Iatrogenic Pneumothorax

Iatrogenic pneumothorax is air in the pleural space caused by a medical procedure or treatment. It accounts for about a quarter to a third of pneumothoraces in hospital, and is more frequent than traumatic pneumothorax in some series.

Common causes are transthoracic needle aspiration and biopsy (the commonest, in about 15 to 25% of procedures, with higher risk in emphysema and for deep lesions), central venous catheter insertion (especially subclavian), thoracentesis, transbronchial lung biopsy, positive pressure ventilation (barotrauma), pleural biopsy, pacemaker and implantable device placement, surgery, percutaneous nerve blocks (supraclavicular and intercostal), acupuncture and tracheostomy.

Pathophysiology. Needles, catheters or ventilator pressure breach the visceral pleura or alveoli, letting air enter the pleural space. Positive pressure and nitrous oxide can create a tension pneumothorax. Underlying emphysema, interstitial lung disease and mechanical ventilation raise the risk.

Often discovered on post-procedure imaging in patients with no symptoms. Others have pleuritic chest pain, dyspnoea, cough and reduced breath sounds on the side of the procedure. In ventilated patients, a sudden rise in airway pressure, fall in saturation and haemodynamic instability suggest tension.

Hypotension, severe dyspnoea, tracheal deviation or a rise in ventilator pressure indicates tension pneumothorax and needs immediate decompression.

• Upright chest radiograph after high risk procedures (needle biopsy, central line, transbronchial biopsy) or with symptoms: a visceral pleural line with absent lung markings beyond it.
• Size: a rim of air of 2 cm or more between the lung edge and the chest wall at the level of the hilum is a large pneumothorax.
• Bedside ultrasound (absent lung sliding, no B-lines, lung point) is quick and more sensitive than supine radiography in ventilated patients.
• CT for small, loculated or unclear cases and the position of drains.
• Arterial blood gas in respiratory compromise.
• In ventilated or unstable patients, diagnose clinically and decompress without waiting for imaging.

Differential diagnosis.

• Subcutaneous emphysema without pneumothorax
• Skin fold or bulla
• Pleural effusion or haemothorax after the procedure
• Pulmonary embolism
• Pneumomediastinum

• Small (under 2 cm), asymptomatic and not ventilated: observe, give oxygen (high flow 10 L/min via a mask unless there is risk of hypercapnic failure, which speeds reabsorption four fold) and repeat the radiograph at 4 to 6 hours and 24 hours. Most resolve in days.
• Large or symptomatic, not ventilated: needle aspiration (a 16 to 18 gauge cannula, aspirating up to 2.5 L) or a small bore chest drain (10 to 14 French) connected to an underwater seal. Remove the drain once the lung is expanded and there is no air leak for 24 hours.
• Ventilated patients: insert a chest drain (small bore or 20 to 28 French), since the air leak will continue under positive pressure. Lower airway pressures and tidal volumes, and avoid nitrous oxide.
• Tension pneumothorax: immediate needle decompression (a 14 gauge cannula, 5th intercostal space in the anterior axillary line, or the 2nd space mid-clavicular line) then a chest drain.
• Persistent air leak beyond 5 to 7 days: surgical review, with thoracoscopic repair, a one way valve or pleurodesis.
• Prevention: ultrasound directed central venous access (internal jugular preferred), use of smaller needles and a minimal number of passes, positioning to reduce pleural traversal, and patient education about symptoms after biopsy.
• Discharge: after a stable radiograph at 4 hours after biopsy, with written advice and ready access to review. No flying until the radiograph shows resolution and at least 1 week afterwards (2 weeks after drainage), and no diving.

Complications and prognosis. Most resolve with simple measures. Re-expansion pulmonary oedema can follow rapid drainage, and mortality is higher in ventilated patients with tension.

Monitoring. Repeat radiograph at 4 to 6 hours and 24 hours for observed cases, and again before drain removal. Review at 1 to 2 weeks after discharge.

Referral and escalation. Refer to respiratory or thoracic surgery for persistent air leak, failure to expand or recurrence, and to intensive care for tension in a ventilated patient.