Asthma Flashcards
Definition of asthma. Prevalence
Asthma is a chronic inflammatory airway disease characterised by intermittent airway obstruction and hyper-reactivity
It is a disease of small airways with variable expiratory airflow limitation
The inflammation is usually reversible either spontaneously or with treatment
12% Uk
Pathophysiology of asthma
Non- atopic inflammation mediated by local IgE production
Atopic: inflammation mediated by systemic IgE production (in response to an allergen)
IgE binds to mast cells -> allergens bind -> degranulation -> histamine, lecotrienes, other mediators
- >
- airway smooth muscle hyper responsiveness, contraction, thickening
- sub epithelial inflammation and fibrosis
- mucus hypersecretion and impaired mucus clearance
- increased eosinophils and neutrophils in airway lumen
Symptoms and clinical signs of asthma
symptoms: Cough (dry and nocturnal - worse at night bc parasympathetic main control -> airway constriction) , Wheeze, Breathlessness ,Chest tightness
Clinical signs: atopy (eczema and hay fever), high resp rate, lower oxygen sats, wheeze heard, increased pulse
Precipitating factors for asthma
Allergens (pollen, pets), dust, cigarette smoke, cold weather, exercise, infection, aerosols
How is asthma diagnosed?
Using a peak flow meter lower than it should be for age/ gender/ height
Spirometry - asthma affects expiration more than inspiration. On expiratory flow rate vs volume scalloping is seen (obstructive airway disease). When plot volume vs time you can measure the FEV1 (forced expiratory volume): FVC (forced vital capacity) ratio. Normally 70-80%, asthmatics <70% FEV1 reduced more
Compare asthma to CoPD in terms of symptoms, history, who it affects and reversibility. How can you investigate whether it is asthma or COPD?
Asthma - dry cough, wheeze, history of atopy, children/ young adults, obstructive pattern, good reversibility
COPD: productive cough, wheeze, history smoking, typically older adults, obstructive pattern, poor reversibility
To distinguish: use spirometry before and after using bronchodilators, asthma will improve much more COPD
How is asthma managed depending on probability?
Depends on the probiotic of asthma:
- high probability e.g. cough, wheezy, atopy, repeated episodes start on treatment
Then can move down scale of poor response to treatment->
- intermediate spirometry with reversibility testing
- low e.g. not as typical, another diagnosis more likely, investigate other causes, refer for further investigations
How is asthma managed in primary and secondary prevention?
Primary: evidence is lacking but avoid potential triggers in pregnancy/ childhood
Secondary: remove triggers if possible e.g. pets, dust, smoke, occupation, vaccinations + pharmacological treatments
What are the two main groups of medications used to treat asthma? Give examples of each and state how they work?
Preventer: B2 agonist short or long acting anti- muscurinics help relax smooth muscle to prevent bronchospasms
e.g. ipratrophin bromide, flixotide. Once/ twice a day
reliever: Inhaled corticoid steroids reduce inflammation by reversing histone acetylation to switch off inflammatory genes (Others target IgE and leukotrine) e.g. salbutamol, serevent. Once/ twice a week
Can have seretide: contains both a preventer and a symptom controller/ reliever
Many types of inhalers
Compare a acute severe asthma attack with a life threatening one
Acute severe: can’t speak full sentences, wheeze heard.
RR _>25,
O2 sats _>92%,
peak expiratory flow 33-50% reduced, HR _>115
Life threatening: extreme fatigue, cyanosis, silence heard on auscultation. RR v low O2 sats <92% PEF <33% of normal V low BP
How do you treat an asthma attack?
Oxygen
Short acting beta agonist e.g. salbutamol through a nebuliser
Steroids (prednisolone, hydrocortisone)
Admit
Consider adding other meds
Consider CXR rule out pneumothorax (more likely for asthmatics)
If life threatening may need: mechanical ventilation, intubation, adrenaline, IV bronchodilators, IV mg2+
