Tension Pneumothorax - Trouble In The Heart And Lungs
Tension pneumothorax is the progressive build-up of air within the pleural space, usually due to a lung laceration which allows air to escape into the pleural space but not to return.
Positive pressure ventilation may exacerbate this “one-way-valve” effect.
Progressive build-up of pressure in the pleural space pushes the mediastinum to the opposite hemithorax, and obstructs venous return to the heart.
This leads to circulatory instability and may result in traumatic arrest.
Pneumothorax - causes, symptoms, diagnosis, treatment, pathology
COPYRIGHT_SPINE: Published on https://spinal-injury.net/tension-pneumothorax/ by Dr. Bill Butcher on 2022-10-24T11:17:32.324Z
Diagnosis
The classic signs of a tension pneumothorax are deviation of the trachea away from the side with the tension, a hyper-expanded chest, an increased percussion note and a hyper-expanded chest that moves little with respiration.
The central venous pressure is usually raised, but will be normal or low in hypovolemic states.
Classic Signs
The signs involve the following:
- Trachea (arrow pointing to the right)
- Expansion (arrow pointing down)
- Percussion Note (arrow pointing up)
- Breath sounds arrow pointing downwards)
- Neck veins (arrow pointing up)
However, these classic signs are usually absent and more commonly the patient is tachycardic and tachypneic, and may be hypoxic.
These signs are followed by circulatory collapse with hypotension and subsequent traumatic arrest with pulseless electrical activity (PEA).
Breath sounds and percussion note may be very difficult to appreciate and misleading in the trauma room.
Tension pneumothorax may develop insidiously, especially in patients with positive pressure ventilation.
This may happen immediately or some hours down the line. An unexplained tachycardia, hypotension and rise in airway pressure are strongly suggestive of a developing tension.
A post-mortem film taken in a patient with severe blunt trauma to the chest and a left tension pneumothorax illustrates the classic features of a tension:
- Deviation of the trachea away from the side of the tension
- Shift of the mediastinum
- Depression of the hemi-diaphragm
With this degree of tension pneumothorax, it is not difficult to appreciate how cardiovascular function may be compromised by the tension, due to obstruction of venous return to the heart.
This massive tension pneumothorax should indeed have been detectable clinically and, in the face of hemodynamic collapse, been treated with emergent thoracostomy - needle or otherwise.
A tension pneumothorax may develop while the patient is undergoing investigations, such as CT scanning or operation.
Whenever there is deterioration in the patient’s oxygenation or ventilatory status, the chest should be re-examined and tension pneumothorax excluded.
The presence of chest tubes does not mean a patient cannot develop a tension pneumothorax.
A patient can have a right sided tension despite the presence of a chest tube. It is easy to appreciate how this may happen when looking at a CT image showing the chest tubes in the oblique fissure.
Chest tubes here, or placed posteriorly, will be blocked as the overlying lung is compressed backwards.
Chest tubes in supine trauma patients should be placed anteriorly to avoid this complication. Haemothoraces will still be drained provided the lung expands fully.
This the reason why the tension is not visible on the plain chest X-ray: the lung is compressed posteriorly but extends out to the edge of the chest wall, so lung markings are seen throughout the lung fields.
Tension pneumothorax may also persist if there is an injury to a major airway, resulting in a bronchopleural fistula.
In this case a single chest tube is cannot cope with the major air leak.
Two, three or occasionally more tubes may be needed to manage the air leak. In these cases, thoracotomy is usually indicated to repair the airway and resect damaged lung.
Beware also the patient with bilateral tension pneumothoraxes.
The trachea is central, while percussion and breath sounds are equal on both sides. These patients are usually hemodynamically compromised or in traumatic arrest.
Emergent bilateral chest decompression should be part of the procedure for traumatic arrest where this is a possibility.
There is one (rare) chest X-ray that shows the characteristic apparent “disappearance of the heart” with bilateral tension pneumothoraxes.
Management
Needle Thoracostomy
Classical management of tension pneumothorax is emergent chest decompression with needle thoracostomy.
A 14-16G intravenous cannula is inserted into the second rib space in the mid-clavicular line.
The needle is advanced until air can be aspirated into a syringe connected to the needle.
The needle is withdrawn and the cannula is left open to air. An immediate rush of air out of the chest indicates the presence of a tension pneumothorax.
The maneuver essentially converts a tension pneumothorax into a simple pneumothorax.
Many texts will state that a tension pneumothorax is a clinical diagnosis and should be treated with needle thoracostomy prior to any imaging.
Recently this dogma has been called into question.
Needle thoracostomy is probably not as benign an intervention as previously thought, and often is simply ineffective in relieving a tension pneumothorax.
If no rush of air is heard on insertion, it is impossible to know whether there really was a tension or not, and whether the needle actually reached the pleural cavity at all.
Some heavy-set patients may have very thick chest walls.
Needle thoracostomies are also prone to blockage, kinking, dislodging and falling out. Thus, a relieved tension may re-accumulate undetected.
More importantly is the possibility of lung laceration with the needle, especially if no pneumothorax is present initially. Air embolism through such a laceration is also a real concern.
In the absence of hemodynamic compromise, it is prudent to wait for the results of an emergent chest X-ray prior to intervention.
This will avoid patients such as that shown below, where a right upper lobe collapse due to endobronchial intubation resulted in hypoxia and tracheal deviation - mimicking a tension pneumothorax on the opposite side.
The patient received an unnecessary left chest tube.
The trauma-list has extensively debated needle thoracocentesis and discussions has been archived. The conclusion of the debate was:
1. Needle decompression can be associated with complications.
2. It should not be used lightly.
3. It should never be used just because we don't hear breath sounds on one side. BUT...
4. ...in clear cut cases: shock with distended neck veins, reduced breath sounds, deviated trachea, it could be life saving.
Chest Drain Placement
Chest tube placement is the definitive treatment of traumatic pneumothorax.
In most centers, chest tubes should be immediately available in the resuscitation room and placement is usually rapid.
The controlled placement of a chest tube is preferable to blind needle thoracostomy. This is provided the patient’s respiratory and hemodynamic status will tolerate the extra minutes it takes to perform the surgical thoracostomy.
Once the pleura is entered (blunt dissection), the tension is decompressed and chest tube placement can be performed without haste.
This is especially true of the patient who is being manually ventilated with positive pressure, and surgical thoracostomies without chest tube placement have been described in the prehospital setting.
Rarities
Tension gastrothorax has been described and may be confused with a tension pneumothorax.
There is hemodynamic compromise, tracheal and mediastinal deviation, and decreased air entry in the affected hemithorax (usually left).
Tension gastrothorax occurs in spontaneously breathing patients with a large diaphragmatic tear (usually blunt trauma).
This emphasizes the importance of blunt dissection and examining the pleural space with a finger prior to chest tube insertion.
About The Authors
Dr. Bill Butcher - With more than two decades of experience, Dr. Bill Butcher aims to provide a repository for educational materials, sources of information, details of forthcoming events, and original articles related to the medical field and about health subjects that matter to you. His goal is to help make your life better, to help you find your way when faced with healthcare decisions, and to help you feel better about your health and that of your family.Bill received his medical degree at Boston University School of Medicine and spent his entire career helping people find the health and medical information, support, and services they need. His mission is to help millions of people feel fantastic by restoring them to optimal health.