Ventilation - Perfusion Relationship (Part 2)

Question 1

What does the Alveolar Gas Equation allow you to calculate?

Answer 1

The oxygen concentration in the alveoli

Question 2

Once you know the oxygen concentration in the alveoli, (and you know the oxygen concentration in the arteries), what can you calculate?

Answer 2

A - a oxygen gradient

Question 3

What does the A - a oxygen gradient determine?

Answer 3

The health of the alveoli

Question 4

Normally, the A - a oxygen gradient should be around what value?

Answer 4

20 mm Hg

Question 5

What is the Alveolar Gas Equation?

Answer 5

PAo2 = PIo2 - (Paco2/RQ)

Question 6

What is PAo2?

Answer 6

Oxygen concentration in the alveoli

Question 7

What is PIo2?

Answer 7

Partial pressure of oxygen in inspired air

Question 8

What must the PIo2 account for?

Answer 8

Water vapor

Question 9

What is the equation to calculate PIo2?

Answer 9

(760 - 47) X oxygen%

Question 10

Normal water vapor value?

Answer 10

47

Question 11

Normal oxygen percentage of inspired air?

Answer 11

21%

Question 12

What is RQ?

Answer 12

Respiratory Quotient

Question 13

What is a normal value of RQ?

Answer 13

0.8

Question 14

What is the equation for RQ?

Answer 14

Volume of CO2 produced/Volume of O2 consumed

Question 15

If you are breathing room air, what is the equation for PIo2?

Answer 15

(760 - 47) X 21%

Question 16

What is the equation for A - a oxygen gradient?

Answer 16

PAo2 - Pa02

Question 17

If there is an increase in the A - a oxygen gradient, what does this mean?

Answer 17

There is a diffusion impairment at the alveoli

>20mmHg

Question 18

What is a normal value for Intrapleural Pressure?

Answer 18

• 5 mmHg

Question 19

At the apex of the lung, what is the amount of Intrapleural Fluid?

Answer 19

LOW

- due to gravity

Question 20

At the apex of the lung, what is the level of the Intrapleural Pressure?

Answer 20

LOWER - MORE Negative

Question 21

At the apex of the lung, what are the sizes of the alveoli?

Answer 21

LARGER

Question 22

Since the alveoli are larger at the apex of the lung, with inspiration, can they grow much in size?

Answer 22

No

Question 23

At the base of the lung, what is the amount of Intrapleural Fluid?

Answer 23

HIGH

- due to gravity it pools there

Question 24

At the base of the lung, what is the level of the Intrapleural Pressure?

Answer 24

HIGHER - LESS negative

Question 25

At the base of the lung, what are the sizes of the alveoli?

Answer 25

SMALL

Question 26

Since the alveoli are smaller at the base of the lung, with inspiration, can they grow much in size?

Answer 26

YES

Question 27

Where are alveoli the largest?

Answer 27

Apex of the lung

Question 28

Where are alveoli the smallest?

Answer 28

Base of the lung

Question 29

What is a V/Q ratio?

Answer 29

Ventilation/Perfusion ratio

Question 30

What is a normal V/Q?

Answer 30

0.8

Question 31

High V/Q means?

Answer 31

Ventilation is HIGH compared to a normal perfusion

Question 32

Low V/Q means?

Answer 32

Ventilation is LOW compared to a normal perfusion

Question 33

With a Low V/Q, what happens with time?

Answer 33

Low ventilation - the alveoli will equilibriate with the blood due to no oxygen coming into the lungs = PO2 = 40; PCO2 = 45; NO GAS EXCHANGE WILL OCCUR

Question 34

With a Low V/Q, what do you expect the Pa of O2 and CO2 to be in arterial blood?

Answer 34

``` PaO2 = 40mmHg (low) PaCO2 = 45mmHg (high) ```

Question 35

With a High V/Q, what happens with time?

Answer 35

``` Low perfusion (blood flow) - the alveoli will equilibriate with the atmosphere due to no exchange occurring with blood = PO2 = 150; PCO2 = 1 Little effects on the blood since there isn't much arriving there ```

Question 36

With a High V/Q, what do you expect the Pa of O2 and CO2 to be in the little arterial blood that does arrive there?

Answer 36

``` PaO2 = 150mmHg (high) PaCO2 = 1mmHg (low) ```

Question 37

What downstream effects does a High V/Q have on a normal alvelous?

Answer 37

It will turn it into a LOW V/Q situation by increasing the blood flow (perfusion) to that area

Question 38

The apex of the lung has a ____ V/Q

Answer 38

HIGH

Question 39

The middle of the lung has a ____ V/Q

Answer 39

Normal - 0.8

Question 40

The base of the lung has a ____ V/Q

Answer 40

LOW