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OSCE PREP > Asthma Pathophysiology > Flashcards

Asthma Pathophysiology Flashcards

1
Q

What is asthma?

A

A chronic inflammatory disorder characterised by episodic, reversible bronchospasm

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2
Q

What does asthma cause?

A

Recurrent attacks of wheezing and breathlessness due to inflammation within the lungs causing the airways to narrow and reduce air flow

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3
Q

Where does asthma predominantly affect?

A

The lower airway, but the upper airway may be affected by excess mucous production

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4
Q

What are the two types of asthma?

A

Atopic and Non-Atopic

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5
Q

How many asthmatics have atopic asthma?

A

70%

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6
Q

How many asthmatics have non-atopic asthma?

A

30%

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7
Q

What is atopic asthma?

A

It is extrinsic and triggered by an allergen/irritant
Inflammation mediated by systemic IgE production

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8
Q

What is non-atopic asthma?

A

It is intrinsic and trigger is unknown as it is not caused by an allergy
Mediated by local IgE production

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9
Q

Why are children with asthma more susceptible to respiratory failure?

A
  • Increased susceptibility to infection
  • Smaller upper and lower airways are more easily obstructed by mucosal swelling and secretions
  • Increased tendency to airway closure and hypoxia
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10
Q

What is the presentation of asthma?

A
  • breathlessness
  • accessory muscle use
  • recession
  • tachypnoea
  • wheeze
  • desaturations
  • tachycardia
  • cyanosis
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11
Q

What are some triggers of asthma attacks?

A

Dust, pollen, moulds, pollution, cold/hot weather, exercise, cigarette smoke, infections

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12
Q

What are the three categories of asthma?

A

Moderate
Acute severe
Life threatening

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13
Q

How does moderate asthma present?

A

Oxygen saturations above 92%, tachycardia, mild accessory muscle use, can talk in sentences

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14
Q

How does acute severe asthma present?

A

Oxygen saturations below 92%, agitated, increased accessory muscle use, tachycardia, can’t complete sentences

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15
Q

How does life threatening asthma present?

A

Oxygen saturations below 92%, silent chest, cyanosis, max accessory muscle use, increased tachycardia, drowsy, exhausted, can’t talk

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16
Q

What are the characteristics of asthma?

A

-Inflammation
-Broncho-constriction
-Bronchospasm
-Mucous production
-Broncho hyper-responsiveness

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17
Q

What can untreated asthma lead to?

A

Airway remodelling

18
Q

What is airway remodelling?

A

Ongoing structural change leading to thickened and narrower airways

19
Q

What may you see in an asthmatic airway at a cellular level?

A
  • Goblet cells produce increased mucous
  • Thickened basement membrane
  • Increase in mast cells that release histamines
  • Cellular infiltration (eosinophils and neutrophils)
  • Smooth muscle hypertrophy
20
Q

What is the cellular response when a pathogen enters an asthmatic airway?

A
  • Allergen/irritant enters the airway
  • B cells act as antigen presenting cells and produce IgE which attach to mast cells causing degranulation
  • Mast cell degranulation release mediators, such as histamine, leukotrienes and prostagladines
  • Mediator effects include increase mucous secretion by goblet cells, bronchiole smooth muscle contraction, vascular permeability and leaking, and eosinophil and neutrophil infiltration
  • Dendritic cells then activate T helper 2 cells to release cytokines, as well as neutrophils also releasing cytokines which amplify inflammatory reactions
  • Cytokines also attract and promote eosinophils which release histamines leading to airway obstruction, air trapping and hypoxaemia and respiratory acidosis
21
Q

What does VQ mean?

A

Measuring whether Ventilation and Perfusion are equal

22
Q

How does VQ and gaseous exchange link?

A

When perfusion and ventilation are similar, gaseous exchange is most efficient
When perfusion and ventilation are unequal, gaseous exchange are less efficient

23
Q

What does a lower VQ ratio imply?

A

Lower VQ ratio impairs gas exchange and causes low partial pressure of oxygen (PaO2) in arteries

24
Q

What is a shunt?

A

perfusion is present but ventilation is absent
(VQ=0)

25
Q

What is deadspace?

A

ventilation is present and perfusion is absent
(VQ=unknown)

26
Q

What are the two types of respiratory failure?

A

Type 1 = hypoxia - inability to get oxygen into the blood (PaO2 = less than 8kPa)
Type 2 = hypercapnia - inability to get carbon dioxide out of the blood (PaCO2 = more than 6kPa)

27
Q

What is the pathophysiology of an asthma attack?

A
  • Allergen triggers IgE mediated response leading to vasodilation and increased capillary permeability leading to mucous production, inflammation and oedema.
  • This inflammation causes lower airway obstruction causing wheezing due to turbulent air flow. Wheezing causes oscillation of the bronchial wall making the airways hyper-responsiveness and narrow
  • This causes bronchospasm, broncho-constriction, oedema, airway obstruction, epithelial shedding, increased lung volume, and abnormal gas exchange, leading to atelectasis
  • Impaired oxygen delivery causes cells to switch from aerobic to anaerobic metabolism which results in lactic acid production at a cellular level
  • Decreased oxygen intake = hypoxia = cyanosis
28
Q

What does epithelial shedding cause?

A

Epithelial shedding causes a build up of epithelial cells in the bronchioles leading to airway remodelling as the airway becomes narrower

29
Q

What is the treatment for moderate asthma?

A
  • O2 sats monitoring
  • High flow O2
  • B2 agonists (2-10 puffs via spacer and repeat every 20 minutes)
  • Ipratropium bromide
  • Oral steroids
30
Q

What is the treatment for acute severe asthma?

A
  • O2 sats monitoring
  • High flow O2
  • B2 agonists nebulised every 20 minutes
  • Nebulised ipratropium bromide
  • Oral/IV steriods
  • Consider IV magnesium and aminophylline
  • Arterial Blood Gas
  • PICU
31
Q

What is the treatment for life threatening asthma?

A
  • O2 sats monitoring
  • High flow O2
  • B2 agonists nebulised every 20 minutes
  • Nebulised ipratropium bromide
  • Oral/IV steriods
  • Consider IV magnesium and aminophylline
  • Arterial Blood Gas
  • PICU
  • Consider single bolus IV salbutamol
32
Q

What is the rationale for the treatments of asthma?

A
  • Oxygen - increases O2 saturations
  • Steroids - reduce inflammation, swelling and mucous production
  • Bronchodilators - dilate airways to improve airflow
  • Ipratropium bromide - control bronchospasm
  • Aminophylline - broncho-dilation and reduced hypersensitivity
    IV magnesium - bronchodilator
33
Q

How may an asthmatic patients airway present?

A

Airway - an inflammatory cellular response causes the hyper-secretion of mucous from the goblet cells so secretions may be seen in the airway

34
Q

What should you do if secretions are seen in the airway?

A

Suctions the secretions from back of the cheeks using a soft tip catheter with 12-20kPa via wall suction

35
Q

What breathing symptoms would you expect an asthmatic patient to present with?

A

Due to the inflammatory cellular response, the lower airways narrow and present with oedema, vascular leaking, mucous plugging and broncho-constriction.
Therefore a wheeze may be present due to turbulent airflow.
Tachypnoea occurs to try and compensate for the
hypoxia
Increased work of breathing due increased oxygen demand
Low oxygen saturations due to hypoxia due to VQ mismatch due decreased ventilation

36
Q

After prolonged asthma symptoms, what may a child present with?

A

A child may also present with muscle fatigue due to prolonged accessory muscle usage and continuation of tachypnoea results in
respiratory failure

37
Q

How does VQ mismatch affect how a child presents?

A

V-Q mismatch occurs due to increased dead space as the airway is distended due to hyperinflation occurring because of airway obstruction

38
Q

How may an asthma attack affect a child’s circulatory assessment?

A
  • Tachycardia may occur as pulmonary vascular resistance increases due to increased lung volume causing right ventricular compromise
  • Cyanosis due to hypoxia due to decreased levels of oxygenated haemoglobin in the blood
  • May present with skin pallor due to vasoconstriction
  • Physiological stress may cause increased heart rate and blood pressure
39
Q

How may an asthma attack affect a child’s neurological (disability) assessment?

A

Reduced cerebral blood flow and oxygenation causes changes to AVPU.
If A or V, the patient may be irritable and confused,
If at P or U, the patient may not be conscious enough to protect their airway

40
Q

How may an asthma attack affect a child’s exposure assessment?

A

Depending on antigen/allergy reaction a rash may
be seen

41
Q

What is a side effect of salbutamol?

A

Tachycardia

42
Q

What intervention can you apply for tachycardia?

A

ECG monitoring

OSCE PREP (12 decks)

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