Lecture 1: Respiratory Cycle and Mechanics Flashcards

1
Q

What does Boyle’s law say?

A

Pressure of gas is inversely proportional to volume

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2
Q

What happens when lung volume increases?

A

Pressure in lungs decrease so air can enter lungs

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3
Q

What happens when lung volume decreases?

A

Pressure in lungs increases so air can exit lungs

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4
Q

What happens during inspiration?

A
  • Inspiratory muscles (external intercostal muscles) contract
  • Diaphragm descends
  • Thoracic volume increases
  • Intrapleural pressure and alveolar pressure decreases
  • Chest wall and lungs will expand due to coupling (lungs want to collapse)
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5
Q

Where is parietal fluid found?

A

Between parietal and visceral pleura

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6
Q

What is intrapleural pressure?

A

Pressure everywhere in thorax except lumens of blood vessels, lymphatics, and airways

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7
Q

What is the intrapleural pressure at rest?

A

-5 cm H2O

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8
Q

What is the intrapleural pressure during inspiration?

A

Reaches -8 cm H2O

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9
Q

What is the alveolar pressure at rest?

A

0 cm H20

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10
Q

What is the alveolar pressure during inspiration?

A

-1 cm H20

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11
Q

What happens during expiration?

A
  • Passive so expiratory muscles not always used
  • Diaphragm ascends
  • Thoracic volume decreases
  • Intrapleural pressure and alveolar pressure increases
  • Chest wall and lungs will shrink due to coupling
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12
Q

What is the intrapleural pressure during expiration?

A

Goes back to rest (-5 cm H2O)

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13
Q

What is the alveolar pressure during expiration?

A

Reaches +1 cm H2O

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14
Q

What four things does the respiratory cycle show change in?

A

1) Volume
2) Alveolar Pressure
3) Intrapleural Pressure
4) Air Flow

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15
Q

What is minute ventilation?

What is the normal value?

A

Volume of air inhaled every minute

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16
Q

How do you calculate minute ventilation?

A

V(dot) = Tidal Volume x frequency

17
Q

What is the normal value of minute ventilation?

18
Q

What is anatomic dead space?

A

Space in the lungs designed not exchange oxygen

  • first 16 generations of airway do not have alveoli
  • called anatomic since it is not designed for air exchange
19
Q

How do you calculate anatomic dead space?

A

Weight of person –> anatomic dead space

Example: 120 lb person has 120 mL of anatomic dead space

20
Q

What is alveolar dead space?

A

Alveoli that receive air but not blood

-this should in theory not exist

21
Q

What is physiological dead space?

A

Dead alveolar space so no gas exchange

-this should in theory not exist

22
Q

How do you calculate minute alveolar ventilation?

A

V(dot alv) = (Tidal volume-anatomic dead space volume) x (frequency)

23
Q

When is it easiest for lungs to stretch during inspiration?

A

After there is a little air in the lungs, a small change in pressure can lead to a huge increase in volume of lungs

24
Q

What is hysteresis?

A

Difference between inspiration and expiration

25
What allows hysteresis to occur?
Surfactant: reduces tension and helps air reach all alveoli
26
What is compliance?
Measure of stretch ability of lungs
27
Where is compliance high in lungs?
``` Tidal volume (middle) -easy to inflate ```
28
How is compliance calculated?
Compliance = (Δ volume)/(Δ pressure)
29
What is the opposite of compliance?
Elasticity: recoil ability
30
How does fibrosis affect compliance?
Lowers compliance | -lungs have to work harder to bring in air
31
How does age affect compliance?
Compliance increases with age | -less elastin and more collagen
32
How does emphysema affect compliance?
Increases compliance | -easier to bring air but air has no where to go since there is an increase in dead space
33
Where do recoil of lungs and chest wall balance each other?
Functional residual capacity (FRC)
34
When a pneumothorax occurs, what happens to chest wall and lungs?
Lungs: get smaller Chest wall: expand *both get their wish
35
How is airway resistance calculated?
Resistance = (8 x viscosity of x length of tube) / (radius^4)
36
What prevents alveoli to collapse?
Interdependence | -shared walls of alveolar and airways prevent collapse as recoil opposes each other