Mechanics of breathing II

Question 1

What is the speed of the air through the airways proportional to?

Answer 1

→ pressure gradient between atmosphere and lungs

Question 2

What is the equation for compliance?

Answer 2

→ compliance = Δ volume/ Δpressure

Question 3

What is compliance?

Answer 3

→How easy it is to get the lungs to expand

Question 4

What is transpulmonary pressure?

Answer 4

→The force required to expand the lungs

Question 5

What is the transpulmonary pressure equation?

Answer 5

→Transpulmonary pressure (Ptp) = Alveolar pressure (Palv) - Intrapleural pressure (Pip).

Question 6

What is the equation for airflow?

Answer 6

→ Pressure / Resistance

Question 7

What happens as the airway radius decreases?

Answer 7

→The resistance increases and airflow decreases dramatically

Question 8

What is the Hagen-Poiseuille equation?

Answer 8

→R = 8nl / πr^4

Question 9

What happens when the lumen diameter increases?

Answer 9

→Increase in luminal area
→Decrease in resistance
→Increase in flow

Question 10

What happens when the lumen diameter decreases?

Answer 10

→Decrease in luminal area
→Increase in resistance
→Decrease in flow

Question 11

How does pattern of airflow affect resistance?

Answer 11

→Laminar flow - no resistance

→Turbulent flow - resistance and produces noise (wheezing)

Question 12

What is FEV 1?

Answer 12

→Forced expiratory volume in 1 second

Question 13

What is FVC?

Answer 13

→Forced vital capacity

Question 14

How do you take into account different lung capacities?

Answer 14

→100 x FEV1/FVC = % of total lung capacity an individual can exhale in the first second
→Ratio of volume in 1 second to total capacity.

Question 15

What happens to FVC and FEV1 in obstructive airway disease?

Answer 15

→The FVC is the same but FEV1 decreases

→Lung capacity is normal

Question 16

What happens to FVC and FEV1 in restrictive airway disease?

Answer 16

→The FVC is decreased but FEV1 is the same

→Lung capacity decreases

Question 17

What is the ratio of someone with obstructive airway disease?

Answer 17

→FEV1 ratio is decreased <70%

Question 18

What is the ratio for someone with a restrictive airway disease?

Answer 18

→The FVC decreases

→The ratio is not affected >70%

Question 19

What are alveoli lined with?

Answer 19

→Lined with fluid to enable gas exchange (gas molecules dissolve into water before diffusing)

Question 20

When does surface tension arise?

Answer 20

→When there is an interface between water and air

Question 21

How does surface tension arise?

Answer 21

→ Generated by H-bonds between the water molecules exerting a collapsing force towards the center of the bubble.

Question 22

Why do small alveoli empty into larger ones when surfactant is present?

Answer 22

→The inward pressure on the smaller alveolus is much higher so the air gets forced into the larger alveolus.

Question 23

What is alveolar surfactant secreted by?

Answer 23

→ Type II pneumocytes

Question 24

What molecules does surfactant contain?

Answer 24

→Surfactant has some molecules that are amphiphatic

Question 25

What is the purpose of amphiphatic molecules in the surfactant?

Answer 25

→ It disrupts the H-bonding between water molecules and reduces the surface tension.

Question 26

What happens with an increased concentration of surfactant molecules?

Answer 26

→The surface tension decreases as water molecules do not have space to bond.

Question 27

What happens with a decreased concentration of surfactant molecules?

Answer 27

→Surface tension increases as water molecules are free to bond.

Question 28

What does pulmonary surfactant help prevent?

Answer 28

→Alveolar oedema

Question 29

What does surface tension reduce?

Answer 29

→Reduces hydrostatic pressure produced at the air-liquid interface.
→Fluid is pulled out of the surrounding capillaries and into the alveoli.

Question 30

When does turbulent air flow occur?

Answer 30

→ Breathing hard

→ Areas of obstruction

Question 31

Why is an increase in lung compliance bad?

Answer 31

→ Easy to expand the lungs but they cannot recoil

Question 32

What does a steep gradient mean on the lung compliance graph?

Answer 32

→ The lungs are easier to expand