Mechanics of breathing II Flashcards

1
Q

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

A

→ pressure gradient between atmosphere and lungs

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2
Q

What is the equation for compliance?

A

→ compliance = Δ volume/ Δpressure

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3
Q

What is compliance?

A

→How easy it is to get the lungs to expand

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4
Q

What is transpulmonary pressure?

A

→The force required to expand the lungs

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5
Q

What is the transpulmonary pressure equation?

A

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

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6
Q

What is the equation for airflow?

A

→ Pressure / Resistance

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7
Q

What happens as the airway radius decreases?

A

→The resistance increases and airflow decreases dramatically

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8
Q

What is the Hagen-Poiseuille equation?

A

→R = 8nl / πr^4

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9
Q

What happens when the lumen diameter increases?

A

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

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10
Q

What happens when the lumen diameter decreases?

A

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

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11
Q

How does pattern of airflow affect resistance?

A

→Laminar flow - no resistance

→Turbulent flow - resistance and produces noise (wheezing)

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12
Q

What is FEV 1?

A

→Forced expiratory volume in 1 second

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13
Q

What is FVC?

A

→Forced vital capacity

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14
Q

How do you take into account different lung capacities?

A

→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.

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15
Q

What happens to FVC and FEV1 in obstructive airway disease?

A

→The FVC is the same but FEV1 decreases

→Lung capacity is normal

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16
Q

What happens to FVC and FEV1 in restrictive airway disease?

A

→The FVC is decreased but FEV1 is the same

→Lung capacity decreases

17
Q

What is the ratio of someone with obstructive airway disease?

A

→FEV1 ratio is decreased <70%

18
Q

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

A

→The FVC decreases

→The ratio is not affected >70%

19
Q

What are alveoli lined with?

A

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

20
Q

When does surface tension arise?

A

→When there is an interface between water and air

21
Q

How does surface tension arise?

A

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

22
Q

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

A

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

23
Q

What is alveolar surfactant secreted by?

A

→ Type II pneumocytes

24
Q

What molecules does surfactant contain?

A

→Surfactant has some molecules that are amphiphatic

25
Q

What is the purpose of amphiphatic molecules in the surfactant?

A

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

26
Q

What happens with an increased concentration of surfactant molecules?

A

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

27
Q

What happens with a decreased concentration of surfactant molecules?

A

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

28
Q

What does pulmonary surfactant help prevent?

A

→Alveolar oedema

29
Q

What does surface tension reduce?

A

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

30
Q

When does turbulent air flow occur?

A

→ Breathing hard

→ Areas of obstruction

31
Q

Why is an increase in lung compliance bad?

A

→ Easy to expand the lungs but they cannot recoil

32
Q

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

A

→ The lungs are easier to expand