pathology of obstructive airway diseases Flashcards
which three conditions are obstructive airway diseases?
emphysema
chronic bronchitis
asthma
which two conditions together are called COPD?
emphysema and chronic bronchitis
what is predicted FVC based on?
age, sex and height
what is a marked fall in PEFR?
<50% of best
what is a moderate fall in PEFR?
50-80% of best
in obstructive lung disease what happens to PEFR, FEV1 and FVC?
reduced (FVC may be reduced)
what is FEVcompared to FVC in obstructive lung disease?
<70%
what causes airway narrowing in bronchial asthma?
- inflammation and oedema
2. twitching/contraction of smooth muscle
when can bronchial asthma become irreversible?
when it becomes chronic
what is the aetiology of COPD?
- smoking
- atmospheric pollution
- occupation: dust
what is your susceptibility to COPD?
how your metabolism handles the chemicals in cigarettes or pollution.
does congenital alpha 1 antitrypsin deficiency cause chronic bronchitis?
no, only emphysema
what is the clinical definition of COPD?
- Cough productive of sputum most days
- in at least 3 consecutive months
- for 2 or more consecutive years
what are the morphological changes in chronic bronchitis in the large airways?
- mucous gland hyperplasia
- goblet cell hyperplasia
- inflammation and fibrosis is a minor component
what are the morphological changes in chronic bronchitis in the small airways?
- goblet cells appear
- Inflammation and fibrosis in long standing disease
what is the pathological definition of emphysema?
Increase beyond the normal in the size of airspaces distal to the terminal bronchiole arising either from dilatation or from destruction of their walls and without obvious fibrosis.
what is centri-acinar emphysema?
loss of alveolar tissue around the middle of the acinus (around the bronchioles)
what type of emphysema is associated with smoking?
centri-acinar
where does centri-acinar emphyema normally occur?
in the apex of the lung
whar is pan-acinar emphysema?
emphysema that causes a “total wipeout” of aleolar tissue, alveolar tissue is lost everywhere
what type of emphysema occurs in congenital alpha 1 antitrypsin deficiency?
pan-acinar
what is peri-acinar emphysema?
loss of aveolar tissue at the distal end of acinar
how can peri-acinar emphysema cause a pneumothorax ?
Bullae (large air spaces) rupture and air enters the pleural space form the lung
what does smoking do to cause emphysema?
it induces the production of neutrophils and macrophages. These produce proteases such as elastase. These damage lung tissue. Normally the body has ways to prevent damage from these enzymes. However, smoking inhibits these processes: it inhibits anti-elastase and other anti-proteases such as alpha 1 antitrypsin, it also inhibits the repair mechanisms of the lung and elastin synthesis.
what are the reversible components of COPD (with pharmacological intervention)
- smooth muscle contraction
- inflammation
what are alveolar attachments?
where alveolar tissue attaches to the bronchioles.
what causes the collapse of bronchioles on expiration in emphysema?
the loss of alveolar attachments so they are no longer able to hold open the bronchioles druing the pressure exerted on them on expiration.
what are the 4 abnormal states associated with hypoxaemia ?
- Ventilation / Perfusion imbalance (V/Q)
- Diffusion impairment
- Alveolar Hypoventilation
- Shunt
why does airway obstruction cause hypoxaemia?
oxygen can’t get to alveoli to diffuse into the blood.
why does reduced respiratory drive cause hypoxaemia?
the central chemoreceptors in people with copd will become sensitised to carbon dioxide as it will be constantly high. So the drive to breath comes from PO2
why does loss of alveolar surface area cause hypoxaemia?
less surface area for gas exchange so O2 levels drop
why does hypoxaemia occur during acute infective exaceration?
pus in the alveoli prevents gas exchange
what is a ventilation/perfusion mismatch?
some ventilation of abnormal alveoli, just not enough
what is shunt?
no ventilation to abnormal alveoli. So blood is unoxygenated when it passes through the lung and enters the left side of the heart
which conditions cause ventilation/ perfusion mismatch?
bronchitis
bronchopneumonia
which conditions cause shunt?
severe bronchopneumonia
what is FIO2?
the fraction of inspired air which is oxygen
does shunt respond to increase in FIO2 treatment?
no
how can hypoventilation be treated?
raising PIO2
what is chronic (hypoxic) cor pulmonale?
hypertrophy of the right ventricle resulting from disease affecting the function and or structure of the lung. Vasoconstriction of arterioles in the lung, loss of capillary beds and secondery polycythaemia increases pulmonary arterial pressure so right side of the heart has to work harder.
which abnormal states cause type I respiratory failure?
shunt and V/Q mismatch
which abnormal states cause type II respiratory failure?
alveolar hypoventilation
