Mechanics of Breathing - Lecture 18 Flashcards

1
Q

What is the first step of respiration?

A

Pulmonary ventilation (breathing): Inspiration and expiration of air between atmosphere and lungs (alveoli)

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2
Q

What is the second step of respiration?

A

External (pulmonary) respiration: exchange of gases between alveoli and blood in pulmonary capillaries

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3
Q

What is the third step of respiration?

A

Exchange of gases between blood in systemic capillaries and tissue cells

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4
Q

What is Boyle’s law?

A

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

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5
Q

What is the atmospheric and intrapulmonary pressure like during inspiration?

A

Intrapulmonary pressure is lower than atmospheric pressure

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6
Q

What is the atmospheric and intrapulmonary pressure like during expiration?

A

Intrapulmonary pressure is higher than atmospheric pressure

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7
Q

What is intrapleural pressure?

A

○ Refers to the pressure within the pleural cavity
○ Always lower than atmospheric and intrapulmonary pressures (always negative)
○ Created by elastic recoil of the lungs
○ Keeps lungs inflated

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8
Q

What forces need to be overcome during breathing?

A

○ Lung compliance (how easily the lungs can expand):
- Elasticity of the lung tissue
- Surface tension of alveoli
- Mobility of chest wall
○ Airway resistance

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9
Q

How does each force affect breathing?

A

○ Elastic recoil: opposes inspiration and aids expiration
○ Airways resistance opposes both

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10
Q

What does lung compliance relate to?

A

Change in volume/Change in pressure

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11
Q

What is Laplace’s law?

A

○ P = 2T/r
○ P - Pressure
○ T = surface tension
○ r = radius of a alveolus

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12
Q

How does the surfactant in the alveoli prevent them collapsing?

A

○ Greatly reduces surface tension and increases compliance
○ Equalises the pressure difference between small and large alveoli (smaller alveoli have more surfactant)

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13
Q

What is neonatal respiratory distress syndrome?

A

○ Lack of surfactant secretion in premature babies
○ Reduced compliance
○ Alveoli collapse on exhalation
○ Difficult to inflate lungs
○ 50% die without rapid treatment

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14
Q

What factors can affect airway resistance?

A

○ Lung volume: bronchi dilate as lung expands
○ Bronchial smooth muscle:
- Parasympathetic nerves: bronchoconstriction
- Sympathetic nerves: bronchodilation

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15
Q

What stimuli can cause bronchoconstriction?

A

○ Smoke, dust, irritants
○ Histamine

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16
Q

What is forced vital capacity and vital capacity?

A

○ VC = Maximum amount of air that can be expired after a maximum inspiratory effort
○ FVC = Forceably breathing out VC

17
Q

What is FEV1?

A

○ Forced expiratory volume in 1 second: the volume of air expired in 1 second
○Used to assess changes in resistance to airflow e.g. asthma patients
○ Above 70% = healthy adult

18
Q

What does it mean if there are no breath sounds?

A

Collapsed lung

19
Q

What is a peak flow meter?

A

○ Measures the speed at which you are able to breathe air out
○ Used by chronic asthmatics on a regular basis: not good if value decreases

20
Q

What does a spirometer measure?

A

Lung volume and capcacities

21
Q

What is tidal volume?

A

○ The volume of air moved per breath
○ 500ml in both men and women

22
Q

What is functional residual capacity?

A

○ Helps to stabilise the composition of alveolar air
○ Volume of air left in the lungs after a normal, passive exhalation
○ Cannot be measured by spirometry as it includes the residual volume

23
Q

What is expiratory reserve volume?

A

○ The amount of air that can be forcibly exhaled after a normal tidal volume exhalation
○ Males = 1000ml, Females = 700ml

24
Q

What is inspiratory reserve volume?

A

○ Amount of air that can be forcibly inhaled after a normal tidal volume inhalation
○ Males = 3300ml, Females = 1900ml

25
Q

What is residual volume?

A

○ Air remaining in the lungs after maximum expiration
○ Males = 1200ml, Females, 1100ml

26
Q

What is the equation for vital capacity?

A

Tidal volume + inspiratory reserve volume + expiratory reserve volume

27
Q

What is the equation for inspiratory capacity?

A

Tidal volume + inspiratory reserve volume

28
Q

What is equation for functional residual capacity?

A

Residual volume + expiratory reserve volume

29
Q

What is the equation for total lung capacity?

A

Tidal volume + inspiratory reserve volume + expiratory reserve volume + residual volume

30
Q

What is anatomical dead space?

A

Volume of air in cocnducting passages that does not participate in gas exchange

31
Q

What is the equation for alveolar ventilation?

A

Respiratory rate x ( tidal volume - anatomical dead space)