When Va / Q is infinity? No exchange of O2 & CO2

When Va / Q is infinity?
a) Partial pressure of O2 becomes zero
b) No exchange of O2 & CO2
c) Partial pressure of CO2 alone becomes zero
d) Partial pressure both CO2 and O2 remain normal
Correct Answer - B
Answer: B - No exchange of O2 & CO2
Va represents the ventilation in alveoli.
Q represents the blood flow through the alveolus.
The ratio of Va and Q explains the respiratory exchange when there
is an imbalance between alveolar ventilation and alveolar blood flow.
The ventilation-perfusion ratio is considered normal there is an equal
amount of blood flow & ventilation through alveolus.
Va /q ratio is Zero -
There is inadequate or nil, but perfusion persists
Va /q ratio is infinity -
There is adequate ventilation but no perfusion.
Both in the Zero and infinity Va /Q ratio, there is no exchange of
gases through the respiratory membranes of corresponding alveoli.
When Va /Q ratio is infinity,
The alveolar air equilibrates the humidified inspired air
No exchange of oxygen and carbon-di-oxide occurs.
Partial pressures of the O2 and CO2 are 149mmHg & 0 mmHg
respectively