Ventilation Lecture

Question 1

Air enters through the nose…

Answer 1

It is filtered, heated to body temperature and humidied as it passes through the nose and turbinates

Question 2

Air enters via the laryngopharynx

Answer 2

Whereby it passes through the glottis and larynx and enters the tracheobronchial tree

Question 3

Inspired air enters the alveolie

Answer 3

Where is comes into contact with the mixed venuous blood in pulmonary capillaries

Question 4

What are the four functions of the pulmonary system?

Answer 4

Pulmonary ventilation
Diffusion of oxygen and CO2 between the alveoli and the blood
Transport oxygen and CO2 in the blood and body fluids to and from the body’s tissue cells
Regulation of ventilation and other facets of respiration

Question 5

What muscles cause lung expansion and contraction?

Answer 5

Downward and upward movement of the diaphragm to lengthen or shorten the chest cavity
Elevation and depression of the ribs to increase and decrease the anteroposterior diameter of the chest cavity

Question 6

Define pleural pressure

Answer 6

Pressure of the fluid in the thin space between the lung pleura and the chest wall pleura

Question 7

Define alveolar pressure

Answer 7

Pressure of the air inside the lung alveoli

Question 8

Define transpulmonary pressure

Answer 8

Difference between the alveolar pressure and the pleural pressure (deciding factor for air movement)

Question 9

How does compliance of the lungs play in?

Answer 9

Extent to which the lungs will expand for each unit increase in transpulmonary pressure (if enough time is allowed to reach equilibrium)
- Total compliance for both lungs together: 200 mL of air/cm of water transpulmonary pressure where transpulmonary pressure above 1 cm water leads to lung volume expanding to 100 mL (after 10-20 secs)

Question 10

Characteristics of the compliance diagram are determined by?

Answer 10

The elastic forces of the lungs

• Elastic forces of the lung tissue (collagen and elastin)
• Elastic forces caused by surface tension of the fluid that lines the inside walls of the alveoli and other lung air spaces

Question 11

Define air-filled

Answer 11

Interface between the alveolar fluid and the air in the alveoli

Question 12

Define saline solution-tilled lungs

Answer 12

No air-fluid interface –> surface tension effect not present; only tissue elastic forces are acting

Question 13

What happens when water forms a surface with air?

Answer 13

The water molecules on the surface of the water have a strong attraction for each other, resulting in the water surface wanting to contract (water droplet)
- inner surface of the alveoli: water is attempting to contract forcing the air out of the alveoli through the bronchi –> causes the alveoli to attempt to collapse (surface tension elastic force) <– net effect is to cause an elastic contractile force of the entire lung

Question 14

Surfactants?

Answer 14

Alveolar epithelium
Secreted by type II alveolar epithelial cells
Mixture of phospholipids, proteins and ions that does not dissolve in fluid
- A surface active agent that when spread over the surface of a fluid it reduces the surface tension

Question 15

Normal elastic alveolar collapse pressure is?

Answer 15

3-4 cm of water, without surfactant it would be 18 cm of water

Question 16

Define spirometry

Answer 16

A simple method for studying pulmonary ventilation by recording the volume movement of air into and out of the lungs

Question 17

Define tidal volume

Answer 17

Volume of air inspired or expired during each normal breath (500 mL)

Question 18

Define inspiratory reserve volume

Answer 18

Extra volume of air that can be inspired over and above the normal tidal volume (3000 mL)

Question 19

Define expiratory reserve volume

Answer 19

Max extra volume of air that can be expired by forceful expiration after the end of a normal tidal expiration (1100 mL)

Question 20

Define residual volume

Answer 20

Volume of air remaining in the lungs after the most forceful expiration (1200 mL)

Question 21

Define inspiratory capacity

Answer 21

Tidal volume + inspiratory reserve volume (3500 mL)

Question 22

Define functional residual capacity

Answer 22

Expiratory reserve volume + residual volume (1300 mL)

Question 23

Define vital capacity

Answer 23

Inspiratory reserve volume + tidal volume + expiratory reserve volume (4600 mL)

Question 24

Define total lung capacity

Answer 24

Vital capacity + residual volume (5800 mL)

Question 25

What is the goal of pulmonary ventilation?

Answer 25

To continually renew the air in the gas exchange areas of the lungs where the air is in close proximity to the blood
- Alveoli, alveolar sacs and ducts, respiratory bronchioles

Question 26

Define alveolar ventilation

Answer 26

Rate at which new air gets to the alveoli, alveolar sacs and ducts and respiratory bronchioles
Va= Freq * (VT-VD)
VT: tidal volume
VD: dead space volume

Question 27

Diffusion is required to do what?

Answer 27

Move air from the terminal bronchioles to the alveoli

Question 28

Define dead space

Answer 28

Air that never reaches the gas exchange areas
Fills the respiratory passages where gas exchange does not occur (nose, pharynx, trachea)
– On expiration the air in the dead space is expired first –> dead space is useless for removing expiratory gases from the lungs