Which factor can reduce drainage when a chest tube is in place and the patient is on high PEEP?

• A. Increased intrathoracic pressure from high PEEP
• B. Adequate lung expansion
• C. Poor cough reflex
• D. Rapid movement

Answer: (A)

When a chest tube drains, the flow depends on the pressure difference between the pleural space and the drainage system. High PEEP raises intrathoracic (pleural) pressure, which reduces or even reverses this gradient. With less driving pressure pushing air or fluid out through the chest tube, drainage slows or stops. So the factor most likely to reduce drainage on high PEEP is the increased intrathoracic pressure from PEEP diminishing the pressure gradient that drives drainage. Adequate lung expansion actually helps restore negative intrapleural pressure and can support drainage, while poor cough reflex or rapid movement don’t directly alter the driving pressure in the same way.