V-Q relationship Flashcards
Describe West Zone 1
In west zone one, the Pulmonary Alveolar presser is higher than both the pulmonary venous and arterial pressure
i.e PA>Pa>Pv
Describe West Zone 3
In west zone three the pulmonary arterial and venous partial pressures are greater than the pulmonary alveolar pressure
i.e. Pa>Pv>PA
In which of the west three zones has the most blood perfusion
In west zone three
Describe West Zone 2
In West Zone 2, the arterial pressure is higher than the alveolar pressure and the the alveolar pressure exceeds the venous pressure
i.e. Pa>Pv>PA
When does West Zone 1 occur
It occurs as a result of haemorrhage with severe loss of blood causing venous and arterial pressure to reduce below alveolar pressure
OR
When you mechanically ventilate a Patient increasing alveolar pressure
What drives blood flow in West Zone 2
Difference between arterial and alveolar pressure
What drives blood flow in West Zone 3
Difference between arterial and venous pressure
How does ventilation vary from apex to base of the lungs
Ventilation increases from the apex of the lung to the base of the lung
How does blood flow vary from apex to base of the lungs
blood flow increases from the apex of the lung to the base of the lung
What does a small V/Q ratio mean
It means there is high ventilation and there is high perfusion
What is the best theoretical V/Q and what is the best healthy V/Q
1.0 is the best theoretical and 0.8 is the best healthy
What is the partial pressure of O2 and CO2 at 0.8 V/Q
PaCO2 = 40mmHg
PaO2 = 100mmHg
Too high or too low V/Q ratio can cause hypoxia and hypoxemia. True or False?
True
What is the V/Q ratio at alveolar dead space
At the alveolar dead space, there’s Ventilation but no Blood perfusion. therefore V/0 = ∞
What is the V/Q ratio when there is perfusion but no ventilation
When there is perfusion but no ventilation it is 0/Q which is zero, this leads to shunting of the pulmonary capillary
