Lec 4 Mechanics and Pulm Function Testing Flashcards Preview

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Flashcards in Lec 4 Mechanics and Pulm Function Testing Deck (52):
1

In a patient with emphysema, lung compliance would be expected to be
A) Decreased
B) Increased
C) Generally unchanged
D) Cannot predict

B) increased

2

Most of the resistance to airflow in the lung comes from
A) Large and medium sized airways
B) Small airways
C) Alveoli

A) large and medium sized airways

3

Functional Residual Capacity is the volume of the lungs
A) When you take the biggest possible breath
B) When you let all your air out
C) When you are dead

B) when you let all of your air out

4

What happens to chest wall and lungs if you open the chest?

- chest wall expands
- lungs get smaller

normally intact pleural space with negative pressure keeps this from happening all the time

5

Are lungs more compliant at smaller or bigger volume?

lungs are more compliant at smaller volume; as you expand more and more you reach a limit and get less compliance

6

What is the zero point of respiratory system?

zero point is the lung volume where opposing elastic forces are balanced = FRC

- negative pressure of chest wall balances positive pressure of lungs

7

What is hysteresis?

s

8

How does a lung filled with saline compare to a normal lung with and without surfactant?

saline = less pressure to inflate b/c air liquid interface adds to the pressure required to expand lungs

normal lung without surfactant = most pressure/ least compliant

normal lung with surfactant = reduces surface tension = in the middle between saline + no surfactant

9

What is action of surfactant?

decreases surface tension

= has greater effect when lung is smaller
prevents small airways + alveoli from collapse

10

What is equation for compliance?

compliance = change in V / change in P

11

What happens to compliance in emphysema?

increased compliance

12

What happens to compliance in pulmonary fibrosis?

decreased compliance

13

What happens to compliance in pulmonary edema?

decreased compliance

14

What happens to compliance in pneumonia?

decreased compliance

15

What happens to compliance in normal aging?

increased compliance

16

What happens to alveolar with inspiration vs expiration?

slightly negative on inspiration
slightly positive on expiration

17

Is pleural pressure positive or negative?

always negative
--> if it becomes atmospheric lung will collapse = pneumothorax

18

What is reynold's number equation? what does it mean?

density * diameter * velocity / gas viscocity

higher number = more likely to have turbulent flow [rather than laminar]

19

What is hysteresis?

idea that different pressure-volume curve when you inflate than deflate

- inflate = lower volume for same pressure
- deflate = bigger volume for same pressure

= lung is more compliant on inspiration

20

What causes hysteresis in lung?

- surface tension of the lung at air-liquid interface and preferential action of surfactant when lung is smallest

21

What does surface tension and LaPlace's law mean for small alveoli?

small alveoli tend to get smaller and bigger alveoli tend to get bigger

this is fixed by surfactant?

22

What is equation for collapsing pressure of alveoli?

step1

P = 2* surface tension / radius

23

What does law of laplace tell you about alveoli's tendency on expiration?

step1

on expiration as radius decreases, alveoli have greater tendency to collapse

24

What is pressure of airway and alveolar pressures and intrapleural pressure at FRC?

step1

At FRC all is balanced
- airway and alveolar pressures are 0
- intrapleural pressure is always negative

25

Is lung's tendency to get bigger or smaller?

step1

smaller

26

What are the forces responsible for lung's elastic recoil?

surface forces = air liquid interface surface tension which is slightly reduced by surfactant

tissue forces = beyond certain point of inflation lungs get stiff and below a minimum alveoli stay open b/c of their structure

27

What is normal lung compliance?

0.2 L/cm H2O

28

What is order from left to right on a P vs V graph of fibrosis, emphysema, and normal lungs?

shift left = more compliant
emphysema --> normal --> fibrotic

emphysema = most compliant
fibrosis = least compliant

29

What happens to lung in emphysema?

- decreased elastic recoil = more compliant
- increased airflow resistance

30

What happens to intrapleural pressure during tidal breath?

always negative

most negative just before end of inspiration

31

What happens to alveolar pressure with tidal breath?

negative pressure with inspiration

positive pressure with expiration

32

What parts of lung have turbulent vs laminar flow?

turbulent = in large airways
laminar = small airways

33

What kind of flow in large airways?

- turbulent flow
- resistance increases as flow increases

34

How can you improve turbulent flow?

- by reducing density --> give heiliox to improve upper airway obstruction

35

What kind of flow in small airways?

laminar flow

36

What determines resistance in turbulent flow vs laminar flow?

in turbulent flow = more resistance with more flow

in laminar flow = use poisseuille's law --> bigger radius = less resistance

37

What is poisseuille's law?

resistance is proportional to

viscosity * length / radius ^ 4

38

Is overall resistance higher in larger or small airways?

- resistance to flow is much higher in smaller airways

BUT you have lots of small airways in parallel which reduces overall resistance

--> overall resistance is highest in large airways

39

What are his 3 basic laws for reading PFTs?

1. reduced FEV1/FVC ratio defines obstructive disease

2. restriction is defined by reduced lung volumes [not just spirometry]

3. reduced "diffusion capacity" implies a "gas transport defect" but not much else

40

What is inspiratory reserve volume?

step1

air that can still be breathed in after normal inspiration

41

What is tidal volume? normal value?

step1

air taht moves into lung with each normal inspiration

usually 500 mL

42

What is expiratory reserve volume?

step1

air that can still be breathed out after normal expiration

43

What is residual volume?

step1

air in lung after maximal expiration

cannot be measured on spirometry

44

What is inspiratory capacity?

IRV + TV

45

What is functional residual capacity?

RV + ERV = volume in lungs after normal expiration

46

Can you measure total lung capacity from spirometry?

NOPE!! because you can't measure residual volume [RV]

47

What happens to FEV1 in obstructive disease?

its decreased

48

How can you measure total lung volumes?

need to measure RV --> do this by using gas dilution technique with helium or a plethysmograph = body box

49

How do you measure diffusion capacity?

pt inhales small amount of CO and its uptake is measured

50

What happens in obstructive lung disease?

obstruction of air flow results in air trapping in lungs
airway closes prematurely at high volume

have increased RV and decrease FVC
very decreased FEV1 so

decrease FEV1/FVC ratio = hallmark

51

Why use CO to measure diffusion capacity

- no consumption
- no back pressure
- similar to O2

--> we don't use CO so everything we inhale goes one way and doesn't really come out.

52

What things are required for normal diffusion capacity?

- adequate surface area
- capillary blood flow
- hemoglobin
- V/Q mismatch