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Pulm > Lec 4 Mechanics and Pulm Function Testing > Flashcards

Lec 4 Mechanics and Pulm Function Testing Flashcards

1
Q 
In a patient with emphysema, lung compliance would be expected to be
A) Decreased
B) Increased
C) Generally unchanged
D) Cannot predict
A

B) increased

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2
Q

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

A

A) large and medium sized airways

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3
Q

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

A

B) when you let all of your air out

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4
Q

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

A
  • chest wall expands
  • lungs get smaller

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

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5
Q

Are lungs more compliant at smaller or bigger volume?

A

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

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6
Q

What is the zero point of respiratory system?

A

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

  • negative pressure of chest wall balances positive pressure of lungs
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7
Q

What is hysteresis?

A

s

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8
Q

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

A

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

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9
Q

What is action of surfactant?

A

decreases surface tension

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

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10
Q

What is equation for compliance?

A

compliance = change in V / change in P

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11
Q

What happens to compliance in emphysema?

A

increased compliance

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12
Q

What happens to compliance in pulmonary fibrosis?

A

decreased compliance

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13
Q

What happens to compliance in pulmonary edema?

A

decreased compliance

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14
Q

What happens to compliance in pneumonia?

A

decreased compliance

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15
Q

What happens to compliance in normal aging?

A

increased compliance

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16
Q

What happens to alveolar with inspiration vs expiration?

A

slightly negative on inspiration

slightly positive on expiration

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17
Q

Is pleural pressure positive or negative?

A

always negative

–> if it becomes atmospheric lung will collapse = pneumothorax

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18
Q

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

A

density * diameter * velocity / gas viscocity

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

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19
Q

What is hysteresis?

A

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

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20
Q

What causes hysteresis in lung?

A
  • surface tension of the lung at air-liquid interface and preferential action of surfactant when lung is smallest
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21
Q

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

A

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

this is fixed by surfactant?

22
Q

What is equation for collapsing pressure of alveoli?

step1

A

P = 2* surface tension / radius

23
Q

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

step1

A

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

24
Q

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

step1

A

At FRC all is balanced

  • airway and alveolar pressures are 0
  • intrapleural pressure is always negative
25
Q

Is lung’s tendency to get bigger or smaller?

step1

A

smaller

26
Q

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

A

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
Q

What is normal lung compliance?

A

0.2 L/cm H2O

28
Q

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

A

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

emphysema = most compliant
fibrosis = least compliant
29
Q

What happens to lung in emphysema?

A
  • decreased elastic recoil = more compliant

- increased airflow resistance

30
Q

What happens to intrapleural pressure during tidal breath?

A

always negative

most negative just before end of inspiration

31
Q

What happens to alveolar pressure with tidal breath?

A

negative pressure with inspiration

positive pressure with expiration

32
Q

What parts of lung have turbulent vs laminar flow?

A 
turbulent = in large airways
laminar = small airways
33
Q

What kind of flow in large airways?

A
  • turbulent flow

- resistance increases as flow increases

34
Q

How can you improve turbulent flow?

A
  • by reducing density –> give heiliox to improve upper airway obstruction
35
Q

What kind of flow in small airways?

A

laminar flow

36
Q

What determines resistance in turbulent flow vs laminar flow?

A

in turbulent flow = more resistance with more flow

in laminar flow = use poisseuille’s law –> bigger radius = less resistance

37
Q

What is poisseuille’s law?

A

resistance is proportional to

viscosity * length / radius ^ 4

38
Q

Is overall resistance higher in larger or small airways?

A
  • 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
Q

What are his 3 basic laws for reading PFTs?

A
  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
Q

What is inspiratory reserve volume?

step1

A

air that can still be breathed in after normal inspiration

41
Q

What is tidal volume? normal value?

step1

A

air taht moves into lung with each normal inspiration

usually 500 mL

42
Q

What is expiratory reserve volume?

step1

A

air that can still be breathed out after normal expiration

43
Q

What is residual volume?

step1

A

air in lung after maximal expiration

cannot be measured on spirometry

44
Q

What is inspiratory capacity?

A

IRV + TV

45
Q

What is functional residual capacity?

A

RV + ERV = volume in lungs after normal expiration

46
Q

Can you measure total lung capacity from spirometry?

A

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

47
Q

What happens to FEV1 in obstructive disease?

A

its decreased

48
Q

How can you measure total lung volumes?

A

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

49
Q

How do you measure diffusion capacity?

A

pt inhales small amount of CO and its uptake is measured

50
Q

What happens in obstructive lung disease?

A

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
Q

Why use CO to measure diffusion capacity

A
  • 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
Q

What things are required for normal diffusion capacity?

A
  • adequate surface area
  • capillary blood flow
  • hemoglobin
  • V/Q mismatch

Pulm (24 decks)

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