Pathology of Respiratory Tract Infections

Question 1

Define the common organisms causing upper respiratory tract infection

Answer 1

• Bacteria e.g. Strep. pyogenes

- Viruses e.g. rhinovirus, adenovirus, parainfluenza, influenza, EB virus

Question 2

Define the mechanisms of defence in the respiratory system

Answer 2

• Macrophage-mucociliary escalator system: alveolar macrophages, muco-ciliary escalator, cough reflex
• General immune system: humoral and cellular

Question 3

Describe the pathogenesis of bronchopneumonia

Answer 3

• Often basal patchy opacification (scans)
• Relates to focal nature of consolidation (stays around bronchioles and select area of alveoli)
• Often facultative pathogens

Question 4

Describe the pathogenesis of lobar pneumonia

Answer 4

• Often unilateral
• One lobe may be completely airless, instead filled with inflammatory secretions
• Often primary pathogens

Question 5

Define bronchiectasis

Answer 5

Mucociliary clearance dysfunction (genetics) –> increased bacterial colonisation –> neutrophil recruitment –> inflammation –> recurrent damage to airways

Question 6

Define lung abscess

Answer 6

• Localised infection within the lung
• Staph. aureus, some Pneumococci, Klebsiella
• Aspiration more likely
• Metastatic in pyaemia

Question 7

Describe the complications and consequences of lower respiratory tract infection

Answer 7

• Pleurisy, pleural effusion, empyema
• Organisation: mass lesion, COP, constrictive bronchiolitis
• Lung abscess
• Bronchiectasis
• Death

Question 8

Describe the clinical features of bronchiectasis

Answer 8

• Cough
• Abundant purulent foul sputum
• Haemoptysis
• Signs of chronic infection
• Coarse crackles
• Clubbing

Question 9

Describe the clinical features of acute bronchitis

Answer 9

Symptoms;

• Sore throat
• Headache
• Runny/blocked nose
• Aches and paints
• Fatigue

Question 10

Describe the clinical features of pneumonia

Answer 10

Symptoms;

• Fever/rigors
• Malaise
• Dysponoea
• Cough
• Purulent sputum
• Haemoptysis
• Pleuritic pain

Signs;

• Pyrexia
• Cyanosis
• Confusion
• Tachypnoea
• Tachycardia
• Pleural rub
• Signs of consolidation
• Pleural rub

Question 11

Understand the physiological changes to pulmonary gas exchange in respiratory tract infections

Answer 11

Normal PaO2 = 10.5-13.5kPa
Normal PaCO2 = 4.8-6.0kPa

Type I;
PaO2 <8kPa (low)
PaCO2 normal/low

Type II;
PaO2 <8kPa (low)
PaCO2 >6.0kPa (high)

Question 12

Name the four abnormal states associated with hypoxaemia

Answer 12

• V/Q mismatch
• Diffusion impairment
• (Global) alveolar hypoventilation
• Shunt