Chronic Bronchitis, Emphysema, Bronchiectasis & Cystic Fibrosis – Comprehensive Study Notes

Chronic Bronchitis

Core Definition

• Type B COPD ("blue bloater").
• Diagnostic time-frame ⇒ productive cough >3\,\text{months} during each of >2 consecutive years.
• Pathology is persistent & irreversible.

Epidemiology & Risk Profile

• Peak age: >30\text{–}40\,\text{yr}.
• Weight: classically overweight/obese; historical male : female ratio 1:2.
• Strongly associated with concomitant emphysema.

Etiology / Major Causes

• Cigarette smoking ≈ 90\% of cases.
• Repeated airway infections & colonisation (viral / bacterial).
• Inhalation of physical or chemical irritants (dust, pollutants, industrial fumes).
• Genetic susceptibility (poorly defined; contrasts with the clear genetic link in emphysema via \alpha_1-antitrypsin deficiency).

Pathogenesis – Stepwise Events

• Chronic mucosal inflammation ⇨ oedema & scarring of bronchial wall.
• Hyperplasia of mucus (goblet) cells + hypersecretion ⇨ formation of thick, purulent mucus plugs.
• Squamous metaplasia of respiratory epithelium (protective ↦ dysfunctional).
• Bronchial wall thickening ↑ airway resistance (Poiseuille concept R\propto\tfrac{1}{r^4}) ⇨ ↑ work of breathing & O_2 utilisation.
• Vascular consequences: inflammatory mediators ➔ vasoconstriction of pulmonary arterioles ➔ pulmonary HTN ➔ right-sided heart failure (cor pulmonale).

Clinical Manifestations

• Early: chronic "smoker’s" cough, most pronounced in the morning.
• Excessive sputum production (muco-purulent).
• Dyspnoea on exertion that progresses slowly.
• Signs of volume overload: peripheral oedema, hepatic congestion, jugular venous distension ("bloater").
• Late: cyanosis (hypoxaemia); secondary polycythaemia.
• Adventitious sounds: coarse crackles, wheezes.

Diagnostic Work-up

• History + examination remain pivotal.
• Chest X-ray:
– ↑ bronchovascular markings.
– "Dirty" or congested lung fields.
– Evidence of previous infections (fibrotic strands, scarring).
• Pulmonary Function Tests (not given in slide but classically show):
– ↓ FEV1, ↓ FEV1/FVC ratio
– Normal/↑ TLC due to air trapping.
• Sputum culture (exacerbations).
• ECG / Echocardiography if cor pulmonale suspected.

Management / Long-Term Care

• Smoking cessation (most impactful).
• Bronchodilator therapy: inhaled \beta2 agonists & anticholinergics. • Corticosteroids (inhaled ± systemic) during exacerbations. • Reduce exposure to irritants (workplace, air quality). • Supportive: adequate hydration (mobilise secretions), judicious rest balanced with graded exercise (treadmill, stationary bike). • Vaccinations: influenza, pneumococcal. • Advanced: long-term O2 therapy, pulmonary rehab, consideration of lung transplant (end-stage).

Emphysema

Core Definition

• Abnormal, permanent enlargement of distal airspaces (respiratory bronchioles → alveoli) with destruction of alveolar walls and no obvious fibrosis.
• Microscopic appearance: "honeycombing".
• Loss of elastic recoil ⇨ dynamic collapse of bronchioles during expiration.
• Classified as Type A COPD ("pink puffer").

Epidemiology / Who Gets It?

• <50\,\text{yr}: uncommon; usually hereditary \alpha_1-antitrypsin deficiency. • >50\,\text{yr}: cumulative injurious exposures (smoking, pollution, occupational dusts).
• Historically thought of as the pulmonary analogue of cirrhosis — an end-stage pattern resulting from many small-airway insults.

Etiological Factors

• Cigarette smoking >70 pack-years:
– Generates inflammation with release of proteolytic enzymes (elastase, collagenase).
– Oxidants in smoke inactivate \alpha1-antitrypsin. • Environmental / occupational exposures: mining, welding, asbestos. • Air pollution (urban). • Genetic deficiency of \alpha1-antitrypsin (PiZZ phenotype).

What is \alpha_1-Antitrypsin?

• Liver-derived serine-protease inhibitor.
• Principal target ⇨ neutrophil elastase.
• Normal physiology: \text{Elastase}\, +\, \alpha_1\text{AT}\;\to\;\text{Neutralised complex} protecting alveolar walls.
• Deficiency ⇒ unchecked elastase → alveolar septal destruction.

Pathogenesis – Key Events

• Imbalance: Protease activity ≫ Anti-protease defence.
• Elastin & collagen loss ⇨ loss of radial traction, ↓ small airway calibre.
• Air trapping (↑ TLC), hyperinflation.
• Reduced diffusion surface → V/Q mismatch is less than in bronchitis; patient maintains near-normal PaO_2 until late.

Clinical Manifestations – "Pink Puffer"

• Progressive exertional dyspnoea (years).
• Minimal cough, scant sputum.
• Weight loss & muscular wasting (↑ work of breathing + ↓ intake).
• Barrel chest (↑ AP diameter).
• Accessory-muscle use, pursed-lip breathing (creates back-pressure to splint airways).
• “Tripod” posture (leaning forward).
• Physical: hyperresonant chest, distant heart & breath sounds, prolonged expiration, possible wheeze.
• Digital clubbing (late).

Complication Highlight – Bullae & Pneumothorax

• Bullae = subpleural, paper-thin air spaces.
• Rupture ⇨ spontaneous secondary pneumothorax:
– Small: may resolve;
– Large: mediastinal shift, CVS compromise → requires chest tube drainage.

Diagnostic Approach

• Physical phenotype: thin, wasted, barrel-chested.
• PFTs:
– ↓ FEV1; ↓ FVC; FEV1/FVC markedly low.
– ↑ TLC, ↑ Residual Volume.
– ↓ DLCO (diffusing capacity) distinguishes emphysema from asthma/chronic bronchitis.
• Chest X-ray: hyperlucent fields, flattened hemidiaphragms, vertical cardiac silhouette, bullae.
• Laboratory: screen for \alpha_1-antitrypsin level in young/non-smokers.

Treatment Principles

• Smoking cessation remains cornerstone.
• Long-term O2 therapy prolongs survival in chronic hypoxaemia. • Pharmacology (similar to bronchitis): – Inhaled short-acting \beta2 agonists.
– Long-acting anticholinergics (tiotropium).
– Inhaled corticosteroids ± LABA.
– Pulmonary rehabilitation & nutrition optimisation.
• Surgical / procedural:
– Bullectomy (selected).
– Lung volume-reduction surgery (upper-lobe disease).
– Lung transplantation (end-stage).

Chronic Bronchitis vs Emphysema – Comparative Snapshot

• Nomenclature:
– CB = "blue bloater";
– EMPH = "pink puffer".
• Obstruction Mechanism:
– CB: luminal narrowing & mucus plugs;
– EMPH: loss of elastic recoil & alveolar support.
• Morphology:
– CB: enlarged mucus glands, bronchial wall thickening;
– EMPH: enlarged distal airspaces, bullae, thin septa.
• Clinical:
– CB: productive cough, oedema, cyanosis;
– EMPH: dyspnoea, weight loss, quiet chest.
• Gas exchange:
– CB: marked V/Q mismatch → early hypoxaemia, hypercapnia;
– EMPH: relatively preserved PaO_2 until late.
• Heart impact:
– CB: cor pulmonale common;
– EMPH: less common, appears late.
• Management: broadly similar inhaled therapies; emphysema may require surgical volume reduction.

Bronchiectasis

Concept & Terminology

• "-ectasis" ⇒ dilation – here, irreversible dilation of large bronchi.
• Not a single disease → a final common pathway of varied insults.

Etiology / Risk Groups

• Childhood predominance.
• Congenital (~50\%) – strong link to cystic fibrosis (CF).
• Acquired causes (adults & children): severe infections (TB, measles, pertussis), immunodeficiency, airway obstruction (tumour, foreign body), ABPA (allergic bronchopulmonary aspergillosis).

Pathogenesis

• Recurrent infection/inflammation → destruction of muscular & elastic bronchial components.
• Loss of ciliated epithelium ⇨ squamous metaplasia, purulent secretion accumulation.
• Vicious cycle: obstruction ↔ infection ↔ inflammation ↔ further dilation.

Clinical Pearls

• Chronic, copious purulent sputum, fetid breath.
• Recurrent haemoptysis.
• Crackles & wheezes over affected lobes.
• Radiology: tram-track sign, signet-ring sign on CT; distinguishes from bullae (parenchymal, not airway).

Cystic Fibrosis (CF)

Genetic Essentials

• Autosomal recessive mutation in CFTR (cystic fibrosis transmembrane conductance regulator) chloride channel.
• Incidence: 1:2000\text{–}1:3000 Caucasian births; survival into adulthood (>18\,\text{yr}) in \approx35\%.

Multisystem Impact

• Lungs: viscous mucus ➔ recurrent infections, bronchiectasis.
• Pancreas: exocrine insufficiency → malabsorption.
• GI tract: meconium ileus (neonates), distal intestinal obstruction.
• Sweat glands: salty sweat basis of diagnostic sweat Cl^- test.
• Reproductive: male infertility (agenesis of vas deferens).

Classification (pulmonary)

• Airflow-obstructive & suppurative phenotype much like chronic bronchitis/bronchiectasis.

Therapeutic Highlights (beyond slides)

• Airway clearance techniques, DNase, hypertonic saline.
• CFTR modulators (ivacaftor, elexacaftor/tezacaftor).
• Aggressive antibiotic protocols for Pseudomonas.
• Pancreatic enzyme replacement & nutritional supplementation.

Integrative & Real-World Considerations

• Smoking cessation is the single greatest modifiable factor across COPD phenotypes.
• Occupational medicine: enforcing mask use & monitoring lung function in high-risk jobs (mining, welding, asbestos) may prevent emphysema.
• Public health: indoor & outdoor air-quality legislation lowers COPD incidence.
• Ethical angle: access to costly CFTR modulators raises global health equity issues.
• Pharmacoeconomics: early pulmonary rehabilitation reduces hospitalisation costs in COPD.
• Climate change → increased air pollution days → rising acute exacerbations; clinicians must counsel vulnerable patients.

Key Numerical / Statistical Reminders

• Chronic bronchitis diagnostic window ⇒ >3 months’ cough in >2 consecutive years.
• Smoking threshold for emphysema risk highlighted: >70 pack-years.
• α _1 -antitrypsin deficiency accounts for ≈1\% of COPD in the West.

Quick Review Checklist for Exams

• Define & contrast Type A vs Type B COPD.
• List FOUR pathologic changes in chronic bronchitis.
• Explain the role of \alpha_1-antitrypsin in emphysema.
• Identify X-ray hallmarks of each condition.
• Outline management priorities in COPD exacerbation.
• Recognise complications: cor pulmonale, pneumothorax, bronchiectasis.
• Recall CF’s inheritance pattern & diagnostic sweat test principle.