Lung Infections: A Comprehensive Medical Review

Excerpt

Lung infections encompass a broad spectrum of conditions caused by bacterial, viral, fungal, or parasitic pathogens. These infections affect lung tissue, the airways, or the alveoli, leading to inflammation, impaired gas exchange, and respiratory distress. Depending on severity, lung infections may range from mild to life-threatening, requiring prompt diagnosis and appropriate treatment. This article provides an in-depth analysis, covering pathology, symptoms, diagnosis, treatment regimens, and statistical data, alongside a clinical case study.

ICD Codes and HCC Classification

ICD-10 Codes:
- J18.9: Pneumonia, unspecified organism
- J15.9: Bacterial pneumonia, unspecified
- J12.9: Viral pneumonia, unspecified
- J17: Pneumonia in diseases classified elsewhere
- J44.0: COPD with an acute lower respiratory infection
HCC Code: HCC 114 (Aspiration and Specified Bacterial Pneumonias)
Related Codes:
- J20.9: Acute bronchitis, unspecified
- J22: Unspecified acute lower respiratory infection
- B44.0: Pulmonary aspergillosis

Definition

A lung infection is an inflammatory condition caused by microorganisms invading the respiratory system. These infections can affect:

Alveoli (Pneumonia) – Can be bacterial, viral, or fungal.
Bronchi (Bronchitis) – Primarily caused by viral infections, though bacterial cases exist.
Pleura (Pleurisy/Pleural Empyema) – Can result from bacterial or viral infections.

Pathology

Bacterial Infections: Cause alveolar inflammation, consolidation, and pus accumulation. Streptococcus pneumoniae, Haemophilus influenzae, and Staphylococcus aureus are common pathogens.
Viral Infections: Lead to interstitial inflammation without consolidation. Influenza, RSV, and coronaviruses are the primary causative agents.
Fungal Infections: Typically affect immunocompromised individuals, causing granulomatous inflammation (Aspergillus, Histoplasma, Cryptococcus).

Aetiology and Risk Factors

Age: Infants, children, and the elderly are at higher risk.
Chronic Conditions: COPD, diabetes, heart disease, or cancer increase susceptibility.
Immunosuppression: HIV/AIDS, chemotherapy, and organ transplant recipients.
Environmental Factors: Smoking, pollution, occupational exposure (e.g., asbestos).

Symptoms and Signs

General Symptoms

Cough (productive/non-productive)
Fever and chills
Shortness of breath
Chest pain (especially pleuritic pain)
Fatigue and weakness

Signs Based on Aetiology

Bacterial: High fever, productive cough (yellow/green sputum), pleuritic pain
Viral: Low-grade fever, dry cough, muscle aches
Fungal: Chronic cough, weight loss, hemoptysis

When to See a Doctor

Seeking medical attention is crucial when experiencing

Persistent or Worsening Symptoms:
- High fever (>38.5°C) lasting more than 3 days
- Cough has persisted for over 2 weeks
Severe Respiratory Distress:
- Shortness of breath at rest
- Difficulty speaking in full sentences due to breathlessness
Cyanosis (Bluish Discolouration):
- Lips, fingers, or face turning blue, indicating low oxygen levels
Altered Mental Status:
- Confusion, drowsiness, or difficulty staying awake (common in elderly patients)
Hemoptysis (Coughing Up Blood):
- May indicate tuberculosis, lung abscess, or severe pneumonia
Underlying Health Conditions:
- Immunocompromised individuals (e.g., cancer, HIV/AIDS) should seek early intervention
Severe Chest Pain:
- Can indicate pleurisy, pulmonary embolism, or severe bacterial pneumonia

Diagnosis

Pharmacologic Therapy

Bacterial Infections:
- First-line:
  - Amoxicillin-clavulanate (875 mg/125 mg twice daily)
  - Azithromycin (500 mg on Day 1, then 250 mg daily for 4 days)
Viral Infections:
- Antivirals (For Influenza A/B):
  - Oseltamivir (75 mg twice daily for 5 days)
- Supportive Therapy: Antipyretics, hydration, rest
Fungal Infections:
- Voriconazole (200 mg twice daily for aspergillosis)

Supportive Therapy

Oxygen Therapy: For hypoxemic patients
IV Fluids & Nutrition: For critically ill patients
Mechanical Ventilation: In severe cases

Surgical Interventions

Drainage of Lung Abscesses: Via percutaneous or surgical intervention
Decortication: Removal of pleural fibrosis in empyema

Statistical Data

Global Incidence: Pneumonia affects ~450 million people annually.
Mortality Rate: ~2.5 million deaths per year, including 740,000 children under five.
Hospitalisation Rates: 1 million cases annually in the U.S.

(Sources: WHO, CDC, Global Burden of Disease Study)