Respiratory System >
Pneumonia
“An infective inflammatory condition of the lung affecting primarily the alveoli (CAP & HAP)“
Risk Factors
- Modifiable:
- Smoking
- Non-Modifiable:
- Age (>65)
- Chronic diseases (respiratory and cardiopulmonary conditions)
- Immunosuppression
- Impaired airway protection – causing aspiration
Aetiology
- Community-Acquired:
- Typical – Streptococcus pneumoniae, haemophilus influenzae, staphylococcus aureus
- Atypical Bacteria – Mycoplasma pneumoniae, Chlamydophila pneumoniae
- Viruses – RSV, CMV
- Hospital-Acquired
- Gram-ve pathogens – pseudomonas aeruginosa, Enterobacteriaceae
- Staphylococcus Aurea
- Streptococcus pneumoniae
Pathophysiology
- Failure of protective pulmonary mechanisms (cough reflex, mucociliary clearance, alveolar macrophages)
- Pathogen infiltrates pulmonary parenchyma → interstitial and alveolar inflammation
- Impaired alveolar ventilation → ventilation/perfusion (V/Q) mismatch with intrapulmonary shunting (right to left)
- Hypoxia due to increased alveolar-arterial oxygen gradient
- Hypoxia is worsened when the affected lung is in the dependent position, as perfusion to the dependent lung is better compared to the nondependent lung.
Clinical Presentation
- Typical pneumonia is characterised by a sudden onset of symptoms caused by lobar infiltration, including:
- Severe malaise
- High fever and chills
- Productive cough with purulent sputum (yellow-greenish)
- Crackles and decreased bronchial breath sounds on auscultation
- Enhanced vocal/tactile fremitus
- Dullness on percussion
- Tachypnoea and dyspnoea (nasal flaring, thoracic retractions)
- Pleuritic chest pain when breathing, often accompanying pleural effusion
- Pain that radiates to the abdomen and epigastric region (particularly in children)
- Suspect bacterial pneumonia in immunocompromised patients with acute high fever and pleural effusion
- Atypical pneumonia typically has a slow course and includes:
- Nonproductive, dry cough
- Dyspnea
- Auscultation often unremarkable
- Common extrapulmonary features include fatigue, headaches, sore throat, myalgias, and malaise
Investigations
- Bloods:
- FBC
- Inflammatory markers – ↑ CRP, ↑ ESR, leucocytosis
- ↑ Serum PCT – PCT is an acute phase reactant that can help to diagnose bacterial LRTI
- ABG – ↓ PaO2
- Blood culture
- Imaging:
- Chest X-Ray
- Lobar – Opacity of 1 or more pulmonary lobes, presence of air bronchograms (translucent bronchi inside opaque areas of alveolar consolidations)
- Bronchopneumonia – poorly defined patchy infiltrates scattered throughout the lungs, presence of air bronchograms)
- Chest CT – can request if X-Ray in inconclusive.
- Chest X-Ray
- Special:
- Sputum culture and gram stain
Management
- Assess the need for hospitalization (clinical judgement and CURB-6)
- Begin antibiotic therapy based on severity and patient risk factors
- Provide supportive care – Oxygen, fluids, analgesia, antipyretics
Complications
- Parapneumonic pleuritis
- Pleural effusion
- Pleural empyema
- Sepsis
- Respiratory failure
- ARDS