Cremo 2: Factors that control CO2 and O2 in alveoli and blood Flashcards Preview

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Flashcards in Cremo 2: Factors that control CO2 and O2 in alveoli and blood Deck (46)
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1

Sensors of blood CO2 levels

1. Central chemoreceptors in medulla
2. Peripheral chemoreceptors in carotid and aortic bodies

2

Arterial CO2 is controlled by two rates. What are they?

1. Metabolic production of CO2 (VCO2)
2. Alveolar ventilation (VA)

3

PCO2 ventilation equation

PaCO2 = VCO2 * 0.863 / VA

4

H-H equation (acid-base)

pH = 6.1 + log [HCO3-]/0.03(PaCO2)

5

Alveolar gas equation (oxygenation)

PAO2 = PIO2 - 1.2(PaCO2)

6

What is a buildup of CO2 in the blood due to?

A failure in some component of the respiratory system (not an increase in metabolic CO2 production)

7

What is VCO2?

Rate of CO2 production by metabolism

8

What two rates control PaCO2?

VA: rate of alveolar ventilation by lung
VCO2: rate of CO2 production by metabolism

9

Alveolar ventilation and CO2 production double during moderate exercise in a 24-year old man. What is the effect on PaCO2?

No effect! Both variables change together!

10

Clinical definition of hypercapnia or hypoventilation.

PaCO2 of >45mmHg

11

Clinical definition of hypocapnia or hyperventilation.

PaCO2 of <35mmHg

12

Normal PaCO2 levels

35-45mmHg

13

A 32 year old male has just run into the classroom after being late for class. He can be considered to be hyperventilating if his PaCO2 is at what level?

<35mmHg

14

The only physiologic reason for elevated PaCO2

A level of alveolar ventilation inadequate for the amount of CO2 produced and delivered to the lungs.

15

What does VA refer to in the PCO2 equation?

VA = VE - VD = total volume of lung - dead space

16

What is the equation for VE, or total ventilation rate?

VE = Total ventilation rate (L/min) = respiratory rate · tidal volume

17

Is dead space ventilated? Is it perfused?

Yes; no

18

Anatomic dead space + all other dead space

Physiologic dead space

19

3 processes required for gas exchange

1. Gas entering and leaving
2. Blood flow = perfusion
3. Diffusion of gases across capillary membrane

20

What is another way to think of VA?

VE - VD

21

Level of VE needed to keep PaCO2 constant

Minute ventilation requirement

22

In a normal lung, what is PACO2? What is PaCO2?

40mmHg

23

In a normal lung, what is PvCO2?

45mmHg

24

What is a typical PAO2 for a normal lung?

100mmHg

25

Is the PAO2 equal to the PaO2 in a normal lung?

No, PaO2 is slightly lower

26

PO2 at sea level

159mmHg = 0.21 * 760mmHg

27

PO2 at the trachea

150mmHg

28

PaO2 at the terminal respiratory units

100mmHg

29

Anatomic unit used by pathologists
10 to 12 terminal respiratory units

Acinus

30

At the terminal respiratory unit, is PAO2 = PaO2?

No