Nursing care
Why the trachea shifts in tension pneumothorax and why it is a late sign
Written and reviewed by Dana Whitfield, RN, MSN · 4 min read · Updated October 2026
Short answer
In tension pneumothorax, a one-way valve lets air into the pleural space but not out. Pressure rises until it stays positive through the whole breathing cycle, collapsing the lung and pushing the mediastinum and trachea toward the opposite side. That shift compresses the other lung and reduces venous return, causing shock. Tracheal deviation appears late, so treatment should not wait for it.
The one-way valve that builds pressure
Normally the pressure in the pleural space is slightly negative, which keeps the lung expanded against the chest wall. In a simple pneumothorax, air enters that space and part of the lung collapses, but pressure does not keep climbing. In a tension pneumothorax, damaged lung or chest wall tissue acts as a flap valve: air enters with each breath and cannot escape.
With every breath the trapped air increases, and the pressure on the affected side rises until it is positive throughout the respiratory cycle. This happens most often in clients receiving positive pressure ventilation, including during resuscitation, because the ventilator actively drives air through the leak. It can also follow chest trauma or a spontaneous pneumothorax.
How pressure moves the mediastinum and causes shock
The mediastinum, which contains the heart, great vessels and trachea, is mobile. As pressure on one side climbs, it pushes the mediastinum toward the opposite side. The trachea, fixed above but movable in the chest, is pushed away from the affected side. The shift compresses the opposite lung, so both oxygenation and ventilation deteriorate.
The more dangerous effect is on circulation. Rising intrathoracic pressure and kinking of the great veins reduce venous return to the heart. With less blood filling the heart, cardiac output falls and the client develops hypotension and shock. Distended neck veins reflect blood backing up because it cannot enter the chest. Cardiorespiratory arrest can follow if pressure is not released.
Early versus late findings
Early findings resemble a simple pneumothorax: breathlessness, chest pain, tachycardia and anxiety. On the affected side, breath sounds are reduced or absent and percussion is hyperresonant; the chest may look overexpanded. Saturation falls as the lung collapses. These findings, in the right setting, are enough to raise suspicion. A ventilated client who suddenly deteriorates, or a trauma client whose breathing worsens after arrival, should be assessed for tension before the classic late signs have time to develop.
Hypotension, tracheal deviation and jugular venous distention are late findings that indicate advanced haemodynamic compromise. Tracheal deviation can be hard to detect, so its absence does not exclude tension. The diagnosis is clinical, based on vital signs and examination, and treatment should not be delayed for a chest radiograph. On an exam, a deviated trachea signals an emergency already well under way.
Nursing actions and emergency treatment
Call for emergency help immediately and stay with the client. Support oxygenation as prescribed, monitor saturation, heart rate and blood pressure continuously and prepare equipment for decompression. In a ventilated client, alert the team to sudden deterioration so that ventilation settings and the possibility of tension can be assessed quickly.
Emergency treatment is needle decompression followed by insertion of a chest tube. Sites differ between references and protocols, including the second intercostal space at the midclavicular line and the fourth or fifth intercostal space in the midaxillary line. After decompression, the nurse monitors for improvement in blood pressure and saturation, assists with chest tube placement and observes the drainage system.
Work a hypothetical scenario
A hypothetical ventilated client after chest trauma suddenly becomes hypotensive and tachycardic, saturation drops, breath sounds are absent on the right and the trachea is deviated to the left. Options include sending for a portable chest radiograph and waiting, increasing intravenous fluids and reassessing, suctioning the airway, or calling the emergency team for immediate decompression.
Calling for immediate decompression is correct, because absent breath sounds, shock and tracheal shift indicate tension pneumothorax, a clinical diagnosis. Waiting for imaging delays life-saving treatment. Fluids do not fix the obstructed venous return. Suctioning may be reasonable if secretions are suspected, but it does not address trapped pleural air. The trachea points away from the problem.
Sources and further reading
MSD Manual Professional: Tension pneumothorax. One-way valve, mediastinal shift, reduced venous return and shock, late findings, clinical diagnosis and needle decompression with chest tube.
MSD Manual Professional: Pneumothorax. Intrapleural pressure positive throughout the cycle, positive pressure ventilation as common setting and decompression without delaying for imaging.
MedlinePlus: Collapsed lung (pneumothorax). Chest pain, breathlessness, rapid heart rate and bluish skin, and treatment with needle or chest tube.
The next step on this is the same as on everything else here: answer questions and read the rationales. Our respiratory practice questions are the closest set to what this page covers.
Common questions
Which way does the trachea move in tension pneumothorax?
Away from the affected side. Trapped air raises pressure on that side and pushes the mediastinum and trachea toward the opposite side.
Why does tension pneumothorax cause hypotension?
High intrathoracic pressure and mediastinal shift reduce venous return to the heart. Less filling lowers cardiac output, producing shock.
Should treatment wait for a chest radiograph?
No. Tension pneumothorax is diagnosed from vital signs and examination, and decompression should not be delayed for imaging.