13a. Respiratory Health - Asthma Flashcards
What is asthma?
Chronic respiratory disorder characterised by variable airway obstruction
Hyper-responsiveness to stimulii
What biomechanical reasons cause narrowing of the arteries in asthma?
Bronchial smooth muscle spasm
Swelling of bronchial mucosa
Excess mucous secretion
Which group sees higher incidences of asthma?
Children
Boys in early childhood
Girls by adulthood
Signs/symptoms of asthma
Wheezing
Intermittent shortness of breath
Chest tightness
Dry cough
Which immunoglobulin is asthma mediated by?
IgE
What triggers an asthma attack?
Allergic response to an allergen
What does an allergic response in asthma lead to?
Release of inflammatory mediators
Which inflammatory mediators are released in response to an allergen?
Histamine
Leukotrienes
Prostaglandins
What do the inflammatory mediators released in response to an allergen cause?
Bronchospasm
(leading to asthma attack)
What other mechanisms cause the airways to narrow?
Mucus production (by goblet cells)
Increased airway tension
Hyper-responsiveness
Airway remodelling
Lipoxygenase products
Arachidonic acid metabolism imbalance
What is airway remodelling?
Enlargement of bronchial smooth muscle cells
Formation of new vessels
Interstitial collagen deposition
(all caused by chronic inflammation)
What are lipoxygenase products?
Chemical mediators more potent stimulators of bronchial constriction than histamine
What can lead to an increase of lipoxygenase products?
Arachidonic acid metabolism imbalance
Causes/risk factors for asthma
Immune tolerance
Hygiene Hypothesis
Antibiotics
Not breastfeeding
Early weaning
Obesity
Preservatives/food colourings
Vit D def
Mg def
Drugs
Female sex hormone fluctuations
Why is immune tolerance a risk factor for asthma?
Excessive Th2 encourages IgE release
Heightened Th2 during pregnancy predisposes infant to allergies
Why are antibiotics a risk factor for asthma?
Leads to gut dysbiosis which disrupts immune system
Increases development of atopic/inflammatory diseases
Heightened Th2 response via antigen stimulation of antibody pathway
Why does not breastfeeding increase the risk of asthma?
Breastfeeding is protective
Supports immune development
Optimises gut microbiome
What does breast milk contain that reduces the risk of asthma?
Microbiota
GOS
Immune factors
Macro and micronutrients
Hormones/growth factors
Colostrum
Through what mechanisms does breast milk more protective against asthma?
Gut microbiome
Epigenetics
Metabolism
Lung function
Immunity
Why is early weaning a risk factor for asthma?
Longer breastfeeding shown to result in lower risk of wheeze
Has a protective effect
What are the factors within obesity that are a risk factor for asthma?
Lung function
Diet
Microbiome changes
Systemic inflammation
Why does obesity affect lung function?
Reduced expiratory reserve volume (ERV)
Reduced functional residual capacity (FRC)
Why does diet causing obesity affect asthma?
Increase sat fat/sugar
High O6:3 ratio
Low fibre/AO
Why do microbiome changes from obesity affect asthma?
Low Bacteroides - major SCFA producer
Alterations in SCFAs increase allergic airway disease
How does systemic inflammation from obesity affect asthma?
Increased cytokines released from adipose tissue contribute to airway hyper-responsiveness and remodelling
Which preservatives may induce asthma in children?
Benzoates
Sulphur dioxide
Sulphites
Which food colourings may trigger an asthma attack?
Azo dyes
(tartrazine)