Acute Asthma

Question 1

What is the pathophysiology behind asthma?

Answer 1

• Airway hyper-responsiveness, leading to (a) bronchospasm – constriction of smooth muscle in small airways (bronchi and bronchioles) – and (b) airway inflammation, leading to mucus secretion.
  
  • Reversible
  • No gold standard definition.

Question 2

What percentage of children are affected by asthma?

Answer 2

• Affects 15% of children.
  
  • Not usually diagnosed in those under 2 years old, due to the difficulty of distinguishing from viral-induced wheeze and frequent URTIs.

Question 3

What are common signs and symptoms of asthma?

Answer 3

• Symptoms:
  
  • SOB and dry cough, which often has diurnal variation, being worse at night and in the morning.
• Signs:
  
  • Wheeze
  • Hyperinflation
  • Pulsus paradoxus in a severe attack.
  • Reduced air entry due to mucous plug in attack.

Question 4

Which features strongly suggest a diagnosis of asthma?

Answer 4

• reversibility to bronchodilators (>12% change in PEFR or FEV1).
  
  • Episodic time course.
  • Triggers: exercise, stress, pets, viral URTIs, cold air, and tobacco smoke.
  • Eczema or hay fever may also be present.

Question 5

Which features might suggest another diagnosis to be more likely than asthma?

Answer 5

• Dizziness and tingling (suggests panic attack).
  
  • Symptoms only with colds.
  • Productive cough without wheeze.
  • Voice disturbances.
  • Smoking. However, if someone has pre-existing asthma, don’t assume it has become COPD just because they later start smoking.

Question 6

What are the risk factors for asthma?

Answer 6

• Atopy

* Family history of atopy or asthma.

Question 7

Which investigations are carried out in a patient with suspected asthma?

Answer 7

• Diagnosis with lung function testing:
  
  • Spirometry: FEV1/FVC ratio <0.7 confirms obstructive airway disease.
  • Then do bronchodilator reversibility (BDR) test, with ≥12% improvement in FEV1 +ve for asthma.
  • In adults, diagnosis should be confirmed with fractional exhaled nitric oxide test (FeNO), with ≥40 ppb +ve for asthma. Use in kids (5-16) only if diagnosis uncertain.
  • If spirometry, BDR, or FeNO -ve, consider 2-4 weeks of peak flow monitoring. >20% variability is +ve for asthma.
  • Specialist referral if these tests are -ve but symptoms continue.
• Who to test:
  
  • NICE advise formal testing for all ≥5 years old.
  • British Thoracic Society advise formal testing for those ≥5 years old with low or intermediate probability based on clinical history, but go straight to treatment if high probability (and then only test formally if there is a poor response).
• In children who cannot perform spirometry – generally those <5 years old – use clinical diagnosis and trial of treatment.
Other tests:
  
  • CXR in adults to rule out other causes. May show hyperinflation in asthma.
  • Allergy testing – skin prick testing or allergen-specific IgE in blood – can identify a specific trigger if it is suspected, but is not routinely recommended.

Question 8

How is asthma managed?

Answer 8

• Overview:
  
  • Aim to achieve patient control over management including an asthma action plan, PEFR monitoring, and symptom diary.
  • Teach inhaler technique as many patients have trouble.
  • Inhaled steroids reduce nocturnal symptoms quickly, but wider effects takes months, so users need to know to be patient.
• In addition to inhalers:
  
  • Remove any identified allergens.
  • Annual flu vaccine, which is via nasal spray in kids.
  • Smoking cessation. Among its many harms, smoking weakens the effectiveness of steroids.
  • Routine antibiotics are not recommended, even if there is purulent sputum as this can be part of normal inflammation. Of course, clinical judgement can override this.
• Stepwise medical treatment
  
  • Most people are at steps 1-2.
  • Start at a level appropriate to disease severity.
  • Remember: you can move down as well as up!
• 1. Inhaled short acting β2 agonist (SABA) as required:
     * Salbutamol 100 μg/puff. Use 2 puffs before exercise if likely to bring on symptoms.
     * Move to step 2 if using >3 times/week, waking at night, or has acute asthma exacerbation.
• 2. Add inhaled corticosteroid (ICS):
     * Fluticasone, beclometasone, or budesonide.
     * Start at low dose.
• 3. Add leukotriene receptor antagonist (LTRA):
     * Montelukast or zafirlukast.
• 4. Add inhaled long-acting β2 agonist (LABA):
     * Salmeterol or formoterol, in combination inhaler with ICS.
     * Continue LTRA if felt to be effective.
     * If remains uncontrolled, switch ICS/LABA combo to maintenance and reliever therapy (MART), a combo which includes a fast-acting LABA (e.g. formoterol) and is used as both maintenance and reliever.
• 5. Increase ICS dose until effective or trial further drug (theophylline or long-acting muscarinic antagonist).
6. Refer to specialist for consideration of systemic immunomodulators such as:
     * Prednisolone PO.
     * Monoclonal antibodies: omalizumab (anti IgE); mepolizumab, reslizumab, or benralizumab (anti IL5).
• 5-16 years old
As for >16 years, except:
  
  • If LTRA insufficient, switch to (don’t add) LABA.
• 0-4 years old
As for 5-16 years, except:
  
  • Stop ICS after 8 weeks to confirm response (and diagnosis), restarting if symptoms recur.
  • Don’t add LABA; just refer to specialist after step 3.

Question 9

In which medications should caution be taken in patients with asthma?

Answer 9

• β-blockers:
  
  • Contraindicated in asthma as they lead to bronchospasm.
  • Non-cardioselective β-blockers especially problematic: propranolol, timolol.
• NSAIDs and ASA:
  
  • Can trigger bronchospasm, either in existing patients or as a standalone cause of new asthma.
  • Affects <10% of asthma patients.
  • OK to use if previously taken, but probably avoid if never taken, and use clopidogrel instead.
  • Can occur as Samter’s triad: aspirin sensitivity, polyps ± rhinitis, and asthma.

Question 10

What is the defining criteria for acute severe asthma?

Answer 10

• Acute severe asthma
≥1 of:
  
  • PEFR 33-50%.
  • RR>25. >30 if 5-12 years old, >50 if <5 years old.
  • HR>110. >120 if 5-12 years old, >130 if <5 years old.
  • Can’t talk fully.

Question 11

What is the defining criteria for life-threatening asthma?

Answer 11

• ≥1 of:
  
  • PEFR <33%.
  • SpO2 <92%, PaO2 <8 kPa, or normal PaCO2.
  • Altered mental status.
  • Arrhythmias, ↓BP.
  • Silent chest or poor respiratory effort, cyanosis.
  • If they are drowsy/sleeping, check if they can be roused to determine if it is pathological.

Question 12

What is the defining criteria for near-fatal asthma?

Answer 12

↑CO2 or needing ventilation.

Question 13

How is acute exacerbation of asthma managed?

Answer 13

• Basics, SONSIS:
  
  • Sit up.
  • 100% O2, aiming for SpO2 94-8%.
  • Oxygen-driven, Nebulized SABA ± Ipratropium.
  • Steroids PO/IV. Takes up to 4 hours to have an effect so give early, preferably PO.
• Further options, MAGAS:
  
  • IV MAGnesium sulfate.
  • IV Aminophylline – including a loading dose if not on theophylline already – or IV SABA.
• ITU transfer if there is ↑CO2 or ventilation is required.
Discharge when stable, PEFR>75%, and on discharge drugs for 12 hours:
  
  • Prednisolone PO: at least 3 days in children, 5 days in adults, or until recovery.
  • ICS
  • Written treatment plan.
  • GP visit in 2 days.
  • Outpatient clinic in 4 weeks.

Question 14

What causes occupational asthma?

Answer 14

• Causes
  
  • High molecular mass substances: flour, wood dust, lab animal allergens. May have specific, detectable IgE.
  • Low molecular mass substances – e.g. isocyanates (furniture foam, paint spray), welding fumes, oil mists – which act as haptens and bind to human proteins. Often hard to detect specific IgE.

Question 15

How might occupational asthma present?

Answer 15

• Typical asthmatic/hypersensitivity symptoms: cough, SOB, wheeze, rhinitis, conjunctivitis.
  
  • Onset within 1 year of starting job.
  • Initial latent interval without symptoms – weeks to months – while hypersensitivity develops.
  • Symptoms may occur at work, or hours post-exposure in the evening or night, reflecting a delayed response.
  • Symptoms worsen throughout week, but improve at weekends and holidays.

Question 16

What are the risk factors for occupational asthma?

Answer 16

• Work involving exposure to known causes, especially if in high volume.
  
  • Atopy
  • FH of atopy or asthma.
  • Smoking
  • Pre-existing asthma.

Question 17

Which investigations are should be carried out in suspected occupational asthma?

Answer 17

• Serial peak flow is the best way to determine a relationship, know as a ‘workplace challenge’. May involve repeated measurements over 24 hours or a week.
  
  • Skin prick testing or allergen-specific serum IgE. Not available for most causes.
  • Inhalation challenge (aka bronchial provocation) test of possible cause in lab. Rarely done due to potential risks.

Question 18

How is occupational asthma managed?

Answer 18

• Change or stop work:
  
  • If work stopped within 2 years of symptoms onset, it usually improves.
  • If stopped after 2 years, it often persists.
  • Eligible for Industrial Injury Benefit if symptoms continue post-work.
• Employer responsibilities for employee safety:
  
  • Must inform HSE of any death, injury causing 3 days off, near misses, or occurrence of a reportable disease. Several respiratory conditions are reportable, including occupational asthma, hypersensitivity pneumonitis, and pneumoconiosis.
  • 1st line response should be removing the causative agent, or failing that, reducing exposure.