Asthma and COPD Flashcards
What is Asthma?
Chronic inflammation of the airways where obstruction is often reversible, either spontaneously or with treatment
What are 5 defining characteristics of Asthma?
- Chronic Inflammatory Process
- Susceptibility
- Variable/intermittent airflow obstruction
- Airway hyper responsiveness
- Reversibility
Describe the pathophysiology of Asthma
- Macrophages process and present antigens to T cells, activating Th2 (T Helper) cells
- Cytokines released, which attract and activate inflammatory cells (mast cells, eosinophils). Th2 cells also activate B cells, which produce IgE
In Atopic Asthma, what does Atopy mean?
Means that patient has a triad of Asthma, Hayfever and Eczema
Typically, exposure to antigens result in a 2 phase response.
What are 2 phases?
What time periods do they occur over?
What type of hypersensitivity are they examples of?
Immediate response;
- Within 20 mins
- Example of Type I hypersensitivity
Late Phase response;
- Within 3 to 12 hours
- Example of Type IV hypersensitivity
Describe the Immediate Response to Antigens being presented to T cells in Asthma
- Caused by interaction of Allergens and specific IgE antibodies
- Leads to Mast Cell Degranulation, Mucus Production and Bronchoconstriction (Bronchial smooth muscle contraction)
Describe the Late Phase Response to Antigens being presented to T cells in Asthma
- Inflammatory cells (Mast cells, Eosinophils, Neutrophils etc) release mediators and cytokines
- These cause Airway Inflammation and Shedding of Epithelial cells
List 5 ways Airway inflammation reduces airway diameter
- Mucosal swelling/ Oedema
- Thickening of bronchial walls
- Excess production of Abnormal Mucus (Thick, slow moving)
- Smooth muscle contraction
- Epithelium shed and incorporated into thick mucus
Describe the usual cough of asthma patients
Due to abnormal mucus cough is usually dry/ only productive of scanty, white sputum
(In severe cases, many airways are occluded by mucus plugs)
Why can non-allergic stimuli like cold air and fumes trigger asthma attacks?
Inflammation causes hyper-responsiveness of airways
Chronic poorly controlled asthma can lead to airway remodelling, which may not be reversible.
What are 3 changes?
- Hypertrophy + Hyperplasia of Smooth Muscle
- Hypertrophy of mucus glands
- Basement membrane thickening
What are 3 effects of airway narrowing in Asthma patients?
- Wheezing + other clinical features of asthma
- Results in an obstructive pattern on Spirometry (Reduced FEV and FVC ratio)
- Air trapping with increased Residual Volume
Describe the effects on Gas Exchange due to ;
- Mild to Moderate Asthma
- Severe attacks of Asthma
Mild/ Moderate;
- Reduced pCO2, reduced pO2
- Type 1 respiratory failure
Severe (Less CO2 can be exchanged due to exhaustion and more extensive involvement of airways);
- Increased pCO2, reduced pO2
- Type 2 respiratory failure
List 8 triggers of Asthma
- Allergens
- Cold air
- Exercise
- Fumes
- Cigarette smoke
- Perfumes
- Emotional distress
- Drugs (NSAIDS and Beta Blockers)
How do you treat Asthma?
- Patient education (Remove triggers)
- Vaccinations (Influenza and pneumococcal)
- Drug treatment, Bronchodilators and Steroids
What are 4 ways Acute Severe Asthma presents?
- Can’t complete full sentences
- O2 sats< 92%
- Tachypnoea (25) and Tachycardia (110)
- Peak Flow Rate at 33-50% of max value
What are 6 ways Life Threatening Asthma presents?
Any 1 of;
- Cyanosis
- Drowsiness, poor respiratory effort
- ‘Silent chest’
- O2 sats< 90%
- Peak Flow rate< 33%
- Arrhythmia, Hypotension
Describe the ABG analysis of Acute Severe Asthma
Hyperventilation leads to;
- Reduced pCO2
- Unchanged pO2
Therefore, Respiratory Alkalosis and pH increases
Describe the Aetiology of COPD
- Tobacco smoking is responsible for 90% of COPD cases
- Air pollution and occupational exposure are other causes
Alpha1 Antitrypsin deficiency is a less common cause;
- Imbalance in proteinases and antiproteinases
- Leads to Destruction of Alveolar Walls-> Emphysema
- Usually presents at an early age
List 6 pathological changes of COPD
- Enlargement of mucus secreting glands
- Increased no. of goblet cells (replace ciliated epithelium)
- Ciliary dysfunction
- Elastin breakdown-> Alveolar Wall destruction-> Loss of Elastic Recoil
- Formation of larger air spaces-> Reduced SA for gas exchange
- Vascular bed changes-> Pulmonary hypertension
What is the final outcome of Chronic Bronchitis, a component of COPD?
- Excessive mucus secretion
- Impaired removal of secretions (due to ciliary dysfunction)
What are 3 ways the changes due to Emphysema and Chronic Bronchitis lead to increased airway resistance
- Airways obstructed by secretions
- Narrowing of small bronchioles (usually kept open by radial traction)
- Reduced elastic recoil-> Reduced expiratory force-> Air trapping
What does Progressive Hypoxia in COPD lead to?
- Pulmonary vasoconstriction + Vascular smooth muscle thickening-> Pulmonary Hypertension
- RH Failure (Cor pulmonale)
Describe the clinical features of COPD before examination
Cough;
- Chronic for 3 consecutive months
- Productive but sputum quality may change
Shortness of Breath;
- Initially on exertion, may progress to at rest
