Asthma

Question 1

Define what asthma is

Answer 1

• It is a chronic inflammatory disorder of the small & large airways secondary to type 1 hypersensitivity.
• The symptoms are variable & recurring and manifest as reversible bronchospasm resulting in airway obstruction.

Question 2

What are the 3 factors which contribute to airway narrowing in asthma ?

Answer 2

1. Bronchial muscle contraction (airway hypersensitivity) - triggered by a variety of stimuli
2. Airway inflammation - caused by mast cell, basophils & eosinophils degranulation resulting in the release in inflammatory mediators
3. Increased mucus production

Pic shows bronchoconstriction, inflammation (pus seen in pic)

Question 3

What type of inflammation is asthma characterised by ?

Answer 3

Eosinophilic inflammation

Question 4

List the risk factors for asthma development

Answer 4

• Personal or family history of atopy
• Antenatal factors: maternal smoking, viral infection during pregnancy (especially RSV)
• Low birth weight
• Not being breastfed
• Maternal smoking around child
• Exposure to high concentrations of allergens (e.g. house dust mite)
• Air pollution
• ‘Hygiene hypothesis’: increased risk of asthma and other allergic conditions in developed countries due to reduced exposure to infectious agents in childhood preventing normal development of the immune system

Question 5

Focusing on atopy, patients with asthma also suffer from other IgE-mediated atopic conditions such as?

Answer 5

• Atopic dermatitis (eczema) and allergic rhinitis (hay fever)

Question 6

List the triggers for asthma that you should ask about in someone presenting with potential asthma/diagnosed asthma

Answer 6

• Allergens; animal dander, dust mites, pollens, fungi
• Exercise
• Viral infection
• Smoking (including passive)
• Cold
• Chemicals/ pollution
• Drugs (NSAIDs, ß-blockers)

Question 7

What arethe 2 most important drug triggers of asthma to check for ?

Answer 7

NSAIDs (such as acetylsalicylic acid) and ß-blockers

Question 8

What drug are a number of asthma patients sensitive to ?

Answer 8

Aspirin

Question 9

What do some patients with asthma also suffer from (excluding atopy here)?

Answer 9

Nasal polyps

Question 10

What are the symptoms of asthma ?

Answer 10

• Cough (non-productive): often worse at night
• Intermittent dyspnoea
• ‘Wheeze’, ‘chest tightness’
• Diruinal variation in symptoms or peak flow - marked morning dipping of peak flow

Question 11

What are the signs of asthma ?

Answer 11

• Expiratory wheeze on auscultation (may be audible) - ‘widespread polyphonic wheeze’
• Tachyponea
• Hyperinflated chest - hyperresonant percussion note
• Reduced peak expiratory flow rate (PEFR)
• Atopy

Question 12

How is asthma diagnosed in someone aged < 5?

Answer 12

Diagnosis should be made on clinical judgement

Question 13

Once a child with suspected asthma reaches the age of 5 y/o what should be done ?

Answer 13

Objective tests should be performed to confirm the diagnosis (normal asthma diagnosis for ages 5-16)

Question 14

What objective tests should be done in someone aged 5-16 with suspected asthma?

Answer 14

• 1st line = All patients should have spirometry with a bronchodilator reversibility (BDR) test
• 2nd line = a FeNO test should be requested if there is normal spirometry or obstructive spirometry with a negative bronchodilator reversibility (BDR) test

Question 15

What objective tests should be done in someone aged ≥ 17 with suspected asthma?

Answer 15

1st line = spirometry + BDR test + a FeNO test

Question 16

When diagnosing asthma in patients ≥ 17, they should be asked if their symptoms are better on days away from work/during holidays. If so what should be done ?

Answer 16

Referal to a specialist as possible occupational asthma

Question 17

What are the main occupational causes of asthma ?

Answer 17

• Isocyanates - the most common cause. Example occupations include spray painting and foam moulding using adhesives
• Platinum salts
• Soldering flux resin
• Glutaraldehyde
• Flour
• Epoxy resins
• Proteolytic enzymes

Question 18

Following referral to specialist for suspected occupational asthma what tests will be done ?

Answer 18

Serial measurements of peak expiratory flow at work and away from work. (will be better on weekends when not working)

Question 19

What 3rd line objective test can be done for diagnosing asthma in patients where there is diagnostic uncertainity after spirometry + BDR test + FeNO test ?

Answer 19

Monitor peak flow variability for 2-4 weeks

Question 20

What is considered a positive FeNO test for asthma ?

Answer 20

• In adults level of ≥ 40 ppb is considered positive
• in children a level of ≥ 35 ppb is considered positive

Question 21

What is considered a positive spirometry result for obstructive airway disease (asthma being one potential cause) ?

Answer 21

FEV1/FVC ratio < 70%

Question 22

What is considered a positive BDR test result for asthma ?

Answer 22

• In adults, a positive test is indicated by an improvement in FEV1 of 12% or more and increase in volume of 200 ml or more
• In children, a positive test is indicated by an improvement in FEV1 of 12% or more

Question 23

What is an asthma diagnosis made on in patients aged 5-16?

Answer 23

• Obstructive spirometry and positive BDR test OR
• FeNO level of 35 ppb or more and positive peak flow variability

Question 24

What is an asthma diagnosis made on in someone aged ≥ 17?

Answer 24

• A FeNO ≥ 40 ppb + either a pos BDR test or pos peak flow variability or bronchial hyperreactivity OR
• A FeNO between 25 and 39 ppb + a pos BDR test OR
• A pos BDR test + pos peak flow variability irrespective of FeNO level.

Question 25

When may the use of direct bronchial challenge test (Airway hyperreactivity measures) with histamine or methacholine be used in the diagnosis of asthma in someone aged ≥ 17?

Answer 25

If there is diagnostic uncertainty after a normal spirometry and either a: * FeNO ≥ 40 ppb and no variability in peak flow readings OR * FeNO ≤ 39 ppb with variability in peak flow readings.

Question 26

What is the step-wise maintanence treatment of asthma ?

Answer 26

* 1st line = SABA (PRN) + low dose ICS * 3rd line = add LABA (as combo inhaler - MART) or add a LTRA if a child * 4th line = increase ICS dose to medium OR add a LTRA * 5th line = Increase ICS dose to high OR add LTRA OR add tiotropium OR add theophylline

Question 27

Explain what is meant by MART therapy in asthma treatment

Answer 27

Maintenance and reliever therapy (MART) * A form of combined ICS and LABA treatment in which a single inhaler, containing both ICS and a fast-acting LABA, is used for both daily maintenance therapy and the relief of symptoms as required * MART is only available for ICS and LABA combinations in which the LABA has a fast-acting component (for example, budesonide/formoterol)

Question 28

For adults what are considered low, medium and high dose corticosteroids in the treatment of asthma ?

Answer 28

* ≤ 400 micrograms budesonide or equivalent = low dose * 400 micrograms - 800 micrograms budesonide or equivalent = moderate dose * \> 800 micrograms budesonide or equivalent= high dose.

Question 29

Define what complete control of asthma is ?

Answer 29

Complete control of asthma is defined as: * No daytime symptoms * No night-time awakening due to asthma * No need for rescue medication * No asthma attacks * No limitations on activity including exercise * Normal lung function (in practical terms FEV1 and/or PEF\>80% predicted or best) * Minimal side effects from medication.

Question 30

What may suggest an asthma attack is occuring in someone ?

Answer 30

Obv features of asthma as discussed already

Question 31

How is the severity of an acute asthma attack graded ?

Answer 31

Moderate, severe & life-threatening

Question 32

Define the criteria for a moderate asthma attack ?

Answer 32

* Typical asthma symptoms + * PEFR \> 50-75% best or predicted * & no features of severe acute asthma

Question 33

Define the criteria for a severe asthma attack ?

Answer 33

* PEFR 33 - 50% best or predicted * Can't complete sentences in one breath * RR \> 25/min * Pulse \> 110 bpm

Question 34

Define the criteria for a life-threatening asthma attack ?

Answer 34

* PEFR \< 33% best or predicted * Oxygen sats \< 92% * PaO2 \<8kPa * PaCO2 normal (should be low due to blowing off, normal indicates tiring and is very bad) * Silent chest, cyanosis or feeble respiratory effort * Bradycardia, dysrhythmia or hypotension * Exhaustion, confusion or coma

Question 35

Define what a near fatal asthma attack is

Answer 35

* Raised PaCO2 * &/or requiring mechanical ventilation with raised inflation pressures

Question 36

What is the treatment of acute asthma ?

Answer 36

* 1st line for all acute asthma attacks = high dose nebulised beta2-agnoists (salbutamol or terbutaline) with O2 + steroids either IV hydrocortisone or PO prednisolone or both * If severe or life-threatening attack or there is a poor inital response to beta2-agonist therapy then add nebulised ipratropium bromide * 2nd line = single dose IV magnesium sulphate for patients with severe or life-threatening which is not responding to treatment note if severe or life-threatening asthma attack you jump straight to using NEB salbutamol but if it is mild-moderate then use high dose inhaled salbutamol or terbutaline and then if poor response move to the nebulised treatments, regardless of severity everyone gets steroids

Question 37

If someone is experiencing a life-threatening asthma attack where should they be referred to?

Answer 37

Refer to ICU urgently

Question 38

What patients presenting with an asthma attack should be admitted ?

Answer 38

Those with life-threatening features or severe features persistent after initial treatment

Question 39

Appreciate this

Answer 39

* The two divisions of the autonomic nervous system are the sympathetic division and the parasympathetic division. * The sympathetic system is associated with the fight-or-flight response, and parasympathetic activity is referred to by the epithet of rest and digest. * Homeostasis is the balance between the two systems.

Question 40

Give a very general overview of the effect of the parasympathetic and sympathetic divisions of the ANS in the regulation of airway function

Answer 40

Stimulation of parasympathetics (cholinergic fibres) which act via M3 muscarinic ACh receptors, causes: 1. Bronchial smooth muscle contraction 2. Increased mucus secretion Sympathetic stimulation which acts via via b2-adrenoceptors, causes: 1. Bronchial smooth muscle relaxation 2. Decreased mucus secretion 3. Increased mucociliary clearance

Question 41

There is no direct innervation by sympathetics to the bronchial smooth muscle (there is for the submucosal glands and blood vessels) ==\> how does sympathetic stimulation cause bronchial smooth muscle relaxation ?

Answer 41

They act on chromaffin cells in the adrenal medulla which when activated release adrenaline which act on b2-adrenoceptors (β2-ADR) on ASM cells to cause relaxtion