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Systems 1 - The Respiratory System > Ventilation and Compliance 2 > Flashcards

Ventilation and Compliance 2 Flashcards

1
Q

What is surfactant?

A

Detergent-like fluid produced by Type II Pneumocytes

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2
Q

What is the function of surfactant?

A

Reduces surface tension on alveolar surface membrane and reduces its tendency to collapse

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3
Q

What is surface tension?

A

Surface tension occurs at air-water interfaces and refers to the attraction between water molecules

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4
Q

What the is the overall effect of surfactant on the compliance of the lung?

A

Increases its distensibility

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5
Q

What is the Law of LaPlace?

A

Shows the relationship between pressure and a equation of surface tension and radius of the alveoli

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6
Q

What is the equation of the Law of LaPlace?

A

P=2T/r

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7
Q

How does the Law of LaPlace marry the different pressures in differently sized alveoli and what role does surfactant play?

A

The Law of LaPlace shows that smaller alveoli have higher pressures, surfactant reduces surface tension and the pressure is equalised

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8
Q

What are the gestational milestones for surfactant production?

A

approx. 25 weeks - Surfactant production begins

Complete by 36 weeks

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9
Q

What hormones stimulate surfactant production in foetuses?

A

Thyroid hormones and cortisol

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10
Q

When babies are born prematurely what pathology can arise to do with incomplete surfactant development?

A

Infant Respiratory Distress Syndrome (IRDS)

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11
Q

What is compliance?

A

Change in volume relative to change in pressure; represents stretchability of the lungs

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12
Q

What is meant by a high compliance?

A

Large increase in volume for a small decrease in pressure

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13
Q

What is meant by a low compliance?

A

Small increase in lung volume for large decrease pressure

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14
Q

Describe the pressure-volume relationship

A

It requires a greater change in pressure (from FRC) to reach a particular volume because the work done during inspiration is recovered in elastic recoil for expiration (why its described as passive at rest)

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15
Q

Describe the pressure-volume relationship associated with Emphysema

A

Loss of elastic tissue means expiration requires effort

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16
Q

Describe the pressure-volume relationship associated with fibrosis

A

Inert fibrous tissue means effort of inspiration increases

17
Q

How does the pressure volume curve vary in different regions of the lung?

A

At the base, the volume change is greater than the apex for a given change in pressure.

Alveolar ventilation and compliance also decrease from base to apex

18
Q

Why is the volume change at the base of the lung greater than the apex for a given change in pressure?

A

At the base, alveoli are more compressed by the rest of the lung and the diaphragm therefore are more compliant on inspiration

19
Q

What is the difference between obstructive and restrictive lung diseases?

A

Obstructive - obstruction of airways, particularly on expiration

Restrictive - restriction of lung expansion (inspiration)

20
Q

What are two examples of obstructive lung disease?

A

Asthma and COPD (a combination of chronic bronchitis and emphysema)

21
Q

What are three examples of restrictive lung diseases/disorders?

A

IRDS
Oedema
Pneumothorax

22
Q

What is spirometry?

A

A technique used to measure lung function. Measurements can either be classes as static or dynamic

23
Q

What is the difference between static and dynamic measurement s in spirometry?

A

States - where the only consideration made is the volume exhaled

Dynamic - where the time taken to exhale a certain volume is being measured

24
Q

What lung volumes and capacities can’t be directly measured by spirometry?

A

RV, TLC and FRC

25
Q

What is a typical FEV1 value for healthy males?

A

4L

26
Q

What is a typical FVC in healthy males?

A

5L

27
Q

What is the typical FEV1/FVC for a healthy male as a percentage?

A

80%

28
Q

What FEV1/FVC percentage is typically seen in obstructive pulmonary diseases?

A

<80%

29
Q

What FEV1/FVC percentage is typically seen in restrictive diseases?

A

> 80%

30
Q

Why are obstructive diseases characterised by an FEV1/FVC percentage <80%?

A

Rate at which air is exhaled is slower; reduced FEV1 and little effect on FVC therefore ratio is reduced

31
Q

Why are restrictive diseases characterised by an FEV1/FVC percentage >80%?

A

Total lung volume is reduced therefore ratio can increase as large proportion of volume can still be exhaled quickly

32
Q

What are the limitations for the FEV1/FVC for both obstructive and restrictive diseases?

A

Both FEV and FVC fall - ratio stays the same despite seriously compromised function

33
Q

What is FEF25-75?

A

Forced expiratory flow - average expired flow one the middle of the FVC

34
Q

What is the advantage of using FEF25-75?

A

Correlates with FEV1 but changes are generally more striking

35
Q

What is the disadvantage of using FEF25-75

A

“Normal” range is greater

Systems 1 - The Respiratory System (25 decks)

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