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Chest drain — insertion, monitoring and removal
A chest drain is inserted in the "safe triangle" over the upper border of the rib, connected to an underwater-seal system, and read by three signs — swing with breathing (patent drain), bubbling (air leak) and drainage volume (blood or fluid); an initial drainage of 1500 mL of blood or 200 mL per hour for 2–4 hours is an indication for thoracotomy.
Why it matters in the exam
Chest drain questions appear in almost every thoracic surgery and trauma exam. The safe triangle is bounded by the anterior border of latissimus dorsi, the lateral border of pectoralis major and a horizontal line at nipple level (5th intercostal space), and insertion over the rib avoids the neurovascular bundle running along its lower border. Most pneumothoraces and free-flowing effusions are now drained with a small-bore drain (14 Fr or less); for traumatic haemothorax ATLS suggests a wider drain (28–32 Fr), although a small drain suits a stable patient. The classic drainage system has three chambers: collection, a water seal 2 cm deep, and suction control, usually -20 cm water.
Interpretation is the heart of the questions: swing of the water column with breathing shows the drain is patent and connected to the pleural space; no swing means a blocked or kinked drain or a fully expanded lung. Continuous bubbling in the water seal means an air leak from the lung or the system — check the connections and the skin site. A bubbling drain must not be clamped, because this may create a tension pneumothorax. When draining a large effusion, drain gradually — up to 1–1.5 litres at once — to prevent re-expansion pulmonary oedema. The drain is removed when there is no air leak, the lung is expanded on X-ray and the daily volume is low (usually less than 200–300 mL per day), at end-inspiration or end-expiration, and the wound is closed at once.
Indications for thoracotomy in haemothorax: initial drainage of 1500 mL or more, ongoing drainage of 200 mL per hour for 2–4 hours, or a continuing need for blood transfusion. Haemothorax that remains on X-ray despite a drain is treated with early VATS.
Key points
- Safe triangle, over the rib.
- Water seal 2 cm deep, suction -20 cm water.
- Swing = patent; bubbles = leak.
- 1500 mL at once or 200 mL per hour for 2–4 hours — thoracotomy.
- Gradual drainage of a large effusion.
Summary table
| Finding | Meaning | Action |
|---|---|---|
| Swing with breathing | Drain patent and connected to the space | Continue monitoring |
| No swing | Blockage, kink or expanded lung | Check the tube and take an X-ray |
| Continuous bubbling | Air leak from the lung or the system | Check connections; do not clamp |
| 1500 mL of blood at once or 200 mL per hour for 2–4 hours | Massive haemothorax | Thoracotomy |
| More than 1–1.5 litres at once from an effusion | Risk of re-expansion oedema | Drain gradually |
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Sources
- BTS Guideline for Pleural Disease, 2023 — Chest drain insertion and management
- ATLS Advanced Trauma Life Support Student Course Manual, 10th edition (2018) — Thoracic trauma
- Shields' General Thoracic Surgery, 8th edition (2019) — Chest tube placement and pleural drainage systems
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.