Pathology of Respiratory Tract Infections

Question 1

What are different kinds of microorganisms in terms of pathogenecity?

Answer 1

Primary, Facultative, and Opportunistic

Question 2

What are primary microorganisms?

Answer 2

Can establish an infection in almost anyone

Question 3

What are facultative microorganisms?

Answer 3

Requires defences to be reduced a little bit to cause disease

Question 4

What are opportunistic microorganisms?

Answer 4

Not very infectious, do not have pathogenic properties to invade human tissue, but if defences are dropped then they can cause a clinically evident infection

Question 5

What does the ability to resist infection depend on?

Answer 5

• State of the host defence mechanism

- Age of patient

Question 6

What are some upper respiratory tract infections?

Answer 6

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

Question 7

What is acute epiglottitiis commonly caused by?

Answer 7

• Group A beta haemolytic streptococci

- Haemophilus influenza

Question 8

Who seems to be most prone to acute epiglottitis?

Answer 8

Young Children

Question 9

What are some examples of lower respiratory tract infections?

Answer 9

Bronchitis
Bronchiolitis
Pneumonia

Question 10

What is pneumonia?

Answer 10

Acute inflammatory process in the alveoli

Question 11

What are some respiratory tract defence mechanisms?

Answer 11

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

Question 12

What is the macrophage-mucociliary escalator system composed of?

Answer 12

• Alveolar macrophages
• Mucociliary Escalator
• Cough Reflex

Question 13

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

Answer 13

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

Question 14

How are particles cleared from the lungs?

Answer 14

Macrophage-mucociliary escalator:

1) Macrophages clear particles by phagocytosis
2) Leave via the mucociliary escalator or through lymph

Question 15

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

Answer 15

Local bronchial obstruction (tumour, foreign body)?

Local pulmonary damage (bronchiectasis)?

Generalised lung disease (cystic fibrosis, COPD)?

Non-respiratory disease (immunocompromised, aspiration)?

Question 16

What are opportunistic infections?

Answer 16

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

Question 17

What are some examples of opportunistic pathogens?

Answer 17

Low grade bacterial pathogens

Cytomegalovirus (CMV)

Pneumocystis jirovecii

Other fungi and yeasts

Question 18

2 types of airflow are

Answer 18

laminar or turbulent

Question 19

What is laminar flow?

Answer 19

Ordered flow

Question 20

What is turbulent flow?

Answer 20

Random or chaotic flow

Question 21

What does bulk flow depend on?

Answer 21

Pressure difference

Question 22

What occurs beyond the terminal bronchiole?

Answer 22

Diffusion

Question 23

What barrier is present in the alveoli?

Answer 23

Blood-air barrier

Question 24

What are 4 abnormal states associated with hypoxemia?

Answer 24

Ventilation/perfusion imbalance (V/Q)

Diffusion impairment

Alveolar hypoventilation

Shunt

Question 25

What is hypoxaemia?

Answer 25

Low levels of oxygen in the blood

Question 26

What happens when alveolar oxygen tension falls?

Answer 26

Pulmonary arteriolar vasoconstriction occurs so blood is not sent to alveoli short of oxygen

Question 27

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

Answer 27

Local alveolar hypoventilation due to some disease

Question 28

What do we need to consider in recurrent lung disease?

Answer 28

Why the defences are failing