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MD3001 Week 8 > Ventilation- The Physics of Breathing > Flashcards

Ventilation- The Physics of Breathing Flashcards

1
Q

What occurs in inspiration to increase size of lungs?

A

Change in volume leads to change in pressure

Role of the diaphragm – main muscle of respiration. Contraction flattens domes. Abdominal wall relaxes to allow abdominal contents to move downwards

Role of the intercostals – externals – with first rib fixed, two movements, forward movement of lower end of sternum, and upward and outward movement of ribs

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2
Q

By how much does inspiration increase thorax volume?

A

By 500 ml

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3
Q

What is normal intrapleural pressure?

A

756mmHg

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4
Q

What is intrapulmonary pressure?

A

760mmHg

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5
Q

What is the collapsing force of the lungs?

A

4mmHg

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6
Q

What happens to the different pressures during inspiration?

A

Intrapleural drops to -6mmHg

Intrapulmonary pressure drops by 1mmHg allowing air to enter the lungs

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7
Q

Describe quiet expiration

A

Passive – no direct muscle action normally

Cessation of muscle contraction

Elastic recoil – drives air out of lungs

Thoracic volume decreases by 500 ml

Intrapulmonary pressure increases

Air moves down pressure gradient

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8
Q

Describe forced expiration

A

Contraction of abdominal walls, forces abdominal contents up against diaphragm, and internal intercostals – pull ribs downwards

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9
Q

What is energy required to do?

A

Contract the muscles of inspiration

Stretch elastic elements

Overcome airway resistance

Overcome frictional forces arising from the viscosity of the lung and chest wall

Overcome inertia of the air and tissues

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10
Q

What is the most significant non-elastic source of resistance?

A

Airway resistance

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11
Q

What is the amount of air that flow determined by?

A

Change of pressure divided by the resistance

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12
Q

What is turbulent flow more likely to occur with?

A

High velocities

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13
Q

Where is the greatest resistance to airflow?

A

Segmental bronchi

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14
Q

Why is the greatest resistance found in the segmental bronchi?

A

Cross sectional area is relatively low and airflow is high and turbulent

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15
Q

How does airway resistance change?

A

In inspiration airway resistance decreases

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16
Q

What diseases cause an increase in airway resistance?

A

Asthma

COPD

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17
Q

What is compliance?

A

Describes the distensibility or ease of stretch of lung tissue when external force applied, or the ease with which the lungs expand under pressure

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18
Q

What does high compliance mean?

A

A large change in volume for a given change in pressure

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19
Q

What are the major determinants of compliance?

A

Elastic components and alveolar surface tension

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20
Q

What is compliance in an average person?

A

1L per kPA

21
Q

What changes compliance?

A

Changes in volume of the chest that results from a given change in intrapleural pressure

22
Q

How do we reduce compliance?

A

replacing elastic tissue with non-elastic tissue –pulmonary fibrosis – lungs become stiffer.

Blocking smaller respiratory passages

Increasing alveolar surface tension

Decreasing the flexibility of the thoracic cage or its ability to expand

23
Q

How can we increase compliance?

A

Pulmonary emphysema. Due to alveoli rupture, creating larger air space and thus reducing surface area of lung. Impaired elastic recoil leads to poor deflation, trapping more air.

24
Q

When is lung compliance at its greatest?

A

Lower lung volumes and smallest at higher lung volumes

25
Q

How does compliance differ from the apex and base of lung?

A

Apex is less compliant than the base allowing the bsae to expand more

26
Q

What would happen if the alveoli were lined with polar water?

A

They’d collapse

27
Q

How does the body stops the alveoli from collapsing?

A

Type II alveolar cells produce surfactant

Surfactant is made up of phospholipids

Increases lung compliance by reducing surface tension- allowing for greater expansion

28
Q

How can we measure respiratory volume?

A

Spirometry

Vitalograph

SEE LECTURE

29
Q

What are the four different lung volumes?/

A

Tidal

Inspiratory reserve volume

Expiratory reserve volume

Residual volume

30
Q

What is tidal volume?

A

Volume of air breathed in and out in a single breath

31
Q

What is inspiratory reserve volume?

A

Volume breathed in by max inspiration at end of normal inspiration

32
Q

What is expiratory reserve volume?

A

Volume of air expelled by max effort at the end of normal expiration

33
Q

What is residual volume?

A

Volume of air in lungs at the end of maximum expiration

34
Q

What is inspiratory capacity?

A

TV add IRV

Volume of air breathed in by max inspirations at the end of normal expiration

35
Q

What is functional residual capacity?

A

ERC add RV

Volume of air left in lungs at end of normal expiration

36
Q

What is vital capacity?

A

IRV add TV add ERV

Volume of air that can be breathed by max inspiration following a max expiration

37
Q

What is total lung capacity?

A

VC + RV

38
Q

What can’t you use a spirometer to measure?

A

Residual volume

Functional residual capacity

Total lung capacity

39
Q

What is dead space?

A

Areas of airway not involved in gas exchange- 150ml on average

Alveolar with poor perfusion as well- 5ml

40
Q

What is intrapleural pressure?

A

Always more negative than the alveolar

41
Q

Slde 7

A

Exam question

42
Q

What is a normal volume for inspiratory capacity?

A

3.8L

43
Q

what is a normal function residual capacity?

A

2.2-2.4L

44
Q

What is a normal vital capacity?

A

4.8L

45
Q

What is a normal total lung capacity?

A

6L

46
Q

What does a vitalograph measure?

A

Measure the maximum forced breath out

Forced expiratory volume

FEV1- volume exhaled during the first second of forced expiration

47
Q

How long should a breath roughly take?

A

4 seconds

48
Q

Describe the effect of expiration and inspiration on intrapulmonary, trans-pulmonary and intrapleural pressures

A

All decreases during inspiration but intrapleural pressure decreases more

Intrapleural pressure stays lower for linger during in expiration but they do both rise again

MD3001 Week 8 (7 decks)

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