Does a Chest Tube Decrease Intrathoracic Pressure?
Yes, a chest tube decreases abnormally elevated intrathoracic pressure by draining air or fluid from the pleural space, thereby restoring normal negative intrapleural pressure and allowing lung re-expansion. 1, 2, 3
Mechanism of Action
A chest tube functions to restore physiologic negative pressure within the pleural space by removing pathologic air or fluid accumulation. 2, 3 The normal intrapleural pressure ranges from -8 cm H₂O during inspiration to -3.4 cm H₂O during expiration. 1 When pneumothorax, hemothorax, or pleural effusion occurs, this negative pressure gradient is disrupted, and the chest tube re-establishes it by draining the abnormal contents. 2, 3
Clinical Context: Tension Pneumothorax
In tension pneumothorax specifically, progressive air accumulation creates a valve mechanism that increases intrathoracic pressure to dangerous positive levels, compressing mediastinal structures and impairing venous return. 1 The chest tube (or initial needle decompression) converts this life-threatening positive pressure back toward normal negative pressure by allowing trapped air to escape. 1
Pressure Management with Chest Drainage Systems
Initial Management Without Suction
- Do not apply suction immediately after chest tube insertion. 1, 4 The tube should function on underwater seal drainage alone for the first 48 hours. 4
- During this period, the chest tube allows passive drainage while maintaining the water seal barrier that prevents air re-entry. 1, 4
When to Add Suction (After 48 Hours)
Apply suction only if either condition persists after 48 hours: 1, 4
- Persistent air leak (continued bubbling through the tube at 48 hours)
- Failure of lung re-expansion on chest radiograph
Suction Specifications
When suction is indicated: 1, 4
- Use high volume, low pressure systems only at -10 to -20 cm H₂O
- This range approximates physiologic negative intrapleural pressures without causing tissue damage
- Avoid high pressure systems that can cause air stealing, hypoxemia, or perpetuate air leaks 1
Important Caveats
Bullous Lung Disease Warning
Never insert a chest tube based solely on chest radiograph in patients with known or suspected bullous disease without CT confirmation of actual pneumothorax. 5 Large emphysematous bullae can mimic pneumothorax on plain films, and inappropriate tube insertion into a bulla can be catastrophic. 5
Pressure Variability
The actual intrapleural pressure delivered can differ significantly from the set suction level depending on: 6
- Fluid accumulation in drainage tubing (can create pressure differentials of 1.14 to 36.69 cm H₂O)
- Degree of air leak present
- Tube patency and positioning
With complete tube obstruction in the off-suction setting, positive intrapleural pressures can paradoxically develop (2.6 to 11.1 cm H₂O). 6
Specialized Care Requirements
Patients requiring suction must be managed only in specialized lung units with experienced staff. 1, 4 This ensures proper monitoring for complications including re-expansion pulmonary edema, which can occur if suction is applied too early, particularly in primary pneumothorax present for several days. 1