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Definitions
of COPD
Chronic
bronchitis = defined in the basis of history as:
q
Persisted cough with
sputum, for at least 3 consecutive months, ≥ 2 successive yrs.
q
Providing other causes
of productive cough (e.g. bronchiectasis & untreated chronic
asthma) have been excluded.
Emphysema
= defined pathologically as:
q
Permanent dilation
& destruction of lung tissue distal to terminal
bronchioles.
q
With destruction of
their walls.
A
mixed syndrome of chronic bronchitis & emphysema is much more
commonly seen.
Pathophysiology
Chronic
bronchitis
õ
Pathology: hypertrophy
of mucus-secreting glands of bronchial tree, which is evenly
distributed throughout lung, esp. in large bronchi.
q
Initially
¡
Small airways are
affected initially without development of significant
breathlessness.
¡
Reversible à
accounts for improvement in airway function if smoking is stopped
early.
q
Progression à
Squamous cell metaplasia + bronchial wall fibrosis à
airflow limitation.
Emphysema
Loss
of lung elastic recoil
à
↑ TLC.
Loss
of alveoli
à
↓ Gas transfer.
à
Expiratory airflow limitation & air trapping
q
Damage & mucus plugging of small airways from
chronic bronchitis
Rapid expiratory
closure of small airways owing to loss of elastic recoil
à
VA / Q mismatch.
õ
Pathology:
Major
|
Minor
|
Centri-acinar =
Centri-lobar (90%)
|
Hyper-inflation
|
Pan-acinar = Pan-lobar
|
Senile
|
Para-septal
à
|
Bullous à
pneumothorax
|
Irregular
|
Interstitial
|
CO2 is normally the major
stimulant of respiratory center.
Prolonged
high PaCO2
à
↓ This sensitivity
à
Hypoxia becomes chief drive to respiration.
Attempt
to correct hypoxemia by administration of O2 à
↓ Respiratory drive à
↑ PaCO2.
Pathogenesis
Cigarette
smoking
q
Inflammation à
PMNs à Release enzymes (protease + elastase + oxidants).
q
Inactivates
anti-protease (e.g. α1-anti-trypsin).
à
Damaged lung tissue
q
> a/w Centri-acinar
(in emphysema).
Infections
q
Aggravating factor (not
a cause!) à
Release enzymes from PMNs à
tissue damage.
α1-anti-trypsin
deficiency (2% of emphysema cases)
q
3 main phenotypes: MM
(normal), MZ (heterozygous), ZZ (homozygous deficiency).
q
> a/w Panacinar (in
emphysema).
Clinical Features
Cough
with sputum + wheeze + breathlessness: follow many years of
smoker’s cough.
Complications
Respiratory
failure
Cor
pulmonale
written
by:
Khalid Bin Yaroof. FMHS, UAE University.
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