L20-VQ relationships-DONE Flashcards
(21 cards)
Is ventilation same or different in all parts of the lung?
No, because of implication-there is different gas composition in different parts of the lung.
Explain the regional differences in the context of compliance.
What does ventilation affects?
gas composition.
Is it the same or different blood gases leaving alveoli?
Blood leaving different alveoli will have different blood gases.
What does flow depend on?
Flow is dependent on pressure gradients.
What is the name of the law practical which teaches about a column of liquid relating to gravity and blood pressure.
Poiseuille’s law practical
What are the zones on gravity and perfusion and name each of them?
Zone 1-No flow
Zone 2-intermittent flow
Zone 3 -continuous flow
Zone 4-continous flow-distended > here the pulmonary blood vessels are easily distended.
What are vessels distended by…. and what does it cause?
internal pressure
-reduces V/Q at top of lung
What controls the pulmonary capillary blood flow?
- Recruitment & distension
-recruiting blood vessels which are not perfused, distending them and gouging them to get more flow through them. - Mechanical effects - There is a very close proximity between the alveoli and the blood vessels to allow gas exchange to occur via diffusion.
ie:- as we increase and stretch out the sponge, holes(airways) and the alveolar spaces get bigger and start to pinch on the blood vessels. This can affect the flow because pinching them prevents them from getting bigger. - vasoactive factors - vascular squeeze muscle can be acted on by different agonists or antagonists. Either constricting or dilating them can affect the dynamics of those vessels and therefore the flow.
True or false:
Perfusion(blood flow) varies in different parts of the lung.
True
What determines alveolar gas exchange?
The relationship between ventilation and perfusion
How are the ventilation/perfusion ratio is distributed around the lung?
-At the base of the alveoli, the ventilation/perfusion ratio is < 1.
-At the apex of the alveoli, the ventilation/perfusion ratio is > 1.
Why a continuous spectrum of V/Q ratio is possible?
The human lung is an intricate and dynamic organ where ventilation (airflow) and perfusion (blood flow) are not perfectly matched across all regions.
What are the values for V/Q ration in an:
1. underventilated alveoli ?
2. ideal alveoli ?
3. underperfused alveoli ?
- In an underventilated alveoli, the V/Q ratio < 1.
- In an ideal alveoli, the V/Q ratio = 0.
- In an underperfused alveoli, the V/Q ratio > 1.
What is the alveolar gas levels are based on ?
Based on what is added and what is removed.
What are the values for V/Q interms of O2 and CO2 ?
- In an underventilated alveoli > V/Q=0.
- In an ideal alveoli > V/Q ratio = 1.
- In an underperfused alveoli > V/Q = 8(infinity) - DEAD SPACE.
How does a mismatch on V/Q ratio affects the gases?
-High V/Q ratio happens when there’s good airflow to the alveoli but insufficient blood flow to pick up the oxygen.
-Low V/Q ratio occurs when there’s good blood flow but poor airflow to the alveoli. Consequently.
Why does blood gases from each V/Q region varies?
-depends on how much goes back to the heart.
-regions with high V/Q, low V/Q and no V/Q determines the overall gas composition.
How is V/Q mismatch minimised physiologically?
Regional control of both ventilation and perfusion.
How is high V/Q ratio is minimised for both👇 PaCO2 and 👆 PaO2 ? (alveolar Pa..)
👇 PaCO2 > Bronchoconstriction > Hyperventilation > CO2 acting on the airway smooth muscle, CO2 👇se in the airways.
👆 PaO2 > Vasodilation > Hyperventilation> Vessels in the lung dilate which brings the V/Q ratio back to original > increase Q.
Both of these cause a DECREASE in regional V/Q.
How is low V/Q ratio is minimised for bot👆 PaCO2 and👇PaO2 ?
👆 PaCO2 > Bronchodilation > Increase ventilation.
👇PaO2 > Vasoconstriction > Low O2 levels cause vasoconstriction, help restore the ratio back to normal. vasodilate the vessels in the lungs.
