EDAIC Clinical Measurement and Physics 4

Question 1

Fick's law of diffusion states that the rate of gas transfer across a membrane is directly proportional to:

Accepted Answer

Surface area, partial pressure gradient, and solubility; and inversely proportional to membrane thickness and square root of molecular weight

Answer

Fick's law: flux = (A × D × ΔP) / T, where D ∝ solubility/√MW; thicker membranes and higher molecular weight reduce transfer, while larger area and pressure gradient increase it.

Question 2

In pulse oximetry, which two wavelengths of light are used to distinguish oxyhemoglobin from deoxyhemoglobin?

Accepted Answer

660 nm (red) and 940 nm (infrared)

Answer

Pulse oximeters use 660 nm red light (absorbed more by deoxyhemoglobin) and 940 nm infrared light (absorbed more by oxyhemoglobin) to calculate the ratio R.

Question 3

A soda lime canister turns violet/purple. This colour change indicates:

Accepted Answer

The pH indicator dye has responded to CO₂ absorption capacity exhaustion

Answer

Ethyl violet indicator in soda lime turns purple when the granules are exhausted and the pH drops, signaling that CO₂ absorption is impaired.

Question 4

When calibrating a Wheatstone bridge circuit used in a pressure transducer, a known resistance is substituted to simulate a known pressure. This technique is called:

Accepted Answer

Electronic calibration (cal factor substitution)

Answer

Electronic calibration substitutes a precision resistor into the bridge to simulate a defined pressure, allowing the displayed value to be verified without a fluid column.

Question 5

The Severinghaus electrode measures which blood gas parameter?

Accepted Answer

PCO₂ via a pH electrode surrounded by a bicarbonate solution and a CO₂-permeable membrane

Answer

The Severinghaus electrode uses a CO₂-permeable membrane; dissolved CO₂ equilibrates with bicarbonate solution whose pH change is sensed by an inner glass pH electrode.

EDAIC - European Diploma in Anesthesiology and Intensive Care Practice Test

EDAIC - European Diploma in Anesthesiology and Intensive Care Practice Test

EDAIC Clinical Measurement and Physics 4