COPD Flashcards
What is COPD
Disease state characterised by limited air flow which is not fully reversible.Limitation is progressive and associated with an abnormal inflammatory response of the lungs to noxious particles or gases.
Umbrella term used to describe the irreversible aspect of chronic bronchitis, emphysema and asthma
Chronic bronchitis
Defined clinically. Productive cough for 3 months over a period of 2 years, where other causes of chronic cough have been excluded
Emphysema
Defined pathologically
Presence of permanent enlargement of the airspaces distal to the terminal bronchioles. Destruction of the alveolar walls without obvious fibrosis
Describe the changes in the large airways of COPD patients
Epithelium often shows metaplasia of the squamous epithelium, hyperplasia of the goblet cells and submucosal glands causes mucus hypersecretion. The airway is infiltrated with neutrophils macrophages and Tc cells.
Unlike in asthma, there is no thickening of the smooth muscle or basement membrane
Describe the changes in the small airways in COPD patients
The airway wall becomes thickened and is infiltrated with inflammatory cells (neutrophils, macrophages, Tc cells) and fibroblasts. The lumen is filled with inflammatory exudate and mucus. There is also peribronchial fibrosis and increase in the smooth muscle of the airway which causes narrowing.
Changes in the lung parenchyma in COPD patients
There is a loss of elasticity and alveolar wall destruction.
Accumulation of inflammatory cells (Macrophages, Tc). Destructive changes reduce the pulmonary capillary bed.
Risk factors for COPD
Exposure: tobacco smoke, dusts (occupation), chemicals, infections
Genetic: alpha1-antitrypsin deficiency
How is COPD classified?
Using spirometry
Patients with COPD have a low FEV1/FVC ratio. FEV1 is reduced due to narrowing of the airway. Patients with a ratio of <0.7 is indicative of COPD
FEV1 gives an indiation of severity.
Diagnosis of COPD incomplete without spirometry
Why does alpha1-antitryptase deficency increase the risk of COPD?
Inflammation of the lung causes teh production of anti-oxidants which increase oxidative stress and proteolytic enzymes which destroy the alveolar walls. This initiates repair mechanisms that cause fibrosis.
Anti-proteinases (such as a1-antitrypsin) inhbit proteinase repair and therefore reduce fibrosis and COPD lung pathology.
Deficency causes increased risk of damage.
Can be genetic or due to smoking (inactivates enzyme)
How does emphysema affect respiration?
Loss of elasticity and alveolar attachments to the airway reduces the elastic recoil in the lung and the airways collapse during expiration.
Premature closure of airways limits expiratory flow while the loss of alveoli decreases capacity for gas transfer.
Inflammation and scarring causes the small airways to narrow, mucus secretion blocks the airways.
This leads to expiratory airflow limitation and air trapping.
Characteristic symptoms of COPD
Productive cough (white or clear sputum)
Wheeze
Breathlessness
Systemic effects: osteoporosis, depression, weight loss, reduced muscle mass and weakness.
Clinical signs of COPD
Prolonged expiration
Accessory muscles of respiration used
Barrel shaped chest
Causes of airflow limitation in COPD
Reversible:
Accumulation of inflammatory cells, mucus and exudate
Smooth muscle contraction in peripheral and central airways
Dynamic hyperinflation during exercise
Irreversible:
Fibrosis and narowing of the airways
Loss of elastic recoil due to alveolar destruction
Destruction of alveolar support that maintains patency of small airways
How can you differentiate asthma from COPD
Asthma:
Symptoms - breathlessness, chest tightness, non-productive cough, wheeze. Show dinural variation
Reversible
Breathless is variable
COPD:
Symptoms - productive cough, wheeze, shortness of breath
Progressive
Breathlessness is persistent
Management of COPD
Stop smoking
Assess and monitor disease
Reduce risk factors
Manage stable COPD (education, pharm, lifestyle)
Manage exacerbations
Drug treatment: b2 agonists/anticholinergics, inhaled steroids
Lifestyle: exercise training programs and pulmonary rehab. Long term O2 administration (.15hrs per day)
