Thursday, July 19, 2012

[RS] Q.13 Define vital capacity(VC), factors affecting vital capacity



 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.


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