Pathology of Respiratory Tract Infections Flashcards

1
Q

What are different kinds of microorganisms in terms of pathogenicity?

A

Primary
Facultative
Opportunistic

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2
Q

What three factors affect the affect likelihood of a lung infection?

A
  • microorganism pathogenicity
  • capacity to resist infection
  • population risk
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3
Q

What is a primary microorganism?

A

a microogranism able to infect anyone

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4
Q

What is a fucultative microorganism?

A

a microorganism that needs a little ‘help’ when infecting a host eg. the host is less able to resist infection.

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5
Q

What is an opportunistic microorgansim?

A

a microorganism that can’t infect a host unless the hosts capacity to resist infection is very compromised.

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6
Q

What two factors affect a patient’s capacity to resist infection?

A
  • state of defence mechanisms

- age of patient

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7
Q

What are some upper respiratory tract infections?

6 points

A
Coryza (common cold)
Sore throat syndrome
Acute laryngotracheobronchitis (coup)
Laryngitis
Sinusitis
Acute epiglottitis
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8
Q

What is acute epiglottis commonly caused by?

A

Group A beta-haemolytic Streptococci

Haemophilus influenza

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9
Q

When is acute epiglottiitis a problem?

A
  • children
  • trachea is smaller
  • inflammation of the epiglottis may cause the airway obstruction.
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10
Q

What are some examples of lower respiratory tract infections?

(3 points)

A

bronchitis
bronchiolitis
pneumonia

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11
Q

Outline some respiratory tract defence mechanisms?

4 points

A
  • Macrophage-mucociliary escalator system
  • General immune system
  • Respiratory secretions
  • Upper respiratory tract as a filter
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12
Q

What is the macrophage-mucociliary escalator system composed of?

(3 points)

A
  • Alveolar macrophages
  • Mucociliary escalator
  • Cough reflex
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13
Q

How are particles and microorganisms removed from the terminal bronchioles and proximal alveoli?

A

Macrophages phagocytose particles and pathogens then transport to lymph nodes via lymph

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14
Q

Where does the mucociliary escalator begin?

A

Respiratory bronchioles

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15
Q

How does the upper respiratory tract help to prevent the lower respiratory tract from becoming infected?

A

Warms and humidifies air, supplying a large surface area where material in the air may be deposited so it does not reach the lower respiratory tract.

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16
Q

How are particles cleared from the lungs?

A

Macrophage-mucociliary escalator:

1) Macrophages clear particles by phagocytosis
2) Leave via the muco-ciliary escalator or through lymph.

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17
Q

How can the influenza virus cause bacterial lung infections ?

A
  • influenza virus is cytopathic
  • destroys the cells of the mucociliary escalator
  • defence mechanism to bacteria is compromised
  • secondary infection is much more likely
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18
Q

How can pneumonia be classified?

3 points

A
  • Anatomical (understand radiology)
  • Aetiological (how acquired, circumstances)
  • Microbiology (tells us how to treat the patient)
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19
Q

What are the further aetiological classifications of pneumonia?

(6 points)

A
  • Community acquired
  • Hospital acquired (nosocomial)
  • Pneumonia in the immunocompromised (e.g. HIV)
  • Atypical pneumonia (caused by unusual organism)
  • Aspiration pneumonia
  • Recurrent pneumonia
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20
Q

What are some different patterns of pneumonia?

6 points

A
  • Bronchopneumonia
  • Segmental
  • Lobar
  • Hypostatic (elderly)
  • Aspiration
  • Obstructive, retention, endogenous lipid
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21
Q

What is hypostatic pneumonia?

A
  • usually occurs in elderly people with cardiac failure
  • extra secretions in the lung, oedema in the lung or suppressed cough reflex.
  • All these thing leads to accumulation of fluid in the lung which acts as a ‘petri dish’ for bacteria.
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22
Q

What is bronchopneumonia?

A
  • acute inflammation
  • very local areas of the lung,
  • Pus from polymorphs replaces air, this is called local consolidation.
  • Accumulation of neutrophils in alveolar space
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23
Q

What is local consolidation?

A

The building of pus in certain localise areas in the lung during a pneumonia infection.

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24
Q

What are infections from hospital more likely to be?

A

Resistant to antibiotics

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25
Q

What is bronchopneumonia characterised by?

A
  • Spots of infection stay around alveoli
  • Rare for infection to reach the pleura
  • Basal parts of the lungs infected
  • bilateral
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26
Q

What does bronchopneumonia look like on an x-ray?

A
  • often bilateral
  • basal site of lung
  • patchy opacification
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27
Q

Where is bronchopneumonia most likely to be found in the lungs?

A

Base

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28
Q

Is pleural effusion likely in bronchopneumonia?

A

No.

The infection is isolated in specific areas and so won’t spread to the pleura.

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29
Q

What is lobar pneumonia characterised by?

A
  • Large amount of lung infected by the same inflammatory process.
  • Could be an entire lobe.
  • Meaning the whole part is airless due to being filled with pus.
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30
Q

What causes lobar pneumonia?

A

Caused by a primary pathogen, infects a whole lobe as the body’s response to the pathogen is vigorous.

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31
Q

What does lobar pneumonia look like on an xray?

A

Complete opacification of one lobe only.

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32
Q

How does segmental and lobar pneumonia differ from bronchopneuonia?

A

Segmental and lobar are at a single site whereas broncho is multi-locational.

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33
Q

What kind of pneumonia could lead to a pleural infection?

A

Lobar, pleural infections are rare with bronchopneumonia as the infection does not reach the pleura.

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34
Q

What are possible outcomes of pneumonia?

5 points

A
  • Most resolve
  • Pleurisy, pleural effusion, empyema
  • Organisation
  • Lung abscess
  • Bronchiectasis
35
Q

What are the complications of pneumonia caused by organisation?

(3 points)

A
  • Mass lesion
  • Cryptogenic organising pneumonia (COP)
  • Constructive bronchiolitis
36
Q

What are the complications of pneumonia that affect the pleura?

(3 points)

A
  • pleurisy (inflammation of pleura)
  • pleural effusion (extra fluid in pleural space)
  • pleural empyema (pus in pleural space)
37
Q

What are some complications/ outcomes of pneumonia?

4 points

A
  • conditions of the pleura
  • problems with organisation
  • lung abscess
  • bronchiectasis
38
Q

What is COP?

A

Cryptogenic organising pneumonia

Its an inflammation of the bronchioles, not actually an infection though.

39
Q

Which organisms cause lung abscesses?

3 points

A
  • Staph aureus
  • some pneumococci
  • klebsiella
40
Q

What is metastatic in pyaemia?

A

Pus travels in the blood to the lung causing an abscess.

41
Q

What could pneumonia lead to instead of resolution? (2)

A
  • Fibrosis

- Abscess (infected area dies which creates a hole in the lung).

42
Q

What can the outcome of pneumonia mimic?

A

Can result in a lump which mimics cancer, only to realise it is not cancer once it has been removed.

43
Q

What is a lung abscess?

A

Necrosis of the lung (2nd degree infection) and formation of a cavity.

44
Q

What can a lung abscess lead to?

A

Blood poisoning (pyaemia)

45
Q

What is pyaemia?

A

A type of septicaemia that leads to widespread abscesses (blood poisoning). Pus-bacteria spread in the blood.

46
Q

What is bronchiectasis?

A

Pathological dilatation of bronchi.

47
Q

What are the causes of bronchiectasis? (4)

A
  • Severe Infective Episode
  • Recurrent Infections - many causes
  • Proximal Bronchial Obstruction
  • Lung Parenchymal Destruction
48
Q

What are the causes of recurrent lung infection? i.e. when are the defences constantly failing?

(4 points)

A
  • Local Bronchial Obstruction eg. Tumour, Foreign body
  • Local Pulmonary Damage eg. Bronchiectasis
  • Generalised Lung Disease eg. Cystic Fibrosis, COPD
  • Non-Respiratory Disease eg. Immunocompromised (HIV, other), Aspiration
49
Q

What are symptoms of bronchiectasis?

6 points

A
  • Cough
  • Abundant purulent foul sputum
  • Haemoptysis
  • Signs of chronic infection
  • Coarse crackle
  • Clubbing
50
Q

What is bronchiectasis diagnosed by?

A

Thin section, CT

51
Q

What is the treatment of bronchiectasis? (3)

A
  • Postural drainage
  • Antibiotics (amoxicillin, flucloxacillin, trimethoprim)
  • Surgery
52
Q

Is bronchiectasis usually localised or widespread?

A

Widespread

53
Q

When can bronchiectasis be removed surgically?

A

When it is localised

54
Q

What can we ask when considering why the defences are failing in recurrent infection?

(4 points)

A
  • Local bronchial obstruction (tumour, foreign body)
  • Local pulmonary damage (bronchiectasis)
  • Generalised lung disease (cystic fibrosis, COPD)
  • Non-respiratory disease (immunocompromised, aspiration)
55
Q

What may aspiration pneumonia be due to? (5)

A
  • Vomiting
  • Oesophageal lesion
  • Obstetic anaesthesia
  • Neuromuscular disorders
  • Sedation
56
Q

What are opportunistic infections?

A

Infections by organisms not normally capable of producing disease in patients with intact lung defences.

57
Q

What are some examples of opportunistic pathogens?

4 points

A
  • Low grade bacterial pathogens
  • Cytomegalovirus (CMV)
  • Pneumocystis jirovecii
  • Other fungi and yeasts
58
Q

What are two ways to describe bulk air flow?

A

Laminar - ordered/smooth

Turbulent - chaotic/random

59
Q

What does bulk flow depend on?

A

Pressure difference

60
Q

What occurs beyond the terminal bronchiole?

A

Diffusion

61
Q

What barrier is present in the alveoli?

A

Blood-air barrier

62
Q

What is the normal PaO2 value?

A

10.5 - 13.5 kPa

63
Q

What is the normal PaCO2 value?

A

4.8 - 6 kPa

64
Q

What defines Type I respiratory failure?

A

Low oxygen levels.

PaO2 <8 kPa (PaCO2 normal or low)

65
Q

What defines Type II respiratory failure?

A

High carbon dioxide levels.

PaCO2 >6.5 kPa (PaO2 usually low)

66
Q

The four abnormal states associated with HYPOXAEMIA are…

A
  • Ventilation / Perfusion imbalance - V/Q
  • Diffusion impairment
  • Alveolar Hypoventilation
  • Shunt
67
Q

What happens when alveolar oxygen tension falls?

A
  • Hypoxic pulmonary vasoconstriction (HPV) occurs so blood is not sent to alveoli short of oxygen.
68
Q

What happens if there is arterial hypoxaemia?

A

All vessels constrict

69
Q

What is the size of a normal breath?

A

4L/min

70
Q

What is the normal cardiac output?

A

5L/min

71
Q

What is the normal ventilation/perfusion (V/Q) value?

A

0.8

72
Q

What is the commonest cause of hypoxaemia?

A

Low V/Q

reduced ventilation

73
Q

What does a low V/Q in some alveoli arise due to?

A

Local alveolar hypoventilation due to some disease.

74
Q

What is shunt?

A

Blood passes from right to left side of the heart without contacting ventilated alveoli.

75
Q

How do large shunts respond to increases in FIO2?

Why?

A

Poorly

The blood leaving the lung is already 98% saturated (no level of oxygen can oxygenate the blood because it cannot be passed onto the blood).

76
Q

What is FIO2?

A

The fraction of inspired air which is oxygen.

77
Q

What is the normal value of FIO2?

A

0.21

78
Q

When might hypoxaemia be a consequence to pneumonia? (2)

A
  • ventilation/perfusion mismatch
    (there may be some ventilation of abnormal alveoli, just not enough)
  • bronchitis/bronchopneumonia
79
Q

Hypoxaemia due to low V/Q responds well to _______ FIO2.

A

even small increases in

80
Q

What are reasons for hypoxaemia in COPD?

A
  • airway onstruction (poor V)
  • reduced resp. drive
  • loss of alveolar surface area
81
Q

Alveolar hypoventilation increases __CO2 and thus increases ____.

A

PA

PaCO2

82
Q

Alveolar hypoventilation increase in PACO2, decreases ___O2, which causes _____ to fall

A

PA

PaO2

83
Q

Fall in PaO2 due to hypoventilation is corrected by ________.

A

raising FIO2.

84
Q

Chronic hypoxic cor pulmonale is…

A
  • RV hypertrophy

- due to chronic HPV, loss of capillary bed, secondary polycythaemia