Respiratory system - Asthma Flashcards
Define asthma.
A chronic disorder characterised by:
- Airway wall inflammation and airway wall remodelling
- Reversible airflow obstruction
- Increase in airway responsiveness to a variety of simuli
What cells are present in the pseudo glandular-stage human lung that aren’t in the embryonic?
Smooth muscle apha actin positive cells in the airways
What is the difference between normal lung and airway walls and those in wheezing disorders?
Asthmatic lung has increased ASM thickness, damaged epithelium and thickened RBM
Smokers lungs/premature birth lungs have all these characteristics plus loss of alveolar septa
How are airway walls remodelled in asthma? What cells are involved?
Structural changes caused by chronic inflammation
Multiple cells and soluble mediators involved
Cytokines, leukotrienes, neutrophils, eosinophils, mast cells, growth factors for repair
What are the triggers to ASM contraction?
Muscarinic agonists (ACH receptors)
Histamine
Cold air
Arachadonic acid metabolites e.g. prostaglandins, leukotrienes
What does a flow volume loop for asthmatics look like?
Cut out expiratory flow, decreased volume, low PEFR and FEV1/FVC ratio. Reversible with salbutamol >12% increase in FEV1
Normal measurements do not exclude asthma
Where is asthma most common?
Developed world. Incidence increases in populations who move from developing to developed countries (prevalence increasing)
5.4 mill in UK currently receiving treatment for asthma
What can cause asthma?
Family risk
Sensitisation to airborne allergens (HDM, pollens) - air-pollution, tobacco smoke, fungal spores
Hygiene hypothesis
Allergic asthma
Viral-induced wheeze (most common under 5)
Aspirin sensitive asthma (adults only)
Occupational asthma
How is asthma diagnosed?
Clinically. No standardised definition of the type, severity or frequency of symptoms, nor of the findings on investigation
What are the recurrent symptoms of asthma?
Wheeze Breathlessness Chest tightness Cough Variable airflow obstruction
AHR and airway inflammation are components of the disease and their assessment aids diagnosis
What is a wheeze?
High pitched, expiratory, musical sound
Originates in airways which have been narrowed by compression or obstruction
Variable intensity and tone in asthma (polyphonic)
What is an asthmatic cough like?
Often worse at night (lack of sleep)
Exercise-induced
Dry
Wet cough = infection
When might a asthmatic patient have trouble breathing?
Exercise
During acute exacerbations
Cold air
What would an objective assessment of an asthmatic patient show?
Tachypnoea
Recession
Tracheal tug
Prolonged expiratory phase +/- wheeze
What parts of a patients history help to diagnose asthma?
Onset and pattern of symptoms Past medical history Family history Occupational history Non-asthma drug history Pets Previous treatment
How would you examine a patient you expect has asthma?
Chest - scars/deformities, hyper-expansion (barrel chest)
General health - eczema/hayfever, lethargy, can they talk?
Percussion - hyper-resonant
Auscultation - polyphonic wheeze
What chest wall deformities might an asthmatic patient have?
Sternal (pectus) deformities are not common signs of asthma Harrisons Suclus (in-drawing of costal cartilages is however common in children)
What investigations are done in the clinic for asthma?
-Allergy testing - skin prick, blood IgE levels to specific aeroallergens
Exercise induced asthma
-CXR. Generally normal in the chronic situation (exclude other diseases esp pneumothorax during severe acute exacerbations)
-Trial of airflow reversibility
-Spirometry/Lung Function Tests - histamine or metacholine challenge
-Peak flow meter
What is the management of asthma?
- Educate patents on correct recognition of symptoms, timely use of medication, services
- Primary prevention - stop smoking, cleaning, fresh air, breast feeding, exposure to allergens/triggers, weight
- Pharmacology - airway relaxants (relievers), anti-inflammatory agents (preventers)
What airway relaxants and anti-inflammatorys may be used to treat asthma?
Airway relaxants: - Beta 2 agonists (short and long acting) - Muscarinic antagonists -Theophylline/Aminophylline Anti-inflammatory agents: -Corticosteroids -Leukotriene receptor antagonists
What is the action of steroids in asthma?
decreases: -secretion number of eosinophils -T-lymphocyte cytokines -mast cell number -macrophage secretion and cytokines -epithelial cell cytokines -mucus secretion from mucus glands -endothelial cell leakage increases beta 2 adrenoceptors in airway smooth muscle
What are the BTS guidelines for asthma?
Start treatment at the step most appropriate to initial severity
Achieve early control
Maintain control by stepping up and down treatment as necessary
Before initiating any new drug, check compliance and technique
What are the sign so mild acute asthma?
Saturations >92% in air
Pulse 75% predicted
What are the signs of moderate acute asthma?
Saturations >92% in air Pulse <25 Speech normal Wheeze PEFR 75-50% predicted
What are the signs of severe acute asthma?
Saturations 110 RR >25 Can't complete sentences No wheeze PEFR 35-50% predicted
When is asthma life threatening?
Saturations <35% predicted
Rising or normal PCO2
What is the ABC of acute asthma?
A - oxygen
B - continuous salbutamol and atrovent nebs
C - IV access - salbutamol, magnesium sulphate, aminophylline
Intubate and ventilate
