Asthma Flashcards
What is asthma characterised by?
Recurrent episodes of dyspnoea, cough and wheeze caused by reversible airway obstruction
What are the 3 factors contributing to airway narrowing?
Bronchial muscle contraction, mucus production, mucosal swelling/inflammation
What often triggers asthma other than exertion?
IgE mediated reactions to specific antigens carried by dust mites and pollen etc
What is atopy
A genetic susceptibility to developing allergic disease such as asthma, excema or rhinitis. Confirmed by IgE skin prick test
What are the symptoms of asthma?
Intermittent dyspnoea, cough (esp nocturnal), wheeze, sputum production
What can precipitate an attack?
Cold air, exercise, emotion, allergens, infection, cigarette smoke, pollution, NSAIDs (inhibit protective PGE2), beta blockers
When might leak flow be especially low?
In the morning there is a dip in peak flow even if it is normal at other times
What information is useful to get from the patient?
Exercise tolerance, disturbed sleep, other atopic illness, acid reflex (40-60% of asthmatics have it), home, pets, smoking, job
Clinical signs of asthma are?
Tachypnoea, audible wheeze, hyper inflation of the chest, hyper resonance, decreased air entry
Clinical signs of a severe asthma attack
Can’t complete sentences, HR >110, resp rate >25, PEF 35-50% of expected
Clinical signs of a life threatening attack
Silent chest, confusion, exhaustion, bradycardia, PEF >33% of expected and PO2 of less than 92%
What partial pressure change indicates the attack is near death?
Raised PCO2 as it indicates the respiratory system is beginning to fail
How is the diagnosis of asthma made?
Asthma is a clinical diagnosis which is made on the presence of characteristic symptoms and spirometry with an unexplained FEV1 and CXR showing hyperinflation
Diagnosis of an acute asthma attack?
PEF, sputum, FBC, U+E, CRP, ABG showing slightly lowered PCO2 and PO2 due to hyperventilation
After assessing the severity of attack what would you give as immediate treatment?
Salbutamol 5mg nebulised with O2
Hydrocortisone 100mg or prednisalone 50mg or both if severe
If O2 sats below 93% aim to get sats of 94-98%
The attack is life threatening what steps must you take?
Inform ICU
Give salbutamol every 15 minutes nebulised
Conduct ECG looking for arrythmias
Add ipatropium 0.5mg to nebuliser
Give a dose of magnesium sulfate IV 2g over 20 minutes
What does magnesium sulfate do?
Shown to inhibit bronchconstriction, acetylcholine release and decrease histamine release from mast cells
If the patient doesn’t improve….
Transfer to ICU and IV salbutamol may be required
How many steps are there available in chronic asthma treatment?
5
What is step 1
Short acting Beta agonist such as salbutamol for as and when needed, if used more than once daily or night time syptoms, move to step 2
What is step 2?
Add an inhaled steroid such as beclometasone 200-800micrograms a day
If control still not adequate then move to step 3 which is?
Add a long acting beta agonist such as salmetrol and if necessary up the dose of beclometasone
What is step 4
Beclometasone upped to 2000micrograms per day and add modified release oral theophylline and modified release oral beta agonist
Step 5
Refer to asthma specialist and give prednisalone 1/day
How does theophylline work?
Inhibits phosphodiesterase raising cAMP levels which reduces bronchrestriction
What percentage of the UK population is affected by asthma?
5-8%
