What are the etiologies and treatment options for lung fibrosis and atelectasis?

Etiology of Lung Fibrosis and Atelectasis

Lung Fibrosis - Etiologies

Pulmonary fibrosis results from dysregulated wound healing following lung injury, with triggers including allergens, chemicals, radiation, environmental particles, and in many cases—particularly idiopathic pulmonary fibrosis (IPF)—the cause remains unknown. 1

Known Causes of Pulmonary Fibrosis

• Occupational/Environmental exposures: Asbestos exposure is a well-documented cause of pulmonary fibrosis, with asbestosis representing parenchymal fibrosis extending from respiratory bronchioles into alveolar ducts and alveoli 2

• Connective tissue diseases: Some patients, particularly younger women, may present with isolated pulmonary abnormalities characteristic of IPF prior to overt manifestations of systemic connective tissue disease, requiring serological monitoring when symptoms arise 2

• Chemotherapy-induced: Chemotherapeutic agents can cause pulmonary fibrosis as a complication of malignancy treatment 2

• Idiopathic pulmonary fibrosis (IPF): The cause remains unclear despite being one of the most common pulmonary fibrotic conditions 1

Pathophysiological Mechanisms

• Three-phase dysregulation: Pulmonary fibrosis develops through abnormalities in (1) injury, (2) inflammation, and (3) repair phases 1

• Chronic inflammation: Leads to imbalanced production of chemokines, cytokines, and growth factors with disrupted cellular recruitment 1

• Pro-fibrotic mediators: Excessive IL-13 and/or TGF-β1 production transforms controlled healing into pathogenic fibrotic responses 1

• Fibroproliferation: Multiple pathways are involved, suggesting successful treatment will require combination therapies targeting these distinct mechanisms 2

Atelectasis - Etiologies

Atelectasis develops through three primary mechanisms: airway obstruction, compression of lung parenchyma, and increased surface tension in alveoli and bronchioli. 3

Mechanisms and Risk Factors

Resorption Atelectasis

• Airway obstruction: Caused by resorption of alveolar air distal to obstructing airway lesions 4
• Mucous plugging: Particularly relevant in conditions like cystic fibrosis where viscous secretions obstruct airways 5

Compression Atelectasis

• Pleural processes: Tension pneumothorax, pleural effusions, or space-occupying intrathoracic lesions 4
• Asbestos-related: Rounded atelectasis (also called shrinking pleuritis or folded lung) results from infolding of thickened visceral pleura with collapse of intervening lung parenchyma, often following asbestos-related pleuritis 2
• Abdominal distention: Can compress lung bases 4

Adhesive Atelectasis

• Surfactant deficiency: Leads to increased surface tension and alveolar instability 3, 4

Passive Atelectasis

• Simple pneumothorax, diaphragmatic dysfunction, or hypoventilation 4

Cicatrization Atelectasis

• Pulmonary fibrosis: Fibrotic changes themselves cause volume loss and atelectasis 4

Perioperative and Clinical Risk Factors

• Low lung volume and high closing volume enhance alveolar collapse 6
• Oxygen therapy: Paradoxically increases atelectasis risk 6
• Rapid shallow breathing patterns 6
• Chronic lung disease, smoking, and obesity 6
• Postoperative pain following abdominal or thoracic surgery 6
• Narcotic-induced ventilatory depression 6
• Neuromuscular diseases with mechanical impairment of respiratory function 6

Treatment Approaches

Lung Fibrosis Management

• Monitoring: Every 4-6 months or sooner as clinically indicated, assessing symptoms, pulmonary function (FVC, DLCO), and oxygenation 7

• Oxygen supplementation: Strongly recommended for hypoxemic patients, prescribed when desaturation falls below 88% during 6-minute walk test 7

• Pulmonary rehabilitation: Recommended to improve exercise capacity and quality of life 7

• Pharmacologic therapy: Should be limited to carefully selected patients willing to accept possible adverse consequences even if expected benefits are small 7

• Corticosteroids: Appropriate for acute exacerbations of IPF (weak recommendation) 7; early treatment with systemic corticosteroids in interstitial lung disease associated with conditions like ataxia telangiectasia showed clinical and radiographic improvement 2

• Lung transplantation: Patients at increased risk of mortality should be evaluated and listed at diagnosis 7

Atelectasis Management

• Prevention is primary goal: Particularly in perioperative settings 6

• Chest physiotherapy and postural drainage: First-line conservative management 3

• Bronchodilator and anti-inflammatory therapy: For underlying airway disease 3

• Bronchoscopic intervention: Persistent mucous plugs should be removed by bronchoscopy 3; bronchoscopic instillation of recombinant human DNase has shown success in treating lobar atelectasis resistant to conventional therapy in cystic fibrosis 5

• Preoperative optimization: Delay elective surgery if substantial improvement can be achieved with antibiotics, bronchodilators, steroids, smoking cessation, and weight reduction 6

• Rounded atelectasis: Generally requires no aggressive therapy; surgical options like decortication are reserved for severe cases with significant functional impairment 2

Key Clinical Pitfalls

• Distinguishing atelectasis from pneumonia: Diagnosis of atelectatic pneumonia requires clinical signs/symptoms plus identification of pathogenic bacteria, not radiographic findings alone 4

• Overlooking minimal atelectasis: Can be missed when pulmonary opacification is minimal or absent 4

• Misdiagnosing rounded atelectasis: May be mistaken for lung tumor; the "comet sign" on HRCT is pathognomonic 2

• Acute worsening in IPF: Must promptly evaluate for alternative etiologies including pulmonary embolus, pneumothorax, respiratory infection, or aspiration—not just acute exacerbation 2