14 - Asthma Flashcards
What is asthma?
Chronic inflammatory airway disease that is characterised by intermittent airway obstruction and hyperreactivity to stimuli
Obstruction is reversible with treatment or spontaneously
What are the five defining characteristics of asthma?
FEV1 being measure with spirometry
What is the pathophysiology of asthma?
- Chronic inflammatory process mediated by TH2. Macrophages present antigents to T cells, activating TH2
- TH2 release cytokines, which attract and activate inflammatory cells like mast cells and eosinophils
- TH2 also activate B cells that produce IgE
What is the 2 phase response when an asthmatic is exposed to an antigen?
Immediate (20 minutes): type 1 hypersensitivity. Interaction of allergen and IgE leads to mast cell degranulation and release of mediates (typtase, leukotriene, prostaglandin) so smooth muscle contraction and bronchoconstriction
Late (3-12 hours): type 4 hypersensitivity. Inflammatory cells like eosinophils and mast cells, release mediators that cause airway inflammation. Eosinophils release LTC4 which causes shedding of epithelial cells (sensitive to steroids
How does airway inflammation in asthma lead to a reduced flow of airway in the bronchi?
- Mucosal oedema due to vascular leak
- Thickening of bronchial walls
- Overproduction of mucus (dry cough)
- Smooth muscle contraction
- Epithelia shed and put into mucus
How does asthma present on history and what are some precipitating factors of this condition?
What can happen in long term poorly controlled asthma?
- Hypertrophy and hyperplasia of smooth muscle
- Hypertrophy of mucus glands
- Thickening of basement membrane
Whyy can cold air trigger asthma?
- Airways are hyperesponsive so non allergic stimuli can trigger attacks
How can asthma present on examination?
- Wheezing
- Increased residual volume due to air trapping
What are some investigations we can do to diagnose asthma?
- PEF
- Obstructive spirometry with FEV/FVC <70% with reversibility after bronchodilators
What are the similarities and differences of asthma and COPD?
What type of respiratory failure is asthma and why?
- Mild to moderate: type 1 as V/Q mismatch but hyperventilation can compensate for the high pCO2
- Severe: type 2 as extensive involvement of airways, not just one area, and exhaustion. Rising pCO2 may need to ventilate as sign of life threatening asthma
How do we decide whether to start treatment for suspected asthma in a newly presenting patient?
- Management depends on probaility of asthma
- Don’t want to wait with high risk as it is an airways disease
How can we manage asthma in general ?
- Primary prevention not possible as would have to avoid triggers as kid etc
- Secondary prevention by educating patient on triggers and telling them to avoid, e.g stop smoking, get rid of cat
- Pharmacological with BTS stepwise approach
What are the different classes of drugs that can be used to treat asthma and how do they work?
What is the stepwise management for adults with asthma?
- Can raise and lower dose
- Still not responding up the stairs then consider another diagnosis
- In children under 5 drugs are different
How can inhaled medication for asthma be administered to younger children who may not be able to master the correct technique of inhalation?
Spacer
What do the different colours of inhalers represent?
- Blue: reliever when needed. Salbutamol, SABA
- Brown: preventer, inhaled corticosteroid
- Purple: mix of LABA (e.g salmeterol) and steroid
- Red and pink are different combinations of LABA and steroid
How does salbutamol work?
B2 agonist
How would we treat acute severe asthma
- Nebulised B2 short acting agonists and ipratropium
- Give oxygen in nebuliser
- IV steroids
- Short course of high dose oral prednisolone
- Magnesium sulphate and Aminophylline (a blocker) may also be needed
How do we recognise the difference between acute sever asthma and life threatening asthma?
Acute severe can go to life threatening so monitor in case need ITU and assisted ventilation
If you perform and ABG on an asthmatic patient and compared to their last one they have a rising pCO2, what should you consider?
- Turning to life threatening asthma, may be exhausted
- Consider sending to ITU and ventilation
Which hypersensitivity is asthma associated with?
Type 1 hypersensitivity is mediated by IgE binding to Mast cells. This leads to an inflammatory response.
