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pathophys 4040 > static and dynamics > Flashcards

static and dynamics Flashcards

1
Q

Transrespiratory Pressure

A

(Prs): what is causing gas to flow into or out of our lungs; how much pressure we lose from mouth to alveoli (Prs = PA - Pao)

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2
Q

Transpulmonary Pressure

A

(PL): difference between alveolar and pleural pressures; distending pressure of the lung (PL = PA - Ppl)

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3
Q

Transthoracic Pressure

A

(Pw): pleural pressure; measure of recoil of the lung and chest wall (Pw = Ppl - Pbs)

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4
Q

Atmospheric Pressure
-abbreviation
-equation/definition

A

abbreviation: PB
definition/description: atmospheric pressure is always 760 mmHg

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5
Q

Airway Opening
-abbreviation:
-equation/definition:

A

abbreviation: Pao
definition/description: pressure at the mouth is always atmospheric = 0

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6
Q

Alveolar Pressure
-abbreviation
-definition
-equation

A

abbreviation: PA
definition: aka intrapulmonary pressure; negative during inspiration; 0 when air flow is absent; positive during exhalation
equation: PA = Ppl + Pel
**Ppl = transpulmonary pressure
**Pel = elastic recoil

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7
Q

Pleural Pressure
-abbreviation
-definition
-equation

A

abbreviation: Ppl
definition: always negative during quiet breathing; pressure between the pleural membranes
equation:

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8
Q

Transpulmonary Pressure
-abbreviation
-definition
-equation

A

abbreviation: PL
definition: difference between alveolar pressure and pleural pressure; distending pressure of the lung
equation: PL = PA - Ppl
**PA = alveolar pressure
**Ppl = pleural pressure

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9
Q

Transrespiratory Pressure
-abbreviation
-definition
-equation

A

abbreviation: Prs
definition: difference between alveolar pressure and airway opening pressure; what is causing gas to flow into or out of our lungs
equation: Prs = PA - Pao

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10
Q

Transthoracic Pressure
-abbreviation
-definition
-equation

A

abbreviation: Pw
definition: measure of recoil of the lung and chest wall
equation: Pw = Ppl - Pbs
**Ppl = pleural pressure
**Pbs = body surface pressure

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11
Q

Describe the role of the diaphragm in inspiration

A

diaphragm contracts, which creates a negative pressure and allows air to flow into the lungs (remember: the diaphragm is connected to the chest wall and rounded; so when it contracts, it pulls down towards the walls creating more space for lungs to expand)

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12
Q

Explain how elastance relates to compliance.

A

elastance is the opposite of compliance; it is the recoil force of the lung
the more elastic the lung, the less compliance
-lung with high compliance has poor elastance – stretches really easily but does not recoil well
-lung with low compliance has high elastance – recoils really well, which is why the lung struggles to expand (the recoil is pulling the lung back in)

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12
Q

Describe the role of the diaphragm in expiration

A

diaphragm relaxes, which creates a positive pressure and allows air to flow out of the lungs (remember: the diaphragm is curved and connected to the chest wall and rounded; contraction pulls it down, so relaxation causes it to move back up and decrease the thoracic volume and force the lungs to push air out)

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13
Q

Calculate compliance and interpret the value.
-what is the equation?
-what is normal static compliance?

A

-equation: change in volume divided by the change in pressure
(pressure expressed in mL/cmH2O)
-normal static compliance: 200 mL/cmH2O

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14
Q

Describe how Laplace’s law can be applied to the alveolar fluid lining.

A

equation: P = 2T/r
*P = distending pressure
*T = surface tension
*r = alveolar radius
describes how a bubble is influenced by the ST of the bubble and the size of the bubble itself
-the smaller the alveolus, the more pressure to inflate (inverse relationship)
-the more surface tension, the more pressure it takes to inflate (direct relationship)

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15
Q

Explain how pulmonary surfactant offsets alveolar surface tension

A

surfactant reduces the work of breathing by:
-reducing counter pressure required to keep the small alveoli open
-stabilizes alveoli of different sizes (makes smaller ones have a smaller ST so they can inflate until all alveoli are the same size then they can all get bigger)

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16
Q

Define critical opening pressure as it relates to alveoli

A

when this pressure is exceeded, the alveoli open rapidly (on inhalation because the pressure in the lungs is increasing as more air comes in; the pressure rises to overcome recoil)

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17
Q

Define critical closing pressures as it relate to alveoli.

A

the pressure has decreased to the point where the alveoli cannot stay open; alveoli “snap shut” (on exhalation because the pressure in the lungs are decreasing as the air moves out and the lungs recoil)

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18
Q

static

A

equilibrium; of or relating to bodies at rest or forces in equilibrium; characterized by lack of movement, animation, or progression (measured during end inspiration because it checks lung expansion, and lungs are expanded at end inspiration; normal: 200mL/cmH2O)

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19
Q

dynamic

A

resistance to gas flow; measured while air is flowing; gives a combination of static lung compliance plus airway resistance; tell us how easily the chest is rising during inspiration (normal is Raw = 0.5-1.5 cm water/L/sec)

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20
Q

Define airway resistance.

A

represents the level of difficulty in taking a breath
resistance to gas flow
pressure difference between the mouth and alveoli divided by the flow rate
(want low airway resistance because high resistance means that it would be more work to breathe)

21
Q

Explain how the pressure-volume curve changes with increases or decreases in compliance.

A

low compliance: shifts the graph to the right; means that the lungs do not want to stretch easily, so more pressure will need to be applied to get the lungs to stretch
high compliance: shifts the graph to the left; means that the lungs stretch very readily bc lungs will need less pressure to get them to stretch

22
Q

Calculate airway resistance and interpret the value.
what is the equation?

A

equation: change in pressure divided by flow – pressure difference between the mouth and alveoli
equation: Raw = change in pressure/flow
(answer in cmH2O/L per second; normal between 0.5 and 1.5 cmH20/L/sec)

23
Q

Transitional Flow

A

found where the airways branch; tracheobronchial flow (where laminar flow turns to turbulent flow or vice versa; a mixture between the two other types of airflow)

24
Q

Laminar Flow:

A

very quiet, organized flow; very little resistance involved; vesicular breath sounds; influenced by gas viscosity, NOT density

25
Q

Turbulent Flow

A

very unorganized, loud airflow; found in the trachea; requires a higher pressure to move; affected by gas density

26
Q

Turbulent flow depends on ____________________.

A

gas density (higher density = harder to move)

26
Q

Laminar flow depends on ____________________ not ________________________.

A

depends on gas viscosity NOT gas density

27
Q

Explain how Poiseuille’s law relates to radius of the airways and airway resistance

A

change in pressure = gas flow rate / radius to the 4th power
if the radius decreases to have of it’s size, it takes 16 times more pressure to maintain the original flow
–if the radius increases, the pressure needed to get gas to flow through the tube will decrease
–if the radius decreases, more pressure is needed to force gas flow through the tube

28
Q

Identify the importance of the plateau pressure

A

Plateau pressure: measures elastic recoil
it is the best representation of our alveolar pressure
must be measured under static conditions
(peak-plateau = air way resistance)

28
Q

What are some things that would cause an airway radius to decrease?

A

asthma
anaphylaxis
bronchoconstriction
mucous

29
Q

Describe how low lung compliance alters one’s ventilatory pattern.

A

the lungs are not going to want to stretch, so more force will need to be applied before the lungs begin to stretch; (recoil force would be much stronger); the lung will be difficult to inflate; this will affect ventilatory pattern because the patient will have to take more frequent, shorter breaths to get enough air; this causes more work of breathing and weakens/exhausts the patient

30
Q

What effect does high compliance have on time constant?

A

take longer to reach pressures, but fill with higher amount of volume (lungs stretch easily, so less pressure is needed to get them to start inflating; takes longer for them to reach max pressure/stretch)

30
Q

Predict the time constants of various disease processes.
-what is a time constant?
-calculation?

A

time constant: if a constant pressure is applied to the trachea, gas flows into the lungs until the lung pressure equals the applied pressure
calculation: compliance x resistance

30
Q

What effect does high resistance have on time constant?

A

lungs need longer time to equilibrate (takes longer for the air to move around the blockages)

30
Q

Describe how high lung compliance alters one’s ventilatory pattern.

A

the lungs will stretch much more readily; therefore, less pressure would be needed to get the lungs to inflate (the lung is easy to inflate); this could alter ventilatory pattern because it means that the lungs’ recoil force will not act as heavily, making the lungs difficult to deflate (the patient will have a harder time exhaling, so they may be increasing their residual volume, which in turn, decreases all the other values - ERV, tidal volume, IRV; this could lead to a pneumothorax/popped lung)

31
Q

What effect does low resistance have on time constant?

A

lungs need less time to equilibrate (air doesn’t have to move around any blockages, so they can get from one place to another quicker because they don’t have to move around anything)

31
Q

What effect does low compliance have on time constants?

A

reach pressure quickly, but fill with a low amount of volume (lungs don’t want to stretch, so max pressure is reached fairly quickly)

32
Q

How would asthma affect a time constant?

A

it would take longer to equilibrate because there is higher resistance

32
Q

How would pulmonary fibrosis affect a time constant? (pulmonary fibrosis: lungs become damaged, making them stiffer)

A

it would take less time because the lungs would have less compliance (therefore, less pressure would be needed to get the lungs to stretch to full capacity)

33
Q

How would emphysema affect a time constant? (emphysema: lungs are very compliant)

A

longer because the lungs are very compliant so they would stretch more; they are also less elastic because the recoil force is diminished, so they would take longer to get the air out of the lungs (less elastic)

34
Q

What are the 4 lung volumes?

A

expiratory reserve volume (ERV)
residual volume (RV)
inspiratory reserve volume (IRV)
tidal volume (VT)

35
Q

maximum amount of air you can exhale at the end of your tidal breath

A

Expiratory Reserve Volume

36
Q

amount of air in your lungs that you cannot get rid of
(amount of air still in your lungs at the end of exhalation)

A

Residual Volume

37
Q

maximum air you can take in on top of a tidal breath

A

Inspiratory Reserve Volume

38
Q

amount of air that you move in one quiet breath

A

Tidal Volume

39
Q

What are the 4 lung capacities?

A

Vital Capacity
Inspiratory Capacity
Total Lung Capacity
Functional Residual Capacity

40
Q

maximum amount of air you can exhale after taking a maximum inhalation
total amount of air you can move
everything except our residual volume

A

Vital Capacity

41
Q

amount of air we can inhale

A

Inspiratory Capacity

42
Q

maximum volume of air in the lungs after a full inhalation

A

Total Lung Capacity

43
Q

amount of air left in the lungs at then end of expiration

A

Functional Residual Capcity

pathophys 4040 (3 decks)

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