Asthma, COPD, bronchiolitis

Question 1

Define asthma

Answer 1

Potential life threatening chronic respiratory disease if it is not well managed. Causes airway obstruction, bronchial hyperresponsiveness, airway inflammation, airway remodelling (hypertrophy of mucus gland, build up of scar tissue)

Question 2

What are the 2 types of asthma ?

Answer 2

Extrinsic (atopic) - consequence of hypersensitive reactions associated with allergy ie pollen. Genetic predisposition for development of immunoglobin E - mediated response to common allergens.

Intrinsic (non atopic) - airway inflammation caused by infection, sudden exposure to cold, stress, smoking, NSAIDS

Question 3

What are the main characteristics of asthma ?

Answer 3

Airflow limitation.
Airway hyperresponsiveness to stimuli or trigger factors → bronchospasm and contraction of the smooth muscle in the wall of the bronchi → narrowing of the airway and obstruction to breathing
Chronic inflammation → increased mucous production, swelling

Question 4

Describe characteristics of chronic asthma

Answer 4

Chronic bronchoconstriction of the airway
Chronic bronchospasm of smooth muscle
Chronic production of mucous
↓
Chronic obstruction of air passage through the airways

Question 5

What role do eosinophils play in asthma ?

Answer 5

release of harmful proteins and reactive oxygen species which damage the lining of the airways

Question 6

Describe the pathophysiology of asthma

Answer 6

T-helper cells stimulated by allergen - atopic asthma
Stimulate cytokines and interleukin (inflammatory mediators)
This simulates B-cell response result in IgE antibody production
IgE antibodies bind with mast cells which are found in the airway resulting in inflammatory airway symptoms

Question 7

Explain asthma exacerbation

Answer 7

Repeated exposure to allergen
Further release of IgE antibodies with mast cells
Release large amounts of histamine
Results in significant/worsening bronchospasm, bronchoconstriction and mucous production
Further worsened by the release of prostaglandins, leukotrienes, and cytokines
These stimulate the parasympathetic nervous system which causes smooth muscle contraction, further narrowing the airway

Question 8

What is the pathophysiology of the characteristics of asthma ?

Answer 8

Airway swelling due to inflammation and fluid exudates – oedema
Increased mucous secretion → mucous plugs
Wheezing, cough, tight chest, breathlessness - Impaired gas exchanged – hypoxaemia, hypercapnia, acidosis (low blood pH) – stimulation of peripheral and central chemoreceptors leading to increase in respiratory rate and pulse

Question 9

Define COPD

Answer 9

Chronic and recurrent obstruction of airflow in the pulmonary airways
Airflow obstruction usually is progressive and is accompanied by inflammatory responses to noxious particles and gases

Question 10

What are the most common causes of COPD ?

Answer 10

Smoking, biomass fuel exposure, air pollution

Question 11

What are risk factors for COPD ?

Answer 11

Genetic abnormalities (deficiency of antitrypsin)., abnormal lung development, accelerated aging, asthma and airway hyperresponsiveness

Question 12

What are the 2 types of COPD ?

Answer 12

Emphysema and chronic bronchitis

Question 13

Explain pathophysiology of emphysema

Answer 13

Chemical irritation of the alveoli walls (e.g.: smoking) causes damage to epithelial cells
Causes inflammatory and immune responses causing the alveolar walls to break down
Enlargement of airspaces in the bronchioles = decreased surface area for gas exchange
Loss of surfactant from walls also worsens effective gas exchange.

Question 14

Explain pathophysiology of chronic bronchitis COPD

Answer 14

Damage to bronchus and bronchioles commonly caused by smoking. Cellular damage = inflammation = swelling and exudate:
Bronchoconstriction – limits airflow to lungs
Bronchospasm – limits airflow to lungs
Hypertrophy of goblet cells – increased mucous production and mucous plugs – limits airflow to lungs
↓
significant coughing, sputum production

Question 15

What are the consequences of COPD ?

Answer 15

Destruction of alveoli wall leads to loss of elasticity of lung movement = easy to breathe in; but hard to breathe out

Enlarged alveoli spaces = air becomes ‘trapped’ resulting in hyperinflation – air remains within the lungs and isn’t breathed out

Hypoxaemia – low arterial oxygen levels - some patients can maintain normal oxygen levels by increasing respiratory effort

Hypercapnia - increased carbon dioxide levels - some patient’s - small percentage; in normal physiology carbon dioxide levels control our breathing; as disease progresses, patients with hypercapnia may loose sensitivity to carbon dioxide levels controlling breathing – hypoxic drive

Question 16

What are the 2 types of acute respiratory failure ?

Answer 16

Type 1 hypoxaemic respiratory failure - failure of respiration (gas exchange function of the lung) leading to hypoxaemia with normal or low carbon dioxide levels

Type 2 hypercapnic/hypoxaemic respiratory failure – failure of ventilation leading to hypercapnia and hypoxaemia

Question 17

What are the causes of ARF ?

Answer 17

Disorders of neuromuscular system Dysfunction of central nervous system
Disorders affecting chest wall and diaphragm
Airway abnormality
Pulmonary parenchymal diseases

Question 18

What are the causes of RF in children ?

Answer 18

Upper airway obstruction (croup, tonsillitis)
Lower airway obstruction (asthma, bronch)
CNS fails to control ventilation
Mechanical impairment of ventilation
Failure to oxygenate tissues (hypovolaemia, septic shock, cardiac, metabolic disorders, intoxication)

Question 19

What are the signs of hypoxaemia and hypercapnia ?

Answer 19

Hypox - cyanosis, confusion, fatigue, anxiety
Hyper - tachypnoea, headache, sweating

Question 20

Signs of respiratory distress in children

Answer 20

Recession, nasal flaring, cyanosis, high HR and BP, tachypnoea. Normal artieral blood gas due to increasing respiratory efforts

Question 21

What are the pre terminal signs of ARF ?

Answer 21

bradycardia, central cyanosis, oxygen <85% in air

Question 22

What are physiological reasons for increased risk of respiratory compromise in children ?

Answer 22

Low lung volume, high metabolism, risk for apnoea, low efficiency of respiratory muscles

Question 23

Define bronchiolitis

Answer 23

Constriction and blockage of the small airways due to the inflammatory response caused by the viral infection. Symptoms worsen 2-3 days after diagnosis

Question 24

Explain the pathophysiology of bronchiolitis

Answer 24

Stimulation of mucous secreting goblet cells – increased mucous production
Excess airway mucous triggers cough reflex
Upper airway mucosal inflammation that leads to cytokine release and mild fever
Airway narrowing causes audible turbulent airflow and a wheeze can be heard on auscultation
Excess mucous in alveoli leads to collapsing alveolar walls and increased intra-alveolar pressure causes inspiratory crackles on auscultation

Question 25

Which patients does bronchiolitis usually occur in ? Who is most at risk ?

Answer 25

Under 2 years old, preterm, under 3 months, CHD, immunodeficiency, chronic lung disease, neurological disorders, tobacco smoke exposure