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Respiratory > Physiology > Flashcards

Physiology Flashcards

1
Q

What is external respiration?

A

Exchange of oxygen and carbon dioxide between body cells and the external environment

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2
Q

What is internal respiration?

A

The intracellular mechanisms that consume oxygen and produce carbon dioxide

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3
Q

Which 4 body systems are involved in external respiration?

A
  1. Respiratory system
  2. Cardiovascular system
  3. Haematology system
  4. Nervous system
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4
Q

In terms of respiration what does the term “ventilation” refer to?

A

The mechanical process of moving air between the alveoli and the atmosphere

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5
Q

What is Boyle’s law?

A

At a constant temperature, the pressure exerted by a gas varies inversely with the volume the gas is continued within (as volume increases, excepted pressure decreases)

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6
Q

Using the Boyle’s Law, describe why the lungs must expand to allow air to enter them during inhalation.

A

As the volume of the lungs (and the thoracic cavity) increase, the pressure decreases. This means atmospheric pressure is higher than intrathoratic pressure. Gas (air) flows down the pressure gradient into the lungs.

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7
Q

Which two forces hold the thoracic walls and the lungs in close contact?

A
  1. The intrapleural fluid cohesiveness (fluid tension)

2. The negative intrapleural pressure

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8
Q

A transmural pressure gradient exists between lung walls. What is this?

A

A difference in pressure between any separation

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9
Q

What causes the increase in thoracic volume during inspiration? (2)

A
  1. Contraction of the diaphragm

2. External intercostal muscle contraction

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10
Q

During expiration, which two factors contribute to the recoil of the lungs?

A
  1. Elastic properties of the involved muscles

2. Alveolar surface tension

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11
Q

What sort of situation would result in a lung collapse?

A

Any situation involving pleural pressure equalising with or exceeding atmospheric pressure e.g. a puncture wound

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12
Q

What is alveolar surface tension?

A

The attraction between water molecules at the liquid air interference of the alveoli- water molecules pull towards each other

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13
Q

What does alveolar surface tension allow for?

A

A resistance to lung stretching- the water molecules are attracted together so oppose stretching forces

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14
Q

What does the law of LaPlace state?

A

Smaller alveoli have a higher tendency to collapse due to the increased proximity of the water molecules

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15
Q

What is the pulmonary surfactant and where is it produced?

A

Pulmonary surfactant is a complex mixture of lipids and proteins. It is produced by type II alveoli

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16
Q

What is the effect of pulmonary surfactant?

A

It reduces surface tension by “diluting” the effect the water molecules have by interspacing them

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17
Q

Why do some infants suffer from respiratory distress syndrome?

A

Foetal lungs cannot synthesise surfactant meaning premature babies do not have enough surfactant in their lungs. Breathing will then become strenuous as the babies must overcome the high surface tension (of the water droplets) to inflate the lungs

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18
Q

Describe alveolar interdependence?

A

Alveolar interdependence describes the fact the adjacent alveoli protect each other from collapse. If one alveoli begins to collapse, others around it will compensate and stretch. As volume increases the surrounding alveoli, pressure decreases meaning air flows to the collapsed alveoli to reinflate it. This is due to the pressure gradient

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19
Q

What are the three types of muscles involved in respiration?

A
  1. Accessory muscles (scalenus, sternocleidomastoid)
  2. Major muscles ( diaphragm, external intercostal muscles)
  3. Muscles of active expiration (abdominal muscles, internal intercostal muscles)
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20
Q

What is the tidal volume?

A

The volume of air entering or leaving the lungs in a normal breath (around 500ml)

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21
Q

What is the inspiratory reserve volume?

A

This is the extra volume of air that can be breathed in over and above the tidal volume (around 3000ml)

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22
Q

What is the inspiratory capacity?

A

The maximal volume of air that can be breathed in ( inspiratory reserve volume + tidal volume)

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23
Q

What is the expiratory reserve volume?

A

This is the extra volume of air that can be breathed out over and above the tidal volume (around 100ml)

24
Q

What is the residual volume?

A

This is the minimum volume of air remaining in the lungs even after a maximal expiration - it is always present

25
Q

What is functional residual capacity and how is it calculated ?

A

Resting lung volume (expiratory reserve volume + residual volume)

26
Q

What is vital capacity and how is it calculated?

A

This is the total volume of air available to be expired in the lungs (inspiratory reserve volume +tidal volume + expiratory reserve volume)

27
Q

What is total capacity and how is it calculated ?

A

This is the total volume of air the lungs can hold (vital capacity +residual volume) around 5.7 L

28
Q

Why is total lung capacity hard to measure in real life?

A

Residual volume must be known and this cannot be measured

29
Q

What could lead to the residual volume to increase?

A

Reduction in elastic recoil of the lungs- as in emphysema

30
Q

Which two measurements can be plotted on volume/ time curve, and what are they?

A

FVC- forced vital capacity - maximum volume of air inspired, the maximum volume of air that can be forcibly expelled
FEV1- Volume of air that can be expelled (after full inspiration) in one second

31
Q

For normal healthy patients, FEV1/ FVC x 100 should equal what?

A

80%

32
Q

What does a low FEV1/FVC ratio indicate?

A

Obstructive lung disease

33
Q

What type of results do individuals with restrictive lung disease give for a FEV1/ FVC ratio test?

A

Normal, if not slightly elevated. They can instead be diagnosed by an initially low FVC

34
Q

What is the primary determinant of airway resistance?

A

The radius of the conducting airway

35
Q

How does the autonomic nervous system affect the resistance to airflow?

A

Sympathetic - decreases resistance (bronchodilation)

Parasympathetic - increase resistance (bronchoconstriction)

36
Q

Why are sufferers from obstructive lung conditions likely to suffer from collapsing airways?

A

Driving pressure (during exhalation) upwards from obstruction cannot occur. Relative airway pressure falls onwards from obstruction leading to airway compression due to rising pleural and lung pressure. The problem is exacerbated if elastic recoil of airways is also lost as in emphysema

37
Q

How is peak flow rate measured?

A

Using a peak flow meter

38
Q

Describe how to use a peak flow meter

A

A short sharp blow is given into the meter. The score on the scale at the side is taken, 3 attempts are given to allow for poor initial technique. The best value is recorded this test an highlight obstructive lung disease

39
Q

What is pulmonary compliance?

A

This is a measure of the effort required to stretch or distend the lungs

40
Q

What are the two methods to measure pulmonary compliance clinically?

A
  1. Static- the change in volume for any given pressure is measured (measures elastic resistance only)
  2. Dynamic - change in volume for any given pressure during the movement of air (measure both elastic resistance and airway resistance)
41
Q

The less compliant the lungs are the ____ work must be done to inflate them

A

more

42
Q

List 3 factors that decrease pulmonary compliance

A 
Pulmonary fibrosis
Pulmonary oedema
Lung collapse
Pneumonia 
Absence of surfactant
43
Q

How may a patient present clinically if they have less compliant lungs?

A

Breathless low exercise tolerance

44
Q

When would pulmonary compliance increase?

A

When elastic recoil is lost

45
Q

Describe a condition in which pulmonary compliance is increased

A

Emphysema hyperinflation occurs causing increased difficulty during exhalation.
Age also increases compliance

46
Q

List 3 factors which will increase the required work done by the lungs

A
  • Decreased pulmonary compliance
  • increased pulmonary compliance
  • increased airway resistance (potentially when bronchoconstricted)
  • decreased elastic recoil
  • increased elastic recoil
  • need for increased ventilation (low O2)
47
Q

What is airway physiological “dead space”?

A

This is the area within the airways (anatomical) and alveoli that is unsuitable for diffusion to occur

48
Q

How is alveolar ventilation calculated?

A

Dead space volume must be subtracted from the tidal volume

49
Q

What is the difference between pulmonary and alveolar ventilation?

A

Pulmonary -volume of air breathed in and out per minute (includes dead space)
Alveolar- volume of air exchanged between atmosphere and alveoli (exclude dead space)

50
Q

How can pulmonary ventilation be increased ?

A

Increasing depth and rate of breathing

51
Q

Why is pulmonary ventilation increase advantageous?

A

About of inhaled air increases but dead space does not- this causes relative increases in alveolar ventilation

52
Q

What is ventilation?

A

Rate at which gas passes through the lungs

53
Q

What is perfusion?

A

Rate at which blood passes through the lungs

54
Q

What is the ventilation perfusion match?

A

This ensures ventilation of gas can match the blood flow for optimised gas transfer- local controls can ensure this can happen

55
Q

What will happen when perfusion is greater than ventilation?

A

CO2 build up in the alveoli airway resistance is reduced in these situations as well as contraction of arteriolar smooth muscle to reduce blood flow to match the airflow

Respiratory (12 decks)

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