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Flashcards in Gas Exchange Deck (54):
1

What does effective respiration mean?

enough oxygen intake to meet metabolic demands

2

In respiratory physio, solution refers to what?

Water vapor, body fluid, interstitial fluid, and cytosol

3

What is Dalton's law of partial gas pressure?

Each gas exerts a portion of the total pressure in an environment. Thus:

Ptotal = (P1+P2+Pn)

4

What happens to the air we inhale? What is the consequence of this for Dalton's law?

Water vapor added, so this much be subtracted to find partial pressure

5

What is the equation for a particular species of gas, once in the lungs and saturated with water vapor?

Px= Fx(Pb-Ph20)

6

What is Henry's law? Equation?

The partial pressure exerted by a gas when dissolved

Partial pressure = [C] of dissolved gas / solubility coefficient

7

Does conjugated oxygen or CO2 exert any pressure?

No, it is the dissolved form of gas that exerts a partial pressure

8

Is CO2 more or less soluble than oxygen? What is the effect of this?

Much more, thus it exerts much less partial pressure than oxygen, and it much more easily uptaken in the tissues

9

What is the ideal gas law? What are the variables in human tissues?

PV=nRT

PV and n

10

Is respiratory physio, gas will continue to flow down its gradient until what point?

P1V1 = P2V2

i.e. until partial pressures in alveoli and blood are equal

11

What is Fick's law of diffusion?

The amount of gas that moves across across a tissue sheet is proportional to the area, but inversely proportional to the thickness

12

What is the equation of Fick's law?

diffusion = dP(A)(S) / D(MW^.5)

13

What are the two variable that need consideration with gas exchange through capillaries?

Diffusion
Perfusion

14

What does A mean in respiratory physio? a?

A = alveolar
a= arterial

15

What is the location of gas exchange?

The respiratory unit

16

What are the components of the respiratory unit?

Bronchiole
Alveolar ducts
Atria
Alveoli

17

How does atelectasis change the Fick's equation?

∆P and A are decreased

18

How does pneumonia change the Fick's equation?

Interstitial tissues and alveoli are inflamed, with increased fluid thickness, so the
distance through which gases must diffuse increases, and diffusion rate decreases

19

How does pulmonary edema change the Fick's equation?

Increases D (thickness)

20

How does pulmonary fibrosis change the Fick's equation?

Increases D (thickness)

21

Where does the blood comes from in hemoptysis?

From the respiratory membrane

22

What happens to the slope of the blood pO2 pressure curve during exercise? Why?

Lowers the slope

Higher perfusion (HR up), meaning less time for diffusion to happen

23

What are the two factors that determine the tissue PO2?

Rate of blood flow

Rate of tissue metabolism

24

Why is there a drop in the PO2 when it arrives at the left side of the heart?

Shunt of the pulmonary circulation from the bronchial arteries

25

Why is only a small pressure difference needed to exchange CO2? (~5 mmHg)

High solubility coefficient

26

What are the two variables that determine [PCO2] in tissues?

1. Rate of tissue metabolism
2. Rate of blood flow

27

What happens to the slope of the PCO2 in alveolar capillaries during exercise? Why?

Lowers slope (absolute value)

Increased HR

28

What is used to measure the lungs ability to transfer gases? Why?

CO because it is taken up, stays in, and is not used by tissues

29

What is the equation for the diffusion capacity of the lung?

DLCO = Jco / PAco

30

A decrease in DlCO means what?

Lower rate of diffusion of oxygen

(e.g. in thickened or damage respiratory membrane or anemia)

31

What does COPD do to DlCO?

Decreases it

32

What does pulmonary fibrosis do to DLCO?

Decreases it

33

What does interstitial lung disease do to DLCO?

Decreases it

34

What does pulmonary HTN do to DLCO? Why?

Decreases it

Increase in capillary wall thickness

35

What does chronic pulmonary thromboembolism do to DLCO?

Decreases it

36

What does anemia do to DLCO?

Decreases it

37

What does polycythemia do to DLCO?

Increases it

38

IS DLCO sensitive? Specific?

Sensitive, but NOT specific

39

What happens to the partial pressure of CO2 as you move from tissues to lungs?

Decreases

40

What is the atmospheric pressure at sea level in mmHg?

760 mmHg

41

What is the solubility coefficient of oxygen? CO2? What does this mean?

Oxygen = 0.024
CO2= 0.57

Thus CO2 is much more soluble in water

42

What are the two variables we can change in the partial pressure equation Px = Fx(Pb-Ph2o)? How?

Fx (with oxygen)
Pb (with hyperbaric chamber)

43

According to Fick's law, the larger the surface area of a tissue, the (higher/lower) the rate of diffusion

Higher

44

According to Fick's law, the thicker a tissue is, the (higher/lower) the rate of diffusion

Lower

45

What is the partial pressure of oxygen in the pulmonary capillaries at the arterial end? Venous end?

Arterial end = 40 mmHg
Venous end = 104 mmHg

46

True or false: under normal. resting conditions, the entire capillary/alveolar surface area is needed to diffuse oxygen.

What is the consequence of this?

False--it's more like a third.

This allows a buffer for times during increased oxygen demand (such as exercise)

47

(Summarizing the O2 diffusion graph): If there is an increase in tissue metabolism, how is the higher demand for oxygen met? How does increase oxygen demand change the curve?

Increasing blood flow

The curve shifts downward (more blood flow is needed to attain each PO2 mmHg)

48

What does the graph of the blood flow to mmHg PO2 look like?

Square root

49

What does the graph of the blood flow to PCO2 mmHg look like?

1/x

50

What happens to the curve of CO2 diffusion with increased metabolism?

Shifts rightward (meaning that a higher blood flow is needed to achieve the same mmHg pCO2)

51

In determining the diffusing capacity of the lungs, why is it that the partial pressure of CO can be used directly in the equation, rather than the amount that is dissolved in blood like the other gases?

Hb picks it up so readily, that the partial pressure = the dissolved pressure

52

How do you convert the DLCO (diffusion rate of CO) to the diffusion rate of O2?

Multiply by the diffusion factor coefficient for oxygen (1.23)

53

Why is there a lower diffusion rate of O2 in pulmonary HTN?

Increases in capillary wall d/t higher pressures

54

What does the alveolar gas equation tell you?

What fraction of oxygen the patient is taking in