COPD Flashcards
What is COPD?
COPD is airflow obstruction which is usually progressive, not fully reversible and does not change markedly over several months. The disease is predominantly caused by smoking.
COPD is umbrella term encompassing emphysema, chronic bronchitis and patients may have features of both.
What is Emphysema?
This is a pathological process in which there is destruction of the terminal bronchioles and distal airspaces. This leads to loss of the alveolar surface areas and therefore the impairment of gas exchange.
The process often progresses to the development of larger redundant airspaces within the lung called bullae. Emphysema causes the destruction of the supporting tissues surrounding the small airways which therefore close/collapse during expiration when the pressure outside the airways rises. This results in airflow obstruction particularly affecting the small airways.
In addition, the loss of elastic tissue in the lung causes the lung to hyperinflate because the lungs are unable to resist the natural tendency of the rib cage to expand outwards.
What is Chronic Bronchitis?
This refers to chronic mucus hypersecretion that frequently occurs in smokers. Mucus hypersecretion is caused by inflammation in the large airways usually due to cigarette smoke leading to proliferation of mucus producing cells in the respiratory epithelium. The result is a chronic productive cough and frequent respiratory infection. In COPD this frequently persists even after smoking has stopped. Chronic bronchitis results in airflow obstruction due to remodelling and narrowing of the airways.
What are the main causes of COPD?
- Smoking
- Alpha 1 antitrypsin deficiency (about 1%…)
- Occupational exposure such as coal dust
- Pollution
15% of smokers will develop COPD the reason why not all is probably genetically determined.
What are the common symptoms of COPD?
Cough and sputum production are frequently the first symptoms of COPD but many patients do no present until they are breathless. Breathlessness is often progressive. Exacerbations are associated with increased breathlessness (compared to baseline) and increase cough and sputum production – may be infective.
Describe the Dyspnoea scoring system
- Not troubled by breathlessness except on strenuous exercise
- Short of breath when hurrying or walking up a slight hill
- Walks slower than contemporaries on level ground because of breathlessness or must stop for breath when waling at own pace.
- Stops for breath after walking about 100m or after a few minutes on level ground
- Too breathless to leave the house, or breathless when dressing or undressing.
What are the common signs of COPD
Purse lip breathing is a protective mechanism that increases the pressure within the airways this causes a reduction or a delay in the closure of the airways, tachypnoea and using accessory muscles.
Hyperinflation is an important cause of breathlessness in COPD because the diaphragm and other respiratory muscles must work much harder to ventilate the lungs making the breathlessness even worse.
Patients may have a wheeze or quiet breath sounds on auscultations
In more advanced cases cyanosis and CO2 retention, right heart failure (co pulmonale) with oedema.
How do we use ariflow obstruction measurements to determine severity of COPD?
Airflow obstruction is measured with spirometry. It is essential for the diagnosis of COPD.
Airflow obstruction = FEV1<80% predicated and FEV1/FVC ratio < 70%.
This also gives us a measure of the severity of the obstruction.
Mild airflow obstruction FEV1 50-80%
Moderate airflow obstruction FEV1 = 30-49%
Severe airflow obstruction FEV1 = <30%
Why does airflow obstruction occur in COPD?
In COPD, there is limitation to the flow of air during expiration and therefore the volume of air expired in the first second is reduced (FEV1). This is made worse by airways collapsing on expiration.
What other examinations must be done to diagnose COPD?
As well as spirometry – must do a CXR to exclude other diagnosis, High resolution CT of the chest to assess severity of damage to the alveoli, arterial blood gases and alpha 1 anti-trypsin test for younger patients.
How do we manage COPD?
- Smoking cessation
- Pulmonary rehabilitation
- Bronchodilators
- Antimuscarinics
- Steroids
- Mucolytics
- Diet – supplements/dietician review – as many COPD patients are under weight
- Supportive such as flu vaccine
- Long term oxygen therapy if appropriate
- Lung volume reduction if appropriate
What treatments are used for stable COPD
Bronchodilators – B2 agonists such as salbutamol. Provides symptomatic relief.
Side effects of B2 agonists include:
Anticholinergics
Work synergistically with the Beta-2 agonists to cause bronchodilation.
Methylxanthines
Cause bronchodilation, increase respiratory drive and have anti-inflammatory effects. They do this by inhibiting phosphodiesterase which would normally break down cAMP so inhibition leads to an increased cAMP - bronchodilation.
Steroids – inhaled – help reduce inflammatory pathways.
Mucolytics such as carbocysteine can reduce sputum thickness
What are the side effects of B agonists such as salbutamol?
Side effects of B2 agonists include: • Tachycardia – atrial B2 receptors • Tremor – skeletal B2 receptors • Anxiety • Palpitations • Hypokalaemia – Skeletal muscle uptake K+.
What are the side effects of anticholinergics?
Side effects include: • Dry mouth, cough and a sore throat • Pharyngitis • URT infection • Bitter taste • Nausea • Supraventricular tachycardia • AF • Urinary difficulty • Urinary retention • Constipation
What are the issues with using Methylxanthines?
They have a very narrow therapeutic window and cause tachycardia/SVT, nausea, seizures and needs blood level monitoring.
