Author Question: During a helium dilution test for functional residual capacity, you notice that it takes 19 min for ... (Read 31 times)

ts19998 · **on:** Jul 16, 2018

During a helium dilution test for functional residual capacity, you notice that it takes 19 min for equilibration between the gas concentrations in the spirometer and the patient's lungs. Based on this information, what can you conclude?

a. The patient has restrictive lung disease.
b. The spirometer is leaking helium.
c. The patient has obstructive lung disease.
d. Insufficient oxygen was added to the system.

Question 2

A patient has an expired minute ventilation of 14.2 L and a ventilatory rate of 25/min. What is the average VT?

a. 568 ml
b. 635 ml
c. 725 ml
d. 410 ml

Joy Chen · **Reply #1 on:** Jul 16, 2018

Answer to Question 1

ANS: C
Patients with obstructive lung disease may require up to 20 min to equilibrate because of slow gas mixing in the lungs.

Answer to Question 2

ANS: A
An alternate approach is to measure the total volume of air exhaled for 1 min (E) and then divide by the breathing frequency (f) counted during the same period. The following formula can be used to calculate the tidal volume: VT = E/f.