Atelectasis

Also written as Lung collapse, Collapsed lung.

Atelectasis is collapse of lung tissue causing reduced gas exchange. It can be caused by airway obstruction, compression, or surfactant deficiency and may lead to infection or respiratory failure.

Overview

Atelectasis occurs when alveoli become deflated, decreasing ventilation and oxygenation. It can be focal or involve an entire lobe, and severity ranges from silent to life‑threatening.

• Chest X‑ray: Does the image show a wedge‑shaped opacity with mediastinal shift? Positive confirms atelectasis; absence does not rule out early disease.
• CT thorax: What is the extent and cause of collapse? Shows detailed anatomy when X‑ray is equivocal or when complications are suspected.
• Pulse oximetry: Is oxygen saturation falling despite supplemental O2? Low values suggest significant ventilation‑perfusion mismatch.

• Classify by mechanism: obstructive, compressive, surfactant‑deficient, cicatricial.
• Common in postoperative patients, immobile bedridden patients, and those with severe infections.

Key concepts

Understanding the pathophysiology helps target the cause and prevent progression.

• Obstructive atelectasis: mucus plug, tumor, foreign body; most common after surgery or in asthma/COPD.
• Compressive atelectasis: pleural effusion, pneumothorax, massive ascites, pregnancy.
• Surfactant deficiency: premature infants, severe ARDS.
• Cicatricial atelectasis: fibrosis after TB, sarcoidosis, or chronic infection.

Clinical relevance

Atelectasis can precipitate hypoxia, infection, and respiratory failure, especially in low‑resource settings where monitoring is limited.

• Rapidly progressive collapse may cause tension physiology—urgent decompression needed.
• Persistent atelectasis predisposes to pneumonia and sepsis.
• In patients with HIV/TB, collapse may mask underlying cavitary disease.

Exam pearls

Exam questions often test recognition, differential diagnosis, and immediate management steps.

• Identify the mechanism from history (e.g., recent surgery → obstructive).
• Interpret radiographic signs: volume loss, mediastinal shift toward the lesion.
• Know first‑line interventions: airway clearance, incentive spirometry, bronchoscopy if needed.

Common mistakes

Students frequently miss the underlying cause or assume normal labs rule out serious disease.

• Treating only the symptom (oxygen) without clearing the obstruction.
• Ignoring that normal chest X‑ray early on does not exclude atelectasis.
• Using high‑flow oxygen alone in tension atelectasis—may worsen mediastinal shift.

Questions an examiner may ask

• A postoperative patient develops hypoxia; chest X‑ray shows a right lower‑lobe opacity with mediastinal shift. What is the most likely mechanism? — Obstructive atelectasis from mucus plug; answer should mention postoperative immobility and need for airway clearance.
• A pregnant woman presents with dyspnea; imaging shows basal lung collapse. Which cause is most plausible? — Compressive atelectasis from diaphragmatic elevation; discuss physiologic changes in pregnancy.
• In a child with cystic fibrosis, a new focal opacity appears. How do you differentiate atelectasis from pneumonia? — Look for volume loss and mediastinal shift (atelectasis) versus consolidation without shift (pneumonia).
• A patient with HIV and TB has a left upper‑lobe collapse. What additional complication should you anticipate? — Post‑TB fibrosis leading to cicatricial atelectasis; monitor for chronic respiratory insufficiency.
• During bronchoscopy you find a mucus plug obstructing the right main bronchus. What immediate step follows removal? — Re‑inflate the lung with positive pressure ventilation and assess oxygenation.
• A neonate born at 28 weeks shows diffuse ground‑glass opacities. Is this atelectasis? — No, it reflects surfactant deficiency (hyaline membrane disease); management differs (surfactant replacement).
• A patient on high‑flow oxygen remains hypoxic; chest X‑ray is normal. Why might atelectasis still be present? — Early atelectasis may not be radiographically visible; rely on clinical signs and consider CT if suspicion persists.
• What bedside maneuver can prevent postoperative atelectasis? — Incentive spirometry combined with early ambulation; explain physiologic rationale.

When to seek help

• Sudden severe dyspnea with chest pain
• Rapidly falling oxygen saturation despite supplemental O2
• Signs of tension physiology: hypotension, distended neck veins

Quick questions

Why does atelectasis cause fever?

Collapsed lung impairs clearance, allowing bacterial overgrowth and secondary infection.

Can atelectasis resolve without intervention?

Mild cases often improve with deep breathing and mobilization, but obstructive causes need specific treatment.

Is bronchoscopy always required?

Only when airway obstruction is suspected and cannot be cleared by physiotherapy or suction.