Ventilation

Question 1

What is the function of ventilation?

Answer 1

• Provide is to provide O2 and remove CO2.

Question 2

How is ventilation function achieved

Answer 2

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.

Question 3

What are the non-respiratory function?

Answer 3

Expulsion of foreign bodies and defence against infection/disease

Question 4

What is alveolar ventilation?

Answer 4

Rate at which new area reaches of alveoli.

Question 5

What is dead space?

Answer 5

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

Question 6

How do you calculate alveolar ventilation

Answer 6

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

Question 7

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

Answer 7

• 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.

Question 8

What are the most important muscles in raising the ribs?

Answer 8

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

Question 9

What are the important muscles that lower the rib cage?

Answer 9

Abdominal recti and internal intercostals

Question 10

Describe the static properties of lungs

Answer 10

• 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.

Question 11

What is the intrapleural pressure?

Answer 11

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

Question 12

Describe the pressure changes that occurs during ventilation

Answer 12

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.

Question 13

What is the transpulmonary pressure?

Answer 13

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.

Question 14

Why is energy needed for respiration?

Answer 14

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.

Question 15

Airflow is determined by what?

Answer 15

Change of pressure divided by the resistance.

Question 16

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

Answer 16

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

Question 17

What is more likely to cause turbulent flow?

Answer 17

High velocity and large diameter airways.

Question 18

What is static compliance?

Answer 18

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

Question 19

What is the elastance of the lungs?

Answer 19

Measure of elastic recoil

Question 20

Compliance is determined by whar 2 elastic forces?

Answer 20

• 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.

Question 21

Describe the changes in the lungs in fibrosis?

Answer 21

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

Question 22

Describe the changes in the lungs in emphysema

Answer 22

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.

Question 23

Describe lung changes in chronic bronchitis?

Answer 23

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

Question 24

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

Answer 24

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.

Question 25

Describe how surfactant is produced and how is it degraded?

Answer 25

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

Question 26

What is the role of macrophages?

Answer 26

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.

Question 27

What is spirometry?

Answer 27

Method for studying pulmonary ventilation

Question 28

What is tidal volume?

Answer 28

Volume of air inspired of expired with each normal breath

Question 29

What is the inspiratory reserve volume?

Answer 29

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

Question 30

What is expiratory reserve volume?

Answer 30

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

Question 31

What is residual volume?

Answer 31

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