Overview Of Respiratory Pathology

Limitation of airflow due to obstruction and increased airway resistance.

Obstructive Disease

Airway narrowing, loss of elasticity, or increased secretions.

Causes of Obstructive Disease

Reduced lung expansion, decreased total lung capacity.

Restrictive Disease

Chronic bronchitis and emphysema; airflow obstruction; caused by smoking.

COPD

Mucous hyper-secretion in large or small airways

Chronic Bronchitis

Hypertrophy, Hyperplasia (of mucus glands)
Hypersecretion of mucus

And Inflammation

What are the 3Hs of bronchitis?

Goblet cell metaplasia

Bronchlior wall fibrosis

Mucus plugging the bronchliar lumen (obstruction)

Inflammation

Pathology of bronchitis

Destruction of alveoli and permanent dilation;

Emphysema

Permanent dilation of respiratory bronchioles and alveoli.

Destruction of elastic wall tissue without significant fibrosis

Key characteristics of emphysema

Destruction of alveolar walls.

Enlarged air spaces

Deformed terminal and respiratory bronchioles.

Pathology of emphysema (DED)

Dyspnea
Barrel chest

Pursed lip breathing

Symptoms of emphysema without bronchitis

Dyspnea (less)

Cyanotic and obese

Hypoxic

Symptoms of emphysema with bronchitis

Imbalance of proteases and anti-proteases resulting in lung parenchymal destruction.

Pathogenesis of emphysema

Centrilobular - Most common (smoking related)

Panlobular - Hereditary

Para-septal - Distal acinar and peripheral emphysema

Types of emphysema

Chronic airway inflammation

Asthma

Intermittent and reversible airway obstruction

Chronic bronchial inflammation

Bronchial smooth muscle hypertrophy and hyperreactivity

Asthma characteristics

Seasonal allergies (atopic), injections/exercise/drugs (non-atopic).

Asthma Triggers

WBC associated with asthma

eosinophils

Shortness of breath, chest tightness, wheezing, cough.

Asthma Clinical Manifestations

mucus hypersecretion.

bronchoconstriction

Asthma Early reaction

Inflammation

Mucosal edema and hypertrophy (Narrow lumen)

Th2 and eosinophils recruitment → inflammation

Asthma Late reaction

Excess mucus production from goblet cells.

Bronchial wall oedema due to inflammation

Smooth muscle hypertrophy and fibrosis

Asthma Morphological Changes

Permanent dilation of bronchi and bronchioles

Bronchiectasis

Pulmonary inflammation and scarring due to repeat infection

bronchial wall obstruction

lung fibrosis.

Cause of bronchiectasis

Chronic cough (sputum production)
Dyspnea

Clubbed fingers

Symptoms of bronchiectasis

Acute inflammation of alveoli with damage to capillaries and endothelium.

ARDS

Direct: pneumonia/aspiration

Indirect: sepsis, severe trauma.

ARDS Causes

WBC associated with ARDS

neutrophil

Alveolar inflammation

Capillary and endothelium damage

imbalance of inflammatory mediators

ARDS Mechanism

acute onset of dyspnea
hypoxemia

vascular leakiness

loss of surfactant

Symptoms of ARDS

Persistent alveolitis

(inflammation of alveolar walls and spaces)

Idiopathic Pulmonary Fibrosis (IPF)

Cell damaged in IPF

Type 1 pneumocytes

Collagen deposits on ECM by fibroblasts.

Patchy interstitial fibrosis that worsens.

Fibroelastic foci

Collapse of alveolar walls → honeycomb fibrosis

Morphology of IPF

resulting from exposure to toxic inhaled particulates (asbestos, silica).

Pneumoconiosis

Particles phagocytosed by macrophages

leading to fibroblast proliferation

Pneumoconiosis Mechanism

Asbestos

Silica

Coal dust

Types of particles involved in pneumoconiosis

Size importance in Pneumoconiosis (in um)

1-5