Asthma Flashcards
What does it mean when you say Asthma is an atopic condition? What are some other atopic conditions?
Atopy is the genetic predisposition to develop an allergic reaction that produces an exaggerated IgE response when a person is exposed to otherwise harmless environmental substances.
Eczema, hay fever and food allergies.
Note: patients with one of these conditions are more likely to have others. These conditions run in the family.
What is Asthma?
chronic inflammatory airway disease leading to variable airway obstruction. The smooth muscles in the airways are hypersensitive to stimuli and constrict to cause airflow obstruction. This is reversible with bronchodilators such as inhaled salbutamol, unlike in COPD.
How do the symptoms of Asthma present, in terms of clinical symptoms and timing of the symptoms?
- shortness of breath
- chest tightness
- dry cough
- wheeze
The symptoms usually present episodically and there is a diurnal variability, which means that the symptoms fluctuate according to the time of day.
What is a key clinical sign found in asthma when auscultating? What does a localized monophonic wheeze suggest?
a widespread polyphonic expiratory wheeze (loud, continuous sound with multiple frequencies).
A localized monophonic (loud, continuous sound with one frequancy/pitch) is not asthma. It could be suggestive of an inhaled foreign body, tumour or thick sticky mucus plug.
What are the typical triggers of asthma?
- infection
- nighttime or early morning
- exercise
- animals
- cold, damp or dusty hair
- strong emotions
What are the counterindications for asthma?
beta-blockers, particularly non-selective beta-blockers such as propranolol and non-steroidal anti-inflammatory drugs (ibuprofen, naproxen) can worsen asthma.
List the investigations you would do to test Asthma, and describe what you would find.
1) spirometry- FEV1:FVC ratio less than 70% suggests asthma or copd
2) reversible testing- the use of bronchodilators improves FEV1 by 12% indicates a diagnosis of asthma
3) Fractional exhaled nitric oxide (FeNO)- measures the concentration of nitric oxide exhaled by the patient. NO is a marker of airway inflammation. Above 40 ppb is a positive test result to diagnose asthma.
4) Peak flow variability of more than 20% is a positive test result, supporting the diagnosis.
5) Direct bronchial challenge testing with inhaled histamine or methacholine.
What are the initial investigations to diagnose asthma according to the NICE guidelines?
- fractional exhaled nitric oxide
- spirometry with bronchodilator reversibility
What are the next steps of investigations, in order, if there is still some diagnostic uncertainty after the initial investigations?
peak flow variability -> direct bronchial challenge test with histamine or methacholine
List the drugs taken to treat asthma.
1) beta-2 adrenergic agonists- bronchodilators
2) adrenalin- acts on smooth muscle to cause relaxation
3) short-acting beta-2 agonists such as salbutamol
4) long-acting beta-2 agonists such as salmeterol
5) inhaled corticosteroids such as beclometasone reduce the inflammation and reactivity of the airways (they are used as maintenance or preventer medications to control symptoms long-term
6) long-acting muscuranic antagonists such as tiotropium (block acetylcholine receptors that are usually stimulated by the parasympathetic nervous system and cause the contraction of the bronchial smooth muscles. blocking these receptors dilates the bronchioles and reverses the bronchoconstriction present in asthma.
7) leukotrine receptos antagonists such as montelukast works by blocking the effects of leukotrienes (produced by the immune system and cause inflammation, bronchoconstriction and mucus secretion)
8) theophylline relaxes the bronchial smooth muscle and reduces inflammation
9) maintainence and reliever therapy involves a combination inhaler containing an inhaled corticosteroid and a fast and long-acting beta-agonist. patient uses this single inhaler both regularly as a preventer and also as a reliever when they have symptoms.
The BTS/SIGN guidelines on asthma (2019) suggest the following steps (adding drugs at each stage):
1) Short-acting beta-2 agonist inhaler (e.g. salbutamol) as required
2) Inhaled corticosteroid (low dose) taken regularly
3) Long-acting beta-2 agonists (e.g., salmeterol) or maintenance and reliever therapy (MART)
4) Increase the inhaled corticosteroid or add a leukotriene receptor antagonist (e.g., montelukast)
5) Specialist management (e.g., oral corticosteroids)
What does the additional management of asthma include?
- Individual written asthma
- self-management plan
- Yearly flu jab
- Yearly asthma review when stable
- Regular exercise
- Avoid smoking (including passive smoke)
- Avoiding triggers where appropriate
What are the clinical presentations of acute exacerbation of asthma? What arterial blood gas result would yo expect?
- progressively shortness of breath
- use of accessory muscles
- raised respiratory rate
- symmetrical expiratory wheeze on auscultation
- the chest can sound tight on auscultation
- on arterial blood gas analysis, patients initially have respiratory alkalosis, as a raised respiratory rate (tachypnoea) causes a drop in CO2. A normal pCO2 or low pO2 (hypoxia) is a concerning sign, as it means they are getting tired, indicating life-threatening asthma. Respiratory acidosis due to high pCO2 is a very bad sign.
Explain the grading for acute asthma.
1) Moderate exacerbation features:
Peak flow 50 – 75% best or predicted
2) Severe exacerbation features:
Peak flow 33-50% best or predicted
Respiratory rate above 25
Heart rate above 110
Unable to complete sentences
3) Life-threatening exacerbation features:
Peak flow less than 33%
Oxygen saturations less than 92%
PaO2 less than 8 kPa
Becoming tired
Confusion or agitation
No wheeze or silent chest
Haemodynamic instability (shock)
Note: The wheeze disappears when the airways are so tight that there is no air entry. This is ominously described as a silent chest and is a sign of life-threatening asthma.
Patients with an acute exacerbation of asthma can deteriorate quickly. Acute asthma is potentially life-threatening. Treatment should be aggressive and they should be escalated early to seniors and intensive care. What is the treatment for it?
- intravenous aminophylline
- salbutamol
- magnesium
1) Mild exacerbations may be treated with:
Inhaled beta-2 agonists (e.g., salbutamol) via a spacer
Quadrupled dose of their inhaled corticosteroid (for up to 2 weeks)
Oral steroids (prednisolone) if the higher ICS is inadequate
Antibiotics only if there is convincing evidence of bacterial infection
Follow-up within 48 hours
2) Moderate exacerbations may additionally be treated with:
Consider hospital admission
Nebulised beta-2 agonists (e.g., salbutamol)
Steroids (e.g., oral prednisolone or IV hydrocortisone)
3) Severe exacerbations may additionally be treated with:
Hospital admission
Oxygen to maintain sats 94-98%
Nebulised ipratropium bromide
IV magnesium sulphate
IV salbutamol
IV aminophylline
4) Life-threatening exacerbations may additionally be treated with:
Admission to HDU or ICU
Intubation and ventilation
