Question

The most complete and informative measurement of pulmonary function is

a Vital capacity.

b Tidal volume.

c Alveolar ventilation.

d Residual volume.

e Total pulmonary ventilation.

Answer 1

Pulmonary Function tests are a group of tests that determine the various lung volumes and lung capacities. Each measurement is indicative of different aspects.

Types of Lung Volumes:

1. Tidal Volume(TV)-volume of air inhaled or exhaled during each breath
2. Inspiratory Reserve Volume(IRV)- maximum volume of air inhaled
3. Expiratory Reserve Volume(ERV)- maximum volume of air that can be exhaled
4. Residual Volume(RV)-Volume of air remaining in the lungs after maximum exhalation

Types of lung capacities:

1. Total Lung Capacity(TLC)-sum of all volumes
2. Vital Capactiy(VC)- TLC-RV=VC
3. Inspiratory Capacity(IC)- IRV+TV
4. Expiratory Capacity(EC)= TV+ERV
5. Functional Residual Capacity(FRC)= RV+ERV
6. Forced Vital Capacity(FVC)- maximum volume of air that can be breathed out as forcefully as possible following a maximum inspiration.

Forced Expiratory Volume in 1 Second(FEV1)- volume exhaled during first second of FVC.

Ratio of FEV1/FVC is an important tool in characterizing the severity of respiratory disorders. It is calculated by determining the lung volumes and capacities.

Alveolar ventilation is the volume of air utilized for gaseous exchange per minute.

Total Pulmonary Ventilation is the volume of air breathed in and out per minute.

Tidal Volume is required to to calculated alveolar and total ventilation.

As such, alveolar and total ventilation are more informative, but all these along with pulmonary functions are calculated by first determining the lung volumes or capacities. In a way, they are dependent on it.