Alveolar ventilation

Question 1

What is meant by minute ventilation?

Answer 1

Total volume of air moved into the respiratory tract per minute

Question 2

What is the calculation for minute ventilation?

Answer 2

Respiratory rate x tidal volume

Question 3

What is the average respiratory rate?

Answer 3

15 breaths/min

Question 4

What is the average minute ventilation?

Answer 4

0.5L x 15 = 7.5L/min

Question 5

What is meant by alveolar ventilation?

Answer 5

Volume of air moved into the respiratory part of the respiratory tract per minute

Question 6

What is the calculaton for alveolar ventilation?

Answer 6

Respiratory rate x (tidal volume - anatomical dead space)

Question 7

How can a person change their minute/alveolar ventilation?

Answer 7

Changing their respiratory rate

Changing their depth of breathing to change the tidal volume

Question 8

What is dead space?

Answer 8

Volume of air in the respiratory tract that is not used in gas exchange

Question 9

What are the types of dead space?

Answer 9

Anatomical dead space

Alveolar dead space

Physiological dead space

Question 10

What is anatomical dead space?

Answer 10

Volume of air in the conducting part of the respiratory tract

Question 11

What is the average anatomical dead space?

Answer 11

0.15L out of 0.5L tidal volume

Question 12

What is the disadvantage of anatomical dead space?

Answer 12

The air in the upper respiratory tract, conducting part is expired before the air in the alveoli

Question 13

What is alveolar dead space?

Answer 13

Volume of air in alveoli that are only partially functional or non-functional because of poor or absent blood flow through adjacent pulmonary capillaries

Question 14

What is physiological dead space?

Answer 14

Anatomical dead space + alveolar dead space

Question 15

What is the average physiological dead space? Why?

Answer 15

Approximately 0.15L

Because alveolar dead space is very small since most alveoli are fully functional

Question 16

What is the average alveolar ventilation?

Answer 16

15 x (0.5L-0.15L) = 15 x 0.35L = 5.25L/min

Question 17

What is the most important factor of resistance in a tube?

Answer 17

Radius of tube

Question 18

How does resistance in a tube relate to the radius of the tube?

Answer 18

It is inversely proportional to the radius of the tube

so if the radius increases, the resistance decreases significantly

Question 19

Is there more resistance in the trachea or in a bronchi/bronchiole? Why?

Answer 19

Bronchi/bronchiole has higher resistance
because it has a smaller radius
which increases the resistance significantly

Question 20

Is there more resistance in the trachea or all of the bronchioles?

Answer 20

Trachea has higher resistance
because there is only one trachea but there are many bronchioles
connected to each other in parallel
reduces the overall resistance of the bronchioles

Question 20

Is there more resistance in the airways during inspiration or expiration? Why?

Answer 20

Expiration has higher resistance
because during inspiration, the airways are pulled open, increasing their radius, decreasing resistance significantly
whereas during expiration, the airways narrow by elastic recoil, decreasing their radius, increasing resistance significantly

Question 22

How does air flow change during expiration? Why?

Answer 22

Decreases from the beginning to the end of expiration
because the airways narrow by elastic recoil, reducing their radius, increasing resistance against air flow significantly

Question 23

Where in the tracheobronchial tree do pathological increases in resistance to air flow mostly occur? Why?

Answer 23

The smaller bronchioles

because they have a smaller lumen so they are more easily occluded

Question 24

What are some examples of pathological causes of increased resistance to air flow in the smaller bronchioles?

Answer 24

Increased mucus

Hypertrophy of smooth muscle in the walls of the airways

Oedema

Loss of radial traction

Question 24

What is radial traction?

Answer 24

Connective tissue surrounding respiratory bronchioles, alveolar ducts, alveolar sacs and alveoli
that hold those airways open

Question 26

How do all of the pathological causes increase resistance to air flow in the smaller bronchioles?

Answer 26

Reduce radius of bronchioles, which increases resistance significantly