Asthma Flashcards
What happens in asthma?
Smooth muscle in the airways is hypersensitive and responds to stimuli by constricting causing airflow obstruction
What might an asthma examination show?
Widespread polyphonic expiratory wheeze
What drugs can worsen asthma?
- Beta blockers
- NSAIDS
What investigations are recommended in patients with suspected asthma?
- Fractional exhaled nitric oxide (FeNO) test
- Spirometry with bronchodilator reversibility
What is Fractional exhaled nitric oxide testing? What can make the results of this test unreliable?
- Measures the concentration of nitric oxide exhaled
- Nitric oxide is a marker of airway inflammation
- A level above 40 ppb is a positive test result
- Smoking lowers the FeNO making the result unreliable
What does spirometry measure?
The volume and flow of air during exhalation and inhalation
What is FEV1?
- Forced expiratory volume
- Volume exhaled at the end of the first second of forced expiration
What is FVC?
- Forced vital capacity
- Volume that has been exhaled after a maximal expiration following a full inspiration
What are the typical FEV1, FVC and FEV1/FVC results in asthma?
- FEV1 - significantly reduced
- FVC - normal
- FEV1/FVC < 70%
What is used in bronchodilator reversibility testing? What is a positive result?
- Salbutamol
- An improvement on FEV1 of 12% or more
- And an increase in volume of 200ml or more
Further investigations if there is diagnostic uncertainty following FeNO testing and spirometry?
- Peak flow diary for 4 weeks - peak flow variability
- Direct bronchial challenge test with histamine/methacholine - opposite of reversibility testing
What are the NICE guidelines for long term asthma management?
- SABA (salbutamol)
- add low dose ICS
- add LTRA (montelukast)
- add LABA (+/- LTRA depending on pt response)
- Switch to MART (with low dose ICS)
- Increase dose of ICS
- Specialist management
What colour are SABA inhalers?
Blue
What is a side effect of SABA inhalers?
Tremer
What are side effects of ICS?
- Oral candidiasis
- Stunted growth in children
What will arterial blood gas show during an acute asthma exacerbation? What is a concerning sign?
- Respiratory alkalosis as raised resp rate causes a drop in CO2
- A normal pCO2 or pO2 is a concerning sign as it indicates they are getting tired
What peak flow reading would indicate:
1. Moderate asthma exacerbation
2. Severe asthma exacerbation
3. Life threatening asthma exacerbation
- 50-75% best or predicted
- 33-50% best or predicted
- <33% best or predicted
What signs indicate a moderate acute asthma attack?
- Speech normal
- RR <25/min
- Pulse <110bpm
What signs indicate a severe acute asthma attack?
- Can’t complete sentences
- RR >25/min
- Pulse > 110bpm
What signs indicate a life-threatening acute asthma attack?
- Oxygen sats <92%
- Normal pCO2
- Silent chest
- Cyanosis
- Bradycardia
- Hypotension
- Confusion
What is ‘silent chest’? What is it a sign of?
- When a wheeze disappears as the airways are so tight that there is no air entry
- Life threatening asthma exacerbation
What is the step-wise management of a mild asthma exacerbation?
- SABA with spacer
- Quadrupled dose of ICS
- Oral steroids if insufficient
Follow up within 48 hrs
What is the step-wise management of a moderate asthma exacerbation?
- Nebulised SABA
- Steriods - oral prednisone/IV hydrocortisone
What is the step-wise management of a severe/life-threatening asthma exacerbation?
Oxygen to maintain sats 94-98%
- Nebulised SABA
- Steriods - oral prednisone/IV hydrocortisone
May be additional treated with:
- Nebulised ipratropium bromide (SAMA)
- IV magnesium sulphate
- IV salbutamol
- IV aminophylline
What are complications of salbutamol treatment?
- Hypokalemia (salbutamol drives K+ into cells)
- Tachycardia
- Lactic acidosis
What is the MOA of salbutamol?
- Beta-2 adrenergic receptor agonist
- Relaxes bronchial smooth muscle through effects on beta 2 receptors
What is the MAO of LAMA?
- E.g. tiotropium
- Long-acting muscarinic antagonist
- Block ACh receptors
- ACh receptors are stimulated by the parasympathetic nervous system and cause contraction of the bronchial smooth muscle
What is the role of ICS in asthma management?
Reduce inflammation and the reactivity of the airways
What is the MOA of LTRAs?
- E.g. montelukast
- Leukotriene receptor antagonists
- Block the effect of leukotrienes
- Leukotrienes are produced the immune system and cause inflammation, bronchoconstriction and mucus secretion in the airways
What is the criteria for discharge following an acute asthma attack?
- Stable on discharge meds for 12-24 hrs
- Inhaler technique checked and recorded
- PEF >75% best or predicted
