Lung Ventilation Flashcards

1
Q

Define ventilation

A

The process of inspiration and expiration

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2
Q

What are the parts of the respiratory tract?

A
  • conducting portion: anatomical dead space
  • respiratory portion
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3
Q

Outline the process of passive expiration

A
  • muscles used in inspiration relax
  • diaphragm moves up
  • thoracic cavity volume reduces
  • volume of lungs reduces and return to original
    volume
  • intrapulmonary pressure increases
  • air expelled
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4
Q

What makes up the conducting portion of the respiratory tract

A

Nasal cavity to the terminal bronchioles

  • nasal cavity
  • pharynx
  • larynx
  • trachea
  • primary + secondary bronchi
  • bronchioles
  • terminal bronchioles
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5
Q

What makes up the respiratory portion of the respiratory tract?

A
  • respiratory bronchioles
  • alveolar ducts
  • alveoli
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6
Q

What is anatomical dead space?

A

The volume of air in the conducting airways

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7
Q

What is alveolar dead space?

A

Air in alveoli which do not take part in gas exchange
e.g. damaged alveoli

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8
Q

What is physiological dead space?

A

PDS = anatomical DS + alveolar DS

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9
Q

How do you calculate tidal volume?

A

TV = anatomical dead space + alveolar ventilation

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10
Q

How do you calculate the total pulmonary ventilation?

A

TPV = tidal volume x respiratory rate

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11
Q

What is the pressure inside the lungs called?

A

Intrapulmonary pressure

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12
Q

Outline the process of inspiration

A
  • external intercostal muscles contract
  • diaphragm contracts + flattens
  • intrathoracic volume increases
  • intrapulmonary pressure decreases below atmospheric pressure
  • elastic tissue in alveoli is stretched
  • air pushed into lungs
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13
Q

What are the accessory muscles involved in forced inspiration?

A
  • sternocleidomastoid
  • scalene muscles
  • serratus anterior
  • pectoralis major + minor
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14
Q

What accessory muscles are used in forced expiration?

A
  • internal intercostals
  • abdominal wall muscles
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15
Q

Describe the pleural seal

A
  • the surface tension of the pleural fluid creates a film that coats the lungs + the thoracic cavity > when chest cavity expands so do the lungs
  • the film prevents the lungs from collapsing + allows for expansion and contraction when breathing
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16
Q

Describe the pleural membranes of the thorax

A
  • Parietal pleura lines the inside of each hemi-thorax
  • Visceral pleura lines the lungs
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17
Q

What does parietal pleura line?

A

Parietal pleura lines each hemi-thorax

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18
Q

What is the hemi thorax?

A

The bony thoracic cage, diaphragm + mediastinal surfaces

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19
Q

What is the intrapleural space?

A

Space between visceral and parietal pleura

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20
Q

What does visceral pleura line?

A

Visceral pleura lines the lungs

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21
Q

What is functional residual capacity?

A

Volume of air remaining after passive expiration

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22
Q

What is compliance?

A

A measure of how distensible the lungs are

23
Q

How do you calculate compliance?

A

C = change in volume / change in pressure

24
Q

What is emphysema?

A
  • condition in which destruction of the terminal bronchioles + distal air spaces occurs via the breakdown of elastin
  • permanent enlargement of air spaces (bullae)
25
Q

What is the opposite of compliance?

A

Lung elastic recoil

26
Q

What is elastic recoil in respiratory system?

A

The ability of something to return to its original size

27
Q

What is elastic recoil directly related to?

A
  • connective tissue surrounding alveoli ( elastic fibres)
  • alveolar fluid surface tension
28
Q

What does lungs returning to their original volume depend on?

A

Elastic recoil

29
Q

Where do interstitial lung disease occur?

A

The interstitium between alveolar epithelium + capillary endothelium

30
Q

What happens in pulmonary fibrosis in terms of compliance and elastic recoil?

A
  • stiff lungs > compliance is reduced
  • elastic recoil is increased > resting lung volume is smaller
  • restrictive disease
31
Q

What impact does surface tension have on compliance?

A

Surface tension decreases compliance

32
Q

What issue can occur in premature babies <35 weeks in relation to the alveoli?

A

Surfactant respiratory distress syndrome
- not enough lung surfactant has been produced > alveoli collapse
- exogenous lung surfactants are needed

33
Q

Clinical features of neonatal respiratory distress syndrome?

A
  • grunting
  • nasal flaring
  • intercostal +subcostal retractions (use of accessory muscles)
  • tachypneoa
  • cyanosis
34
Q

Treatment for neonatal respiratory distress syndrome

A
  • surfactant replacements via endotracheal tube
  • O2/assisted ventilation
35
Q

At how many weeks do babies have enough surfactant?

A

35 weeks

36
Q

How could you calculate the patient’s total pulmonary ventilation?

A

Tidal volume x respiratory rate

37
Q

What is the negative intrapleural pressure?

A
  • lungs have a natural inward elastic recoil
  • chest wall has a natural outward elastic recoil
  • opposing forces create a negative pressure in the intrapleural space
38
Q

Role of negative intrapleural pressure

A

Keeps alveoli/lungs from fully collapsing with each expiration

39
Q

How does intrapulmonary pressure change between inspiration and expiration relative to the atmosphere

A
  • inspiration: intrapulomnary pressure in negative relative to atmosphere > air pushed in
  • expiration: intrapulmonary pressure is positive relative to atmosphere
40
Q

How does intrapleural pressure change during inspiration and expiration?

A

ALWAYS negative

41
Q

What is transpulmonary pressure?

A

Intrapulmonary pressure - intrapleural pressure

42
Q

What type of lung disease is pulmonary fibrosis?

A

Restrictive

43
Q

How do bronchioles stay open in expiration?

A

Radial traction
Of the surrounding alveolar walls on bronchioles

44
Q

Describe airways resistance across the lung

A

Individual resistance is high
Altogether is low

45
Q

Is there lower resistance in the upper or lower airways?
Why?

A

lower airways
- connective branches create alternative routes
- combined resistance of downstream branches is less than higher up
- it’s easier for air to flow deeper into lungs

46
Q

Compare the structure of a bronchus compared to a bronchiole

A
  • bronchus: has cartilage + glands
  • bronchioles: no cartilage (require radial traction to stay open) or glands
47
Q

What is Gillian Barre syndrome?

A

Autoimmune condition where the body attacks its own peripheral nerves.

48
Q

What is the function of the plerual seal?

A

To ensure the lungs expand as the thoracic cavity does using the surface tension of the pleural fluid

49
Q

What types of cells produce surfactant?

A

Type II pneumocytes

50
Q

What happens to compliance and elastic recoil in a patient with emphysema?

A
  • Compliance increases
  • Elastic recoil decreases
  • Due to breakdown of elastin > less pull in
51
Q

What is interstitial lung disease?

A

Umbrella term for disease that cause fibrosis + inflammation to lungs
Collagen is deposited into interstitium

52
Q

What happens to compliance and elastic recoil in a patient with interstitial lung disease?

A

Compliance decreases
Elastic recoil increases

53
Q

Function of surfactant

A
  • decreases surface tension of alveoli
  • prevents small alevoli collapsing into larger alveoli