Session 6 - Anti-Asthmatic drugs Flashcards
What two main histopathological features is asthma characterised by?
Airway wall inflammation and remodelling (reversible airflow obstruction).
What are three possible causes of asthma?
Genetic
Pre/post-natal exposure to airborne allergens
Hygien Hypothesis
What is asthma defined as
One or more of: Wheeze Cough Breathlessness Chest tightness Variable airflow obstruction
Describe an asthmatic wheeze
High pitches expiratory sound which is of variable intensity and tone (polyphonic)
Describe an asthmatic cough
Often worse at night (Lack of sleep, poor performance at school)
Exercise induced (Decreased participation in activities)
Dry cough
What do you look for in inspection of someone with asthma?
o Chest Scars, deformities Hyper-expansion (Barrel Chest) o General health Eczema, hay-fever Lethargy Can they speak?
What do you look for in percussion in asthma?
Hyper-resonant
What would you see in asthma spirometry
o Low PEFR
o Low FEV1/FVC Ratio
o >12% increase in FEV1 following salbutamol
How could you test the trigger of asthma allergens?
o Skin prick to aero-allergens, e.g. cat, dog, HDM
o Blood IgE levels to specific aero-allergens
What are chest x-rays for in asthma?
o Performed to exclude other diseases/inhalation of foreign body/pneumothorax
What is autonomic innervation of bronchial smooth muscle?
Sympathetic Activity -> Bronchodilation
Parasympathetic Activity -> Maintains airway smooth muscle tone
What do sympathetic nerves innervate in bronchioles?
Blood vessels and glands, NOT bronchial smooth muscle
What responds sympathetically and is attached to bronchial smooth muscle, epithelium, glands and mast cells?
B2 adrenoceptors
What does binding of noradrenaline to B2 adrenoceptors do?
bronchodilation, reduced histamine release and increased mucociliary clearance.
What does parasympathetic innervation of the airways do?
Parasympathetic activity is normally dominant in maintaining smooth muscle tone in the airways. Muscarinic Receptors are present on airway and vascular smooth muscle and glands. The M3 Receptor is pharmacologically the most important.
What are the three main categories of asthma pathophysiology in affected tissues
Smooth muscle dysfunction
Inflammation
Airway remodelling
What happens in smc dysfunction in asthma?
Increased contraction and mass of SMC
Increased cyto/chemokines
What are the immune cells involved in asthma?
Th2, mast cells
What are the five different remodelling factors which occur in Asthma
Mucus gland hyperplasia Airway wall thickening Increased smooth muscle mass Subepithelial fibrosis Epithelium desquamation
What is the early phase response in asthma?
In allergic asthma, initial response to allergen provocation is due to interaction with mast cell fixed IgE, resulting in histamine release and other potent spasmogens -> Bronchospasm
What occurs in the asthmatic late phase response?
Co-release of a range of mediators and chemotaxins activate a complex immune system response that brings leucocytes to the area. This sets off a further chain of event leading to exacerbated bronchospasm and congestion due to:
o Epithelial damage
Increased exposure of the sensory irritant receptors, further exacerbating bronchial hyperactivity and sensitivity
o Thickening of the basement membrane
o Oedema
o Mucus production
Define bronchial hyperesponsiveness
exaggerated bronchoconstrictor response to direct pharmacological stimuli such as histamine, or indirect stimuli such as exercise