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T3 resp system > 3.2 lung mechanics > Flashcards

3.2 lung mechanics Flashcards

1
Q

What is the pleura ?

A

a continuous double layered membrane which surrounds the lungs

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2
Q

Which surfaces are the pleura in contact with ?

A

contact with cavity wall = parietal layer

layer on lung surface = visceral layer

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3
Q

What are the lungs and chest wall ‘locked together’ by ?

A

intrapleural fluid in the intrapleural space

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4
Q

Ventilation is the process of ….?

A

air flowing by bulk flow into the lungs during inspiration (inhalation) and out of the lungs during expiration (exhalation)

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5
Q

why does air flow in bulk ?

A

because od pressure difference between the atmosphere and the gases inside the lungs

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6
Q

During inspiration what is responsible for the following ?
1. increasing the volume of the thorax
2. decreasing the pressure

A
  1. ribs and sternum raised
  2. diaphragm contracts
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7
Q

During expiration what results in the following ?
1. decreasing the volume of the thorax
2. increasing the thoracic pressure

A
  1. ribs and sternum lower
  2. diaphragm relaxes
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8
Q

What does the elasticity of lung tissure reduce ?

A

energy required during expiration (elastic recoil )

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9
Q

In inspiration following the expansion of the chest cage what is enough to hold the 2 layer of pleura firmly together ? [change Q]

A

expansion of chest cage pulls outwards on the lungs and intrapleural pressure becomes more negative. This small negative pressure is enough to hold the two layers of pleura firmly together

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10
Q

split Q above !!!

A
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11
Q

What is forced expiration ?

A

active process dependent on the abdominal muscles and internal intercostal muscles

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12
Q

What conditions is forced expiration affected in ? & why ?

A
  • pregnancy & obesity cos diaphragm can’t easily move
  • COPD & asthma due to narrowing of airways
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13
Q

what 2 factors cause the lungs to recoil during expiration ?

A
  1. elastic connective tissue in the lungs
  2. alveolar surface tension
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14
Q

what is alveolar surface tension?

A

attraction between water molecules at the water-air interface

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15
Q

What is equation for laplace’s law ?

A

P = 2T/ r

P = inward directed collapsing pressure
T = surface tension
r = radius

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16
Q

why are collapsed alveoli hard to reinflate ?

A

walls tend to stick together

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17
Q

What are septal cells ?

A

type II penumocytes that produce surfactant

found in the septa between alveoli

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18
Q

what is surfactant ?

A

a phospholipoprotein dissolved in a watery secretion that lines the alveolar sac

reduces the surface tension in the alveoli and stops the alveoli collapsing during expiration

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19
Q

What’s the difference between smaller and larger alveoli during inspiration and expiration with and without surfactant ?

A

without:
During expiration smaller alveoli collapse completely , larger alveoli change little

with:
during expiration both alveoli decrease proprtionately in size, alveoli shrink evenly during expiration

20
Q

What is respiratory distress syndrome of a new born ? [shorten !]

A

foetal lungs unable to synthesise surfactant until late in pregnancy so premature babies may not have enough pulmonary surfactant

so lungs are hard to inflate and some alveoli may fail to open at all during inspiration

baby has to make very strenuous inspiratory efforts in an attempt to overcome the high surface tension and inflate the lungs

21
Q

If the pleural cavity is damaged/ruptured where does air enter ?

A

pleural space because pleural pressure is less than atmosphere

22
Q

Differences between atmospheric pressure and alveolar pressure to result in the following ?
1. no airflow
2. airflow into lungs
3. airflow out of lungs

A
23
Q

What may lead to pneumothorax ? [alter Q !]

A

when intrapleural pressure becomes equal to or exceeds the atmospheric pressure and the pressure surrounding the lungs will increase and lungs may collapse

24
Q

what is pleuritis or pleurisy ?

A

parietal pleura can become inflamed causing pain

25
Q

what is pleuritic pain associated with ?

A

sharp , localised pain worse on inspiration , on one side of chest

26
Q

what results in pleuritic pain ? [alter Q!]

A

2 layers of the pleural lining rub against each other

27
Q

List causes of pleuritis :

A

Viral infection (e.g., influenza).

Bacterial infection, such as pneumonia.

Fungal infection.

Autoimmune disorder, such as rheumatoid arthritis or lupus.

Lung cancer near the pleural surface.

Pulmonary embolism.

Tuberculosis.

Rib fracture or trauma.

Inherited diseases, such as sickle cell disease.

Certain medications and recreational drugs.

28
Q

what is complicance ?

A

the change in volume per unit pressure: represents the slope of the curve

29
Q

When is the lung very compliant and when is the compliance smaller (flattened slope of the curve) ?

A

very compliant = normal range

smaller complicance = at high expanding pressure the lung is stiffer

30
Q

Conditions resulting in reduced compliance ?

A
  • Increase of fibrous tissue in the lung (pulmonary fibrosis)
  • Collapse/closure of lung (Atelectasis)
  • Increase in pulmonary venous pressure
31
Q

Conditions resulting in increased compliance ?

A
  • age
  • emphysema (elasticity reduced , but volume increased) [check! remeber sock!!]
32
Q

Why is that even without any expanding pressure the lung always has some air in it ? when does this increase ?

A

airway closure, where small airways close, trapping gas in alveoli.

Airway closure increases in certain conditions, such as age and lung disease.

33
Q

What happens to lungs in emphysema ?

A
  • destruciton of the normal lung architecture (elastic fibres + collagen)
  • impaired elastic recoil , lungs don’t deflate as easily
  • lung is more easily distended & complicance of lung is increased
34
Q

In diseases that cause ..1.. , …2.. tissure replaces …3… tissue so the lungs become ..4.. and ..5.. decreases

A
  1. fibrosis
  2. scar
  3. normal interstitial
  4. stiffer
  5. compliance
35
Q

Give examples of structural changes in the thorax that will reduce compliance ?

A
  • kyphoscoliosis - disorder characterised by progressive deformity of spine
36
Q

what are 2 types of airway flow?

A

laminar & turbulent

37
Q

difference between laminar and turbulent flow ?

A

laminar = movement is orderly and streamlined
turbulent = movement is chaotic

38
Q

As a first approximation in most circumstances flow can be considered ..1… and at high rates of ventilation flow can be ..2..

A
  1. laminar
  2. turbulent
39
Q

How is laminar flow described ?

A

by Poiseuille’s law: .relationship between driving pressure and flow.

The equation can be roughly applied to breathing.

40
Q

what results in relatively big changes in flow ?

A

small changes in the diameter of airways
e.g. narrowing

41
Q

What is involved in the equation for poiseuille’s law ?

A

v = flow
r = radius
triangle P = driving pressure
weird n = viscosity
L = length of tube

V = ( pi * r^4 * triangle P) / (8 * weird n \8 L)

42
Q

Sites of airway resistance ?

A
  • upper respiratory tract (nose , pharynx, larynx)
  • significant resistance in nose (e.g. inflammation and cold)
43
Q

what are the most important parts of the bronchial tree in terms of physiological control of airway resistance ?

A

small bronchi and bronchioles, which are innervated smooth muscle.

44
Q

How is airway resistance defined as ?

A

resistance to the flow of gas within the airways of the lung

45
Q

Give one example of a disease that affects the resistance of the airflow ?

A

asthma

46
Q

what is the reduction of airway diameter due to ?

A

contraction of smooth muscle or swelling due to inflammation

T3 resp system (12 decks)

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