Management of Asthma & COPD (Davidsons Medicine) 

COPD

What is it?: There is reduced maximum expiratory flow. 

Aetiology + Risk Factors: Smoking, Pollution, Chemicals, a1-antitrypsin deficiency, Socio-economic status, Infections

Types: Emphysema (PaCO2 = 50, PaO2 = 50), Chronic Bronchitis (Blue Bloaters: PaCO2 = 60, PaO2 = 55), Bronchiolitis

Pathophysiology:

Chronic Bronchitis: In response to the smoking, the bronchial wall becomes inflamed, the respiratory epithelium loses its cilia, there is marked hypertrophy of the submucosal glands, and increase in no. of goblet cells. All of this causes mucus plugs and decreased mucociliary action, therefore causing obstruction. 

Emphysema: In response to smoking + a1-antitrypsin deficiency, the alveolar wall breaks down and therefore there is 'fusion' of the alveoli --> leading to collapse of the airways above the alveoli --> leading to marked hyperinflation of the lungs. 

Investigations: 
Sputum: Culture the sputum (if any). This will give an indication as to whether there is an infection or not. 

Lung function Spirometry Testing: FEV1/FVC <= 80%. Also give them bronchodilators (salbutamol / ipratropium bromide) and measure the lung function again to see the prognosis. Good prognosis requires about 15% increase.

Blood gases: Arterial blood gases is important because it gives an indication as to the extent of the hypoxaemia. 

CXR: This is not useful for COPD but useful to exclude other diagnosis

CT: Useful for quantifying the extent of the emphysema of the lung. 

MANAGEMENT: Is there infection?, Is there symptoms?, IQOL?

Infection: Always treat the infection first. Usually its S. Pneumoniae & H. INfluenzae. Give antibiotics: amoxycillin

Symptoms: Short acting b2-agonists (salbutamol, terbutaline), anti-muscarinics (ipratropium bromide), corticosteroids. Theophyllines (low therapeutic window) + Long acting b2-agonists are okay, but maybe not needed in all cases. Always prescribe inhalers: MDI's, spacers, nebulisers. Use oral only if absolutely necessary. O2 therapy is needed in some cases, and it has been shown to improve symptoms of pul HTN, hypoxaemia, polycythaemia

IQOL: Stop smoking, Stop exposure to chemicals / passive smoking. 


ASTHMA

What is it?: Recurrent episodes of airflow limitation. There are two types: 1) atopic (allergy, most common), 2) non-atopic (non-allergy, least common)

Aetiology & Risk Factors: There is an exogenous antigen that sparks a hypersensitivity reaction. 

Pathophysiology:

There are four cardinal features of asthma: airway hypersensivity, oedema, mucus plugs, and airway constriction. The airway hypersensivity + airway constriction occurs because of the inflammatory mediators such as histamine and metacholine, and can even be triggered by exercise. The oedema is caused by the inflammatory reaction to the exogenous antigen therefore increase vascular permeability. The mucus plugs is caused by excessive secretion of mucus due to hyperplasia of submucosal glands (similar to chronic bronchitis). 

Investigations:
Sputum: Check for infection if need be. Depends on whether they present with rocketing fevers or not?

Lung Fn Spirometry Test: FEV1, FEV1/FVC, PEF all are reduced. Also give them bronchodilators (salbutamol) and measure the lung fn again to see if there is any significant reversibility. Dx of asthma is made if >= 15% improvement in FEV1 or PEF after administering bronchidilators OR if there is spontaneous improvement in PEF over 1 week of home monitoring. 

Blood gases: This is important because it gives an indication as to the level of the hypoxaemia. 

Skin test; This test is useful if the asthma is early onset (atopic). The skin test is to make sure if there is a specific IgE antibody to a specific allergen. If so, then it is atopic asthma --> then you need to categorise it into: exercise induced, acute exacerbation, chronic or episodic asthma. 

MANAGEMENT: Is there infection?, Is there symptoms, IQOL?

Infection: Usually there is no infection. You can culture the sputum to find out for sure. 

Symptoms: Mild asthma: short acting B2 agonists (salbutamol, terbutaline) + inhaled low dose corticosteroids (beclamethasone, budesonide, fluticasone) if need be only. Moderate asthma: Inhaled corticosteroids + short acting B2 agonists, Severe: Inhaled corticosteroids high dose + short acting B2 agonists + any 1 of (if need be): ipratropium bromide, theophylline, long acting B2 agonists. Na cromoglycate + nedocromil are useful in children  (instead of corticosteroids) but not otherwise. 

IQOL: Stop taking precipitating agents (propanolol), Exercise, and Better monitoring of your asthma.