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Critical Care OSCE > Asthma > Flashcards

Asthma Flashcards

1
Q

Why are children with asthma more susceptible to respiratory failure?

A
  • 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
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2
Q

What are the four steps in respiration?

A

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

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3
Q

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

A

-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

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4
Q

How are acid levels effected by control of breathing?

A

-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

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5
Q

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

A

-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

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6
Q

What is the role of chemoreceptors in control of breathing?

A

-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)

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7
Q

What is the definition of asthma?

A

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

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8
Q

What are the 3 conditions in the atopic triad?

A

Atopic dermatitis
Asthma
Allergic Rhinitis

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9
Q

List some asthma triggers

A
  • Food
    -Dust
    -Mould
    -Pollution
    -Smoke
    -Temperature changes
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10
Q

What are the most common asthma symptoms?

A

Shortness of breath
Wheeze
Chest tightness
Dry irritating cough

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11
Q

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

A

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

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12
Q

What are the four main characteristics of asthma attacks?

A

Inflammation
Bronchoconstriction
Mucous Production
Broncho-hyperresponsiveness

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13
Q

Define airway modelling

A

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.

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14
Q

What specifically in children with asthma causes changes?

A

Epithelial shedding and hyperplasia in the airway smooth muscles

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15
Q

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

A

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

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16
Q

What is the role of IgE in the inflammatory response?

A

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

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17
Q

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

A

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

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18
Q

What are the mediator effects?

A

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

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19
Q

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

A

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

20
Q

What is the role of cytokines in the inflammatory response?

A

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

21
Q

What is the role of eosinophils in the inflammatory response?

A

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

22
Q

What is the role of neutrophils in the inflammatory response?

A

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

23
Q

What is a V/Q mismatch?

A

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

24
Q

Where is gaseous exchange most efficient?

A

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

25
Q

What is an area termed shunt showing?

A

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

26
Q

What is an area termed dead space showing?

A

V/Q undefined
An area with ventilation but no perfusion

27
Q

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

A

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

28
Q

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

A

Smooth muscle contraction (bronchoconstriction) and increased mucous production

29
Q

What affect does airway obstruction have on the lungs?

A

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

30
Q

What is the effect of air trapping?

A

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

31
Q

What leads to a V/Q mismatch?

A

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

32
Q

What are the effects of hypoxaemia?

A

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

33
Q

What happens in a severe obstruction?

A

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

34
Q

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

A

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

35
Q

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

A

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

36
Q

What contributes to narrowing of the airways?

A

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

37
Q

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

A

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

38
Q

What is the difference between hypoxia and hypoxaemia?

A

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

39
Q

Why does impaired cellular metabolism occur?

A

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

40
Q

What causes increased intrathoracic pressure?

A

Hyperventilation- causing an increase in the left ventricular afterload

41
Q

What are the 5 treatments for asthma?

A

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

42
Q

What treatment may you consider in more severe asthma?

A

IV magnesium and aminophylline
?IV salbutamol

43
Q

Why would you administer oxygen

A

To increase oxygen levels

44
Q

What is the purpose of steroids?

A

To reduce inflammation, swelling and mucous production in the airways

45
Q

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

A

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

46
Q

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

A

Helps control bronchospasms

47
Q

Why may you give fluids as a treatment for asthma?

A

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

Critical Care OSCE (14 decks)

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