Pneumonia is an acute respiratory infection that affects the alveoli in one or both lungs. It can be caused by bacteria, viruses, fungi, or parasites. The alveoli fill with pus and fluid, making breathing painful and limiting oxygen intake.
Causes
Pneumonia can be caused by various pathogens, each with distinct characteristics:
- Bacterial Pneumonia:
- Streptococcus pneumoniae is the most common cause.
- Haemophilus influenza,
- Staphylococcus aureus, and
- Legionella pneumophila are other notable bacteria.
- Viral Pneumonia:
- Influenza virus,
- Respiratory Syncytial Virus (RSV), and
- coronaviruses (including SARS-CoV-2) are common viral causes.
- Fungal Pneumonia:
- Histoplasma capsulatum,
- Coccidioides spp., and
- Cryptococcus neoformans can cause pneumonia, especially in immunocompromised individuals.
- Aspiration Pneumonia:
- Occurs when food, liquid, or vomit is inhaled into the lungs, often seen in patients with swallowing difficulties.
Signs & Symptoms
The symptoms of pneumonia can range from mild to severe and typically include:
- Cough: Often productive with greenish, yellow, or even bloody mucus.
- Fever: Usually high, accompanied by chills.
- Shortness of Breath: Difficulty breathing or rapid, shallow breathing.
- Chest Pain: Sharp or stabbing pain that worsens with deep breathing or coughing.
- Fatigue: General feeling of tiredness or weakness.
- Confusion: Particularly in older adults.
Pathophysiology
The pathophysiology of pneumonia involves the following steps:
- Infection and Inflammation:
- Pathogens enter the respiratory tract and reach the alveoli.
- The body’s immune response triggers inflammation in the alveolar spaces.
- Alveolar Filling:
- The inflammatory response leads to the accumulation of fluid, white blood cells, and other immune components in the alveoli.
- This results in consolidation, where the alveoli fill with exudate (pus), making gas exchange difficult.
- Impaired Gas Exchange:
- The filling of alveoli with fluid and inflammatory cells reduces the surface area available for gas exchange.
- This leads to hypoxaemia (low blood oxygen levels) and, in severe cases, hypercapnia (high blood carbon dioxide levels).
- Systemic Effects:
- The infection and inflammation can cause systemic effects such as fever, increased heart rate, and malaise.
- Severe cases may lead to sepsis and septic shock, particularly in vulnerable populations.
Management
The management of pneumonia involves several steps, tailored to the severity and cause of the infection:
- Antibiotic Therapy:
- Bacterial Pneumonia: Treated with appropriate antibiotics based on the suspected or confirmed pathogen. Common antibiotics include amoxicillin, macrolides (e.g., azithromycin), and fluoroquinolones.
- Empirical Therapy: Often started before the specific pathogen is identified, especially in severe cases.
- Antiviral and Antifungal Therapy:
- Viral Pneumonia: Antiviral medications may be used for certain viruses, such as oseltamivir for influenza.
- Fungal Pneumonia: Treated with antifungal medications like amphotericin B or fluconazole.
- Supportive Care:
- Oxygen Therapy: To maintain adequate oxygen levels.
- Fluids: Intravenous fluids to prevent dehydration.
- Analgesics and Antipyretics: To manage pain and fever.
- Hospitalisation:
- Required for severe cases, especially in patients with significant respiratory distress, hypoxaemia, or comorbid conditions.
- Intensive care may be needed for patients with respiratory failure or septic shock.
- Vaccination:
- Pneumococcal Vaccine: Recommended for children, older adults, and individuals with certain chronic conditions to prevent Streptococcus pneumoniae infections.
- Influenza Vaccine: To prevent influenza-related pneumonia, especially in high-risk populations.
- Preventive Measures:
- Good hygiene practices such as hand washing.
- Avoidance of smoking to reduce lung damage and susceptibility to infections.