Resp 3 Flashcards

1
Q

What is the function of pleural fluid?

A

Thin layer of fluid that ensures lungs fill the thoracic cavity during inspiration by ensuring visceral pleura moves with parietal

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2
Q

What is a pneumothorax?

A

Breach in integrity of the pleural seal

Leads to lung collapse (lung(s) do not expand with thoracic cavity)

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3
Q

Describe the forces exerted by the lung and on the lung at resting expiratory volume

What happens if these forces are disturbed?

A

Lungs pull in and up

Thoracic cage pulls out

Passive stretch of diaphragm pulls down

Forces are in equilibrium

If Disturbed:

If disturbed (E.g. in inspiration) the lungs and surrounding structures will spring back to resting expiratory volume (equilibrium regained)

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4
Q

What is the difference between and inspiration from resting expiratory volume and quiet expiration?

A

Quiet Expiration:

Passive process, just stop breathing in

Inspiration from resting expiratory volume:

Active

Via intercostals and diaphragm (major muscle of quiet respiration)

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5
Q

How does forced expiration differ from quiet expiration?

A

Active not passive

Force exerted by abdominal muscles

Then inspiration back to resting expiratory level is passive

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6
Q

In what scenarios would quiet breathing require additional work?

A

If diaphragm cannot move into abdomen

  • Pregnancy
  • Obesity
  • Corsets
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7
Q

What is lung complicance?

A

The stretchiness of the lungs

Volume change per unit pressure change

Therefore higher complience means easier to stretch (lower pressures needed to acheive desired volume)

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8
Q

What are the 3 major factors that affect lung compliance?

A

Surface tension of surfactant

Elasticity of walls

Detergents

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9
Q

Describe how surface tension affects the lungs

A

At interface of water and air surface tension arises

Created by attraction of underlying molcules to surface molecules

This force reduces compliance

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10
Q

Describe the involvement of detergents in the lung and how they affect compliance and breathing

A

Produced by type 2 alveolar cells (surfactant)

At low lung volume detergents lower surface tension

They disrupt interactions between surface molecules

At higher volumes this effect is reduced

Therfore bigger breaths are harder than smaller breaths as lung compliance lowers as volume increases

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11
Q

What is hysteresis and how does it affect respiration?

A

Hysteresis is a phenomenon wherby there are different energies required to move a system in different directions

Respiration:

Energy put into stretching a film of surfactant is not recovered when the film recoils

This loss is greatest when tibal volume is maximal

Therefore smaller breaths are more energy effiecient

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12
Q

How is hysteresis in the lungs represented?

A

Graph

Y = Surface tension

X= Surface area

A loop is formed, the area of this loop respresents energy loss

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13
Q

What are bubbles?

A

A film of fluid surrounding gas (like an alveolus)

There is equilibrium between gas pressure and tension

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14
Q

What is Laplace’s law and what can we take from it?

A

Pressure in bubble = (2 x Surface tension) / radius

Therefore:

  • Bigger bubbles have lower pressure than smaller bubbles
  • If a big bubble is connected to a smaller bubble gas will flow from smaller bubble into lower pressure bigger bubble
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15
Q

Describe how Laplace’s law is not an accurate respresentative of lung function

A

Alveoli form an interconnecting set of bubbles

If Laplace’s law applied, bigger aveoli would ‘eat’ smaller alveoli

However:

As alveoli get bigger surface tension increases (as detergents lose effect)

Therefore raising pressure in bigger bubbles, preventing Alveoli ‘cannabilisation’

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16
Q

Describe the causes and features of respiratory distress syndrome

A

Causes:

In babies born premature there is too little surfactant

This can also be triggered in adults by trauma

Features:

Lungs are stiff and only few, large alveoli

Small alveoli collapse into bigger ones without surfactant/detergent

17
Q

What is airway resistance like:

  • In individual bronchi
  • The entire respiratory tree

Why is this?

A

Bronchi:

Relatively High

Airway:

Relatively low

Because:

Poiseulle’s law

Smaller tubes have higher flow resistance

Large number of small airways in parallel compensates for increase in resistance (lower resistance)

At each branch resistance decreases

18
Q

Compare airway resistance in:

  • The trachea
  • All Small airways (Bronchioles)
A

Trachea:

Relatively high

All Bronchioles:

Relatively low

19
Q

How is airway resistance affected by forced expiration?

A

Lung compressed and hence the small airways are narrowed

This increases resistance to airflow

Air is ‘trapped’ in alveoli

20
Q

What are the causes of obstructive airway disease?

What are the consequences regarding airway resistance?

A

Causes:

Narrowed airways from disease (Asthma, Bronchitis)

Consequences:

Airway resistance increases earlier in expiration (due to narrowed airways)

Breathing out can become very difficult (pursed lip breathing)