Asthma

Question 1

Why are children with asthma more susceptible to respiratory failure?

Answer 1

• They have lower acquired immunity to organisms
  -Have smaller upper and lower airways that are easily obstructed by mucosal swelling, secretions, foreign body causing increased resistance
  -Infants and young children have a small surface area for gaseous exchange and increase in ventilation-perfusion mismatch

Question 2

What are the four steps in respiration?

Answer 2

1- Ventilation (inspiration and expiration)
2-Exchange between alveoli and pulmonary capillaries (external respiration)
3- Transport of gases in blood
4- Exchange between blood and cells- internal respiration and cellular respiration; use of oxygen in ATP synthesis

Question 3

What is the role of nerve impulses in control of breathing?

Answer 3

-The respiratory centre in the brainstem controls respiration by transmitting impulses
-Nerve impulses are transmitted from brainstem to respiratory muscles by phrenic and intercostal nerves to initiate breathing
-Medulla oblongata sets basic respiratory rate
-Pons smooths out the rhythm of inspiration and expiration is set by the medulla

Question 4

How are acid levels effected by control of breathing?

Answer 4

-In the case of increased CO2 levels, there is an increase in carbonic acid therefore a lower pH
-Both breathing rate and volume will increase to attempt to buffer the effects of blood acidosis
-Changes in CO2 blood levels change the pH in the cerebral spinal fluid- that acts directly on the medulla

Question 5

What is the role of stretch receptors in control of breathing?

Answer 5

-They are a protective reflex
-Bronchioles and alveoli have stretch receptors that respond to overinflation
-These send impulses to the medulla oblongata via the vagal nerve- to slow down these respirations

Question 6

What is the role of chemoreceptors in control of breathing?

Answer 6

-Peripheral chemoreceptors in aortic branch and carotid body are sensitive to changes in paCO2 and pH
-They detect a drop in oxygen and an increase of carbon dioxide
-As a result, impulses are sent to the medulla to increase respiratory rate (to breathe in more oxygen and to breathe out more CO2)

Question 7

What is the definition of asthma?

Answer 7

A chronic inflammatory disorder of the airways characterised by episodic, reversible bronchospasm resulting from an exaggerated bronchoconstrictor response to various stimuli

Question 8

What are the 3 conditions in the atopic triad?

Answer 8

Atopic dermatitis
Asthma
Allergic Rhinitis

Question 9

List some asthma triggers

Answer 9

• Food
  -Dust
  -Mould
  -Pollution
  -Smoke
  -Temperature changes

Question 10

What are the most common asthma symptoms?

Answer 10

Shortness of breath
Wheeze
Chest tightness
Dry irritating cough

Question 11

What are signs that someone is having an exacerbation of asthma?

Answer 11

Breathlessness
Chest recession
Accessory muscle use
Tachypnoea/tachycardia
Low sats
Cyanosis
Wheeze
Silent chest
Exhaustion
Abdominal pain

Question 12

What are the four main characteristics of asthma attacks?

Answer 12

Inflammation
Bronchoconstriction
Mucous Production
Broncho-hyperresponsiveness

Question 13

Define airway modelling

Answer 13

An ongoing structural change caused by asthma that leads to thickened airway walls and the narrowing of the airways. Untreated inflammation leads to long-term airway damage that is irreversible.

Question 14

What specifically in children with asthma causes changes?

Answer 14

Epithelial shedding and hyperplasia in the airway smooth muscles

Question 15

What are the inflammatory cells present in the pathophysiology of asthma?

Answer 15

IgE
Mast Cells
T-Helper (1 and 2)
Dendritic Cells
Cytokines
Eosinophils
Beta Cells
Neutrophils

Question 16

What is the role of IgE in the inflammatory response?

Answer 16

Attaches to the mast cell and causes degranulation upon response to the allergen

Question 17

What is the role of the mast cell in the inflammatory response?

Answer 17

Recognises the allergen and starts releasing inflammatory mediators- histamine, leukotrienes and prostaglandins

Question 18

What are the mediator effects?

Answer 18

Mucous secretion from goblet cells
Airway smooth muscle constriction (bronchospasm)
Oedema from increased permeability

Question 19

What is the role of dendritic cells in the inflammatory response?

Answer 19

They detect the antigen and present it to TH2 cells to produce cytokines

Question 20

What is the role of cytokines in the inflammatory response?

Answer 20

They cause Beta-cells to further produce IgE
Eosinophil activation
Act as antigen presenting cells

Question 21

What is the role of eosinophils in the inflammatory response?

Answer 21

They are a type of WBC that help fight disease and release histamine. They damage the respiratory epithelium

Question 22

What is the role of neutrophils in the inflammatory response?

Answer 22

Express and release cytokines amplifying inflammatory reactions by several other cell types

Question 23

What is a V/Q mismatch?

Answer 23

A V/Q mismatch happens when part of your lung receives oxygen without blood flow or blood flow without oxygen. There is less efficient gaseous exchange and could lead to respiratory failure

Question 24

Where is gaseous exchange most efficient?

Answer 24

Areas of the lung where perfusion and ventilation are similar (matching)

Question 25

What is an area termed shunt showing?

Answer 25

V/Q of 0 An area with perfusion but no ventilation

Question 26

What is an area termed dead space showing?

Answer 26

V/Q undefined An area with ventilation but no perfusion

Question 27

What are the consequences of a lower V/Q ration?

Answer 27

Impairs pulmonary gas exchange and causes low arterial paO2. Causes an impairment of CO2 excretion

Question 28

What are the main causes of airway obstruction in an asthmatic child?

Answer 28

Smooth muscle contraction (bronchoconstriction) and increased mucous production

Question 29

What affect does airway obstruction have on the lungs?

Answer 29

When an obstruction is present, there is an increased resistance to airflow and therefore a decreased flow rate. As a result, there is impaired expiration leading to hyperinflation and increased work of breathing. As a response to the increased lung volume and obstruction, hyperventilation is triggered causing air trapping

Question 30

What is the effect of air trapping?

Answer 30

There is an increased in alveoli pressures leading to decreased perfusion of the alveoli

Question 31

What leads to a V/Q mismatch?

Answer 31

Increased alveolar pressure, decreased ventilation and decreased perfusion- leading to hypoxaemia

Question 32

What are the effects of hypoxaemia?

Answer 32

An increase in hyperventilation causing paCO2 to decrease and pH to increase leading to a respiratory alkalosis

Question 33

What happens in a severe obstruction?

Answer 33

Number of alveoli that are inadequately ventilated increases. The lungs and thorax become hyperinflated putting extra mechanical effort on respiratory muscles

Question 34

What is the consequence of lung and thorax hyperinflation and extra respiratory effort?

Answer 34

CO2 retention causing a decrease in pH- leading to respiratory acidosis and hypoxia. This is a precursor to respiratory failure

Question 35

Describe the series of events in reference to the pathophysiology of an asthma attack

Answer 35

1- IgE response triggered by an allergen 2- Inflammatory cells are released leading to vasodilation, capillary permeability, mucous production, oedema and generalised inflammation 3- Lower airway obstruction leading to wheezing- wheezing generated by turbulent airflow causing oscillation of the bronchial wall 4-The airways eventually become hyper-responsive and narrow easily in reaction to a wide range of stimuli. 5- Bronchospasm occurs 6- Bronchoconstriction, oedema, airway obstruction, epithelial shredding, increased lung volume and abnormal gaseous exchange occurs 7- Areas of atelectasis

Question 36

What contributes to narrowing of the airways?

Answer 36

Invasion of mucosa, sub-mucosa and muscle tissues by inflammatory cells Mucous

Question 37

What is the role of stretch receptors in response to asthma?

Answer 37

They are triggered due to bronchoconstriction and oedema and send signals to the brain

Question 38

What is the difference between hypoxia and hypoxaemia?

Answer 38

Hypoxaemia is low blood oxygenation Hypoxia is where the body or a particular region of the body is deprived of adequate oxygenation at tissue level

Question 39

Why does impaired cellular metabolism occur?

Answer 39

Impaired O2 delivery. Without oxygen, cells change from aerobic to anaerobic metabolism. As a consequence, there is lactic acid production

Question 40

What causes increased intrathoracic pressure?

Answer 40

Hyperventilation- causing an increase in the left ventricular afterload

Question 41

What are the 5 treatments for asthma?

Answer 41

Continuous O2 saturation monitoring High flow O2 Beta-2 agonists (bronchodilators) (repeat every 20mins and review after an hour) Ipratropium bromide Oral steroids ?Fluid

Question 42

What treatment may you consider in more severe asthma?

Answer 42

IV magnesium and aminophylline ?IV salbutamol

Question 43

Why would you administer oxygen

Answer 43

To increase oxygen levels

Question 44

What is the purpose of steroids?

Answer 44

To reduce inflammation, swelling and mucous production in the airways

Question 45

What is the purpose of salbutamol, aminophylline and IV magnesium?

Answer 45

They are bronchodilators therefore dilate the airways to improve airway flow and consequently oxygenation levels

Question 46

What is the purpose of using ipratropium bromide as a treatment?

Answer 46

Helps control bronchospasms

Question 47

Why may you give fluids as a treatment for asthma?

Answer 47

As it is likely the child will have low oral intake due to increased respiratory rate/vomiting. Not to give full fluid maintenance to prevent further oedema