asthma Flashcards
how is asthma an obstructive resp disease?
inflam mechanism
bronchioles constrict - narrowing of airways
makes it more difficult to get air in and out
describe the prevalence of asthma?
increasing across developing world
linked to modern lifestyles - potentially lacking exposure
what is meant be atophy?
allergy
what type of hypersensitivity is asthma?
type 1
how does type 1 hypersensitivity work?
- Allergen is presented to mast cell after entering cell and passing through epithelial
- Ig receptor in mast cell receives antigen from allergen
- Triggers response of mast cell degranulation mediator release
- Inflammation cycle induced – release of histamine, proteinoids (lipid mediators), platelet activating factor and leukotrienes
what are TH2 a response to?
helminth infection
describe an asthmatic airway?
- Inflamed wall and thickened
- Tightened smooth muscle
- Air trapped in alveoli
name some causes of asthma
environmental allergens
genetic susceptibility
how can cigarette smoke affect asthmatics?
could be beneficial in children - exposure to pollutant
but bad in asthmatics
is asthma episodic?
yes - variability of all symptoms and broader history
what does spirometry?
forced expiratory volume - forces all out
what does peak flow meter measure?
measures how fast you can blow
usually more later in the day - treatment can improve peak flow - reduced the variability
what are tests involved in asthma?
spirometry
peak flow meter
exhaled nitric oxide
methacholine challenge test - can induce asthma symptoms - see effect
skin prick test - allergies
define asthma
heterogenous diseases usually characterised by chronic airway inflammation. Defined by history of respiratory symptoms such as wheeze, SoB, chest tightness and cough that vary over time in intensity together with variable expiratory airflow limitation.
how is asthma linked to genetic deposition?
concordance is higher in monozygotic twins than dizygotic twins
having a parent with asthma increases risk and having two parents have a further increased risk
what allergies are associated with asthma?
dust mites
pets
what is basic management of asthma?
regular inhaled steroids - preventer and reliver
beta agonist reliver - SABA
what is SABA
short acting beta agonist
what is the most common chronic childhood disease?
asthma
what is the most common childhood asthma symptom?
wheeze
what conditions are common alongside asthma?
eczema, hayfever
what are the risk factors for adults to have asthma?
family history, exposure to allergens – dust mites, pets, tobacco smoke, history of atopic diseases, smoking (tobacco and E-cigarettes), obesity, GORD – chronic irritation and inflammation of airways following exposure to gastric contents
what are the symptoms in adults’ asthma?
- Recent upper respiratory infections can make symptoms worse
- Dyspnoea: caused by exposure to allergen, cold air, tobacco smoke
- Cough: caused by exposures and can disrupt sleep
- Expiratory wheezes: polyphonic, high pitched expiratory wheezes
- Nasal polyposis; small growths inside nose
what are first line investigations of asthma?
- FEV1/ FVC ratio - <80% via spirometry
- Peak flow – long term daily PEFR can help detect early changes in disease states or to evaluate responses to changes in therapy
- CXR: indicate pathologies – can show acute exacerbation or pneumothorax
- FBC: test for eosinophils/ neutrophils (helminths- TH2 inappropriate response – atopy) and infection
what are second line investigations for asthma?
- Bronchial challenge test – if spirometry and peak expiratory flow may not show reversibility and variability.
- IgE- allergens
- Skin prick testing – allergens
- Fractional exhaled nitric oxide – reflective of degree of eosinophilic inflammation
what is a gas transfer test?
measures how eell lungs can take up oxygen from air
compares partial pressure
what is bronchial hyperresponsiveness?
increase in sensitivity to a wide variety of airway narrowing stimuli - seen in asthma and COPD
what is hypersensitvity?
exaggerated or inappropriate immunological response in a persons response to an antigen/ allergen
how is asthma a type 1 hypersensitivity?
has an exaggerated IgE response
why might asthmatic wheeze?
may result from localised or diffuse airway narrowing or obstruction
- bronchoconstriction, mucosal oedema, external compression
what is a bronchospasm?
when muscles lining bronchi tighten
what is an adverse reaction to salbutamol
fine tremor, nervous tension and tachycardia
what is salbutamol?
short acting beta 2 adrenergic agonist
what is salmeterol?
long acting beta 2 adrengic agonist
why are steroids useful in asthmatics?
increase airway calibre by reducing bronchial inflammatory reactions eg oedema and mucus hypersensitivty - modifies allergic reactions
how do you perform a peak flow test (step by step)
- Stand up and take deep breath (arms open)
- Lips form a tight seal around plastic
- Like a dart blowing
- Do not obstruct tab that moves
- Best out of 3 attempts
- Monitor throughout the day – diaries – will show diurnal characteristics (helps diagnose asthma)