COPD Flashcards
COPD is a combination of?
chronic bronchitis and emphysema
what are the histological changes in chronic bronchitis
hypertrophy of mucus secreting glands and hyperplasia of goblet cells
which cytotoxic T cell is involved in COPD?
CD8 - alveolar epithelial cells
what is the immune response in COPD?
Cigarette smoke activates macrophages and airway epithelial cells which release neutrophil chemotactic factors – including IL-8 and leukotriene B4
Neutrophils and macrophages then release proteases that break down connective tissue + stimulate mucus hypersecretion
what is the affect of inflammation of the airway?
scarring and fibrosis of tissue
bronchoconstriction
epithelial cells can become ulcerated - healing with columnar cells rather than squamous cells
what is the mechanism of increased mucus production?
hypertrophy and hyperplasia of mucus glands increase mucus production = airway obstruction
irritants cause cilla shortening - hard to remove mucus
what are the mechanisms behind emphysema?
Loss of elasticity of the alveoli
Alveolar destruction and loss of bronchial support
Inflammation and scarring – reducing the size of the lumen, as well as reducing elasticity
Mucus hypersecretion.
Causes enlarged airspaces distal to the terminal bronchioles
Most common cause of COPD
smoking
genetic causes of COPD
A1-antitrypsan deficiency
how does A1-antitrypsan
Enzyme that destroys other enzymes – destroys proteases including trypsin, elastases and collagenases
If this is deficient, these enzymes eat away at lung tissue
clinical features of COPD (13)
• Breathlessness • Cough • Regular Exacerbations • Tachypnoea • Use of accessory muscles of respiration • Hyperinflation • reduced breath sounds? • Wheeze • Crackles (rales) • Hypoxemia • Hypercapnia vasoconstriction, lung infections
what is the mechanism of hypercapnia in COPD
This is because the mucus flux in the airway block air flow right which causes the partial pressure of CO2 to go up in the lungs
Increases partial pressure of CO2 means that the partial pressure of O2 or oxygen in the lungs goes down and a lower PO¬2 means less oxygen gets into the blood causes hypoxemia.
This trapped CO¬2¬ also makes it harder for CO2 to get out of the bloodstream which explains the hypercapnia
what is the mechanism of vasoconstriction in COPD
Blood vessels undergo vasoconstriction in an attempt to shunt blood to an area with better exchange but when a large proportion of the lungs aren’t exchanging oxygen a large proportion of blood vessels start to constrict = increasing pulmonary vascular resistance and to maintain pulmonary blood flow the body responds by developing pulmonary hypertension
what feature of COPD causes increased risk of lung infection?
mucous plugs develop lung infections behind them
what organisms are common in COPD lung infections?
Strep pneumoniae, h.influenzae
what are the features of pink puffers?
normal PaO2, and a normal or low PaCO2
emphysema
hyperventilate to increase alveolar ventilation and keep blood gases normal
Type 1 resp failure
what are the features of blue bloaters?
low PaO2 and a high PaCO2 cyanosed but not breathless decreased alveolar ventilation hypoxic drive cor pulmonale type 2 failure
what are the spirometry features of COPD
FVC<80% predicted
FEV1/FVC<0.7, OR
what mechanisms account for the altered spirometry
- Airway become obstructed and lungs don’t empty properly, leaves air trapped in lung
- Maximum amount of air in a single breath is known as the FVC is reduced (4L compared to 5L) – reduction more noticeable in the first second of air breathed out FEV1 (this reduction is even more than FVC, 2L compared to 4L)
- = FEV1/FVC ratio <75%
- TLC – air in – actually often higher because they are trapping
what investigations should be considered for COPD?
lung function tests CXR ECG ABG A1-antitrypsin test FBC
what features will be present in a COPD ECG?
large P waves
what will the ABGs of COPD show
decreased PaO2 and increased PaCO2
what can FBC in COPD show?
o Polycythaemia – measure the haematocrit – >45
o Normocytic normochromic anaemia of chronic disease – prevalence of up to 20%.
o HB and PCV may be raised
what is the stage classification of COPD
0 – at risk ≥80% I – Mild ≥80% II – Moderate 50-70% III – Severe 30-49% IV – very severe <30%
