Ventilation Flashcards

1
Q

What is the function of ventilation?

A
  • Provide is to provide O2 and remove CO2.
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2
Q

How is ventilation function achieved

A

The function is achieved by:

  • Pulmonary ventilation,
  • Regulation of ventilation,
  • Matching of pulmonary blood flow to alveolar ventilation,
  • Movement of O2 and CO2 between alveoli and blood,
  • Transport of O2 and CO2 in blood and body fluids.
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3
Q

What are the non-respiratory function?

A

Expulsion of foreign bodies and defence against infection/disease

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4
Q

What is alveolar ventilation?

A

Rate at which new area reaches of alveoli.

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5
Q

What is dead space?

A

It is air breathed in but never reaches gas exchange areas but fills respiratory passages eg, nose, pharynx and trachea.

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6
Q

How do you calculate alveolar ventilation

A

Respiratory rate x (Volume (total) - Volume in dead space)

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7
Q

Name the two ways in which the lungs can be expanded and contracted?

A
  • Downward and upward movement of diaphragm to lengthen or shorten chest cavity
  • Elevations and depression of the ribs increase anteroposterior diameter of the chest cavity.
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8
Q

What are the most important muscles in raising the ribs?

A
  • External intercoastal,
  • Sternocleidomastoid (lifts the sternum upwards)
  • Anterior Serrati
  • Scaleni
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9
Q

What are the important muscles that lower the rib cage?

A

Abdominal recti and internal intercostals

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10
Q

Describe the static properties of lungs

A
  • The lung is an elastic structure collapses like a balloon when no forces to keep inflated.
  • Lymphatic drainage of excess fluid between lung pleural membrane and pleural surface of thoracic wall leads to a suction effect.
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11
Q

What is the intrapleural pressure?

A

The pressure of fluid in thin space between lung and chest wall pleura - creates negative pressure

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12
Q

Describe the pressure changes that occurs during ventilation

A

The pressure decreases during inspiration which draws in air in. Then during expiration the pressure increases which forces air out. When the glottis is open and no air is flowing then the pressure in all parts of the respiratory tree is equal to atmospheric pressure.

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13
Q

What is the transpulmonary pressure?

A

The pressure difference between the alveoli and that on the outer surfaces of the lung. Therefore it is a measure of the elastic forces that then to collapse the lungs.

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14
Q

Why is energy needed for respiration?

A

It is required by:

  • Contract the muscles of inspiration,
  • Stretch elastic elements,
  • Overcome airway resistance,
  • Overcome frictional forces arising from the viscosity of the lung and chest wall
  • Overcome inertia of air and tissues.
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15
Q

Airflow is determined by what?

A

Change of pressure divided by the resistance.

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16
Q

What has the greatest effect in airway resistance? Where is the greatest resistance found?

A

Airway radius. The greatest resistance to airflow is found in segmental bronchi

17
Q

What is more likely to cause turbulent flow?

A

High velocity and large diameter airways.

18
Q

What is static compliance?

A

The extend to which the lungs expand for each unit increase in transpulmonary pressure.

19
Q

What is the elastance of the lungs?

A

Measure of elastic recoil

20
Q

Compliance is determined by whar 2 elastic forces?

A
  • Elastic forces of the lung tissue itself (determined by elastin and collagen fibres, in deflated lungs the fibres are kinked. In expanded lungs the fibres are unkinked)
  • Elastic forced caused by surface tension of fluid that lines alveoli.
21
Q

Describe the changes in the lungs in fibrosis?

A

Increased deposition of fibrous tissue so lungs become stiff, compliance decreases. Patients breathing becomes shallow and rapid.

22
Q

Describe the changes in the lungs in emphysema

A

Alveolar and capillary walls are progressively destroyed, especially elastic tissue. The lung compliance is increased however so does airway resistance which can cause the airway to collapse.

23
Q

Describe lung changes in chronic bronchitis?

A

Mucus and airway inflammation produce an increase in airway resistance. However compliance is normal

24
Q

What is surface tension and what does this result in, in the lungs

A

Surface tension - Measure of force acting to pull a liquid surface molecules together. In the lungs this results in the alveoli trying to force air out of them allowing the alveoli to collapse.

25
Q

Describe how surfactant is produced and how is it degraded?

A

It is a complex mixture of phospholipids secreted by type two alveolar epithelial cells. It is degraded by alveolar macrophages.

26
Q

What is the role of macrophages?

A

It greatly reduces the surface tension of water which increased compliance so it is easier to inflate lungs. Reducing surface tension minimises fluid accumulation in alveoli. Surfactant also helps keep alveolus size relatively uniform.

27
Q

What is spirometry?

A

Method for studying pulmonary ventilation

28
Q

What is tidal volume?

A

Volume of air inspired of expired with each normal breath

29
Q

What is the inspiratory reserve volume?

A

Extra volume of air that can be inspired over and above normal tidal volume

30
Q

What is expiratory reserve volume?

A

Maximum of extra volume that can be expired by forceful expiration after end of normal tidal expiration

31
Q

What is residual volume?

A

Volume of air remaining in the lungs after most forceful expiration.