Asthma Flashcards
What is bronchial asthma?
A chronic inflammatory disorder characterised by hyper active airways leading to episodic reversible bronchoconstriction.
Recurrent and reversible (in the short term) obstruction in response to normally harmless stimuli or may be due to a chronic inflammatory response in the airways.
How many people does asthma affect?
5 - 10% of the population.
Do asthmatics find inspiration or expiration easier and why?
Inspiration as the bronchioles widen and vice versa.
What are the symptoms of asthma?
Wheeze, cough and dyspnoea.
What changes occur in the airways of chronic asthmatics?
Hyperplasia and hypertrophy of smooth muscle.
Airway oedema.
Increased mucus secretion.
Epithelial shedding from long term inflammation. Causes damage exposing sensory nerve endings.
Describe neurogenic inflammation in asthma.
Sensory nerves have multiple branches. A blow sends an action potential to the CNS and around the branches. Causes release of inflammatory substances (substance P and calcitonin gene related peptide -CGRP). Histamine works on sensory endings and excite them causing bronchi spasm.
What causes bronchial hyper responsiveness in asthma?
Epithelial damage exposes sensory nerve endings (C-fibre irritant receptors). Airways are increasingly sensitive and may have neurogenic inflammation. Two components: hypersensitivity and hyperreactivity.
What drugs are used in asthma provocation tests?
Spasmogens e.g. Histamine and methacholine (muscarinic ach receptor agonist).
What do provocation tests look for?
Falls in FEV1 compared to the inhalation of the bronchiconstrictor.
What is an aero allergen?
Allergen in the air e.g. Pollen.
How can we tell if a patient is suffering from allergic asthma?
After allergen is phagocytosed by dendritic cell. Atopic individuals will have a strong Th2 antibody mediated IgE response. Non atopic will have a low level Th1 response with cell mediated immunity using IgG and macrophages.
What happens in the immediate phase of allergic asthma?
Allergen binds to IgE on the surface of mast cells and de granulation causes release of histamine causing: bronchospasm, inflammatory eosinophil influx and mucosal inflammation and oedema. The inflammatory infiltrate tends to lead to chronicity.
What happens in late phase asthma?
Chemotaxins and chemokines released during early phase infiltrate cytokine releasing Th2 cells and monocytes, activate inflammatory cells particularly eosinophils. This cause epithelial damage, airway inflammation, airway hyper reactivity and bronchospasm.
What forms of airway obstruction are common in asthma?
Airway lumen narrowing due to spasm and inflammation and mucus plugs.
How can asthma obstruction become irreversible?
If collagen is deposited and the airways become remodelled.
What does early/late onset mean in reference to asthma?
Refers to age.
What does atopic/non-atopic mean In reference to asthma?
Refers to allergic status.
What does extrinsic mean in reference to asthma?
The response to an inhaled antigen.
What does intrinsic mean in reference to asthma?
It has a non immune mechanism e.g. Cold, exercise or aspirin.