Asthma Flashcards
DEFINITION
- Most common chronic childhood disease and the major cause of hospitalisation for children.
- It is a common chronic inflammatory condition affecting the airways and displays a varied phenotypic picture.
- At present we have no cure for asthma !!
4.Paediatric asthma represents a lifelong problem, although modern and optimal treatment do offer a good disease control.
5.Recently, paediatric asthma has been reported as a major risk factor for COPD in adult life.
DEFINITION ‘
There is no universally accepted definition of asthma but:
1. reversible airway obstruction
2. airway hyperresponsiveness
3. chronic inflammation
→ are key features
It is a chronic disease with:
- repeated attacks of airway obstruction
- intermitent symptoms of responsiveness to triggering factors such as allergens,smoke, exercise, viral infections
PREVALENCE
1.Asthma prevalence has increased during the last 2 decades
2.It is causes considerable morbidity and healthcare utilisation
3.High frequency of sleep disturbance due to asthma/ absence from school/ limitation of activities.
4.Asthma is associated with reduced growth of lung function( lung function at a young age is a determinant of lung function in adult life).
EPIDEMIOLOGY
1.Worldwide , 1-30% / some countries having come through the epidemic and others still experiencing increasing prevalence.
2.Are more common in boys compared to girls / female predominance after puberty
3.Asthma is more common in younger children and although symptoms apparently resolve in many, episodic wheeze recurs in adulthood in approximately 25%
4.Asthma is associated with allergic conditions such as- eczema, hay fever and food allergy → but most allergic individuals do not have asthma and approximately 20% of children with asthma - are not allergic !!
5.Strong hereditary component to asthma( identical twins are more concordant for asthma compared to fraternal twins)
6.There is no single asthma gene( aprox 20 genes each making a modest contribution towards asthma risk,and these differ between populations)
7.Genetic predisposition in combination with environmental exposures occuring at certain critical times →often in the first 2 years of life→ are implicated in asthma causation.
ETIOLOGY (1)
- Highest prevalence of asthma in Western countries , including UK, Australia, New Zeeland and USA ,suggesting an association between asthma and a„Westernized lifestyle“
2.A number of related hypotheses have been proposed including the hygiene and dietary hypotheses/
3.The hygiene hypothesis being proposed - exposure to infections contracted from older siblings during early life - or to live on a farme when they exposure to different allergen – may protect against the development of allergy
ETIOLOGY (2)
1.the dietary hypothesis – an excess of dietary oxidant or lack of dietary antioxidants(vit E,C) in maternal diet during pregnancy lead to increased asthma
2.Reduced birth weight , antenatal exposures to paracetamol or products of tobacco smoke ,place exposures in early life as crucial to asthma causation
(many children with asthma are initially symptomatic in preschool years)
3.Sedentary lifestyle, obesity,indoor and outdoor air quality- may also be related to asthma causation
4.Changes in outdoor air quality (increasing concentrations of fine particulates, ozone, sulphur dioxide and oxides of nitrogen)-are associated with increased presentation of children with acute asthma
ETIOLOGY (3)
80% - asthma exacerbations in primary care are associated with viral upper respiratory tract infections- predominantly due to rhinovirus (common cold virus)
There is substantial literature/ studies to support the role of early respiratory infection in the later development of asthma → the common cold viruses are implicated
Exposure to allergens wich include house dust mite , cat ,dog and grasses are also associated with increased risk for acute asthma exacerbation
Precipitants for acute asthma symptoms in children include :
- viral upper
- respiratory tract infections,
- change in the weather,
- poor air quality,
- allergen exposure and exercise
PATHOPHYSIOLOGY
Asthma- chronic inflammatory airway disease characterised by:
- reversible airway obstruction
- bronchial hyperresponsivenes (BHR)
Chronic inflammation is often characterised by:
- eosinophilic activity
- allergic inflammation
Bronchial obstruction is a result of:
- bronchial muscle constriction (acting particularly through the β receptors)
- mucosal oedema
- increased airway secretios (resulting from airway inflamation)
PATHOPHYSIOLOGY
All contribute →
reduced airway flow → reduced lung function→classical symptom →wheezing + dyspnea + cough.
Reversibility of the bronchial obstruction may occur:
- spontaneously
or - with bronchodilator( particularly β agonists)
Airway inflammation
in asthma is generally considered to be eosinophilic
Allergen exposure
may lead to a break in natural tolerance – triggering alergic
inflammation – with an allergen-specific immune response involving T and B lymphocytes
The adaptative immune system classically involves T cellular responses to antigens or allergens ,with production of specific IgE antibodies from B-cell,adapts to environmental challenges
Pathophysiology of allergens
binds to the high-affinity receptor for IgE (on the antigen presenting cells)– that facilitate presentation to T-cells – IgE is synthesised in the presence of interleukins(Ils – IL4,IL13) + other cytokines
Allergic inflammation – is characterised by a T-helper cell(Th) type 2 cascade involving Th2 cytokines + other immune mediators
Viral infections
important triggers of symptoms and exacerbations of asthma in childhood( many children with viral wheeze may later not have asthma)
Recent studies suggest that respiratory viruses, like human rhinovirus – play a role in triggering the immune system
( mechanisms are currently not known, but cycles of inflammation, with repeated insults - the inflammatory
resolution becomes less complete with prolonged periods of pathological changes – may progress to deterioration in respiratory function/ remodelling )
PATHOPHYSIOLOGY
atopic asthma
There is accumulating evidence that interaction between respiratory viral infection and atopy is important in the cause and pathogenesis of atopic asthma
Bronchial hyperresponsiveness + airway remodelling
Some research are suggested that allergic sensitisation precedes
rhinovirus-induced wheezing !!
BHR is a common / but not obligate feature of childhood asthma
BHR presents as a general liability to develop symptoms by exposure to various physiological or environmental stimuli (exercise is a classical childhood asthma symptom trigger)
Airway remodelling is less clear, particularly as to when it starts and what elicits the process ( lung function reductions in older children are likely to reflect structural changes in the airway)
DIAGNOSIS
Classical symptoms are:
-wheeze
- cough (particularly at night or during exertion)
- dyspnea
- chest tightness
For diagnosis asthma we neeed
- history taking
- physical examination
- lung pulmonary function testing
- objective documentation of reversible bronchial obstruction
- allergy and bronchial hyperresponsiveness(BHR) - testing
- assesing airway inflammation whenever possible
DIAGNOSIS
In all children ask about:
1.wheezing, cough
2.Specific triggers - passive smoker,pets, humidity,mold and dampness, respiratory infections, cold air exposure, exercise/ activity, cough after laughing / crying
3.Altered sleep paterns:awakening, night cough, sleep apnea
4.Exacerbatios in the past year
5.Nasal symptoms: running,itching, sneezing, blocking
DIAGNOSIS
In infants ask about :
1.Noisy breathing, vomiting with cough
2.Retractions, changes in respiratory rates
3.Difficulty with feeding (poor sucking, grunting sounds)
DIAGNOSIS
In children(˃ 2 yr) ask about:
1.Shortness of breath day/ night
2.Fatigue( decrease in playing compared to peer group, increased irritability)
3.Complaints about „ not feeling well“
4.School absence/ poor school performance
5.Reduced frequency or intensity of physical activity
6.Avoidance of other activities, e.g visits to friends with pets
7.Specific triggers :sports, PE classes ,exercise, activity
DIAGNOSIS
In children(˃ 2 yr) ask about:
1.Shortness of breath day/ night
2.Fatigue( decrease in playing compared to peer group, increased irritability)
3.Complaints about „ not feeling well“
4.School absence/ poor school performance
5.Reduced frequency or intensity of physical activity
6.Avoidance of other activities, e.g visits to friends with pets
7.Specific triggers :sports, PE classes ,exercise, activity
DIAGNOSIS
In children(˃ 2 yr) ask about:
1.Shortness of breath day/ night
2.Fatigue( decrease in playing compared to peer group, increased irritability)
3.Complaints about „ not feeling well“
4.School absence/ poor school performance
5.Reduced frequency or intensity of physical activity
6.Avoidance of other activities, e.g visits to friends with pets
7.Specific triggers :sports, PE classes ,exercise, activity
