Obstructive Pulmonary Disorders (physiology) Flashcards

1
Q

what are three obstructive airway diseases?

A

asthma, chronic bronchitis, emphysema

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2
Q

what are chronic bronchitis and emphysema known as ?

A

COPD

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3
Q

what is normal FEV1 volume?

A

3.5L-4L

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4
Q

What is normal FVC volume?

A

5L

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5
Q

what are spirometry values predicted upon?

A

age sex and height

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6
Q

how does peak expiratory flow work?

A

the first time a peak expiratory flow is done, a baseline is established. Consecutive readings are then compared to the baseline:
80-100% baseline= normal
<50%= airway obstruction

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7
Q

What does a peak expiratory flow allow a patient to do?

A

allows patient to measure respiratory rate at home

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8
Q

what is a normal peak expiratory flow range?

A

400-600litres/min

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9
Q

what is the clinical definition of chronic bronchitis?

A

cough productive of sputum most days for at least 3 consecutive months for 2 or more consecutive years

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10
Q

what may chronic bronchitis be confused with due to the similar presentation?

A

bronchial asthma - difficult to differentiate by history alone so investigations essential

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11
Q

when is ‘complicated’ chronic bronchitis?

A
  • acute infective exacerbation i.e. bronchopneumonia

- FEV1 falls

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12
Q

what are the 4 main characteristics of chronic bronchitis?

A
  • mucous hyper secretion (occludes lumen)
  • fibrosis of BRONCHIOLAR WALLS
  • airway oedema
  • bronchoconstriction
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13
Q

what are the morphological changes in chronic bronchitis in large airways?

A
  • increase in number and size (hyper plastic) of mucous glands and goblet cells
  • inflammation and fibrosis is a minor component
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14
Q

what are the morphological changes in chronic bronchitis in small airways?

A
  • goblet cells appear - normally none

- respiratory epithelium changes its character to produce more mucous (protective mechanism to chronic irritation)

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15
Q

what do all processes in chronic bronchitis lead to?

A

narrowing airway & hence airflow limitation

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16
Q

What is Emphysema?

A

Increase beyond normal in the size of airspaces distal to the terminal bronchiole arising from either dilatation or destruction of alveolar wall and without obvious fibrosis –> have hyper inflated lungs

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17
Q

what airway is the last one to have respiratory epithelium?

A

terminal bronchiole

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18
Q

what does the loss of alveolar walls in emphysema account for?

A

bigger spaces

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19
Q

where may this loss of alveolar wall occur within the acinus?

A
  • Centriacinar
  • Panacinar
  • Periacinar
  • Scar (irregular)
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20
Q

what is an acinus

A

terminal + respiratory bronchiole
alveolar duct
alveolar sac

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21
Q

describe centriacinar emphysema

A

This is the most important- mostly related to smoke particles (causes inflammation)
These are the alveolar walls immediately surrounding the terminal and respiratory bronchioles
In this region that most material inhaled into lung and deposited therefore inflammation & irritation at its maximum - result is hole in middle of acinus

22
Q

where is centriacinar maximal?

A

In apex of lung / whole upper lobe -because clearance mechanisms to get rid of particles inhaled into lungs are worse at apex and more efficient at base due to better perfusion

23
Q

describe panacinar emphsyema

A

massive destruction of entire acini - end up with huge areas of destroyed lung –> all gas exchange tissue disappears
mostly due to alpha-1-antitrypsin deficiency

24
Q

where is panacinar emphysema maximal?

A

lower regions of lung

25
Q

describe periacinar emphysema

A

loss of tissue at edge of acinus, particularly in acini against pleura
Don’t cause problems until they burst - in which case may cause a spontaneous pneumothorax, leak of air into pleural space –> bulla/bleb (air that escapes into surrounding tissue and forms a bubble in the lung)

26
Q

What is scar ‘irregular’ emphysema?

A

emphysematous spaces around scar tissue in lungs

27
Q

what is the pathogenesis of emphysema?

A
  • smoking –> which leads to alpha-1-antitrypsin deficiency
  • ageing
  • alpha-1-antitrypsin deficiency
28
Q

How does alpha-1-antiryspin deficiency lead to emphysema?

A

In normal people, inflammation results in the release of elastase and protease enzymes which destroy foreign material & bacteria, however these enzymes could also potentially start to dissolve own tissue. This process is kept in check by anti-elastases and anti-protease enzymes. In absence of alpha-1-antitrypsin, this process is no longer regulated and results in tissue destruction and emphysema

29
Q

how does smoking lead to alpha-1-antitrypsin deficiency?

A

chemicals in smoking which damage function of these protective enzymes

30
Q

is there a reversible component in COPD and if so, how?

A

Yes there is, using asthma drugs to target certain mechanisms of airflow obstruction, however most obstruction cannot be overcome

31
Q

what are the ways of airflow obstruction which can be targeted by pharmacological intervention?

A

inflammation & smooth muscle tone aka bronchoconstriction

32
Q

what contributes to airflow obstruction in small airways?

A
  • smooth muscle tone
  • inflammation
  • fibrosis
  • partial collapse of airway wall on expiration
  • loss of alveolar attachments most important
33
Q

how does small airway stay open & not collapse especially on expiration when pressure is high?

A

because of attachments to alveolar walls - radial pull of alveolar wall around airway

34
Q

what happens to alveoli if they lose their wall?

A

they collapse & will not stay open long enough for normal breathing

35
Q

Where is air flow laminar ?

A

lower airways

36
Q

where is air flow turbulent?

A

upper airways

37
Q

what are the normal values of Normal PaO2 in kPa

A

10.5 - 13.5 kPa

38
Q

what are the normal values of normal PaCO2 in kPa

A

4.8-6.0 kPa

39
Q

what characterises type 1 respiratory failure?

A

Pa02 < 8kPa (PaCO2 normal or low)

40
Q

what characterises type 2 respiratory failure?

A

Pa02 < 8kPa AND PaCO2 >6.5kPa (Pa02 usually low)

41
Q

what are 4 abnormal states associated with hypoxaemia ?

A
  • low V/Q ratio
  • diffusion impairment
  • alveolar hypoventilation
  • Shunt
42
Q

what is commonest cause of hypoxaemia encountered clinically?

A

V/Q mismatch

43
Q

what does hypoxaemia due to low V/Q respond well to?

A

even a small increase in FIO2

44
Q

what do diseases which affect gas diffusion usually not affect?

A

CO2 levels since co2 diffuses 20 times faster than oxygen

45
Q

do shunts respond well or poorly to an increase in FIO2?

A

poorly - no ventilation in shunt so oxygen wont help

46
Q

what is chronic (hypoxic) Cor Pulmonale?

A

RHF in isolation- Hypertrophy of the RV resulting from a disease affecting the function and or structure of the lung, expected when this is due to a disease affecting the left side of the heart

47
Q

what are some features of Cor Pulmonale?

A
  • pulmonary vasoconstriction
  • RV has to work harder
  • RH fails due to hypoxaemia
48
Q

why is there hypertension in cor pulmonale?

A

pulmonary vasoconstriction

49
Q

what else happens in a state of chronic hypoxia such as in COPD?

A

decreased oxygenation of lungs–> chronic hypoxaemia –> bone marrow produces more RBC (polycythaemia)–> increases viscosity of blood –> have to pump thicker blood through thinner vessels

50
Q

who does COPD lead to cor pulmonale?

A

hypoxic alveoli cause pulmonary arterioles to vasoconstrict –> since most alveoli in lung hypoxic, vasoconstriction occurs across entire lung –> increase BP in vasculature –> pulmonary hypertension –> RH has to work harder –> RV hypertrophy –> cor pulmonale