Pul 5 - Ventilation And Perfusion

Question 1

What is the V/Q mismatch?

Answer 1

It is ventilation(V) to perfusion (Q). Ideally, this ration is 1. However, perfusion is better at the base of the lung than at the apexes.

Question 2

What is the difference of V/Q in the apex of the lung vs the base of the lung?

Answer 2

• Apex: Gravity is working against blood flow.
  1. Low perfusion.
  2. V/Q ratio is greater than 1. (Ventilation better than perfusion)
  3. Wasted ventialtion: Physiologic dead space.
• Base: Gravity is pulling more blood into the lung bases than the ability for you to ventilate.
  1. Low ventilation
  2. V/Q ratio is less than 1. (More perfusion than ventilation).
  3. Wasted perfusion: Shunting.

-In the end, perfusion and ventilation are both greater at the base of the lung.

Question 3

What happens to the V/Q ratio during exercise?

Answer 3

Vasodilation in the lung apecies, causing the V/Q ratio to go down.

Question 4

What would be the cause of V/Q approaching zero?

Answer 4

• In airway obstruction: edema, pus, tumor.

- This is called a shunt, too. Raising supplemental oxygen will not do much due to the physical obstruction.

Question 5

What happens when V/Q approaches infinity?

Answer 5

1. Blood flow obstruction: pulmonary embolism.
2. Physiologic dead space.

• Supplemental oxygen will help in this case.

Question 6

What are the tree ways that the body transports carbon dioxide?

Answer 6

1. Transported as bicarbonate (HCO3-): Carbonic anhydrase takes CO2 and H2O to form carbonic acid (H2CO3). The additional H+ is removed, leaving bicarbonate.
2. Transported bound to hemoglobin at N terminus, making carbominohemoglobin (about 5% of CO2 is transported this way).
3. Dissolved in blood (measured in ABG).

Question 7

What are all the physiological changes that happen during excersice?

Answer 7

1. Increase in O2 consumption.
2. Increase in CO2 production.
3. Increase in ventilation rate to meet O2 demand.
4. V/Q apex and base becomes more uniform.
5. Increase in pulmonary blood flow due to increase cardiac output.
6. Decrease in pH.
7. No change in arterial PO2 and PCO2 but increase in venous CO2 content.

Question 8

What is the V/Q ratio at the Apex of the lung?

Answer 8

Greater than 1.

Question 9

What is the V/Q ratio at the base of the lung.

Answer 9

Less than 1.

Question 10

What is the V/Q ratio during airway obstruction?

Answer 10

Towards zero.

Question 11

What is the V/Q ratio during blood flow obstruction?

Answer 11

Towards infinity.

Question 12

What CO2 levels change during excersice?

Answer 12

No change in arterial CO2 levels but increase in venous CO2.

Question 13

What is ventilation and what is oxygenation?

Answer 13

• Ventilation is the process of moving gas from outside the body into the alveoli.
• Oxygenation is the process of oxygen from the alveoli into the blood.

They are two independent things.