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Pulm by Minnie: AH Update > SM 150a, 152a, 153a, 154a - Mechanics I-IV > Flashcards

SM 150a, 152a, 153a, 154a - Mechanics I-IV Flashcards

1
Q

What is transthoracic pressure (Ptt)?

[Equation, explanation]

A

Ptt = PiP - PB

Transthoracic pressure acts to suck the chest wall inward

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2
Q

When is transpulmonary pressure (Ptp) equal in magnitude to PiP?

A

When the glottis is open, PA = 0

(Ptp = PA - PiP)

[Transpulmonary pressure is the pressure that gives rise to ventilation]

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3
Q

If transrespiratory pressure (Ptr) is positive, where will air flow when the glottis opens?

A

Out of the alveoli

Ptr = PA - PB

If Ptr is positive, PA is higher than PB, and air will flow down the pressure gradient, out of the alveoli

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4
Q

If there is obstruction to expiratory airflow, what would happen to FRC?

A

FRC would increase

-> Increases elastic recoil of the lung, helping the expiratory effort and reducing the amount of dynamic compression

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5
Q

During a maximal expiratory effort, what happens to the maximum flow that can be generated by that expiration?

A

The maxmum flow decreases as lung volume decreases due to compression of the airways

During a forced, maximal inspiration, PA increases and PiP increases.

At first, the elastic recoil of the lung keeps PA > PiP and air flows out of the alveolus. However, as lung volume decreases the elastic recoil force diminishes, resulting in PA iP - When this occurs, the airway compresses and air does not flow until the recoil of the chest wall increases PA > PiP, and the process begins again

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6
Q

What is tidal volume (TV)?

A

The volume of air that is inspired and expired during free, easy breathing

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7
Q

Does surface tension act in the same direction as capillary hydrostatic pressure or capillary oncotic pressure?

A

Capillary hydrostatic pressure: pushes into the alveoli (out of the capillary)

As a result, surfactant helps to prevent edema from the pulmonary capillaries to the alveoli

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8
Q

An alveolus with a smaller radius will experience a stronger/weaker inward force due to surface tension than an alveolus with a larger radius

A

An alveolus with a smaller radius will experience a stronger inward force due to surface tension than an alveolus with a larger radius

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9
Q

Which airways in the lung are most susceptible to dynamic compression?

A

Small airways in the basilar parts of the lung

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10
Q

What substance causes surface tension to vary as a function of the surface area of the lung?

A

Surfactant

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11
Q

What is the Alveolar Gas Equation (PA O2)?

A

Note: In a healthy individual, PA CO2 is usually assumed to be equal to arterial PCO2

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12
Q

What is the equation for total compliance of the lung and chest wall together?

A

1/CResp (total) = 1/CLung + 1/CChest

The lung and the chest wall together are in series, but they act like resistors in parallel

Total compliance will be less than the compliance of any one component

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13
Q

If you are starting from RV (after a really, really big exhalation), which part of the lung recieves more ventilation, the base or the apex?

Why?

A

The apex

The starting PiP at the apex of the lung is in the beefy part of the volume/PiP curve; slight changes in PiP starting from this point will result in more volume change (better ventilation)

The PiP at the base is higher than zero; these alveoli are collapsed/compressed and are not well ventilated unless PiP becomes a bit more negative

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14
Q

What is the expiratory reserve volume?

A

The amount of air that can be expelled from the lungs after tidal volume has been expelled

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15
Q

What is hysteresis?

What causes it?

A

Hysteresis refers to the difference in the PV relationship between a lung that is inflating and a lung that is deflating.

Hysteresis occurs because the force of surface tension is stronger in an inflating lung than in a deflating lung

  • Surfactant must change phases from solid -> liquid when the lung begins to inflate; more pressure is required to begin expanding the volume of the lung at the beginning of inspiration
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16
Q

What is inspiratory capacity (IC)?

A

IC = TV + IRC

IC is the total amount of air that can be inhaled into the lungs

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17
Q

List two stimuli that cause the release of surfactant

A
  • Lung distension
  • Stimulation of Beta-2 adrenergic receptors

Occurs during inspiration

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18
Q

What is the equation for compliance?

A
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19
Q

What is total lung capacity (TLC)?

How is it different from inspiratory capacity (IC)?

A
  • TLC
    • The maximum volume in liters that the lungs can hold
    • TLC = TV + IRV + RV + ERV
  • IC
    • Maxmimum volume that can be inspired
    • IC = TV + IRV
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20
Q

When the lungs are contracted…

Is the recoil force large or small?

How is PiP affected?

A

When the lungs are contracted (think expiration),

Recoil force is small (imagine a resting rubber band)

PiP is less negative than during inspiration, returns to equillibrium (eq ~ -5 cm/H20)

The chest wall is not expanding and elastic recoil is not as strong; the forces that act to pull the chest wall out and the lungs in during inspiration are not active during expiration

(The chest wall and lungs love each other and when they are able to reunite PiP is happy and less negative :) )

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21
Q

What is the inspriatory reserve volume (IRV)?

A

The amount of air that could fit into the lungs after inspiring the tidal volume

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22
Q

If patient has normal lungs but a chest wall that stiffer than normal, how will FRC change?

How will PiP be affected?

A

FRC will be larger

PiP will be more negative
(The recoil force of the lung will be larger - It will be more stretched than normal, so it will pull more inward more strongly)

(The chest wall won’t “give” as much to meet the lung)

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23
Q

If PA > PB, is inspiration or expiration occurring?

A

Expiration

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24
Q

What is transpulmonary pressure (Ptp)?

[Equation and explanation]

A

Ptp = PA - PiP

Acts to inflate the lungs

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25
Q

If you are starting from FRC (as one does in normal, easy breathing), which part of the lung recieves more ventilation, the base or the apex?

Why?

A

The base

The starting PiP at the base of the lung is less negative than the PiP at the apex, which puts the base in the beefy part of the volume/PiP curve; slight changes in PiP (due to inspiration) starting from this point will result in more volume change (better ventilation)

Compliance of the lung is low at the more negative PiP that the apex is in; change in volume will be small for a given inspiration

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26
Q

If transrespiratory pressure (Ptr) is negative, where will air flow when the glottis opens?

A

Into the alveoli

Ptr = PA - PB

If Ptr is negative, PA is lower than PB, and air will flow down the pressure gradient, into the alveoli

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27
Q

Does surfactant act more strongly on small or large alveoli?

Why?

A

Small alveoli

As the lung contracts, the surface area decreases and surfactant becomes concentrated into a smaller space (basically, the layer of surfactant gets thicker)

This works unless alveoli gets so small (lung size is below FRC) that surfactant phase-changes to a solid; at this point, surface tension is ~0

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28
Q

Which alveolus has a greater tendency to collapse?

A) An alveolus with a radius of 0.05 mm

B) An alveolus with a radius of 0.08 mm

A

A) An alveolus with a radius of 0.05 mm

Smaller alveoli have an increased tendency to collapse becaues they experience greater inward forces due to surface tension

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29
Q

What are the major determinants of lung volume?

A

Body size (height)

Age

Gender

Race

30
Q

What is the vital capacity (VC)?

A

The total amount of air that can be expired in one breath

VC = TV + ERV

31
Q

What is the equation for the ideal gas law?

A

PV = nRT

  • P = pressure
  • V = volume
  • n = number of moles of gas
  • T = temperature
  • R = proportionality factor, the gas constant, the values of which are dependent upon the units of P, V, n & T.
32
Q

What is the active ingredient in surfactant?

A

Dipalmitoyl phosphatidyl choline

33
Q

The balance between the outward force of the ____________ and the inward force of the ____________ determines the functional residual capacity

A

The balance between the outward force of the chest wall and the inward force of the elastic recoil of the lungs determines the functional residual capacity

34
Q

Which transmural pressure works to suck the chest wall inward?

A

Transthoracic pressure (Ptt)

35
Q

What is the functional residual capacity (FRC)?

A

FRC = ERV + RV

Expiratory reserve volume + Residual volume

The amount of air left in the lungs after tidal volume is exhaled

36
Q

Why does dynamic compression of the airways occur during forced, maximal expiration?

A

During a forced, maximal expiration, PA increases and PiP increases.

At first, the elastic recoil of the lung keeps PA > PiP and air flows out of the alveolus. However, as lung volume decreases the elastic recoil force diminishes, resulting in PA iP - When this occurs, the airway compresses and air does not flow until the recoil of the chest wall increases PA > PiP, and the process begins again

37
Q

What are the conditions of ATPS?

A

Ambient termperature and pressure, saturated H2O

38
Q

What is the equation for the partial pressure of a gas, in the gas phase (Pg) in dry air?

A

Pg = Fg, dry * (PB - PH2O)

  • Fg, dry = gas fraction, dry
  • PB = barometric pressure
  • PH2O = water vapor pressure
39
Q

The gas dissolved in solution depends on the ______________ of the gas, as well as its ________ constant

A

The gas dissolved in solution depends on the partial pressure** of the gas, as well as its **solubility constant

Two gases with the same partial pressure might have different concentrations in solution if one is more soluble than the other

40
Q

Is the airway more compressible at large volumes or small volumes?

Why?

A

The airway is more compressible at small volumes

At small volumes, there is less tethering and less elastic recoil, resulting in increased susceptibility to compression of the airway

41
Q

What is transrespiratory pressure (Ptr)?

[Equation, explanation]

A

Ptr = PA - PB

The potential pressure gradient for flow into or out of the alveoli

The difference between PA and PB when the glottis is closed and the respiratory muscles are relaxed

42
Q

Resistance through a rigid tube is proportional to _____

(In terms of the radius)

A

Resistance through a rigid tube is proportional to 1/r4

43
Q

List 2 stimuli that are likely to cause bronchial constriction by activating autonomic reflexes

A
  • Irritant gases
  • Mast cell histamine release
44
Q

List 4 clinical conditions that decrease compliance

A
  • Respiratory distress syndrome
  • Edema
  • Atelectasis
  • Fibrosis
45
Q

What are the conditions of STPD?

A

Standard Temperature and Pressure, dry air

Ex: Metabolic rates

46
Q

What is the equation for Henry’s Law for the concentration of a dissolved gas?

A

Cg = K * Pg

  • Cg = concentration of dissolved gas (g)
  • K = solubility coefficient
  • Pg = partial pressure of the gas
47
Q

In an abnormal lung in which the only pathological change is loss of elastic tissue, would compliance be increased or decreased?

A

Compliance would increase if the only change was a loss of elastic tissue (there will be less recoil force resisting expansion of the lung)

Note: Clinically, loss of elastic tissue is usually associated with an increase in fibrous tissue, which could result in a decrease in lung compliance

48
Q

What is the equation for ventilation?

A
49
Q

What are the conditions of BTPS?

A

Body temperature, ambient pressure, saturated H2O

Ex: Ventilated gas

50
Q

What causes inflation and deflation of air-filled lungs to take different paths in this graph?

A
  • Inflation
    • At the beginning (bottom), surfactant is a solid; it is not working to reduce surface tension, and a large amount of pressure is required to begin to increase the volume
    • When surfactant phase-changes from solid to liquid, the lung becomes more compliant because surface tension decreases
  • Deflation
    • At the beginning (top), the elastic recoil force of the lung is less strong because the alveolus has a larger radius, and surface tension is mitigated by surfactant. As a result, it takes a large pressure decrease for volume in the lung to respond
51
Q

What is the equation for respiratory quotient (RQ)?

A
52
Q

What is the Reseidual Volume (RV)?

A

The air left in the lungs after maximum expiration

53
Q

What is the equation for surface tension in an alveolus, according to La Place’s law?

A

P = (4T)/R

=> As radius increases, surface tension decreases

54
Q

Diffusion of a gas into a substance of a different phase (ex: gas to liquid) is down its ______________.

A

Diffusion of a gas into a substance of a different phase (ex: gas to liquid) is down its partial pressure.

Not necessarily down its concenration gradient!

55
Q

If PA B, is inspiration or expiration occurring?

A

Inspiration

56
Q

Which part of this graph indicates resting/tidal breathing?

A

Indicated in green

57
Q

How does PiP differ between the apex and the base of the lung?

Why?

A

PiP is more negative at the apex of the lung and less negative at the base of the lung due to gravity

The weight of the lung pushes down on the base of the lung, which kind of pushes it against the chest wall, resulting in less negative PiP at the base

58
Q

How would filling a lung with saline affect its compliance?

Why?

A

Filling a lung with saline would increase its compliance; less pressure would be required to increase its volume

A lung filled with saline does not have any surface tension because there is no fluid-air interface between the membrane of the lung and the substance inside of it.

59
Q

A patient with emphysema has a lung compliance of 0.4 liters/ cm H2O and a chest wall compliance of 0.2 L/cm H2O.

What is the compliance of the chest wall and the lung together?

A

The lung and the chest wall are in series, so:

1/Ctotal = 1/Cchest wall + 1/Clung

= 1/0.2 + 1/0.4

Ctotal = 0.133 L/cm H2O

60
Q

Which parts of the flow-volume curve are effort-independent?

A

Indicated in pink

61
Q

How would you calculate the total compliance of the right and left lung together?

A

The rigth and left lungs are in parallel

CTotal = CRight lung + CLeft lung

62
Q

When the lungs are expanded…

Is the recoil force large or small?

How is PiP affected?

A

When the lungs are expanded (think inspiration, when the diaphragm and chest wall is ),

Recoil force is large (imagine a v. stretched rubber band)

PiP is more negative than equillibrium (-30 cm/H20)

The chest wall/diaphram are expanding and the lungs are trying to recoil - PiP becomes more negative when there is more force trying to pull the chest wall and lungs apart

(The chest wall and lungs love each other and when they are pulled apart their child PiP is sad and it is a negative experience :’( )

63
Q

List 3 stimuli that are likely to cause bronchial dilation by activating autonomic reflexes

A
  • Mild lung stretch
  • Hypercapnia
  • Hypoxia
64
Q

What are the 3 major effects of surfactant on the respiratory cycle?

A
  • Less work is required to breath
  • Alveoli are stabilized
  • Surface tension varies with surface area of the lung
65
Q

List 3 clinical conditions that increase compliance

(may be physiologic or pathologic)

A
  • Increasing age
  • Increasing body size (especially height)
  • Emphysema
66
Q

During expiration, compression of the airway occurs when
PA ___ PiP

The airway expands to allow air to flow again when
PA ___ PiP

____ is the force driving air out of the alveolus

A

During expiration, compression of the airway occurs when
PA PiP

The airway expands to allow air to flow again when
PA > PiP

PA is the force driving air out of the alveolus

67
Q

If a lung is more compliant than normal (ex: emphysema), how will FRC change?

How will PiP be affected?

A

FRC will be larger

PiP will be larger (less negative)
(The lung wont be pulling very hard to go back to its happy volume)

(closer to the resting volume of the chest wall than normal)

68
Q

What is the equation for the partial pressure of a gas, in the gas phase (Pg) in saturated air?

A

Pg = Fg, saturated * PB

  • Fg, saturated = fraction of gas saturated with water vapor
  • PB = barometric pressure
  • PH2O = water vapor pressure
69
Q

In some diseases, portions of a lung can collapse. Would it be better to prevent a predicted collapse, or to re-expand the portion after it collapses?

A

In general, it is easier to prevent collapse (by increasing thoracic pressure) than re-expand a collapsed portion.

Re-expansion is hard because the collapsed portion will tend to stick to itself

70
Q

Which transmural pressure works to inflate the lungs?

A

Transpulmonary pressure (Ptp)

Pulm by Minnie: AH Update (34 decks)

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