Thu7October0140PM 4

Which one of the following lung volumes is most likely to be measured indirectly?

(Please select 1 option)

Functional residual capacity Correct

Forced expiratory volume in 1 second

Tidal volume

Vital capacity

Inspiratory reserve volume

Explanation

Functional residual capacity (FRC) is the volume of air present in the lungs, specifically the parenchyma tissues, at the end of passive expiration.

At FRC, the elastic recoil forces of the lungs and chest wall are equal but opposite and there is no exertion by the diaphragm or other respiratory muscles.

FRC is the sum of expiratory reserve volume (ERV) and residual volume (RV) and measures approximately 2400 ml in a 70 kg, average-sized male.

It cannot be estimated through spirometry, since it includes the residual volume. In order to measure RV precisely, one would need to perform a test such as nitrogen washout, helium dilution or body plethysmography.

The helium dilution technique is a common way of measuring the functional residual capacity of the lungs.

Answer Statistics

1

83%

2

2%

3

1%

4

7%

5

9%

Times answered: 226