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Body Systems > Mechanics Of Breathing > Flashcards

Mechanics Of Breathing Flashcards

1
Q

What is respiration?

A

Exchange of gases (oxygen & carbon dioxide) between atmosphere, blood and cells.

Contributes to homeostasis and regulates the pH of the internal environment.

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2
Q

What are the three steps of respiration?

A
  • Pulmonary ventilation (breathing)
  • External (pulmonary) respiration
  • Internal (tissue) respiration
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3
Q

Define pulmonary ventilation (breathing)

A

Inspiration and expiration of air between atmosphere and lungs (alveoli).

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4
Q

What is external (pulmonary) respiration?

A

Exchange of gases between alveoli and blood in pulmonary capillaries
Blood gains oxygen and loses carbon dioxide

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5
Q

What occurs during internal (tissue) respiration?

A

Exchange of gases between blood in systemic capillaries and tissue cells
Blood loses oxygen and gains carbon dioxide
Carbon dioxide is generated from cellular respiration

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6
Q

What is Boyle’s Law?

A

When the temperature of a gas is constant, the pressure of the gas varies inversely with volume.

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7
Q

What happens to air flow according to Boyle’s Law?

A

Air flows from an area of high pressure to an area of low pressure.

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8
Q

What is intrapleural pressure?

A

The pressure within the pleural cavity, always lower than atmospheric and intrapulmonary pressures (about -2 to -6 mmHg lower than atmospheric pressure)

Created by elastic recoil of the lungs

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9
Q

List the forces to overcome for resistance to breathing.

A
  • Lung (pulmonary) compliance
  • elasticity of lung tissue (connective tissue structure)
  • surface tension of alveoli
  • mobility of chest wall
  • Airway resistance = major non-elastic source
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10
Q

What is lung compliance?

A

The ease with which the lungs can be expanded.

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11
Q

What factors affect lung compliance?

A
  • Elasticity of lung tissue
  • Surface tension of alveoli
  • Mobility of chest wall
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12
Q

What is surface tension in the context of alveoli?

A

The force that opposes expansion of the alveolus, caused by intermolecular forces between liquid molecules.

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13
Q

What is Laplace’s Law?

A

Describes the relationship between pressure (P), surface tension (T), and the radius (r) of an alveolus.

P = 2T/ r

At equilibrium (when no air movement), the tendency of increased pressure to expand the alveolus balances the tendency of surface tension to collapse it

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14
Q

What is the role of surfactant?

A

Pulmonary surfactant greatly reduces surface tension, increasing compliance

It equalises the pressure differences between small & large alveoli

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15
Q

What is the effect of airway resistance on airflow?

A

Opposes both inspiration and expiration.

By causing friction (determined by radius)

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16
Q

What factors affect airway resistance?

A
  1. Lung volume
    - bronchi dilate as lung expands
  2. Bronchial smooth muscle
    - parasympathetic nerves = bronchoconstriction
    - sympathetic nerves & adrenaline = bronchodilation

Stimuli causing bronchoconstriction - smoke, dust, irritants, histamine (e.g. allergic response)

17
Q

What is Forced Vital Capacity (FVC)?

A

The maximum amount of air that can be forcefully exhaled after a maximum inspiratory effort.

18
Q

What does FEV1 measure?

A

The volume of air expired in the first second of a forced breath.

19
Q

What is tidal volume (TV)?

A

Volume of air inhaled or exhaled in one quiet breath. (Normal breathing)

ALWAYS 500ml

20
Q

What is the formula for calculating vital capacity (VC)?

A

VC = TV + IRV + ERV.

21
Q

What is functional residual capacity (FRC)?

A

Volume of air remaining in the lungs after a normal passive expiration

22
Q

What does anatomical dead space refer to?

A

Volume of air in conducting passages that does not participate in gas exchange.

23
Q

How is alveolar ventilation calculated?

A

Respiratory rate x (TV - anatomical dead space).

24
Q

What is the typical tidal volume for males and females?

A

Males = 500ml; Females = 500ml.

25
Q

What is the difference between pulmonary ventilation and alveolar ventilation?

A

Pulmonary ventilation is the total volume of air moved per minute, while alveolar ventilation is the volume of air reaching the alveoli each minute.

26
Q

True or False: The intrapulmonary pressure increases during expiration.

A

True.

27
Q

What happens during inspiration & expiration?

A

Atmospheric pressure = 760 mmHg (at sea level, decreases when higher up)

Inspiration
- Lung volume increases
- Intrapulmonary pressure decreases (in alveoli in lungs)
- Air moves in
- Pressure is 759 mmHg (-1)

Expiration
- Lung volume decreases
- Intrapulmonary pressure increases
- Air moves out
- Pressure is 761 mmHg (+1)

28
Q

How do the forces affect resistance to breathing?

A
  • elastic recoil of lungs opposes inspiration and aids expiration
  • surface tension of alveoli must be overcome to stretch the alveoli
  • airway resistance opposes both
29
Q

What is elasticity of lung tissue and how is it measured?

A

Measure of elastic recoil
A measure of lung volume changes resulting from a given change in pressure

Compliance = V/P (litres/cmH2O)

30
Q

What role does surfactant play in the lungs?

A
  • helps keep uniform alveolar size
  • more concentrated in smaller alveoli
  • lower surface tension helps equalise pressure among alveoli of different sizes
  • easier to inflate smaller alveoli
  • work needed to expand alveoli with each breath greatly reduced
31
Q

What is neonatal respiratory distress syndrome?

A
  • lack of surfactant secretion in premature babies (28-32 weeks)
  • reduced compliance
  • alveoli collapse on exhaustion
  • difficult to inflate lungs
  • 50% die without rapid treatment
32
Q

How is lung function assessed?

A

Breath sounds
- presence of mucous/fluid
- absence of breath sounds = collapsed lung?

Pulmonary function tests
- peak flow meter = measures the speed at which you are able to breathe air out
- used by chronic asthmatics on a regular basis

33
Q

What is the expiratory reserve volume (ERV)?

A

Amount of air that can be forcibly exhaled after a normal tidal volume exhalation

Males = 1000ml
Females = 700ml

34
Q

What is the inspiratory reserve volume (IRV)?

A

Amount of air that can be forcibly inhaled after a normal tidal volume inhalation

Males = 3300ml
Females = 1900ml

35
Q

What is the residual volume (RV)?

A

Air that remains in lungs after maximum expiration

Males = 1200ml
Females = 1100ml

36
Q

What is the formula for inspiratory capacity (IC)?

A

IC = TV + IRV

37
Q

What is the formula for calculating functional residual capacity (FRC)?

A

FRC = RV + FRV

38
Q

How is total lung capacity calculated (TLC)?

A

TLC = TV + IRV + ERV + RV

Males = 6000ml
Females = 4200ml

39
Q

How is the pulmonary ventilation rate calculated?

A

Also called respiratory minute volume

Tidal volume X breathing frequency

Body Systems (19 decks)

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