5.2 Pulmonary Ventilation

Question 1

What is rough atmospheric pressure in mmHg?

Answer 1

~760mmHg

Question 2

What is “minute ventilation”?

Answer 2

The volume of air breathed into the lungs in one minute

Question 3

What is ventilation?

Answer 3

The movement of air through the respiratory system

Question 4

What is vital capacity?

Answer 4

The volume of air that can be expired following a maximal inhalation

Question 5

What is residual volume?

Answer 5

The volume of air remaining in the lungs after a maximal expiration

Question 6

What is functional residual capacity?

Answer 6

The amount of air remaining in the lungs after a normal expiration during tidal breathing

Question 7

What is alveolar ventilation?

Answer 7

The amount of air reaching the alveoli for gas exchange

Question 8

In which direction does the diaphragm move when it is relaxed/contracted?

Answer 8

Relaxed: Up
Contracted: Down

Question 9

By what two muscular mechanisms does breathing usually occur? Which is most prominent at rest?

Answer 9

1. Diaphragm moves up and down
2. Rib cage elevation/depression alters anteroposterior diameter of chest cavity

Diaphragm movement is more prominent at rest

Question 10

What role do the abdominal muscles play in fast expiration?

Answer 10

They contract to help increase the pressure in the lungs and squeeze air out faster

Question 11

What is the role of pleural pressure in ventilation?

Answer 11

• Negative pressure relative to atmospheric pressure
• Creates a suction effect
• This way, when the chest wall moves, the lungs also move, helping to create the pressure gradients that enables the cyclic flow of air

Question 12

What is pressure of air inside the alveoli called?

Answer 12

Alveolar Pressure

Question 13

How can we calculate compliance?

Answer 13

Change in volume / change in pressure

The more the volume of an object changes for a given change in pressure, the more compliant it is

Question 14

Broadly, what is transmural pressure?

Answer 14

The pressure inside a hollow object vs outside

Question 15

What is transpulmonary pressure?

Answer 15

Difference between alveolar pressure and intrapleural pressure

Question 16

Why would shifting the pressure volume loop of a lung to the left or right alter its elastic recoil?

Answer 16

• Under static conditions, the transmural pressure is equal to the elastic recoil
• If the pressure volume loop shifts laterally, then the pressure acting on the lung at rest has changed, and thus the elastic recoil has been altered

Question 17

How can elastin-collagen ratio and surface tension influence lung compliance?

Answer 17

• Ratio of elastin to collagen in lung tissue (more elastin, more elastic)
• Surface tension of fluid lining of alveoli (more surface tension, more tendency to collapse inward)

Question 18

List eight factors that can affect lung compliance

Answer 18

• Age
• Pulmonary blood volume
• Lung volume
• Posture
• Disease
• Bronchial smooth muscle tone
• Surface tension
• Ratio of elastin to collagen

Question 19

Does surfactant reduce alveolar surface tension by less than or more than 50%

Answer 19

More than 50%

Question 20

Define surface tension

Answer 20

Tension of the surface film of a liquid caused by the attraction of the particles in the surface layer

Question 21

List four factors that can cause turbulent air flow

Answer 21

• High flow rate (freeway)
• Branches (intersections)
• Changes in diameter (merging)
• Sharp angles (corners)

Question 22

What are the 3 major components of respiratory resistance

Answer 22

• Airway resistance (how the air gets to the lungs)
• Lung tissue resistance (when the air is in the lungs)
• Chest wall resistance (the area that the lungs are in)

Question 23

Effect of vagal innervation on airway resistance of bronchi

Answer 23

Acetlycholine causes contraction of smooth muscle; increases resistance

Question 24

Describe humoral control of airway resistance

Answer 24

B2 adrenergic receptors initiating bronchodilation in response to adrenaline

Question 25

There is parasympathetic innervation of the airwarys, enabling bronchoconstriction that increases airway resistance. Is there also a lot of sympathetic innvervation, and how does this influence the activation of B2 receptors?

Answer 25

• There is very little sympathetic innervation
• B2 receptors are activated in response to circulating adrenaline in the bloodstream (hence, largely humoral in nature)

Question 26

How does parasympathetic innvervation control bronchodilation? After all, it’s responsible for bronchoconstriction!

Answer 26

We can mediate parasympathetic innervation, much like the heart

Question 27

What is work of breathing?

Answer 27

The amount of energy expended to inhale and exhale enough to meet the demands of the body.

Question 28

What is transmural pressure, and why is it important in pulmonary ventilation?

Answer 28

• Pressure difference between the inside and outside of a hollow structure (inside - outside)
• During inspiration, pleural pressure decreases more than alveolar, increased transmural pressure and keeping the alveoli open
• During expiration, pleural pressure increases, decreasing transmural pressure

Question 29

Simply put, what is transpulmonary pressure?

Answer 29

The transmural pressure of the alveoli