Pathology of Respiratory Tract Infection

Question 1

What is croup?

Answer 1

Acute Laryngotracheobronchitis - Upper respiratory tract infection

Question 2

What infective agents can cause acute epiglottitis?

Answer 2

Group A beta-haemolytic Streptococci
Haemophilus influenzae

*Rarely caused by Parainfluenza virus type 4 - other viruses may also be responsible

Question 3

List common upper respiratory tract infections

Answer 3

Coryza - common cold
Sore throat syndrome 
Croup
Laryngitis 
Sinusitis 
Acute Epiglottitis

Question 4

List common lower respiratory tract infections

Answer 4

Bronchitis
Bronchiolitis
Pneumonia

Question 5

What structures and systems work as respiratory tract defence mechanisms

Answer 5

Macrophage-mucocilliary escalator system
General immune system (humoral and cellular)
Respiratory tract secretions acting as filters

Question 6

Failure in any of the respiratory tract defence mechanisms results in what?

Answer 6

Increased risk of respiratory tract infections

Question 7

What three components make up the macrophage-mucocilliary escalator system/

Answer 7

Alveolar macrophages
Muscociliary escalator
Cough reflex

Question 8

How does particle clearance from the lungs work in the terminal bronchioles/proximal alveoli?

Answer 8

Clearance by alveolar macrophages phagocytosis

Interstitial pathways via lymph to lymph nodes

Question 9

How does particle clearance from the lungs work in the conducting airways?

Answer 9

Clearance by the mucociliary escalator - expelled by cough or swallow reflexes

Question 10

What are the aetiological types of pneumonia?

Answer 10

Community acquired pneumonia 
Hospital acquired (nosocomial) pneumonia 
Pneumonia in the immunocompromised
Atypical pneumonia 
Aspiration pneumonia 
Recurrent pneumonia

Question 11

What is bronchopneumonia?

Answer 11

Pneumonia arising in the bronchi

Question 12

What is lobar pneumonia?

Answer 12

Pneumonia localised to a lobe of the lung

Question 13

What is meant by the term hypostatic pneumonia?

Answer 13

Refers to pneumonia characterised by collection of fluid in the dorsal regions of the lungs

Question 14

What are the outcomes of pneumonia?

Answer 14

Most resolve
Pleurisy, Pleural effusion and emphysema (puss in pleural cavity)
Organisation
Lung abscess
Bronchiectasis (widened lungs which fill with sputum; characterised by productive cough)

Question 15

Organisation of pneumonia can result in what three outcomes?

Answer 15

Mass lesion
Cryptogenic organising pneumonia (COP)/BOOP
Constrictive bronchiolitis

Question 16

What are the two types of respiratory failure?

Answer 16

Type 1 PaO2 <8kPa

Type 2 PaCO2 >6.5kPa

Question 17

What are the four abnormal states associated with hypoxaemia?

Answer 17

Ventilation/Perfusion mismatch
Diffusion impairment
Alveolar hypoventilation
Shunt

Question 18

What does hypoxaemia lead to?

Answer 18

Pulmonary vascular changes

Question 19

What are the pulmonary vascular changes associated with hypoxaemia?

Answer 19

Physiological pulmonary arteriolar vasoconstriction - pulmonary hypertension - occurs as a result of a fall in oxygen tension

Question 20

What is the most common cause of hypoxaemia clinically?

Answer 20

Vent/Perf mismatch

Question 21

What is the normal V/P value?

Answer 21

.8

Question 22

What is a cause of local low V/P?

Answer 22

Local alveolar hypoventilation due to local disease

Question 23

How is hypoxaemia typically treated?

Answer 23

Responds well to even a small increase in FiO2 (Fraction of inspired oxygen)

Question 24

When does shunt occur in the lungs?

Answer 24

When there is no ventilation of alveoli

Question 25

What is shunt?

Answer 25

Blood passing from right to left side of heart without contacting ventilated alveoli

Question 26

What is the normal percentage of shunt?

Answer 26

2-4%

Question 27

What can be the cause of pathological shunt?

Answer 27

Arteriovenous malformations
Congenital heart disease
Pulmonary disease (Our important one for this topic)