In both the helium dilution test and nitrogen washout functional residual capacity (FRC) determinations, at what point should the patient normally be connected to the system to begin the test?

Question

Quizplus · Accepted Answer

In both the helium dilution and nitrogen washout methods, the patient should be connected to the system at resting expiration. This is because at the end of expiration, the lungs contain the functional residual capacity (FRC), which is the volume of air left in the lungs after a normal expiration. By starting the test at resting expiration, we can measure the FRC accurately. Connecting the patient at full forced inspiration or expiration would not give accurate results.

In Both the Helium Dilution Test and Nitrogen Washout Functional