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Respiratory > Lec 2 - Ventilation and Lung mechanics > Flashcards

Lec 2 - Ventilation and Lung mechanics Flashcards

1
Q

What are some disorders that present as quiet expiration?

A

Emphysema –> This is the destruction of elastic fibres leading to a decrease in the elastic recoil of the lungs.

Asthma and COPD –> The increases airways resistance.

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2
Q

What are some disorders that present as difficulty in lung expansion?

A

Diffuse lung fibrosis –> increased collagen in alveolar walls, makes the lungs stiff.

Respiratory distress in the newborn –> This is due to decreased surfactant leading to increased surface tension.

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3
Q

What is a brief description of pneumothorax?

A

Pleural seal lost and lung collapsed.

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4
Q

What is a brief description of Hypoventilation?

A

Inspiratory muscles not working.

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5
Q

What are parts of the conducting portion in the respiratory tract?

A
  • Nasal Cavity
  • Pharynx
  • Larynx
  • Trachea
  • Primary bronchi
  • Secondary bronchi
  • Bronchioles
  • Terminal bronchioles
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6
Q

What are parts of the respiratory portion of the respiratory tract?

A
  • Respiratory bronchioles
  • Alveolar ducts
  • Alveoli
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7
Q

What is the epithelium for the conducting portion excluding the bronchioles and terminal bronchioles?

A

Pseudostratified epithelium with cilia and goblet cells.

-This lines the airways from the nasal cavity to the largest bronchioles.

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8
Q

What is the epithelium for the bronchioles and terminal bronchioles?

A

-Simple columnar epithelium with cilia and Clara cells but no goblet cells.

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9
Q

What is the epithelium for the respiratory portion excluding the alveoli?

A

-Simple cuboidal epithelium with a few sparsely scattered cilia and Clara cells.

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10
Q

What is the epithelium for the alveoli?

A

-Simple squamous/ type 1

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11
Q

What is the role of mucus and cilia on the inhalation of large particles?

A
  • They are filtered in the nose.
  • They are then deposited on the mucus layer in the nose, nasopharynx and swept by cilia to the oropharynx before they are swallowed.
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12
Q

What is the role of mucus and cilia on the inhalation of medium sized particles?

A
  • They are deposited on mucus lining the trachea, bronchi and larger bronchioles.
  • They are then wafted up to the pharynx by cilia (muco-ciliary escalator) and then they are swallowed.
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13
Q

What is the role of mucus and cilia on the inhalation of Small particles?

A
  • They are carried down to alveoli.

- They are engulfed by macrophages and then removed by lymphatics and via airways (muco-ciliary)

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14
Q

What do pulmonary and bronchial arteries carry?

A
  • pulmonary arteries carry deoxygenated blood.

- bronchial arteries carry oxygenated blood.

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15
Q

What is radial traction?

A

It is the outward tugging action of the alveolar walls on the bronchioles.
– This prevents the collapse of the bronchioles during expiration.

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16
Q

What do type I and type II alveolar cells do?

A

Type I –> these permit gas exchange.

Type II –> These secrete surfactant.

17
Q

What is compliance?

A

Compliance is a measure of how stretchy the lung is.

18
Q

What is elastance?

A

Elastance is a measure of elastic recoil.

– It is the tendency to return to their original shape when stretched.

19
Q

Relate compliance to elastance?

A

Compliance is directly proportional to 1/elastance.

  • When compliance increases, elastic recoil decreases.
  • When compliance decreases, elastic recoil increases.
20
Q

What is the interstitium and what does it contain?

A

it is the microscopic space between the alveolar epithelium and capillary endothelium.

Contains:

  • elastin fibres
  • collagen fibres
  • fibroblasts
21
Q

What can lead to interstitial lung fibrosis?

A
  1. a specific exposure such as asbestos, drugs and mouldy hay etc.
  2. autoimmune mediated inflammation.
  3. Unknown injury such as idiopathic pulmonary fibrosis.
22
Q

Describe the mechanisms of pulmonary fibrosis?

A

-Overall the function residual capacity is decreased.

  • There is fibrous tissue in the interstitium.
    1. The lungs are stiff, therefore are harder to expand.
    2. The lung compliance is low.
    3. elastic recoil of the lungs is high.
    4. The lung volume is lower than normal.
    5. The airways are not obstructed.
    6. Restrictive type of ventilatory defect.
    7. There is a restrictive pattern on the spirometry testing.
23
Q

What are the signs and symptoms of pulmonary fibrosis?

A

breathlessness
dry cough
relevant previous history such as occupation and drug history etc.

signs are: chest expansion is reduced bilaterally.

24
Q

Describe the pathology of interstitial lung disease (diffuse lung fibrosis)?

A
  1. The alveolar capillary membrane is thickened.
  2. this increases diffusion distance for oxygen and carbon dioxide.
  3. This impairs gas exchange.
25
Q

What is emphysema?

A
  • It is the abnormal, permanent enlargement of the air spaces distal to the terminal bronchiole.
  • This is done by the destruction of the alveolar wall.
  • There is no fibrosis.
  • protease mediated destruction of elastin is an important feature.
  • There is the reduced elasticity.
  • The large air spaces mean that there is a reduced surface area for gas exchange.
26
Q

What are the causes of emphysema?

A
  1. smoking and inhaled pollutants –> This causes inflammatory cells to accumulate, which releases elastase and oxidants, which destroy alveolar walls and elastin.
  2. Most have Chronic bronchitis concurrently.
  3. Chronic obstructive pulmonary disease (COPD) for example emphysema and bronchitis.
  4. Chronic bronchitis is seen in the larger airways
    - –> you get mucus hyper secretion from goblet cells and sub mucous glands
    - –> Mucus is also not cleared effectively due to the reduced cilia.
27
Q

Why is airway obstruction worse in expiration than inspiration?

A
  • In inspiration there is negative pressure in the pleural space during inspiration, which helps to keep the lower airways open.
  • In expiration, there is a positive intrapulmonary pressure during expiration, which exacerbates the narrowing of the intra thoracic airways.
28
Q

Describe the mechanism of emphysema.

A
  • There is the loss of elastic tissue, so elastic recoil is decreased.
  • This means that compliance is increased.
  • Small airways collapse in expiration due to the loss of radial traction.
  • There is the trapping of air due to airway obstruction and reduced elastic recoil.
  • You can get hyper inflation known as barrel chest.
  • You also see an obstructive pattern on spirometry testing.
29
Q

What is barrel chest?

A

It is the increase in the anterior posterior diameter of the chest wall.
-The lungs are chronically overinflated with air so the ribcage stays partially expanded at all time.

30
Q

Describe the mechanism of a pneumothorax.

A
  1. If the chest wall or the lung is breached (stabbing), a communication is created between pleural space and atmosphere.
  2. Air flows from the atmosphere into the pleural cavity from a higher pressure to a lower pressure.
    - - This is until the pleural pressure is equal to atmospheric pressure.
  3. The pleural seal is lost.
  4. Lung elastic recoil is not counter-balanced by negative pleural pressure so the lung collapses to unstretched size.
31
Q

When does Atelectasis (lung collapse) occur?

A
  1. In new-born babies –> there is the failure of alveoli to expand at birth due to lack of surfactant.
  2. Compression collapse due to:
    - ->air in pleural cavity –> pneumothorax.
    - -> Fluid in the pleural cavity –> pleural effusion.
  3. Resorption collapse due to obstruction –> if the airway is obstructed, the air downstream of blockage is slowly absorbed into the blood stream.
32
Q

What is resorption collapse?

A

-This is the collapse due to obstruction of a large airway due to things such as lung cancer and mucus plugs.

33
Q

What is surfactant produced by and when?

A
  • Produced by Type II alveolar cells.
  • production starts at 24-28 weeks gestation.
  • Increasing amounts by 32 weeks.
  • usually sufficient by 35-36 weeks.
34
Q

What is surfactant like in preterm babies?

A
  • There is insufficient surfactant, which results in high surface tension.
  • As a result lung expansion at birth is incomplete.
  • So some alveoli remain collapsed (airless), so there is no gas exchange here.
35
Q

What are some features of respiratory difficulty from birth?

A
  • grunting
  • nasal flaring
  • intercostal and subcostal retractions
  • rapid respiratory rate (tachypnea)
  • cyanosis
36
Q

What are treatments for respiratory difficulty?

A
  • surfactant replacement via an endotracheal tube.

- supportive treatment with oxygen and assisted ventilation.

Respiratory (9 decks)

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