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Respiratory Block > Ventilation and compliance 2 > Flashcards

Ventilation and compliance 2 Flashcards

1
Q

What is surfactant?

A

Detergent like fluid that reduces surface tension on alveolar surface membrane

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2
Q

What cells produce surfactant?

A

Type 2 alveolar cells

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3
Q

Describe briefly surface tension

A

Due to the attraction between water molecules causing an air-water interface

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4
Q

Does surface tension cause a net force and movement forwards or backwards?

A

Forwards

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5
Q

What does surfactant reduce? (3)

A

Tendency for alveoli to collapse
Tendency for alveoli to recoil
Attraction between air and water

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6
Q

What does surfactant increase? (1)

A

Lung compliance => distensibility

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7
Q

Does surfactant make breathing easier or more difficult?

A

Easier

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8
Q

Is surfactant more effective in small or large alveoli? Why?

A

Small

Surfactant molecules come closer together and are more concentrated

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9
Q

When does surfactant start in gestation and when is it complete?

A

About 25 weeks

About 36 weeks

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10
Q

What is surfactant production stimulated by which are produced at the later stages of pregnancy?

A

Cortisol

Thyroid hormone

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11
Q

If a baby is premature what may they suffer from and how can this be treated?

A

Infant respiratory distress syndrome (IRDS)

Synthetic surfactant

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12
Q

What is seen when saline is used to demonstrate lung inflation in utero?

A

Less change in pressure is required as no need to overcome surface tension

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13
Q

Compliance

A

Change in volume relative to change in pressure

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14
Q

Does compliance represent stretchability or elasticity?

A

Stretchability

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15
Q

Stretchability

A

How easy to stretch open the lungs

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16
Q

Elasticity

A

How easy it is to get the air out of the lungs

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17
Q

High compliance

A

Large increase in lung volume for small decrease in Pip

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18
Q

Low compliance

A

Small increase in lung volume for a large decrease in Pip

19
Q

What 2 factors can change Compliance?

A

Disease states

Age

20
Q

Is more pressure needed to reach a particular lung volume during inspiration or maintain this same volume during expiration?

A

Inspiration

21
Q

Why does inspiration require a larger pressure change?

A

Expiration is passive as the effort from inspiration is recovered as elastic recoil and at the start of inspiration the chest cavity is constricted leading to a greater resistance

22
Q

Emphysema

A

Loss of elastic tissue so expiration takes a lot of effort

Pip becomes positive so PA = -ve

23
Q

Fibrosis

A

Inert fibrous tissue means effort of inspiration increases

Decreased compliance

24
Q

Is the greatest compliance at the base or apex of the lung?

A

Base - due to gravity

Volume change is greater for a given change in pressure

25
Q

Does alveolar pressure incline or decline with height from base to apex?

A

Decline eg most at base

26
Q

Why is the compliance highest at the base?

A

Alveoli are compressed at the base by the weight of the lung and diaphragm below
Small change in Pip leads to a large change in volume
Top alveoli are already quite full

27
Q

Obstructive lung disease - brief description and example

A

Obstruction of flow especially in expiration eg asthma and an increases airway resistance

28
Q

Restrictive lung disease - brief description and example

A

Restriction of lung expansion eg fibrosis with a loss of compliance

29
Q

COPD

A

Chronic bronchitis - inflamed bronchi
emphysema - destroyed alveoli
80 M word wide with about 1% in UK with 10% over 75s

30
Q

Restrictive lung disease

A

IRDS, pneumothorax and oedema which is a fluid build up around alveoli

31
Q

Spirometry

A

Technique used to measure lung function

32
Q

Name the 2 types of spirometry

A

Static and dynamic

33
Q

Describe the differences between the 2 kinds of spirometry

A

Static only considers the volume exhaled

Dynamic takes into account the time taken to exhale a certain volume in 1 second

34
Q

Which type of spirometry is more useful?

A

Dynamic

35
Q

What can be directly measured by spirometry?

A

Tidal volume, vital capacity, inspiratory capacity, inspiratory reserve volume and expiratory reserve volume

36
Q

What is the reason why not everything can be measured by spirometry

A

Anything containing residual volume cannot which also includes functional residual capacity and total lung capacity

37
Q

What is the difference between volume and capacity

A

Capacity are 2 or more volumes added together

38
Q

What does the ratio FEV1/FVC mean?

A

Forced expiratory volume in 1 second

39
Q

What is the normal FEV1/FVC?

A

80%

40
Q

Describe the FEV1/FVC ratio in obstructive lung disease

A

Both volumes fall but FEV1 falls more so the ratio is reduced

41
Q

Describe the FEV1/FVC ratio in restrictive lung disease

A

Both ratios fall so same ratio or even increases

42
Q

Why is the FEV1/FVC ratio limited?

A

Not always an indicator of health as in restrictive lung disease there is a severe compromise of function although the ratio does not change much from normal or will even increase

43
Q

Forced expiratory flow rate

A

The average expired flow over the middle of an FVC

44
Q

Compare FEF25-75 to FEV1

A

They both correlate but changes are more striking

Greater “normal” range

Respiratory Block (29 decks)

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