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RCR1 Physiology > Pulmonary Mechanics > Flashcards

Pulmonary Mechanics Flashcards

0
Q

What muscles are used for expiration?

A

Quiet - none, it’s passive.

Forced - abdominal muscles and internal intercostals

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1
Q

What muscles are used in inspiration?

A

Quiet - diaphragm and external intercostals

Forced - as above, and sternocleidomastoid, scalenes

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2
Q

What makes up the alveolar pressure?

A

Alveolar pressure = pressure on outside of alveoli + pressure generated by elastic recoil of alveoli

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3
Q

What is compliance?

A

The stretchiness of the lung tissue

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4
Q

What is maximal expiratory flow limited by?

A

Resistance!
Increased effort causes an increase in resistance as the airways are compressed by the raised external pressure.
This means that increasing effort may increases expiratory flow to a certain point!

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5
Q

What keeps the bronchioles open?

A

Radial traction (the outwards pull of surrounding tissue)

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6
Q

What keeps the upper airway open?

A

Cartilage

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7
Q

What happens when the pressure on the outside of the bronchioles is more negative than the inside?

A

They may collapse

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8
Q

What is dynamic airway compression?

A

In diseases which decrease the elasticity of lung tissue, muscular effort cannot compensate for lack if recoil as the muscles compress the airway, making it harder to expire.

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9
Q

In what conditions is dynamic airway compression a problem?

A

COPD and Emphysema

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10
Q

Can muscular effort compensate for increased airway resistance?

A

No.

Asthma and Bronchitis

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11
Q

What is surfactant?

A

Mostly lipid. Lowers surface tension allowing easy expansion or lungs

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12
Q

What is respiratory distress syndrome?

A

Lack of surfactant. Common in premature babies.

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13
Q

What receptors control ventilation?

A

Mechanoreceptors and chemoreceptors

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14
Q

What do mechanoreceptors detect?

A

Inflation and deflation of the lungs

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15
Q

What are central chemoreceptors?

A

Detect pH changes.

Desensitised by prolonged periods of high CO2

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16
Q

What is hypoxic drive?

A

When central chemoreceptors are desensitised by prolonged periods of high CO2 so ventilation is now being controlled by the detection of hypoxia (peripheral chemoreceptors)

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17
Q

What is the problem with treating hypoxic drive?

A

Giving O2 treats the hypoxia, and so the chemoreceptors think conditions are normal again. Patient may stop ventilating. CO2 levels are dangerously high.

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18
Q

What are peripheral chemoreceptors?

A

In carotid and Aortic bodies. Detect pH.

ESSENTIAL when CO2 sensitivity is lost. Most sensitive during hypercapnia.

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19
Q

What are ‘restrictive’ diseases?

A

Decreased compliance

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20
Q

What are obstructive diseases?

A

Impaired airflow

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21
Q

What is Asthma?

A

An obstructive airway condition caused by bronchoconstriction and airway inflammation in response to an allergen.

22
Q

What is bronchitis?

A

Mucus overproduction and periods of infection.

23
Q

What is Emphysema?

A

A respiratory condition caused by the destruction of alveoli due to excessive protease activity.
Chronic over inflation.

24
Q

What is COPD?

A

Chronic obstructive pulmonary disorder.

Features of bronchitis and emphysema.

25
Q

What is Henry’s law?

A

[gas] = partial pressure x solubility coefficient

26
Q

What is Dalton’s law?

A

The total pressure is the sum of all of the constituent partial pressures.

27
Q

Where is the respiratory centre?

A

Medulla

28
Q

What are the 2 groups of the respiratory centre?

A

Dorsal respiratory group and the ventral respiratory group

29
Q

What does the dorsal respiratory group do?

A

Causes inspiration (expiration is passive)

30
Q

What does the ventral respiratory group do?

A

Involved in inspiration and expiration when there is an increased demand to breathe

31
Q

Where does the dorsal respiratory group receive its stimuli from?

A

Mechanical stretch receptors in the lung.

32
Q

How does the ventral respiratory group cause forced inspiration and expiration?

A

Signals for the usage of accessory muscles (scalenes, sternocleidomastoid, internal intercostals etc) for inspiration and abdominal muscles for expiration.

33
Q

What is the pontine respiratory group?

A

The pons!

Limits ventilation by controlling the rate and depth of breathing.

34
Q

What do central chemoreceptors respond to?

A

Increased CO2 and decreased pH

35
Q

What do peripheral chemoreceptors respond to?

A

Increased CO2, decreased pH and decreased oxygen

36
Q

Where are peripheral chemoreceptors?

A

Aortic and carotid bodies

37
Q

Where are central chemoreceptors?

A

Medulla

38
Q

How are central chemoreceptors stimulated?

A

H+ can’t cross BBB so the bicarbonate buffering system converts it to CO2 which diffuses across and forms H2CO3. This lowers the pH or cerebral spinal fluid and so stimulates chemoreceptors.

39
Q

How else can respiration be controlled?

A

Higher centre afferents (muscles controlled during pain and emotion)

Proprioceptors - joint movement stimulates respiration (exercise)

40
Q

What is congenital hypoventilation syndrome (Ondine’s curse)?

A

Breathing is absent during sleep.

41
Q

What is type 1 respiratory failure?

A

Low PaO2

Normal or low PaCO2.

42
Q

What is type 2 respiratory failure?

A

Low PaO2

High PaCO2

43
Q

When is respiratory adaptation necessary?

A

Exercise
Altitude
Depth
Illness

44
Q

What is the forced vital capacity (FVC)?

A

Total volume of air that can be exhaled from total lung capacity, measured in litres.

45
Q

What is the forced expiratory volume (FEV1) ?

A

The volume of air that can be forcefully expired in one second.

46
Q

What is a normal FVC?

A

80+%

47
Q

What is a normal FEV1?

A

Over 75%

48
Q

What is the forced expiratory flow (FEF25-75) ?

A

Mean forced expiratory flow in the middle half of the FVC

Over 60% is normal

49
Q

What impact do obstructive airway conditions have on FEV1?

A

Decrease

50
Q

What impact do obstructive conditions have on total lung capacity?

A

No effect.

51
Q

What impact do restrictive airway conditions have on total lung capacity?

A

Decreased

52
Q

What impacts do restrictive airway conditions have on FEV1?

A

Very little

RCR1 Physiology (5 decks)

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