Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

SMP - Cardiopulmonary Exam 2 > Lecture 27 - Compliance > Flashcards

Lecture 27 - Compliance Flashcards

1
Q

What is the slope of the pressure(x)/volume(y) curve of the lung? What does a steeper slope mean?

A

Compliance

Steeper slope = more compliant

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the recoil pressure of the lung? Other name?

A

Force or tension as a result of distending force exerted on the lung that when released recoils the lung toward a resting volume

= elastic pressure (Pel)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are static and dynamic properties?

A
  1. Static = snapshot or point in time when all muscles are relaxed, lack motion, time, or dynamic forces
  2. Dynamic = occur over time
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is elastic recoil?

A

Tendency of the lung to collapse from an inflated volume

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Compliance of lungs that expand easily?

A

High

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Compliance of lungs that does not expand well? What do we call this?

A

Low = stiff lung

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Factors influencing STATIC lung compliance?

A 
Tissue structure and composition:
1. Collagen fibers
2. Elastin fibers
3. Cellularity of interstitium 
Others:
4. Vascular distention/engorgement
5. Surface tension
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How do collagen fibers affect static lung compliance?

A

If they accumulate in the interstitium they will add stiffness and create final restraint at total lung capacity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How do elastin fibers affect static lung compliance?

A

They contribute to the recoil properties of the lung

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

In what category can we include sarcoidosis and pulmonary fibrosis?

A

Restrictive lung diseases that increase the cellularity of the interstitium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Definition of surface tension?

A

Tendency of surface molecules to pull inward

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is LaPlace’s Law?

A

P = 4T/R

T = surface tension
R = radius
P = recoil pressure
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

LaPlace’s Law for alveolus?

A

P = 2T/R because only one surface is involved

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How does an alveolus with a small radius will compare to an alveolus with a larger radius with regards to surface tension? What is the problem with this? How is it corrected for?

A

Without surfactant, the surface tension in all alveoli would be the same regardless of size, so the recoil pressure of small alveoli would be higher.

Issue: if lung only relied on surface tension to keep alveoli open, since the lungs do not inflate uniformly (especially at lower volumes), the smaller alveoli would collapse and the larger ones would over inflate => areas of hyperventilation + areas of atelectasis

Solution: surfactant produced by Type II pneumocytes lines the alveolar walls to decrease surface tension that occurs in alveoli

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How does surface tension affect static lung compliance?

A

Loss of surface tension = increased compliance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How can you remove surface tension in a lung?

A

Fill it with saline

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

When does surfactant production begin during development?

A

24-26 weeks

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is surfactant primarily composed of?

A

Dipalmitoyl lecithin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Good indication of fetus lung development sufficient for child delivery?

A

Lecithin:sphingomyelin ratio of 2:1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is hysteresis?

A

Inspiratory compliance curve is different from expiratory compliance curve because it is easier (requires less pressure) to deflate the lung than to inflate it: lung volume at any given pressure during deflation is larger than during inflation = to achieve a particular volume, more pressure must be applied on the inflation limb of the compliance curve than on the deflation limb

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What drives gas to the terminal bronchioles during inspiration in active inflation?

A

Pressure gradient applied across the thorax that expands the lungs and chest wall = effective transpulmonary pressure = Palv-Ppl

Ppl = pressure in pleural cavity

SO, when the pleural pressure is negative, then the transpulmonary pressure is positive and air will enter and expand the lungs (per a volume on the compliance curve)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What drives gas to the terminal bronchioles during inspiration in passive inflation?

A

Manual expansion of the lungs (e.g. via a ventilator) pushing air into the lungs with a positive pressure in the alveoli and a pressure of 0 in the pleura

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

How is the lung’s elasticity counterbalanced under static conditions?

A

Palv-Ppl counterbalances the elastic forces of lung recoil

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

When can lung transpulmonary pressure be measured?

A

Only when a patient is passively inflated: inflate the lungs with positive pressure, hold the breath, and at the end of the breath a positive pressure will be exerted on the pleural space = plateau pressure distending pressure counterbalancing the lung recoil (Palv is 0)

Not possible in a spontaneously breathing patient (aka active patient) because the pressure distending the chest wall cannot be measured since the pressures are generated by the muscles in the chest wall itself

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Describe the compliance curve of the lung and chest wall.

A
  • X-axis: airway pressure in cm H2O

- Y-axis: vital capacity %, meaning volume

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Describe the compliance curve of the lung in isolation.

A
  1. In a resting state the lung is at a volume much lower than when it’s in the chest wall
  2. Can reach a minimal volume depending on the elasticity of the lung
  3. Inflates to a maximum where the curve becomes asymptotic and the lung is non-compliant
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Describe the compliance curve of the chest wall in isolation. What does it represent?

A

Represents the compliance of the respiratory muscles, ribs, and diaphragm together:

  1. In a resting state the chest wall is at a volume much higher than when the lungs are in it
  2. Chest volume can be expanded to a much higher volume than when the lungs are in it because of how compliant the diaphragm is
  3. Chest volume can be decreased to a volume limited by the ribs
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What is the most compliant structure in the respiratory system?

A

Diaphragm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Describe the compliance curve of the chest wall and the lung together (aka the respiratory system).

A
  1. Exhalation is limited by the chest wall (it sets the residual volume)
  2. Inhalation is limited by the lung and its elastic skeleton (it sets TLC)
  3. Resting state of 0 airway pressure at the functional residual capacity: takes -5 cm H2O pleural pressure to pull the chest inward and +5 cm H2O to expand the lung which counterbalance each other out
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

In healthy individuals what pressure is necessary to reach TLC? What does this mean?

A

30-35 cm H2O

If a lung is exposed to more, it will rip

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What happens to the respiratory system with pneumothorax?

A

The chest and lungs become uncoupled => air rushes in pleural cavity (from -5 to 0 cm H2O) and lung collapses to its resting volume, chest wall expands to its resting volume

32
Q

How to find volume of pneumothorax on a compliance curve of the chest wall and the lung together?

A

Difference in volume between chest and lung at an airway pressure of 0 cm H2O

33
Q

Which is worst: a sucking blowing chest wound or a sucking wound? When does it often happen?

A

Sucking wound because the pneumothorax gets bigger and bigger with each breath and the positive pressure will push the lung volume down => tension pneumothorax

This often happens if the patient is on a ventilator (positive pressure breathing)

34
Q

What is a lung resection? How is it done?

A

Surgical procedure during which the surgeon removes a small portion of the lung containing the cancerous cells

Need for intubation of both lungs with the one being worked on collapsed down to make space

35
Q

What is the steepest part of ALL compliance curves (lung, chest, and respiratory system)? Which curves are steeper?

A

FRC to slightly higher volume

Individually, the curves are steeper than their combined curves at FRC, each with a slope of 200 ml/cm water, meaning the chest wall and lungs are more compliant individually than when combined.

36
Q

When is hysteresis more pronounced?

A

When surfactant is lacking

37
Q

When does the convexity of the compliance curve become apparent?

A

High volumes

38
Q

What is a dynamic compliance curve?

A

Loop curve showing hysteresis

39
Q

Which curve is more compliant: static or dynamic compliance curve?

A

Static one

40
Q

What should compliance be expressed in terms of? Why? What is this called?

A

Compliance should be expressed in terms of absolute volumes because the uncorrected compliance of respiratory system after a pneumonectomy for example is greatly reduced from pre-op value but the specific compliance is unchanged => SPECIFIC compliance

41
Q

What can be said of the elasticity of the lung and chest wall? What does this mean? What can this be used for?

A

They are additive, so the following formula for their compliances can be written:

1/Crs = 1/Cl + 1/Ccw

We can use this information to calculate the slope of our combined curve because the elasticity of the lung and chest wall are additive, and elasticity is the inverse of compliance => the slope of the combined curve = (1/200 + 1/200)^(-1) = (1/100)(^-1) = 100 ml/cm water

42
Q

What happens to the compliance curve of the respiratory system as the lung or chest wall stiffens? What does this mean for treatment?

A

Compliance curve of respiratory system shifts to the right and flattens between 2 inflection points: bottom one (PEEP) and top one

Treatment: if patient is on a ventilator, the goal is to keep their respiratory system between the 2 inflection points or else the lung will be damaged

43
Q

What is the peak pressure? What does it correspond to?

A

Pressure it takes to get air in thorax => dynamic compliance

44
Q

What does the difference between static and dynamic compliance account for?

A

Accounts for the difference in pressure it takes to get the air into the airways and the pressure it takes to hold it there (dynamic is higher than static)

45
Q

What is the plateau pressure? What does it correspond to?

A

Pressure it takes to hold air in the thorax => pressure overcoming the elastic recoil of the lung and chest wall = static compliance

46
Q

Why is dynamic pressure higher than static pressure?

A

Because the dynamic pressure is not only overcoming the elastic recoil of the respiratory system, but also the airway resistance

47
Q

Is the fully inflated alveolar pressure static or dynamic pressure?

A

STATIC

48
Q

In an ICU, the ventilator pressure is kept below 30 to 35 cm of H2O: is this static or dynamic pressure?

A

Static

49
Q

Equation for dynamic compliance?

A

Dynamic compliance = TV / (peak pressure - PEEP)

TV = tidal volume 
PEEP = positive end expiratory pressure
50
Q

What is positive end expiratory pressure? How is it maintained?

A

Pressure due to FRC in patients on ventilators because without a positive pressure at rest, their FRC would be too low due to the fact that they are sedated (muscles relaxed) and laying down (gravity not helping diaphragm) and we need to keep them between the 2 inflection points of their compliance curve = PEEP RECRUITS NORMAL FRC

Maintained with:

  • Ventilator (ends expiration at 5 cm H2O)
  • Continuous positive airway pressure mask (does not let patients expire all the way)
51
Q

Normal end expiratory pressure in healthy individuals that is NOT in hospital?

A

0 cm H2O

52
Q

Normal positive end expiratory pressure in healthy individuals that supine and sedated? AKA physiologic PEEP?

A

5 cm H2O

53
Q

Equation for static compliance?

A

Static compliance = TV / plateau pressure - PEEP

TV = tidal volume 
PEEP = positive end expiratory pressure
54
Q

Which is larger: static or dynamic compliance? Why?

A

Static because denominator is smaller (using plateau instead of peak pressure)

55
Q

Equation of resistance of airways?

A

R = peak pressure - plateau pressure / flow

56
Q

Equation for peak pressure - PEEP?

A

This is dynamic pressure, which needs to overcome both the airway resistance and the elasticity of the respiratory system:
ΔP = 1/Crs x TV + Raw x flow = (1/Cl + 1/Ccw) x TV + Raw x flow

57
Q

What 4 factors will cause peak pressure to increase?

A
  1. Decrease compliance
  2. Increased airway resistance
  3. Large tidal volume
  4. Higher flow
58
Q

What 2 factors will cause plateau pressure to increase?

A
  1. Decrease compliance

2. Large tidal volume

59
Q

If a patient on a ventilator’s peak pressure is rising, what is the issue? Assume volume mode. How is the plateau pressure affected?

A

Ventilator keeps TV and flow constant, so either compliance is decreasing (meaning plateau pressure is increased) or airway resistance is increasing (plateau resistance unchanged)

60
Q

Equation for plateau pressure - PEEP?

A

ΔP = 1/Crs x TV + Raw x flow BUT flow = 0 so ΔP = 1/Crs x TV

61
Q

If a patient on a ventilator’s plateau pressure is rising, what is the issue?

A

Ventilator keeps TV constant, so compliance must be decreasing

62
Q

If a patient on a ventilator’s peak pressure is decreasing, what is the issue?

A
  1. Air leak

2. Hyperventilation

63
Q

What can cause increased airway resistance?

A
  1. Aspiration
  2. Bronchospasm
  3. Tracheal tube with kink or biting
  4. Endobronchial partial obstruction
  5. Asthma
  6. Secretions
64
Q

What can cause decreased compliance?

A
  1. Abdominal distention
  2. Asynchronous breathing
  3. Atelectasis
  4. Auto-PEEP
  5. Pneumonia
  6. Pulmonary edema
  7. Pneumothorax
  8. Pulmonary fibrosis
  9. Sarcoidosis
65
Q

What is happening if a patient is in respiratory failure but their peak pressure is unchanged?

A
  1. Pulmonary embolus

2. Extrathoracic process

66
Q

What is aspiration?

A

Entry of material from the oropharynx or gastrointestinal tract into the larynx and lower respiratory tract

67
Q

Does compliance decrease with age?

A

YUP

68
Q

Compare airway resistance in base and apex of lung.

A

Airway resistance is higher at base than at apex because they alveoli are more open

69
Q

At FRC, does inspiration cause a larger increase in volume at base or apex of lungs?

A

BASE!

70
Q

Is surfactant a protein?

A

NOPE, it’s a phospholipid

71
Q

How does the presence of surfactant affect the hydrostatic pressure in the interstitium around the pulmonary capillaries? What does this mean?

A

Surfactant reduces inward pull of alveolar wall => hydrostatic pressure in interstitium around capillaries is less negative => surfactant prevents transudation of fluid from capillary to interstitium or alveoli

72
Q

How does intrapleural pressure change during expiration?

A

Increases (becomes less negative)

73
Q

Compare velocity of gas in larger airways and terminal bronchioles during expiration.

A

Velocity of gas in terminal bronchioles is smaller because of larger cross-sectional area

74
Q

Compare alveolar pressure and atmospheric pressure during expiration.

A

Alveolar pressure is higher

75
Q

If the lung is held at a constant volume, which 2 pressures must be the same? What about the intrapleural one?

A

Mouth and alveolar are equal

Intrapleural is negative

SMP - Cardiopulmonary Exam 2 (15 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions