Respiratory Disorders: Asthma, Bronchitis, Emphysema,

Respiratory disorders are diseases that interfere with breathing, gas exchange or the airways, making it hard to get enough oxygen or remove carbon dioxide. Asthma, bronchitis and emphysema are three of the most common and each damages the system in a different way.

These disorders matter because they affect hundreds of millions of people, limit exercise and work, and can become life-threatening during attacks. Most are worsened by smoke, dust and infections, which means prevention and early treatment make a real difference.

Key Concepts

Asthma is a chronic allergic inflammation of bronchi and bronchioles. The airway wall swells, muscles constrict and excess mucus forms, causing reversible narrowing, wheezing, cough and breathlessness. Triggers include dust, pollen, cold air and smoke. Bronchitis is inflammation of the bronchi, acute from infections or chronic from long smoking, with persistent cough and mucus production. Emphysema is permanent destruction of alveolar walls, often from smoking. Alveoli merge into large air spaces, elastic recoil is lost, surface area falls and air gets trapped. Emphysema and chronic bronchitis together are called chronic obstructive pulmonary disease (COPD).

• Bronchospasm: sudden tightening of airway muscles in asthma.
• Chronic bronchitis: productive cough for at least 3 months in 2 consecutive years.
• Barrel chest: over-inflated chest seen in advanced emphysema.

How It Works

1. In asthma, an allergen triggers immune cells in the airway wall.
2. The wall swells, muscles contract and mucus plugs form, narrowing the airway within minutes.
3. Air enters with effort but leaves even more slowly, causing wheeze and chest tightness.
4. In chronic bronchitis, smoke paralyses cilia and enlarges mucus glands.
5. Thick mucus accumulates, bacteria infect it and cough becomes daily.
6. In emphysema, protease enzymes, unchecked because of smoke or genetic deficiency, digest alveolar walls.
7. Fewer, larger alveoli reduce diffusion surface and lungs lose elasticity, so exhalation collapses small airways.

Worked Example

Consider alveolar surface area. A healthy adult has about 70 square metres for diffusion. In moderate emphysema, destruction of walls might reduce this to about 35 square metres, roughly half. By the diffusion relationship, halving area at the same pressure difference halves maximum oxygen transfer. At rest the person may still cope, needing perhaps 250 mL oxygen per minute, but while climbing stairs demand may rise to 1,000 mL per minute, exceeding the reduced capacity. The result is breathlessness on exertion, exactly what emphysema patients report. In asthma, the problem is different: area is normal, but a narrowed bronchiole of half radius offers about 16 times more resistance, explaining sudden attacks.

Common Misconceptions

• Misconception: Asthma is only a childhood disease that always disappears. Correction: It can persist or start in adults and needs long-term control.
• Misconception: Bronchitis and emphysema are the same. Correction: Bronchitis is airway inflammation with mucus, while emphysema is alveolar wall destruction.
• Misconception: Inhalers are addictive and should be avoided. Correction: Controller inhalers prevent attacks and are safe when used as prescribed; delaying them is riskier.

Real-World Applications

Peak flow meters and spirometry diagnose and monitor asthma and COPD. Reliever inhalers open airways quickly, while steroid inhalers reduce inflammation. Smoking cessation is the single most effective step to slow bronchitis and emphysema. Vaccination against influenza and pneumococcus prevents infections that trigger attacks, and pulmonary rehabilitation improves exercise tolerance.

Asthma narrows airways reversibly, bronchitis fills them with mucus, and emphysema destroys alveoli permanently. Avoiding smoke and dust, using inhalers correctly and treating infections early protect breathing for life.