DIMS Lectures Respiratory Pathology PDF

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Summary 

1. Obstructive Lung Diseases

Obstructive lung diseases are characterized by airway obstruction leading to difficulty in exhalation.

A. Chronic Obstructive Pulmonary Disease (COPD)

COPD is a progressive and irreversible lung disease caused by long-term exposure to irritants like smoking and pollution.

Pathophysiology:

Chronic inflammation leads to narrowing of airways.

Mucus hypersecretion causes bronchial obstruction.

Destruction of alveoli leads to reduced gas exchange.

Key Features:

Chronic cough with sputum production.

Dyspnea (shortness of breath).

Prolonged expiration with wheezing.

Clinical Correlation:

Spirometry shows decreased FEV1/FVC ratio.

Patients present with barrel chest due to air trapping.

B. Asthma

Asthma is a chronic inflammatory disease that causes episodic airway constriction.

Pathophysiology:

Bronchial hyperreactivity leads to airway narrowing.

Histamine release triggers bronchospasm.

Mucosal edema and mucus plugging exacerbate obstruction.

Symptoms:

Intermittent wheezing.

Shortness of breath, often triggered by allergens or exercise.

Cough, particularly at night.

Clinical Correlation:

Reversible airway obstruction on spirometry.

Increased eosinophils in sputum.

2. Restrictive Lung Diseases

Restrictive lung diseases limit lung expansion, reducing lung volume and compliance.

Pulmonary Fibrosis

A chronic interstitial lung disease leading to fibrosis and scarring of lung tissue.

Pathophysiology:

Excess collagen deposition in lung interstitium.

Thickened alveolar walls impair gas exchange.

Symptoms:

Progressive dyspnea.

Dry cough.

Clubbing of fingers.

Clinical Correlation:

Decreased TLC and FVC on lung function tests.

Honeycombing pattern on HRCT scan.

3. Pulmonary Embolism (PE)

A life-threatening condition where a blood clot blocks a pulmonary artery.

Pathophysiology:

Deep vein thrombosis (DVT) dislodges and travels to the lungs.

Obstructed pulmonary circulation leads to hypoxia.

Symptoms:

Sudden onset dyspnea.

Pleuritic chest pain.

Hemoptysis (coughing up blood).

Clinical Correlation:

D-dimer test is elevated.

CT pulmonary angiography (CTPA) confirms diagnosis.

4. Respiratory Failure

Respiratory failure occurs when the lungs fail to oxygenate blood or remove CO₂ effectively.

Types of Respiratory Failure:

1. Type 1 (Hypoxemic) – Low oxygen, normal CO₂ (e.g., ARDS).

2. Type 2 (Hypercapnic) – High CO₂, normal or low oxygen (e.g., COPD).

Symptoms:

Cyanosis (bluish skin).

Altered mental status.

Tachypnea or bradypnea (rapid or slow breathing).

Clinical Correlation:

Arterial Blood Gas (ABG) analysis shows low PaO₂ and/or high PaCO₂.

5. Tuberculosis (TB)

A chronic bacterial infection caused by Mycobacterium tuberculosis.

Pathophysiology:

Bacteria infect the lungs and form granulomas.

The Ghon complex is seen in primary TB.

Symptoms:

Chronic cough lasting more than 3 weeks.

Night sweats and fever.

Weight loss.

Clinical Correlation:

Positive Mantoux (PPD) test.

Cavitary lesions on chest X-ray.

6. COVID-19 and Respiratory Complications

COVID-19 primarily affects the lungs, causing severe pneumonia in critical cases.

Pathophysiology:

Viral invasion leads to alveolar damage.

Cytokine storm causes massive lung inflammation.

Symptoms:

Persistent fever.

Shortness of breath.

Loss of taste and smell.

Clinical Correlation:

Ground-glass opacities on CT scan.

Hypoxia requiring oxygen therapy.

7. Prevention and Management of Respiratory Diseases

A. General Preventive Measures

1. Quit smoking – Prevents COPD and lung cancer.

2. Vaccinations – Influenza and pneumococcal vaccines.

3. Pollution control – Reduces asthma triggers.

4. Regular exercise – Improves lung capacity.

B. Medical Treatment Approaches

Bronchodilators for COPD and asthma.

Antibiotics for pneumonia and TB.

Anticoagulants for pulmonary embolism.

Oxygen therapy for severe respiratory failure.

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