Ans.
Vital capacity:
(FVC or FEV)
The maximum
amount of air that a person can expire forcefully after a forceful inspiration
is called vital capacity (VC).
Amount –
about 4600 ml.
Factors
affecting vital capacity:
1) Age
– It more in young.
2) Sex
– 20-25% less is female.
3) Surface
area – It is proportional to surface area.
4) Posture
– Lying – Lowest (↑ Pulmonary blood volume)
Sitting – More than
lying
Standing – Highest
5)
Strength of respiratory muscles - More the strength,
more vital capacity such as athletes.
6)
Disease in the lungs and pleura causes decrease vital
capacity such as-
· Tuberculosis
· Ch. Asthma
· Ch. Bronchitis
· Pulmonary edema,
etc.
Importance:
It is an
index of lung function and provides useful information about-
a)
Abnormal ventilation due to airway obstruction, fibrosis
of lungs.
b)
Mechanical interference with chest expansion and
compression.
c)
Strength of respiratory muscles.