When Things Go Wrong In The Respiratory System

Question 1

What is the primary focus of obstructive respiratory diseases?

Answer 1

Conditions which impede the rate of flow into and out of the lungs.

Question 2

What are the main types of respiratory diseases?

Answer 2

• Obstructive
• Restrictive
• Infection & inflammation

Question 3

What is a key characteristic of obstructive respiratory disease?

Answer 3

Increased airway resistance (due to narrowing of airways)

Outflow pressure reduced (due to loss of elastic recoil in the lungs = can’t exhale as much air)

Question 4

What does reduced compliance in restrictive lung disease indicate?

Answer 4

Decreased lung volume and reduced vital capacity (VC)

Question 5

What is Forced Expiratory Volume in 1 second (FEV1)?

Answer 5

A measure of airway resistance using spirometry.

Question 6

What percentage of vital capacity does FEV1 normally represent?

Answer 6

Approximately 80%.

Question 7

What are the two main diseases classified under Chronic Obstructive Pulmonary Disease (COPD)?

Answer 7

• Chronic bronchitis (narrowing of airways)
• Emphysema (loss of recoil)

Question 8

What is the global impact of COPD as of 2021?

Answer 8

Approximately 3.5 million deaths globally (5% of all global deaths).

4th leading cause of deaths worldwide

Question 9

What is the primary cause of chronic bronchitis?

Answer 9

Due to smoking (80% of time) and environmental irritants

Question 10

How long must chronic bronchitis last to be diagnosed?

Answer 10

At least 3 consecutive months in 2 consecutive years.

Question 11

What are common treatments for chronic bronchitis?

Answer 11

• Stop smoking
• Bronchodilators (opens airways)
• Antibiotics

Question 12

What is the mechanism of damage in emphysema?

Answer 12

• smoking
• neutrophils & macrophages release elastase
• elastase destroys alveolar walls (so poor gas exchange)
• emphysema is developed

Elastase normally inactivated by a1 antitrypsin
Genetic a1 antitrypsin deficiency (in 2% of COPD patients) also causes emphysema as elastase is secreted

Question 13

What is are significant symptoms of emphysema?

Answer 13

Shortness of breath on exertion
Hyperventilation (to remove CO2)
Expanded chest

Question 14

What is the main treatment for asthma?

Answer 14

• Short term = Bronchodilators e.g. salbutamol reliever inhaler (B2 adrenoreceptor antagonists = work against bronchoconstriction)
• Long term = Anti-inflammatories e.g. preventer inhaler (for mild to medium asthma)

Question 15

What are the key causes of asthma?

Answer 15

• Hypersensitivity to allergens
• Air pollution
• Exercise and cold air
• Emotional stress
• Genetics?

Question 16

What is the primary characteristic of restrictive lung disease?

Answer 16

Decreased lung compliance.

Question 17

What is a common cause of intrinsic restrictive lung disease?

Answer 17

Long-term exposure to dust (e.g., pneumoconiosis)
Drugs (e.g. methotrexate)
Rheumatoid arthritis (inflammatory condition)
ARDS & IRDS
Or may be idiopathic (no cause, just develops)

Question 18

What is the effect of fibrosis on lung compliance?

Answer 18

It causes a decrease in lung compliance.

Question 19

What are upper respiratory tract infections commonly caused by?

Answer 19

Minor infections such as the common cold.

Question 20

What bacterium is commonly responsible for pneumonia?

Answer 20

• Streptococcus pneumoniae
• Staphylococcus aureus
• Klebsiella pneumoniae

Question 21

What is tuberculosis caused by?

Answer 21

Inhalation of Mycobacterium tuberculosis.

Highly contagious

Question 22

What are the two phases of tuberculosis?

Answer 22

• Latent - asymptomatic, non-infectious, granuloma in lung tissue
• Active - spreads to bronchioles and circulation = becomes contagious

Question 23

What is the primary target of the COVID-19 virus?

Answer 23

Lung epithelial cells.

Question 24

What receptor does SARS-CoV-2 bind to for infection?

Answer 24

Angiotensin-converting enzyme 2 (ACE2) receptor.

Question 25

What is the significance of the Omicron variant of COVID-19?

Answer 25

It represented over 98% of sequenced samples as of February 2022.

Question 26

What is a common misconception about COVID-19 vaccines?

Answer 26

Vaccines are only for high-risk groups.

Question 27

What is the average number of upper respiratory tract infections an adult experiences per year?

Answer 27

2-4 URTI/year.

Question 28

What is COPD characterised by?

Answer 28

- Narrowing of airways —> increases airway resistance - Elastic recoil of lungs is lost —> reduced outflow pressure - Thus decreased FEV1 - Increased residual volume (RV) —> appearance of chest over-inflation (due to retention of air)

Question 29

What causes bronchitis?

Answer 29

Inflammation of the bronchi - mucus hypersecretion

Question 30

What causes acute bronchitis?

Answer 30

Bacteria/ virus Lasts days/ weeks

Question 31

What happens in chronic bronchitis?

Answer 31

- irritants cause inflammation in bronchi - abnormal mucus secretion (causes inflammation) - plugs airways - prone to infection - further inflammation

Question 32

What are symptoms of chronic bronchitis?

Answer 32

- airway obstruction - shortness of breath / wheezing (due to obstruction) - chest pain, chronic cough (in attempt to clear airway of mucus)

Question 33

What happens to compliance in emphysema?

Answer 33

Significantly above normal SO Increased residual volume (RV) —> increased functional residual capacity (FRC) = chronically **over-inflated** lung

Question 34

What causes emphysema?

Answer 34

20% of smokers develop COPD Lifelong smokers Loss of alveoli is permanent and irreversible Treatment: - stop smoking - supplement O2 - lung transplant - enzyme supplements in a1 antitrypsin deficiency

Question 35

What are the symptoms of asthma?

Answer 35

- Bronchconstriction - Oedema of airway mucosa - Mucus secretion All these increase airway resistance

Question 36

What is the mechanism of asthma?

Answer 36

- Mast cell activation - Histamine (causes allergic response) and cytokine (causes inflammation) release - Oedema, mucus, smooth muscle contraction = bronchoconstriction

Question 37

What is extrinsic cause of restrictive lung disease?

Answer 37

Non-muscular disease of upper thorax

Question 38

What is fibrosis in restrictive lung disease?

Answer 38

Fibrosis is development of excess connective tissue - Alveoli are replaced by fibrotic tissue = harden & become stiffer - Decreased lung compliance - Irreversible decrease in oxygen diffusion capacity

Question 39

What causes fibrosis?

Answer 39

- Inhaled environmental and occupational pollutants - Cigarette smoke - Autoimmune disease No effective treatments for fibrosis

Question 40

What are respiratory tract infections caused by?

Answer 40

**Upper respiratory tract infections** - common but minor - average adult has 2-4 URTI/year **Lower respiratory tract infections** - less common but serious - e.g. bronchitis, pneumonia, tuberculosis…

Question 41

How does pneumonia affect the lungs?

Answer 41

- Affects bronchi and alveoli - Inflammatory exudate (liquid) fills alveoli - Leads to ‘consolidation’ - Lung tissues become firm and airless

Question 42

Describe the mechanism of tuberculosis

Answer 42

- Replicate in alveolar macrophage - This is know as Ghon focus = site of primary infection (latent phase) - Initial infection has ineffective immune response - Bacteria moved to lymph nodes so can spread to the body - Collagen deposited around bacteria = can break down lung structure - Lymph nodes erode releasing bacteria into: bronchioles or blood vessels - Destruction of alveoli Treatment of tuberculosis is difficult due to antibiotic resistance