxygen content monitored in blood?
a) By Korotkoff Sounds
b) By Pulse Oximetry
c) By Fluorescence
d) By luminescence
View Answer

Answer: b
Explanation: Pulse Oximetry is used to measure the oxygen saturation of the blood. In this process, light a light and a detector is used. It is normally in a band or a clip with the light source and the detector at the opposite ends. The light is projected at the finger and it is detected on the nail side. The light has an absorbance ratio which determines the amount of oxygen that is present in the blood.

4. What principle does pulse oximetry follow?
a) Law of Absorbance
b) Law of Reflection
c) Beer – Lambert Law
d) Law of Irradiance
View Answer

Answer: c
Explanation: Beer-Lambert relates the emerging light with the concentration of the solution and the thickness of vial/object containing the solution. When light is incident on the solution, some of the light is absorbed. This absorption depends on the concentration of the solution and the distance the light travels before it emerges. This light is measured on the outgoing end and it gives a measure of how much oxygen exists in the blood.

5. The normal BP cuff using instrument is called as____________
a) Spirometer
b) Sphygmomanometer
c) Stethoscope
d) Oscilloscope
View Answer

Answer: b
Explanation: The most commonly seen and used BP measuring instrument is the sphygmomanometer. It consists of a cuff, a bulb for inflation and a mercury column to show the pressure. When the cuff is inflated, the pressure exerted on the cuff is shown on the mercury scale. The mercury rises up and once external pumping of the air stops, the mercury falls down. It stops two times and this is the recorded blood pressure.
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6. What is the normal range of blood pressure?
a) 70/40 – 90/60
b) 90/60 – 120/80
c) 120/80 – 140/90
d) 140/90 – 190/100
View Answer

Answer: c
Explanation: The normal blood pressure in an adult human is found to be in the range of 120/80 – 140/90. BP above or below it leads to high blood pressure or low blood pressure. Blood pressure is represented by systolic pressure/diastolic pressure. Systole is when the ventricles of the heart contract, thus the pressure exerted is more and diastole is when the atria pump blood into the ventricles.

7. Which instrument is used to listen to the Korotkoff sounds?
a) Stethoscope
b) Pneumotachometer
c) Piezoelectric Microphone
d) Sphygmomanometer
View Answer

Answer: c
Explanation: Korotkoff sounds are heard while BP is measured using a cuff. The microphone is placed on the brachial artery, near the inner side of the elbow (antecubital fossa). The cuff is inflated to a [reset pressure level, around up to 30mmHg/s. The pressure is then released at around 3 – 5 mmHg/s. When the air is leaking out, Korotkoff sounds are heard. When the first Korotkoff sound (systolic) is heard, the system starts recording and when the last Korotkoff sound (diastolic) is heard, the system stops recording. The cuff gets completely deflated with 2 – 3 seconds after the last sound is heard.

8. For infants, the pulse oximetry band is attached to their ______
a) arm
b) leg
c) palm
d) foot
View Answer

Answer: d
Explanation: The infant’s fingers and ears are too small and too delicate to attach the pulse oximeter band or the pulse oximeter clip. For infants, the blood vessels of the foot are more prominent and they give a better reception as compared to the rest of the body. Also, the infant may also move their arms/ legs so the band is attached to their foot. This way, the band won’t slip off, nor will it impede any tubes or even the diaper changing process.

9. Which of the following devices/ methods do not use a cuff?
a) Rheographic Method
b) Automatic Blood Pressure Measuring using Korotkoff method
c) Oscillometric Measurement Method
d) Continuous Slow Flow Flushing Method
View Answer

Answer: d
Explanation: Continuous Slow Flow Flushing Method is used to measure the Central Venous Pressure (CVP) and is an invasive or a direct method to measure blood pressure. CVP reflects the pressure of the right atrium. A needle is inserted in the arm to monitor and record the blood pressure.

10. Which type of transducer is commonly used for invasive blood pressure measurement?
a) Capacitive
b) Rheostatic
c) Piezoelectric
d) Potentiometric
View Answer

Answer: c
Explanation: A Piezoelectric transducer converts the applied mechanical pressure into electrical pressure. Thus, the exerted blood pressure is converted into electrical impulses by the piezoelectric crystals which are amplified and recorded by the systems.

11. Which of the following uses ultrasound to check the blood flow?
a) Doppler Shift Method
b) Catheter Tip Method
c) Differential Auscultatory Technique
d) Oscillometric Method
View Answer

Answer: a
Explanation: The Doppler method is used to check the flowing blood. The ultrasound waves are projected to the blood flowing in the vessels causing Doppler effect. The returning sound waves are received and projected as images onto the screen.

12. In the differential auscultatory technique, where is the pressure sensor located?
a) In the middle of the cuff
b) In the upper portion of the cuff
c) In the lower portion of the cuff
d) Outside the cuff
View Answer

Answer: c
Explanation: In the differential auscultatory method of pressure sensing, two sensors together make the pressure sensor. One sensor is in contact with the skin while the other is in contact with the cuff. The pressure exerted by the skin due to the atrial blood flow is picked up by the sensor that is close to the skin while the pressure exerted by the cuff measured by the sensor that is close to the cuff. These sensors together give the blood pressure. Since the length of the cuff exerts pressure on the blood vessels, placing the sensor at the end of the length of the cuff ensures that the pressure is measured properly.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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