CR: PBL 5 (Asthma) Flashcards
(40 cards)
What is asthma?
Spasm in bronchi of lungs, causing difficulty in breathing, resulting from an allergic reaction or hypersensitivity
What is peak flow?
Device measures maximum air flow out of lungs during forced expiration
What does salbutamol do?
Causes bronchodilation
Describe the pathophysiology of asthma
Allergen exposure –> antigen moves through epithelia of bronchi –> antigen binds to IgE-mast cell complex –> degranulation of mast cell –> release of histamine, proteases and chemotactic factors –> bronchoconstriction, vasodilation and increased vascular permeability –> eosinophils and neutrophils drawn in from the blood –> inflammation and redness
What is status asthmaticus?
Asthma attacks follow one another without pause
How can asthma be diagnosed with peak flow tests?
When the volume of air that can be forced out of the lungs in one breath is reduced
How can asthma be diagnosed with spirometry tests?
Measures FEV1 and FVC and compares them to averages measurements for people of same age, sex and height
How is asthma treated?
Reliever inhalers and preventer inhalers predominantly (can use oral steroids)
Describe how ‘reliever inhalers’ work
Contain short-acting beta 2 agonist
Describe how ‘preventer inhalers’ work
Reduce inflammation and sensitivity of airways to prevent asthma attack by containing an inhaled corticosteroid
Why may oral steroids be given in the treatment of asthma?
To regain control of asthma when it’s temporarily upset or when long-term control of asthma remains a problem despite maximal doses of inhalers
Why are steroids not commonly used as a long-term treatment of asthma?
Have serious possible side effects
What are some of the potential side effects of oral steroids taken for more than 3 months?
Osteoporosis, hypertension, diabetes, increased appetite, cataracts, glaucoma, skin thinning, muscle weakness
Describe the mechanism of action of salbutamol
Bind to b2 adrenoreceptors on bronchial smooth muscle –> activation of adenyl cyclase –> catalyses ATP to cAMP –> cAMP lowers intracellular Ca2+ concentration –> smooth muscle relaxation and high cAMP levels inhibit bronchoconstrictor mediators e.g. histamine and leukotriene from mast cells
Describe how corticosteroids work
Inhibit the recruitment of inflammatory cells (T cells, mast cells, eosinophils and dendritic cells) by suppression of chemotactic factors and adhesion molecules
Why was the patient in status asthmaticus suffering from alkalaemia?
Tachypnea/hyperventilation removed more CO2 than normal so there is less CO2 to combine with water and form H2CO3 and therefore H+ ions are used to buffer this change, and therefore the pH increases
What is involved in a long-term asthma plan
Proactive monitoring and managing of symptoms, reducing exposure to allergens,
What controls respiration?
Respiratory centres in the brainstem
How do higher centres of the brain contribute to respiratory control?
Involved in voluntary control (pain, emotion, temperature) and changes the impulses from the pontine respiratory centre to the medullary respiratory centre to affect the lungs
How do peripheral chemoreceptors contribute to respiratory control?
Carotid and aortic bodies detect changes in blood composition, and if there is more CO2, less O2 and decreased pH –> stimulates increased breathing rate
Do chemoreceptors respond more quickly to CO2 or O2 changes?
CO2 accumulation
How do central chemoreceptors contribute to respiratory control?
Medullary chemoreceptors and respond to increase in CO2 –> increased breathing rate
How do receptors in muscles and joints contribute to respiratory control?
Respond to contraction/exercise to increase the breathing rate
How do irritant receptors in the lungs contribute to respiratory control?
Aim to help exhale irritant –> supress inhalation in medullary respiratory centre –> blowing off substance
