Pathology of Pulmonary Infection

Question 1

Name some common upper respiratory tract infections

Answer 1

• common cold
• laryngitis
• sinusitis
• acute epiglottitis

Question 2

What agents may cause acute epiglottitis

Answer 2

• group A beta-haemolytic strep

- haemophilus influenzae

Question 3

Name some examples of common lower respiratory tract infections

Answer 3

• bronchitis
• bronchiolitis
• pneumonia

Question 4

Give ways in which the respiratory tract defends against infection

Answer 4

• general immune system
• secretions
• filtering air with complex shape, large surface area and turbulent air flow
• macrophage-mucociliary escalator system

Question 5

Name the three constituents of the macrophage-mucociliary escalator system

Answer 5

• alveolar macrophages
• mucociliary escalator
• cough reflex
• warmed/humidified air in upper tract

Question 6

What two ways can macrophages go along the escalator system

Answer 6

• up to trachea and into mouth

- pass through wall and into lymph system

Question 7

How can the escalator system be damaged and what effect can this have

Answer 7

viral infections can give rise to abnormal, non-functional epithelium or can progress to the complete destruction if bronchial epithelium

bacterial infections can now thrive due to the loss of the escalator system

Question 8

In what three ways can pneumonia be classified

Answer 8

• anatomical
• aetiological
• microbiological

Question 9

What ways can pneumonia be classified in an aetiological sense

Answer 9

• community acquired
• hospital acquired
• immunocompromisation
• atypical pneumonia (unusual agents)
• aspiration pneumonia
• recurrent pneumonia

Question 10

Name two types of pneumonia

Answer 10

• bronchopneumonia

- lobar pneumonia

Question 11

Describe the pathology of bronchopneumonia

Answer 11

• infection takes hold and causes patches of acute inflammation
• pun/neutrophils/inflammatory exudate
• often as a result of bronchitis
• uninvolved pleura (due to patchy nature)
• where laminar flow becomes gaseous diffusion, depositing pathogens
• fluid at the base of the lung due to gravity

Question 12

Describe the pathology of lobar pneumonia

Answer 12

• same process as bronchopneumonia, only a more invasive organism
• increased bodily response created more fluid which washes the organisms throughout a whole lobe
• lobe becomes solid and airless

Question 13

Give some outcomes/complications of pneumonia

Answer 13

• may resolve
• pleurisy/pleural effusion/empyema
• organisation into fibrous tissue (COP/BOOP)
• lung abscess
• bronchiectasis

Question 14

How may a lung abscess arise

Answer 14

• will be distal to a bronchial tumour
• stomach acid from aspiration
• necrosis caused by certain organisms
• movement of pus from pyaemia
• from a secondary infection

Question 15

What is bronchiectasis

Answer 15

abnormal dilatation of the bronchi

Question 16

What may cause bronchiectasis

Answer 16

• severe infection
• recurrent infections
• proximal bronchial obstruction (e.g. tumour)
• lung tissue destruction

Question 17

What are the main clinical symptoms of bronchiectasis

Answer 17

• cough
• abundant/foul/purulent sputum
• haemoptysis (coughing up blood)
• coarse crackling sounds
• clubbing

Question 18

How may bronchiectasis be managed

Answer 18

• thin section CT

- drainage/antibiotics/surgery

Question 19

What may cause a recurrent lung infection

Answer 19

• bronchial obstruction (e.g. tumour, foreign body)
• local lung tissue damage (e.g. bronchiectasis)
• generalised lung disease (e.g. CF, COPD)
• non-respiratory disease (e.g. HIV/AIDS

Question 20

What is type 1 respiratory failure

Answer 20

PaO2 is less than 8kPa, leading to hypoxaemia

Question 21

What is type 2 respiratory failure

Answer 21

PaCO2 is more than 6.5kPa

Question 22

Why may PaCO2 levels in type 1 respiratory failure be normal

Answer 22

functioning bits of lung may compensate for the parts that have failed

Question 23

Give four mechanisms of hypoxaemia

Answer 23

• ventilation/perfusion imbalance
• diffusion impairment
• alveolar hypoventilation
• shunt

Question 24

What happens to pulmonary blood vessels in hypoxia

Answer 24

pulmonary arterial vasoconstriction - don’t send blood to alveoli that are short of oxygen!

Question 25

Why is hypoxaemia a symptom of bronchopneumonia

Answer 25

• narrowing of airways causes a ventilation/perfusion imbalance where there is limited ventilation
• damaged alveoli cause shunt, and an increase in severity means the body cannot accommodate

Question 26

Why is hypoxaemia a symptom of lobar pneumonia

Answer 26

• areas of fibrosis mean there is no ventilation of certain areas of lung
• no venous blood is oxygenated
• cannot be improved with increased FlO2

Question 27

Why is hypoxaemia a symptom of COPD

Answer 27

• V/Q mismatch due to obstruction
• alveolar hypoventilation due to decreased respiratory drive
• shunt during acute exacerbation (infection)

Question 28

Why does alveolar hypoventilation occur in COPD

Answer 28

• insufficient air moved in/out of lungs leads to decreased repiratory drive as the body becomes accustomed to high levels of CO2
• increased PA/aCO2 causes decreased PA/aCO2, giving rise to the hypoxia

Question 29

What is hypoxic cor pulmonale

Answer 29

failure of the right side of the heart

Question 30

How does hypoxic cor pulmonale arise

Answer 30

pulmonary vasoconstriction in hypoxia causes pulmonary hypertension as the right ventricle has to work harder to pump oxygen

Question 31

What is secondary polycythaemia in relation to hypoxic cor pulmonale

Answer 31

• increased levels of RBCs that cause blood viscosity to be more that 55%
• the bone marrow’s reaction to hypoxaemia, putting further load on the right ventricle of the heart