Mechanism of Breathing/Compliance

Question 1

Name 3 pulmonary obstructive diseases

Answer 1

1. Bronchitis
2. Asthma
3. Emphysema

Question 2

Name 1 pulmonary restrictive disease

Answer 2

Pulmonary fibrosis

Question 3

What are the 4 steps of inspiration?

Answer 3

1. Contraction of inspiratory muscles
2. Inflation of Chest Cavity
3. Inflation of Lung
4. Inward Air-Flow

Question 4

What are the main inspiratory muscles?

Answer 4

1. Diaphragm

2. External intercostals

Question 5

When the diaphragm contracts, does it move up or down?

Answer 5

Down

Question 6

What are the main expiratory muscles?

Answer 6

Expiration is primarily a passive process. During normal/quiet breathing, there are no muscles used for expiration.

During some activities/exercise or during forced expiration, some muscles do contract (e.g. muscles in abdominal wall, or internal intercostals which assist by pulling the ribs inward and downward to decrease the thoracic volume)

Question 7

What is one of the effects of obstructive diseases in inspiratory muscles?

Answer 7

The inspiratory muscles are shorter. so they have a lower % maximal force.

E.g. the diaphragm is shorter and more flattened. As a result, the diaphragm is unable to produce as much force.

Question 8

What is PIP?

Answer 8

Intraplural pressure. This helps the lung stay stuck to the chest wall.

Question 9

What are typical values of PIP at the end of expiration and inspiration?

Answer 9

• 5 cm-H2O at the end of expiration
• 30 cm-H2O at the end of inspiration

The heightened (more negative) intrapleural pressure near the end of inspiration is mainly the result of the tendency of the lung to recoil towards its intrinsic equilibrium position and the resulting forces on the intrapleural space; these are their largest when the lung is maximally inflated

Question 10

What is the elastic recoil pressure?

Answer 10

This is the positive pressure of the lung that is present during expiration. This pressure is what brings the lung back closer to its intrinsic equilibrium position.

Question 11

What is a characteristic/factor of the lung that can affect the inflation of the lungs?

Answer 11

Lung Compliance

Question 12

What is compliance?

Answer 12

Measure of how easily an applied pressure induces a volume change

Question 13

What is the transpulmonary pressure?

Answer 13

It is the difference between the lung pressure and the intraplural pressure. This is the pressure that dictates how easily a lung inflates.

For example, if you’re blowing up a balloon, it’s not just the pressure that you apply inside a balloon that matters for how it blows up, it’s actually the pressure difference between the inside and the outside of the balloon that is causing it to blow up.

PTP = Plung - PIP

Question 14

Is the compliance curve of a lung linear?

Answer 14

No. It is curved. The compliance curve has Transpulmonary pressure (PTP) on the X axis and Lung Volume on the Y axis. As you increase PTP, you also increase Lung Volume, but the Lung Volume starts to plateau as you reach the maximum capacity of the lungs.

Question 15

What does pulmonary fibrosis do to the compliance of lungs? Does this cause problems with inspiration or expiration?

Answer 15

Decreases compliance. Problems w/ Inspiration.

Question 16

What does emphysema do to the compliance of lungs? Does this cause problems with inspiration or expiration?

Answer 16

Increases compliance (decreased elastin causes less elastic recoil pressure). Problems with expiration.

In emphysema, the lung is often called “floppy lung”

Question 17

What is a characteristic/factor of the chest wall that can affect the inflation of the chest cavity?

Answer 17

Chest wall compliance

Question 18

What are 3 things that cause a reduction in chest wall compliance?

Answer 18

1. Old age (more fibrotic)
2. Obesity (fat impedes)
3. Scar tissue

Question 19

What is tidal volume?

Answer 19

The amount of air you take in with each breath

Question 20

What happens to tidal volume when chest wall compliance goes down?

Answer 20

It decreases

Question 21

What are two accessory inspiratory muscles?

Answer 21

Sternomastoid and scalenes. These are generally silent during normal breathing but can be recruited when respiratory load is increased, such as during exercise. Their function is to elevate the rib cage.

Question 22

The lung is more ____ than its intrinsic equilibrium position, and thus there is a force that tend to make the lung ____.

Answer 22

Inflated, deflate

Question 23

The chest wall is more ____ than its intrinsic equilibrium position, and thus there is a force for it to ____.

Answer 23

Deflated, expand

Question 24

What creates the negative intrapleural pressure? (vacuum)

Answer 24

The two opposing forces of the lung wanting to return to its deflated position and the chest wall wanting to return to is expanded position creates the negative intrapleural pressure.

Question 25

What is the main cause of PL achieving negative values during inspiration which result in lung inflation?

Answer 25

Increase in negativity in PIP

Question 26

Compliance is inversely proportional to the _____ of the lungs

Answer 26

elasticity