Author Question: Which of the following represents the relationship used by body plethysmography to calculate ... (Read 48 times)

leo leo · **on:** Jul 16, 2018

Which of the following represents the relationship used by body plethysmography to calculate functional residual capacity?

a. VFRC = V P (PB PH2O) c. VFRC = V T (PB PH2O)
b. VFRC = P V (PB PH2O) d. VFRC = (PB PH2O) V

Question 2

The end point of a helium dilution test occurs when:

a. nitrogen is washed out.
b. there is no more helium.
c. the change in pressure remains steady.
d. the helium percentage remains steady for 2 minutes.

joechoochoy · **Reply #1 on:** Jul 16, 2018

Answer to Question 1

ANS: A
VFRC = V P (PB PH2O), where V and P are the box volume and alveolar pressure changes measured during the panting maneuver, PB is the ambient barometric pressure, and PH2O is the water vapor pressure (assume 47 mm Hg for 37 C).

Answer to Question 2

ANS: D
The end point of the helium dilution test is reached when the helium percentage remains steady for 2 minutes, indicating that the helium is equilibrated between the spirometer and the patient's lungs.