DIMS Lectures Respiratory Medicine PDF
Overview of Respiratory Medicine
Respiratory medicine focuses on the diagnosis, treatment, and management of diseases affecting the lungs and respiratory system. The respiratory system is responsible for oxygen exchange, removal of carbon dioxide, and maintaining acid-base balance. Disorders affecting this system can have profound impacts on systemic health, making it essential for medical students to understand the pathophysiology, clinical features, and management of respiratory diseases.
Chronic Obstructive Pulmonary Disease (COPD)
Definition: A chronic inflammatory lung disease causing airflow limitation that is not fully reversible.
Epidemiology:
- Affects over 300 million people worldwide.
- Strongly associated with smoking, biomass fuel exposure, and environmental pollutants.
- More prevalent in older adults due to cumulative exposure to risk factors.
Pathophysiology:
- Emphysema: Characterized by alveolar destruction, loss of elastic recoil, and air trapping, leading to increased compliance of the lungs.
- Chronic Bronchitis: Persistent inflammation leads to mucus hypersecretion, ciliary dysfunction, and airway narrowing, increasing airway resistance and reducing airflow.
- Airway Remodeling: Recurrent inflammation causes fibrosis and smooth muscle hypertrophy, contributing to irreversible airflow limitation.
Clinical Features:
- Chronic productive cough lasting more than 3 months per year for at least 2 consecutive years.
- Progressive dyspnea, initially on exertion and later at rest.
- Wheezing and prolonged expiration due to obstructive pathology.
- Barrel chest due to air trapping and hyperinflation.
- Use of accessory muscles for respiration, leading to fatigue.
- Cyanosis (in chronic bronchitis) vs. pursed-lip breathing (in emphysema).
Diagnosis:
- Spirometry: FEV1/FVC ratio < 70% confirms airflow obstruction.
- Chest X-ray: Hyperinflation, flattened diaphragms, increased anteroposterior diameter.
- Arterial Blood Gas (ABG): Chronic hypercapnia and hypoxemia in advanced cases.
- CT Scan (HRCT): Detects emphysematous changes.
- Alpha-1 Antitrypsin Levels: To identify genetic deficiency-related COPD.
Management:
- Smoking cessation (most effective intervention).
- Bronchodilators (SABA, LABA, LAMA).
- Inhaled corticosteroids (ICS) for frequent exacerbations.
- Oxygen therapy for chronic hypoxemia.
- Pulmonary rehabilitation to improve exercise tolerance.
Asthma
Definition: A chronic inflammatory disorder of the airways characterized by reversible airflow obstruction.
Triggers:
- Allergens: Pollen, dust mites, pet dander.
- Infections: Viral URTIs.
- Environmental factors: Smoke, pollution.
Pathophysiology:
- Bronchial hyperresponsiveness leads to airway inflammation.
- Mast cells, eosinophils, and T-cells play key roles.
- Reversible bronchoconstriction occurs due to increased mucus production.
Clinical Features:
- Intermittent wheezing and dyspnea.
- Cough, often nocturnal.
- Chest tightness.
Diagnosis:
- Spirometry: Reduced FEV1/FVC ratio with post-bronchodilator improvement.
- Peak Expiratory Flow Rate (PEFR): Used for monitoring asthma control.
Management:
- Stepwise Approach:
- SABA as needed.
- ICS for persistent symptoms.
- LABA + ICS for moderate asthma.
- Oral corticosteroids for severe cases.
- Leukotriene receptor antagonists (Montelukast) for maintenance therapy.
Pneumonia
Definition: Acute infection of the lung parenchyma.
Etiology:
- Community-acquired pneumonia (CAP): Streptococcus pneumoniae, Mycoplasma pneumoniae.
- Hospital-acquired pneumonia (HAP): Pseudomonas aeruginosa, Klebsiella pneumoniae.
- Aspiration pneumonia: Due to gastric content aspiration.
Clinical Features:
- Fever, productive cough, pleuritic chest pain.
- Dyspnea, tachypnea, hypoxia.
- Dullness on percussion, bronchial breath sounds.
Diagnosis:
- Chest X-ray: Lobar or interstitial infiltrates.
- Sputum Gram stain and culture.
Management:
- Empirical Antibiotics:
- CAP: Amoxicillin + Clavulanate or Azithromycin.
- HAP: Piperacillin-Tazobactam or Meropenem.
- Oxygen therapy for hypoxic patients.
Pulmonary Embolism (PE)
Definition: A life-threatening blockage of pulmonary arteries, usually due to a deep vein thrombosis (DVT) embolism.
Risk Factors:
- Virchow’s Triad: Venous stasis, endothelial injury, hypercoagulability.
- Immobility, recent surgery, malignancy, pregnancy.
Clinical Features:
- Sudden dyspnea, pleuritic chest pain.
- Tachycardia, hypoxia, hemoptysis.
Diagnosis:
- D-dimer: Elevated in PE but non-specific.
- CT Pulmonary Angiography (CTPA): Gold standard for diagnosis.
Management:
- Anticoagulation (Heparin, Warfarin, DOACs).
- Thrombolysis for massive PE.
- IVC Filter for recurrent embolism.
Case Example: A 50-Year-Old with Dyspnea
A 50-year-old male with a history of chronic smoking (20 pack-years) presents with sudden-onset breathlessness and pleuritic chest pain. Clinical examination reveals tachypnea, tachycardia, and reduced breath sounds on the right side. ECG shows sinus tachycardia, and D-dimer is significantly elevated. CT Pulmonary Angiography confirms a pulmonary embolism (PE). The patient is immediately started on low-molecular-weight heparin (LMWH) followed by oral anticoagulation (Apixaban). This case emphasizes early recognition and treatment of pulmonary embolism to prevent fatal outcomes.
1.A 60-year-old smoker presents with chronic productive cough and progressive dyspnea. Spirometry shows an FEV1/FVC ratio of 60%. What is the most likely diagnosis?
A) Asthma
B) COPD
C) Pneumonia
D) Pulmonary Embolism
2.Which of the following is the most common causative agent of community-acquired pneumonia?
A) Mycobacterium tuberculosis
B) Pseudomonas aeruginosa
C) Streptococcus pneumoniae
D) Klebsiella pneumoniae
3.A patient with pulmonary embolism is started on low-molecular-weight heparin (LMWH). What is the next step in long-term management?
A) Continue LMWH indefinitely
B) Transition to oral anticoagulation (Apixaban)
C) Perform an immediate thrombolysis
D) Stop anticoagulation after 48 hours
4.Which of the following conditions is characterized by reversible airway obstruction?
A) COPD
B) Asthma
C) Pulmonary Fibrosis
D) Tuberculosis
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1.Correct Answer: B) COPD
Explanation: COPD presents with chronic airflow limitation that is not fully reversible, confirmed by spirometry (FEV1/FVC < 70%). Unlike asthma, COPD does not show significant reversibility after bronchodilator use.
2.Correct Answer: C) Streptococcus pneumoniae
Explanation: Streptococcus pneumoniae is the most common bacterial cause of community-acquired pneumonia (CAP), especially in elderly patients and those with chronic conditions.
3.Correct Answer: B) Transition to oral anticoagulation (Apixaban)
Explanation: LMWH is used for initial anticoagulation, but long-term management typically involves transitioning to oral anticoagulants such as Apixaban, Rivaroxaban, or Warfarin.
4.Correct Answer: B) Asthma
Explanation: Asthma is characterized by episodic and reversible airflow obstruction, bronchial hyperresponsiveness, and inflammation, which improve with bronchodilator therapy.
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