# Biomedical Instrumentation Questions and Answers – Spirometry

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

1. What is the pH range of extracellular fluid?
a) 7.25 to 730
b) 7.30 to 7.35
c) 7.35 to 7.45
d) 7.50 to 7.60

Explanation: The normal pH of the extracellular fluid lies in the range of 7.35 to 7.45, indicating that the body fluid is slightly alkaline. When the pH exceeds 7.45, the body is considered to be in a state of alkalosis. A body pH below 7.35 indicates acidosis. Both acidosis or alkalosis are disease conditions widely encountered in clinical medicine.

2. What is the pH of Arterial blood?
a) 7.25
b) 7.30
c) 7.35
d) 7.40

Explanation: Arterial blood has a pH of approximately 7.40. As venous blood acquires carbon dioxide, forms carbonic acid and hydrogen ions, the venous blood pH falls to approximately 7.36. This pH drop of 0.04 units occurs when the CO2 enters the tissue capillaries. When CO2 diffuses from the pulmonary capillaries into the alveoli, the blood pH rises 0.04 units to bring the normal arterial value of 7.40.

3. What is the pH range of intracellular fluid?
a) 7.0 to 7.2
b) 7.3 to 7.35
c) 7.35 to 7.45
d) 7.50 to 7.60

Explanation: When CO2 diffuses from the pulmonary capillaries into the alveoli, the blood pH rises 0.04 units to bring the normal arterial value of 7.40. It is quite difficult to measure the pH of fluids inside the tissue cells, but from estimates based on CO2 and (HCO–3) ion concentration, intracellular pH probably ranges from 7.0 to 7.2.
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4. What is E0 in given equation?

a) induced emf
c) pH value deviation from 7
d) standard potential

Explanation: The potential (E) of the glass electrode may be written by means of the Nernst
equation:

where, Eo = standard potential R = gas constant T = absolute temperature F = Faraday constant DpH = pH value deviation from 7.The above relation shows that the emf developed in the electro-chemical pH cell is a linear function of DpH.

5. What is E in given equation?

a) induced emf
c) pH value deviation from 7
d) standard potential

Explanation: The potential (E) of the glass electrode may be written by means of the Nernst
equation:

where, Eo = standard potential R = gas constant T = absolute temperature F = Faraday constant DpH = pH value deviation from 7. The above relation shows that the emf developed in the electro-chemical pH cell is a linear function of DpH.

6. With a 1°C change in temperature, the emf changes by ________ mV.
a) 0.1
b) 0.2
c) 0.5
d) 0.8

Explanation: The factor –2.3036 RTF is called the slope factor and is clearly dependent upon the solution temperature. With a 1°C change in temperature, the emf changes by 0.2 mV. It is also obvious that the measurement of pH is essentially a measurement of millivolt signals by special methods.

7. The venous blood pH falls to approximately 7.36.
a) True
b) False

Explanation: True, as venous blood acquires carbon dioxide, forms carbonic acid and hydrogen ions, the venous blood pH falls to approximately 7.36. This pH drop of 0.04 units occurs when the CO2 enters the tissue capillaries. When CO2 diffuses from the pulmonary capillaries into the alveoli, the blood pH rises 0.04 units to bring the normal arterial value of 7.40.

8. How much amount of capillary blood is required by a micro-electrode for determination of pH?
a) 5 to 10 ml
b) 10 to 12 ml
c) 12 to 18 ml
d) 20 to 25 ml

Explanation: A micro-electrode for clinical applications requires only 20–25 ml of capillary blood for the determination of pH. The electrode is enclosed in a water jacket with circulating water at a constant temperature of 38°C. The water contains 1% NACI for shielding against static interference.

9. The micro-electrode is enclosed in a water jacket with circulating water at a constant temperature of ___________ °C for determination of pH.
a) 25
b) 34
c) 38
d) 42

Explanation: A micro-electrode for clinical applications requires only 20–25 ml of capillary blood for the determination of pH. The electrode is enclosed in a water jacket with circulating water at a constant temperature of 38°C. The water contains 1% NACI for shielding against static interference.

10. Internal Reference electrode is of _______
a) gold
b) silver
c) platinum
d) graphite

Explanation: The internal reference electrode is silver/silver chloride and the calomel reference electrode is connected to a small pool of saturated KCI, through a porous pin. Accuracy of 0.001 pH can be obtained with this electrode against a constant buffer.

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