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Respiratory > Mechanics Of Breathing > Flashcards

Mechanics Of Breathing Flashcards

0
Q

Which extra muscles are needed for deep inspiration?

A

Sternocleiodomastoid (elevates the sternum) Middle, anterior and posterior scalene (elevate and fix the upper ribs)

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1
Q

Which muscles are used in normal inspiration?

A

External intercostals Diaphragm Interchondral parts of internal intercostal muscles

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2
Q

Which muscles are required for normal expiration?

A

None Results from passive recoil of the lungs and ribcage Expiration is passive

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3
Q

Which muscles are required forced expiration?

A

Internal intercostals Rectus abdominis External and internal obliques Transversus abdominis

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4
Q

What is a pneumothorax?

A

When the integrity of the pleural sac is broken by air, causing the lungs to collapse

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5
Q

What is in the pleural space?

A

Fluid

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6
Q

What holds the lungs to the thoracic wall?

A

Surface tension of the fluid in the pleural space

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7
Q

Define compliance of the lungs

A

Stretchiness of the lungs So equals the volume change per unit of pressure change

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8
Q

What does it mean if the lungs have a high compliance?

A

The lungs are easier to stretch

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9
Q

How does compliance change with lung volume?

A

The greater the lung volume, the greater the compliance

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10
Q

What are the main factors that affect compliance of the lungs?

A

Surface tension Surfactant Bubbles

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11
Q

How does surface tension affect the compliance of the lungs?

A

Interactions between molecules at the surface of a liquid makes the surface resist stretching

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12
Q

As surface tension increases, how does this affect lung compliance?

A

As Durga e tension increases, the harder the lungs are to stretch

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13
Q

Why is the surface tension of the lungs much lower than expected than if lungs were lined with saline?

A

Presence of surfactant

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14
Q

How does surfactant reduce surface tension?

A

Disrupts interactions between the surface molecules The hydrophilic ends of molecules lie in alveolar fluid while the hydrophobic ends project into alveolar gas

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15
Q

What is surfactant?

A

A mixture of phospholipids and proteins

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16
Q

What is surfactant produced by?

A

Type II alveolar cells

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17
Q

What is hysteresis?

A

The energy put into stretching a film of surfactant is not all recovered when the film recoils because need to overcome the surface tension when inhaling https://uk.answers.yahoo.com/question/index?qid=20100605085048AAbWQGy

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18
Q

When is the energy loss in hysteresis greatest?

A

When tidal volume is maximal - reason why little breaths are best

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19
Q

What is the equilibrium in a bubble?

A

When the film shrinks around gas until an equilibrium between tension and pressure is reached

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20
Q

What is Laplace’s law?

A

Pressure is inversely related to the radius of the bubble As radius increases, pressure decreases Bigger the bubble, lower the pressure

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21
Q

What will happen if a big bubble is connected to a smaller bubble?

A

Air will flow from high to low pressure -small bubble collapses into the big bubble

22
Q

What prevents the alveoli (bubbles) from swallowing eachother and how?

A

Surfactant Keeps a high pressure in the larger bubbles As alveoli get bigger, the surface tension increases because surfactant is less effective - stops them eating the little bubbles

23
Q

What is respiratory distress syndrome?

A

When premature babies have too little surfactant in their lungs so they are very stiff with fewer, larger alveoli. Breathing and gas exchange is compromised.

24
Q

What is Poiseulle’s law?

A

Small rubes have high flow resistance

25
Q

Where is the respiratory system is the highest resistance and why?

A

Trachea In the lung there are many small airways but there are many in parallel, reducing the resistance

26
Q

Why is there such a thing as residual volume?

A

When the lung is compressed in forced expiration, small airways are narrowed so resistance increases dramatically and air is trapped in the alveoli

27
Q

What is obstructive airway disease and what does it do?

A

When small airways are narrowed by disease Increases the resistance much earlier in expiration so breathing out can become difficult

28
Q

What are all the forces in equilibrium at resting respiratory level?

A

Lungs trying to pull inwards and upwards Thoracic cage trying to pull outwards Diaphragm pulling downwards

29
Q

What are lung function tests used to assess?

A

Mechanical condition of the lungs Resistance of the airways Diffusion across alveolar membrane

30
Q

What does a spirometer measure?

A

The vital capacity (max inspiration to max expiration)

31
Q

What does maximum inspiration test?

A

Compliance Force of inspiratory muscles

32
Q

What does max expiration measure?

A

Airway resistance

33
Q

How is single breath spirometry done?

A

Fill lungs with air Breath our as far and as fast as possible through a rapid responding spirometer

34
Q

What is the name of the graph that spirometry gives you?

A

A vitalograph trace

35
Q

What does single breath spirometry show?

A

FEV1.0 - forced expiration in one second. Affected by how quickly airflow slows down Can work out the FEV1.0/FVC ratio which is normally >70% So FEV1.0 should be more that 70% of the FVC a

36
Q

Define forced vital capacity. Typical value?

A

Maximum volume that can be expired from full lung. 5L

37
Q

What is a restrictive deficit?

A

Problem with inspiration

38
Q

What can cause a restrictive deficit?

A

Due to stiffness, weak muscles, problem with chest wall

39
Q

How does a restrictive deficit affect FEV1.0 and FVC?

A

FVC will be reduced (PICTURE) FEV1.0 will be normal

40
Q

What is an obstructive deficit?

A

Problem with expiration

41
Q

What causes an obstructive deficit?

A

When airways are narrowed so increased resistance in expiration.

42
Q

What happens to FEV1.0 and FVC in an obstructive deficit?

A

FEV1.0 will be reduced FVC will be normal PICTURE

43
Q

What are on the axes of a flow volume curve?

A

Volume expired against flow rate Derived from a vitalograph

44
Q

Explain the shape of a flow volume curve

A

When lungs are full, little air expired. Airways are stretched so resistance is minimum Flow rate will reach its maximum (peak expiratory flow rate PEFR) As lungs are compressed, airways narrow and resistance increases so flow rate decreases The narrower the airways to begin with, the more rapidly it falls

45
Q

Why is a flow volume curve better than a vitalograph trace?

A

It is a more sensitive indicator of airway narrowing Can discriminate between large and small airway narrowing

46
Q

What can peak expiratory flow rate be used to measure?

A

Screening test for airway narrowing Very insensitive

47
Q

How is residual volume measured?

A

Use a spirometer with helium dilation

48
Q

How does helium dilation work?

A

Helium is not normally present in the air and is insoluble in blood Patient breaths in a known concentration starting at a functional residual capacity See how much the helium concentration reduces by mixing it with air already in the lungs to give a measure of residual volume

49
Q

What does a nitrogen washout measure?

A

Serial dead space Ventilation perfusion matching (indirectly)

50
Q

How is a nitrogen washout done?

A

Patient takes one normal breath of pure oxygen and breaths out via a meter measuring percentage nitrogen Initially, only oxygen will be breathed out, then a mixture of oxygen and air with nitrogen from the alveoli. Volume expires at transition is the serial deadspace.

51
Q

How is diffusion conductance measured?

A

See how easily carbon monoxide crosses from alveolar air to the blood.

52
Q

How does an obstructive deficit affect a flow volume curve?

A

Respiratory (17 decks)

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