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Respiratory system > Lung Mechanics - L2 > Flashcards

Lung Mechanics - L2 Flashcards

1
Q

What are the 3 different pressure considerations important in ventilation?

A

Atmospheric pressure (barometric)
Intra-alveolar pressure (intrapulmonary pressure)
Intrapleural pressure (intrathoracic pressure)

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2
Q

What relationships are important in ventilation?

A

Interrelationships among pressures inside and outside the lungs are important in ventilation

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3
Q

When does atmospheric pressure decrease?

A

It decreases as altitude increases

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4
Q

What is atmospheric pressure at sea level?

A

760mm Hg at sea level

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5
Q

What is P atm set to?

A

P atm = 0 mm Hg

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6
Q

What is intra-alveolar pressure?

A

It is the pressure of air in alveoli - not a closed system, it is opened

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7
Q

When does intra-alveolar pressure vary?

A

It varies with phases of respiration

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8
Q

What happens to intra-alveolar pressure during inspiration?

A

It is negative - less than atmospheric

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9
Q

EXAM Q B4: Describe how pressure gradients are involved and how they affect flow rate

A
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10
Q

What drives ventilation?

A

The differences between P alv and P atm

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11
Q

What happens to intra-alveolar pressure during expiration?

A

It is positive - more than atmospheric

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12
Q

What is intra-pleural pressure?

A

It is pressure inside the pleural sac - it is a closed sysetm

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13
Q

What is intra-pleural pressure at rest?

A

756 (or -4) mmHg

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14
Q

Is intra-pleural pressure always more or less than P alv?

A

Always less than P alv

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15
Q

When is intra-pleural pressure always negative?

A

Its always negative under normal conditions at rest

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16
Q

Why is there negative pressure for intra-pleural pressure? HINT reason and 5 points of how

A

Negative pressure is due to elasticity in the lungs and chest wall:
1. Lungs recoil
2. Chest wall recoils outward
3. Opposing pulls on intrapleural space
4. Surface tension of intrapleural fluid hold wall
and lungs together (H2O molecules are polar, attract
each other)
5. Sub-atmospheric P: due to vacuum in the pleural cavity

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17
Q

what happens for us to breathe in?

A

pressure must drop for us to breathe in

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18
Q

What is FRC - Functional Residual Capacity?

A

It is the volume of air in the lungs between breaths that is defined as rest: P alv = P atm : 2.2L

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19
Q

Formula for Air FLOW?

A

FLOW = Patm-Palv
—————
R

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20
Q

When is atmospheric pressure constant?

A

During the breathing cycle

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21
Q

What does changes in alveolar pressure cause?

A

Changes in alveolar pressure creates or changes gradients

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22
Q

Boyle’s Law:

A

Pressure is inversely related to volume in a closed system - airtight container.

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23
Q

What does R in the FLOW formula stand for?

A

R = Resistance to air flow
Resistance is related to radius of airways and mucus

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24
Q

lecture slide figures from diagrams

A

needed

25
Q

Thus due to Boyle’s Law how can you change alveolar pressure?

A

Can change alveolar pressure by changing its volume

26
Q

2 factors that determine intra-alveolar pressure?

A
  1. Quantity of air in alveoli
  2. Volume of alveoli
27
Q

Are the intra-pleural sacs independent of one another?

A

The left intra-pleural sac is independent from the right - so if you damage 1 the other one should be fine

28
Q

What happens if the lung tissue is broken, for example due to disease?

A

If lung tissue is broken due to disease it can eventually damage the pleural sac and this can break the sac and eliminate the pressure defence and then the lung will collapse and the thoracic will expand

29
Q

What happens during inspiration? what happens to the lungs + 5 Points

A

The lungs expand:
- Alveolar volume increases
- P alv decreases
- Pressure gradient occurs and air is drawn into lungs
- The quantity of air in alveoli rises
- P alv increases

30
Q

What happens during expiration - to the lungs + 5 points:

A

Lungs recoil:
- Alveolar volume decreases
- P alv increases
- Pressure gradient occurs and air is pushed out of the lungs
- Quantity of air in alveoli decreases
- P alv decreases

31
Q

Opened system uses what pressure?

A

Intra-alveolar pressure

32
Q

Closed system that follows Boyle’s Law uses what pressure?

A

Intra-pleural pressure

33
Q

Respiratory muscle activity during inspiration - ribs?

A

Elevation of ribs

34
Q

How much % of total energy expenditure does quiet breathing require?

A

3%

35
Q

What do lungs normally operate at?

A

About 1/2 full

36
Q

What situations is the work of breathing increased? 4 points and example

A
  1. When pulmonary compliance is decreased
  2. When airway resistance is increased
  3. When elastic recoil is decreased
  4. When there is a need for increased ventilation
    For instance, COPD: 30% EE at rest
37
Q

Factors that affect pulmonary ventilation? 2

A

Lung compliance and Airways resistance

38
Q

What is lung compliance?

A

It is the ease at which lungs can be stretched

39
Q

What is required the less compliant the lungs are?

A

The less compliant the lungs are, the more work is
required to produce a given degree of inflation

40
Q

What 2 things is lung compliance affected by?

A

Affected by (i) elasticity (elastic recoil) and (ii) surface
tension of lungs (alveoli)

41
Q

What do type 2 alveoli cells make?

A

They make surfactant to decrease surface tension

42
Q

When is airway resistance increased?

A

Increased in pathologies

43
Q

What is airway resistance affected by? 3

A

Passive forces, contractile activity of
smooth muscle and mucus secretion

44
Q

Obstructive lung disease

A

Resistance is much higher and pressure is reduced and the intra-pleural pressure is also much higher and capacity to recoil lung is also reduced - same pressure
Not able to empty lungs properly - air accumulates
Limits capacity of exercise in individuals - but if its very severe it can happen at rest

45
Q

What can total energy expenditure go up to in someone with lung disease?

A

can go to 30%

46
Q

Tidal Volume? in mL

A

500 mL

47
Q

What does the elevation of the ribs during inspiration cause?

A

It causes sternum to move upward and outward, which increases front-to-back dimension of thoracic cavity

48
Q

What happens to the respiratory muscle activity during inspiration - external intercostal muscles?

A

The contraction of external intercostal muscles causes elevation of ribs, which increases side to side dimension of thoracic cavity.

49
Q

What happens to the diaphragm: respiratory muscle during inspiration? What does this do?

A

Lowering of diaphragm on contraction increases vertical dimension of thoracic cavity.

50
Q

What happens to the respiratory muscles - internal intercostal muscles during expiration? What does this do?

A

Contraction of the internal intercostal muscles flattens the ribs and sternum which further reduces side-to-side and front-to-back dimensions of thoracic cavity

51
Q

What happens to the respiratory muscles - abdominal muscles during expiration? What does this do?

A

They contract, the contraction of abdominal muscles causes the diaphragm to be pushed upward, further reducing the vertical dimension of thoracic cavity

52
Q

What restores the thoracic cavity to pre-inspiratory size?

A

Return of the diaphragm, ribs and sternum to resting position on relaxation of inspiratory muscles

53
Q

Inspiratory reserve volume (IRV) in mL?

A

3000 mL

54
Q

Inspiratory capacity (IC) in mL?

A

3500mL

55
Q

Expiratory reserve volume (ERV) in mL?

A

1000 mL

56
Q

Residual volume (RV) in mL?

A

1200 mL

57
Q

Functional residual capacity (FRC) in mL?

A

2200mL

58
Q

Vital capacity (VC) in mL?

A

4500 mL

59
Q

Total Lung Capacity (TLC) in mL?

A

5700mL

Respiratory system (7 decks)

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