Asthma

Asthma has a prevalence of 5.8% in the UK and is responsible for 1500 deaths annually.

Diagnosis

• Features that increase the probability of asthma: 




• Wheeze, breathlessness and cough, particularly if 




• Worse at night/early morning


• Occur in response to exercise, allergens, cold air, aspirin or beta blockers 




• Family or personal history of atopy 


• Widespread wheeze on auscultation 


• Otherwise unexplained low FEV1 or PEF 


• Otherwise unexplained peripheral blood eosinophilia




• Features that lower the probability of asthma:




• Prominent dizziness/light-headedness


• Chronic productive cough in absence of wheeze or breathlessness 


• Voice disturbance 


• Significant smoking history

Management

• If high probability of asthma – trial of treatment 


• If intermediate probability – perform spirometry




• FEV1/FVC <0.7 – trial of treatment 


• FEV1/FVC >0.7 – consider referral to specialist 




• Low probability – consider referral to specialist 

An increase of PEF >15% from baseline or increase of FEV1 > 400mls following a trial of treatment supports the diagnosis of asthma 

Treatment

Chronic asthma

• Step 1: 




• Inhaled short-acting beta 1 agonist PRN 




• Step 2: 




• Step 1 + inhaled steroid 




• Step 3: 




• Step 2 + long-acting beta 2 agonist 


• If control still inadequate consider 




• Stopping long-acting beta 2 agonist if no response


• Increasing inhaled steroid 


• Trial of leukotriene receptor antagonist or SR theophylline






• Step 4: 




• Step 3 + Further increase of inhaled steroid 


• Addition of leukotriene receptor antagonist or SR theophylline or beta 2 agonist tablet




• Step 5: 




• Step 4 + oral steroid 

Acute asthma attacks 

• Assement of severity of asthma 




• Acute severe




• Any one of




• PEF 33-50% best or predicted 


• Respiration rate ≥ 25/minute 


• Heart rate ≥ 110/minute 


• Inability to complete sentences in one breath 






• Life-threatening




• Any one of 




• PEF <33% best or predicted


• SpO2 < 92%


• PaO2 < 8 kPa 


• Normal PaCO2


• Silent chest 


• Cyanosis


• Poor respiratory effort 


• Arrhythmia 


• Exhaustion, altered conscious level






• Near fatal 




• Raised PaCO2 and/or requiring mechanical ventilation with raised inflation pressures 

• Treatment of acute severe asthma 




• Oxygen 


• Nebulised salbutamol 


• Nebulised ipratropium bromide 


• Prednisolone 40-50mg od – continue for at least 5 days or until recovery 


• Consider single dose of IV magnesium sulphate 

• Admit patients: 




• With any feature of life threatening or near fatal attack 


• Any feature of severe attack persisting after initial treatment


• Patients whose peak flow is >75% predicted or best one hour after initial treatment may be discharged from ED unless there are other indications for admission 

• If patient is admitted, prior to discharge patient should: 




• Have been on discharge medication for 12-24 hours


• Have PEF >75% predicted or best and PEF diurnal variability <25% 


• GP follow up arranged within 2 working days 


• Respiratory clinic follow up within 4 weeks 

Small print gem: female gender is a risk factor for persistence of asthma from childhood to adulthood.

References:

BTS/SIGN Asthma guidelines. 2009. Available at http://www.brit-thoracic.org.uk/guidelines/asthma-guidelines.aspx

Pinnock, H. and Shah, R. Asthma. BMJ. 2007; 334(7958): 847-850.