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Systems: Resp. WK > 11. Pathology of Respiratory Tract Infection > Flashcards

11. Pathology of Respiratory Tract Infection Flashcards

1
Q

Are lung infections multifactorial or dependent on a single factor?

A

multifactorial

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2
Q

What is a primary pathogen?

A
  • Organism that causes the disease when it gains entrance to the host’s body and stresses victim’s immune system.
  • “the bad ones”
  • cause an infection in any human they encounter
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3
Q

What is a facultative pathogen?

A
  • seen the most in patients in clinical practice
  • can reproduce either inside or outside host/ cells
  • “need a bit of help”
  • predisposing pulmonary pathology can lead to establishment of facultative organisms
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4
Q

What is an opportunistic pathogen?

A
  • takes advantage of a host with a weakened immune system or disrupted gut flora for example
  • least pathogenic organism
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5
Q

What are the two most important factors that influence the capacity to resist an infection?

A
  1. state of host defence mechanism (patient’s immunity)

2. age of patient

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6
Q

What level of sterility are upper resp. tract and lower resp. tract?

A 
URT= non-sterile 
LRT= sterile
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7
Q

What are 6 very common URT infections?

A
  1. coryza (common cold)
  2. sore throat syndrome
  3. acute laryngotracheobronchitis (croup)
  4. laryngitis
  5. sinusitis
  6. acute epiglottis
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8
Q

What is the main cellular pathology of the URT infections?

A

inflammation (acute or chronic)

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9
Q

What is epiglottis?

A
  • cartilaginous flap which prevents food and liquid from falling into airways
  • stays open to allow easy movement of air but closes during swallowing for protection
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10
Q

Describe features of acute epiglottitis.

A
  • inflammation of epiglottis causing swelling and blockage of airways
  • affects young children often
  • can be severe and life threatening
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11
Q

What 2 types of bacteria cause acute epiglottitis?

A
  • Group A beta-haemolytic streptococci

- haemophilus influenze (type b- Hib)

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12
Q

What are common LRT infections?

A
  1. bronchitis
  2. bronchiolitis
  3. pneumonia
  4. consequences (of another infection)
  5. possible complications (of other infections)
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13
Q

What is the MOST important respiratory tract defence mechanism?

A

macrophage-mucocilliary escalator system

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14
Q

What 3 other respiratory tract defence mechanisms exist?

A
  1. General immune system (humoral and cell mediated immunity)
  2. Respiratory tract secretions (antibacterial components of secretions which contribute to mucociliary system)
  3. Upper respiratory tract acts as a “filter” (nose)
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15
Q

Failure in the 3 respiratory tract defence mechanisms can lead to what?

A

increasing risk for respiratory tract infections as viruses and bacteria are not removed

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16
Q

How does the URT act as a “filter”?

A
  • Nose (component of URT) acts as a filter as when air flows into the nose, the flow is turbulent
  • Surface of resp. tract is lined with mucus, cilia and moisture
  • Particles are deposited in the resp.tract (e.g. nasal hair)
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17
Q

What features of the air are important in the mucociliary escalator system? (2)

A

humidity and temperature

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18
Q

What are the 3 components of macrophage-mucociliary escalator system?

A
  1. alveolar macrophages
  2. mucociliary escalator
  3. cough reflex
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19
Q

Describe the role of cilia in particle clearance of the lungs.

A
  • Cilia beat the mucus in coordinated fashion as escalator moves only up and out of the lung (flowing carpet of mucus)
  • Mucus sweeps any foreign particles away from the resp. tract
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20
Q

Describe the role of alveolar macrophages in in particle clearance of the lungs.

A
  • found in alveoli region
  • phagocytose foreign particles which enter lower resp. tract by clearing up
  • macrophages deposit particles onto the moving mucociliary escalator which removes it via the escalator moving upwards towards URT
  • macrophages enter interstitial pathway via lymph to the lymph nodes to be used again
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21
Q

Where are many foreign particles found in the LRT?

A

deposition on the terminal bronchioles/proximal alveoli

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22
Q

Where is muco-ciliary escalator found?

A

on the conducting airways towards URT (build up at the back of throat that is often swallow is due to particles building up that have been removed from the lungs)

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23
Q

What clearance mechanism is used to keep the LRT sterile?

A

muco-ciliary escalator

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24
Q

What happens if defence mechanism fail?

A

secretions with bacteria and viruses are retained in the lung leading to infection

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25
Q

What happens if a respiratory virus is inhaled?

A
  • virus infects cells to survive and kills the cell which it uses for replication
  • causes damage to respiratory epithelium
  • this leads to abnormal cells with no cilia and sometimes the whole epithelium is stripped
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26
Q

When do bacterial infections often occur in relation to viral infections?

A

Often AFTER viral infections because viruses cause the damage first which makes person more susceptible to bacteria

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27
Q

What are the 3 classifications of pneumonia when approaching the disease?

A
  1. anatomical (radiology, how it looks on imaging)
  2. Aetiological (cause/circumstance, how the disease occured, allows doctors to predict organism)
  3. Microbiological ( appropriate ultimately for treatment, material from patient obtained and sent to microbiology for testing)
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28
Q

What are the 5 aetiological classifications of pneumonia?

A
  1. community acquired pneumonia
  2. hospital acquired (nosocomial) pneumonia
  3. pneumonia in immunocompromised
  4. atypical pneumonia
  5. aspiration pneumonia
  6. recurrent pneumonia
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29
Q

What is meant by community acquired pneumonia?

A
  • Person had little contact with healthcare system

- Most common type

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30
Q

What is meant by hospital acquired pneumonia (nosocomial)?

A
  • contracted in healthcare environment

- more antibiotic organisms exist

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31
Q

What is meant by atypical pneumonia?

A

-unusual agents (bacteria) present

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32
Q

What is meant by pneumonia in immunocompromised?

A

high mortality rates for patients with weak immune systems

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33
Q

What is meant by aspiration pneumonia?

A
  • Entrance of foreign material into bronchial tree; usually oral or gastric contents such as saliva, food, nasal secretions or vomit causing infection
  • acidity of the aspirate can lead to chemical pneumonitis
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34
Q

What is meant by recurring pneumonia?

A
  • patient comes back episode after episode especially in the same place in the lung
  • indicates serious infection that needs attention
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35
Q

What is the most common bacterium to cause pneumonia outside hospitals?

A

Streptococcus pneumoniae (causes half of all pneumonias)

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36
Q

What are 2 bacteria can cause pneumonia?

A
  1. haemophilus influenzae; common in patients with pre-existing lung disease such as chronic bronchitis
  2. staphylococcus aureus; more common in children and intravenous drug users
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37
Q

Can pneumonia be also caused by viruses?

A

Yes, most commonly influenza A virus

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38
Q

What are 3 types of patterns of pneumonia?

A
  1. bronchopneumonia
  2. segmental
  3. lobar
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39
Q

What is bronchopneumonia?

A

More widespread infection in bronchi and bronchioles (widespread lung inflammation)

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40
Q

What is lobar/segmental pneumonia?

A
  • refers to infection of one lobe of the lung
  • lobar and segmental almost the same thing
  • segmental refers to segment of lobe affected
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41
Q

What is hypostatic pneumonia?

A
  • has accumulation of fluid in the lung as they settle in one part of the lung increasing chance of infection
  • common in elderly who remain in one position for long periods
  • failure to drain bronchial secretions or pulmonary oedema from chronic bronchitis or heart failure patients
  • fluid builds up in R.ventricle causing infection as it sits in lower part of lung
  • fluid lies at the bottom ready for infection and doesn’t move
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42
Q

What is aspiration pneumonia?

A
  • develops due to entrance of foreign materials into bronchial tree
  • usually gastric or oral contents; saliva, food, nasal secretions, vomit
  • moves to the LRT causing infection
43
Q

What is obstructive, retention, endogenous lipid pneumonia?

A
  • develops when lipids enter the bronchial tree
  • can be exogenous if oil droplets inhaled
  • can be endogenous if body itself is causing it, when lipid-laden macrophages and giant cells fill the lumen of disconnected airspace
44
Q

What does lobar pneumonia look like on an x ray?

A
  • very cloudy
  • secretions wash microorganisms around lungs and fill anatomical segment until pleura is reached
  • lobes look solid (loss of function)
45
Q

Why might pneumonia not resolve?

A
  • fibrous tissue can form, which is a normal reaction for inflammatory process that will not resolve on its own
  • happens on the inside on the lung
46
Q

What are the main complications of pneumonia? (7)

A
  1. Pleurisy
    - inflammation of lung pleura
  2. Pleural Effusion (fluid)
    - excess fluid accumulating in pleural cavity
  3. Empyema
    - pockets of pus collected in body cavities
  4. Organisation
    - mass lesion
    - COP (cryptogenic organising pneumonia) -BOOP (bronchiolitis obliterans organising pneumonia; alternative name
  5. lung abscess
    - cavity filled with necrotic debris/ fluid caused by infection
  6. bronchiectasis
    - airways become abnormal widened; long term condition leading to build up of mucus and more susceptible to infection
  7. fatal outcome (death)
47
Q

What is an example of organising pneumonia that has 2 names?

A
  1. COP; cryptogenic organising pneumonia

2. BOOP; bronchiolitis obliterans organising pneumonia

48
Q

What happens in a lung abscess?

A

-Formation of cavities filled with necrotic tissue and fluid caused by microbial infection
Leads to destruction of lung tissue
-leads to gathering of pus

49
Q

What can cause a lung abscess?

A
  • obstructed bronchus (tumour)
  • aspiration
  • alcoholism
  • following a lung infection (suppressed immunity)
  • particular organism
50
Q

What 3 organisms commonly cause lung abscesses?

A
  • staph aureus
  • pneumococci
  • klebsiella
51
Q

When are are lung abscesses metastatic?

A

in pyaemia (pus spreads through blood)

52
Q

Which degree of infection is a necrotic lung?

A

2nd degree

53
Q

What is the most common type of pneumonia?

A

staphylococcal pneumonia (biggest killer during influenza pandemics)

54
Q

What is bronchiectasis?

A

Pathological and abnormal widening of bronchi ( widening of airway vessels)

55
Q

What are 4 most common causes of bronchiectasis?

A
  1. severe infective episodes (e.g. childhood infections)
  2. recurrent infections/immunodeficiency (many causes e.g. tumours)
  3. proximal bronchial obstruction
  4. lung parenchymal destruction (part involved in gas transfer) due to connective tissue disease or cilia abnormalities (muco-ciliary escalator failure)
56
Q

What common childhood infective episodes could contribute to bronchiectasis? (4)

A
  • whooping cough
  • TB
  • measles
  • severe pneumonia
57
Q

What percentage of bronchiectasis patients have the condition start in early childhood?

A

75%

58
Q

What are signs of bronchiectasis?

A
  1. cough
  2. abundant purulent foul sputum
  3. haemoptysis
  4. signs of chronic infection
  5. coarse crackles
  6. clubbing
59
Q

What 2 tests should be done for patients with bronchiectasis?

A
  1. bronchography

2. thin section CT (dilated bronchi appear too close to the pleura)

60
Q

What are the common treatment options for bronchiectasis?

A
  1. postural drainage
  2. antibiotics
  3. surgery
61
Q

What causes should be investigated if there is a recurrent local bronchial obstruction? (2)

A
  • tumour?

- foreign body?

62
Q

What cause should be investigated if there is a recurrent local pulmonary damage? (1)

A

bronchiectasis?

63
Q

What cause should be investigated if there is a recurrent generalised lung disease? (3)

A
  • cystic fibrosis?
  • COPD?
  • pneumonia?
64
Q

What cause should be investigated if there is a recurrent non-respiratory disease?

A
  • immunocompromised patient?
  • HIV or other?
  • aspiration?
65
Q

What is the most common place for aspiration pneumonia?

A

right bronchus (obstruction most likely to happen there as it’s more vertical than the left)

66
Q

What are common causes of aspiration pneumonia? (5)

A
  1. vomiting
  2. oesophageal lesion
  3. obstetric anaesthesis
  4. neuromuscular disorders
  5. sedation
67
Q

What opportunistic organisms?

A
  • Organisms not normally capable of producing disease in patients with intact lung defences and only attack patients who are immunocompromised (weak).
  • they take their opportunity to arrack
  • increased chance of ordinary infections
68
Q

What are 4 common opportunistic pathogens?

A
  1. low grade bacterial pathogens
  2. CMV: cytomegalovirus
  3. pneumocystis jirovecii (yeast-like fungus)
  4. other fungi and yeast
69
Q

What 2 types of bulk flow are there?

A
  1. laminar

2. turbulent

70
Q

Where does laminar airflow occur?

A

LRT

71
Q

Where does turbulent air flow occur?

A

URT

72
Q

What occurs BEYOND the terminal bronchiole?

A

diffusion (gas exchange)

73
Q

Where is the blood-air barrier found?

A

in the alveolar walls

74
Q

What does the bulk flow highly depend on?

A

the pressure difference

75
Q

Is Hb 100% saturation of O2 possible?

A

No

76
Q

What is the usual Hb saturation?

A

98% saturated for O2 of only 21% (in the air)

77
Q

Why does CO2 rapidly equilibrate between blood and air?

A

because CO2 is very soluble

78
Q

What are the normal PaO2 parimeters?

A

10.5-13.5 kPa (usually 13.3)

79
Q

What are the normal PaCO2 parimeters?

A

4.8-6 kPa (usually 5.3)

80
Q

What can respiratory failure be defined by?

A

levels of oxygen and carbon dioxide

81
Q

When does Type 1 respiratory failure occur?

A

When PaO2<8kPa (PaCo2 is normal or low)

82
Q

When does Type 2 respiratory failure occur?

A

When PaCO2 >6.5kPa (PaO2 is usually low )

  • hypoxaemia
  • hypercapnia
83
Q

Which type of respiratory failure affects the whole respiratory system?

A

Type 2; as both O2 and CO2 affected, CO2 accumulation that cannot be eliminated by the body

84
Q

What 4 abnormal states are associated with hypoxemia? (low oxygen in blood)

A
  1. ventilation/perfusion imbalance (V/Q)
  2. diffusion impairment
  3. alveolar hypoventilation
  4. shunt
85
Q

What happens to pulmonary vessels during hypoxia? (perfusion>ventilation when alveolar oxygen tension falls)

A
  • pulmonary arteriolar vasoconstriction (all vessels constrict if there is arterial hypoxaemia)
  • protective mechanism
  • it doesn’t send blood to alveoli short of oxygen (it redirects blood to better oxygenated areas; SHUNT)
86
Q

In what disease does ventilation/perfusion abnormality (mismatch) occur?

A

Bronchitis (bronchopneumonia) although some ventilation of abnormal alveoli still occurs (just not enough)

87
Q

When does shunt happen in disease?

A
  • in severe bronchopneumonia
  • lobar pattern with large areas of consolidation
  • occurs when there is ZERO and NO ventilation
88
Q

What is the normal V/Q ratio?

A

~80% (normal breath= 4L and cardaic output= 5L so 4/5)

89
Q

Is low V/Q the commonest cause of hypoxaemia encountered clinically?

A

Yes; low V/Q in some alveoli arises due to local alveolar hypoventilation due to focal disease

90
Q

Doe hypoxaemia due to low V/Q respond well to even small increase in FlO2?(filtered O2)

A

Yes

91
Q

When does pathological shunt occur? In what 3 circumstances? (3)

A
  1. arteriovenous (AV) malformations
  2. congenital heart disease
  3. PULMONARY DISEASE
92
Q

When does shunt occur?

A

Blood passes from right to left side of heart WITHOUT contacting ventilated alveoli as blood is redirected to better ventilated areas

93
Q

Do large shunts respond well to increases in Fl O2?

A

No, large shunts respond poorly (blood leaving normal lung is already 98% saturated)

94
Q

Why does ventilation/perfusion abnormality (mismatch) arise in COPD? (hypoxaemia)

A

due to airway obstruction

95
Q

Why does alveolar hypoventilation arise in COPD? (hypoxaemia)

A

due to reduced respiratory rate

96
Q

Why does diffusion impairment arise in COPD? (hypoxaemia)

A

due to loss of alveolar surface area

97
Q

When does shunt arise in COPD? (hypoxaemia)

A

only during acute exacerbation (worsening of symptoms)

98
Q

What happens during alveolar hypoventilation? (in terms of O2 and CO2)

A
  • insufficient amount of air moved in and out of lungs
  • increases PACO2 and thus increases PaCO2
  • this leads to decrease in PAO2 and thus decrease in PaO2
99
Q

What is falling in PaO2 corrected by?

A

FlO2 (fraction of inspired air which is oxygen)

100
Q

What is hypoxic Cor Pulmonale?

A

Impairment in right ventricular function as a result of a respiratory disease leading to increased resistance to blood flow in pulmonary circulation leading to pulmonary hypertension

101
Q

Why is pulmonary hypertension caused by hypoxic cor pulmonale?

A
  • pulmonary vasoconstriction occurs
  • leads to pulmonary arterioles causing muscle hypertrophy and intimal fibrosis (r. ventricle becomes thicker)
    -loss of capillary bed occurs
  • ## secondary polycythaemia (high conc. of RBCs)
102
Q

What surgical procedure is required for hypoxic cor pulmonale? (which causes pulmonary hypertension)

A

bronchopulmonary arterial anastamoses

103
Q

What is chronic (hypoxic) cor pulmonale?

A

-hypertrophy of the r. ventricle resulting from disease affecting the function and/or structure of the lung

104
Q

What is so unusual about chronic (hypoxic) cor pulmonale?

A

exception is that pulmonary arterations are the result of diseases primarily affecting the left side of the HEART or congenital heart disease

Systems: Resp. WK (40 decks)

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