Ventilation and Perfusion

Question 1

What is equala to [oxygen]alveolar= [oxygen in lungs] - [oxygen used by tissue] (calculation) ALVEOLAR GAS EQUATION

Answer 1

PAo2 = Pio2 - PaCo2 / R PAo2= alveolar partial pressure of oxygen PiO2= inspired partial pressure of oxygen, including water vapor (760-47 x oxygen%) AT SEA LEVEL PaCO2= arterial CO2 R= respiratory quotient (co2 produce/O2 used tissues)

Question 2

What does alveolar has equation tell us?

Answer 2

What inspired O2 needs to be to produce a desired alveolar/arterial O2 level

Question 3

The alveolar gas equation is not very useful. However it allows you to calculate what, which is useful for determind the health of the alveoli?

Answer 3

The A-a O2 gradient!

Question 5

What is the calculation for A-aO2 gradient?

Answer 5

PAO2 - PaO2 = number! gradient

Question 6

What is the normal A-aO2 gradient?

Answer 6

Less than 20mmHg

Question 7

An increase in the A-aO2 gradient could suggest what?

Answer 7

That something is wrong with alveolar diffusion

Question 8

Quick review of regional blood flow in the lungs. Which regions will have high, medium and low blood flow/pressures?

Answer 8

Zone 1 at apex is low flow/pressure Zone 2 is average Zone 3 is high at base d/t gravity

Question 9

As we know. Gravity works on blood in our bodies. When we stand, hydrostatic pressure in our legs increases compared to the level of the heart of brain. Does this occur in the lungs?

Answer 9

YES

Question 10

What is the regional blood flow of the lungs?

Answer 10

Apex of the lung- decreased BP; decreased blood flow

Middle regions of the lung- BP is normal; blood flow is normal

Base region of the lung- BP high; Blood flow is high.

Question 11

Is the intrapleural fluid acted on by gravity?

Answer 11

Yes. Thus, it affects the intrapleural pressure.

Question 12

Due to gravity, there is more intrapleural fluid where?

Answer 12

Near the base, than the apex.

Question 13

What is the intrapleural pressure and fluid concentration at the

• Apex
• Base

Answer 13

Apex- less intrapleural fluid= intrapleural pressure is more negative (up to -10cm H20)

Base- more intrapleural fluid=intrapleural pressure is less negative (-2–3 cmH20)

Question 14

How does the intrapleural pressure differences of the lungs affect the sizes of the alveoli?

Answer 14

Apex=

• intrapleural fluid=

more negative pressure (-10)=

larger alveoli

Base=

+ intrapleural fluid=

Less negative pressure (-2-3 mmHg)

smaller alveoli

Question 15

Since intrapleural pressure is more negative at the apex, the alveoli are large at rest. What happens at the base?

Answer 15

pressure is less so alveoli are small because they are not as expanded by the pressure

Question 16

What occurs in the large alveoli at the apex of the lung due to the high intrapleural pressure during inspiration?

Answer 16

The alveoli get a little larger (because they are already pretty big).

For a given change in pressure, you will not produce a big change in volume.

Question 17

What occurs in the small alveoli at the base of the lung due to the low intrapleural pressure during inspiration?

Answer 17

The alveoli get much larger

For a given change in pressure, you will get a higher change in volume, compared to the alveoli in the apex.

Question 18

Apex: ____ fluid, pressure is _______, size of alveoli= ____

Base: ____ fluid, pressure is ______, size of alveoli= _____

Answer 18

Apex= little fluid, pressure is more - than other regions, alveoli are larger than base

Base: more fluid, pressure is less negative than other regions, alveoli are smaller than apex, however, they will get a bigger change in volume

Question 19

Overall, the aleveolar volume between apex and base alveoli are much difference. With base alveoli have 20-40% volume and apex having 90-95% volume. Why?

Answer 19

Alveoli are larger in the apex due to the lack of intrapleural fluid, which allows for volume in the apex to be increased, decreasing the intrapleural pressure, and increasing the size of alveoli.

In the base, there is more intrapleural fluid d/t gravity, so there is less room for the lungs to expand, so less volume, leading to a less negative intrapleural pressure. So the alveoli are small and do not increase in size much due to the intrapleural fluid

Question 20

What is the ventilation perfusion ration?

Answer 20

V/Q

In a normal person, the ventilation/perfusion ratio is 4L min/ 5L/min= 0.8/

But this varies depending on the region.

Question 21

High V/Q?

Answer 21

ratio is >0.8.

Ventillation is high compared to perfusion.

Question 22

Low V/Q

Answer 22

<0.8

Ventilation is low compared to perfusion

Question 23

What occurs when the V/Q ratio is 0.8?

PAO2=100mmHg

PACO2=40mmHg

PaO2= 40mmHg

PaCO2= 45mmgHg

Answer 23

The aveoli (lungs) and capillary will become to an equillbrium

Question 24

What happens if we have a low V/Q (ventillation is low due to the airway being blocked by something).

Answer 24

• Blood will continue to travel to the alveolus, even though ventilation is low.
  1. At first, our blood will come to an equillibrium with lungs (alveolus)
  2. However, the O2 in the alveolus decreases (because the blood is removing the oxygen), while the CO2 increases (as the blood delivers CO2).
  3. The same changes will occur in the blood.
  4. Overtime, the alveolus will equillibriate with the venous blood and the blood that enters the alveolus will leave without exchanging O2 or CO2.

Question 25

When blood enters and leaves the alveolus without exchanging O2 and CO2, what is this called?

Answer 25

A shunt.

- The blood gained nothing by going to the lungs; thus, it was as if it never went.

Question 26

What is an example that would leave to a high V/Q?

Answer 26

If there is no blood coming to the alveolus; as a result, less blood is removing O2 and adding CO2.

Question 27

What happens when there is a high V/Q?

Answer 27

-Perfusion is decreased. Thus, less blood will go to the area.

As a result, the alveolar O2 will increase, CO2 will decrease, bringing the alveolus closer to atmospheric conditions.

Eventually, the alveolar air will be similar to the air outside the body (atomospheric). because no the blood is not taking away the O2 or adding CO2.

Question 28

BUT WAIT; a high V/Q ratio sounds great. We have a high O2 and less CO2. Is it a dream come true?

Answer 28

No. Because remember. Blood flow to the area is v low. Thus, not much benefits from it.

Question 29

After time, with no blood picking up the O2, the alverolar air in the areas will be similar to the air outside the body.

What happens to the blood that couldnt get to the alveolus?

Answer 29

The blood will go to normal alveolus turn it from

normal alveolus–> alveolus wiith a low V/Q ratio, even though the airflow is normal.

This is due to the increase in blood flow (increase in perfusion) to the aveoli.

(decreases alveolar O2 and increases alveolar CO2)

Question 30

In a High V/Q region

—-What is the—

PaO2

PaCO2

pHa

Volume of blood

Answer 30

PaO2= high

PaCO2= low

pHa= high

Volume of blood= low (the volume of blood that went to this area is low)

Question 31

In a Low V/Q region,

what is the

PaO2

PaCO2

pH

volume of blood?

Answer 31

-PaO2–> low

PaCO2–> high

pH–> low

Volume of blood–> high relative to air.

BAD NEWS: tends to to get alot of blood that goes to this area.

Question 32

Do we have V/Q inequalities in our bodies?

Answer 32

Yes, throughout our body we have minor V/Q inequalities.

Question 33

What is the V/Q ratio in the apex (zone 1)?

Answer 33

• BP is decreased
• Blood flow is decreased (Perfusion is decreased)

== High V/Q ratio, results in a higher PaO2, lower PaCO2 and a higher pH

Question 34

What is the V/Q ratio in the zone 2?

Answer 34

V/q ratio is 0.8.

Blood gases are PaO2= 100 mmHg,

PaCO2= 40 mmHg.

Question 35

What is the V/Q ratio at the base zone 3?

Answer 35

High BP,

High blood flow (high perfusion)

= Low V/Q

Blood gases are not as good as we expect: