How To Treat Tension Pneumothorax?

Overview

Tension pneumothorax, also known as a collapsed lung, is a potentially lethal emergency caused by a build-up of air outside of the lung but within the chest cavity that puts excessive pressure on the lung, causing it to collapse. A characteristic feature is the structural shift of the organs associated with life-threatening disruption of cardiopulmonary function. Thus, it requires immediate recognition and management. Evaluation and diagnosis of tension pneumothorax must be followed immediately with high flow oxygen to provide oxygen reservoirs and maximise oxygenation. Treatment may include thoracic needle decompression, a large bore needle catheter inserted in a gap between the ribs, known as the second intercostal space, to release the trapped air. Usually, this is followed by re-expansion of the lung and stabilisation of the patient.

What is pneumothorax? 

Pneumothorax, also known as a collapsed lung, is a life-threatening emergency caused by a build-up of air outside the lung but within the chest cavity that puts excessive pressure on the lung, causing it to collapse.⁹  Pneumothorax can be either traumatic (triggered by open chest injury) or atraumatic (no associated trauma). Accordingly, the trapped air can originate from the outside of the body or the lung. This condition often has a spontaneous onset, with young people assigned male at birth (AMAB) affected most. 

Further classification is made in association with the origin and nature of this condition. 

• Primary spontaneous or simple pneumothorax occurs with no apparent reason in mostly healthy young people AMAB. It is closely linked to physiological abnormalities of the lung, such as small tears in the upper lung area, which cause small air blebs to escape the lung and get trapped inside the chest cavity. Approximately 5 in 10 people affected with simple pneumothorax are likely to have repeated episodes of pneumothorax on the same side of the thoracic cavity. In the United Kingdom, approximately 2 in 10,000 young people AMAB (~ 20 years old) are diagnosed with spontaneous pneumothorax annually. Interestingly, people AMAB are affected significantly more than people assigned female at birth.⁶ The predisposing risk factors of spontaneous pneumothorax include tobacco smoking, genetics, and previous episodes of pneumothorax.  

• Secondary spontaneous pneumothorax is a consequence of an existing lung disease that may predispose individuals to mini-tearing of the lung tissue, allowing air to pass through. Lung diseases can affect the lung tissues and pleura and contribute to loss of pressure gradient between lungs and pleural cavity, which generally prevents lung collapse. For instance, lung diseases known to be complicated by secondary spontaneous pneumothorax are tuberculosis, necrotising pneumonia, chronic obstructive pulmonary disease (COPD), lung cancer, sarcoidosis, cystic fibrosis, endometriosis, severe acute asthma, idiopathic pulmonary fibrosis and many more. Patients struggling with these diseases may experience severe complications, such as hypoxemia and hypercapnia, and sudden onset of breathlessness.
• Traumatic pneumothorax is caused by open injury to the chest, particularly chest wall trauma, resulting from stab or gunshot wounds.

What is Tension Pneumothorax?

Tension pneumothorax is a more critical variant of pneumothorax; this condition is linked to a gradual accumulation of air between the two opposing layers of the lungs - the one that covers the lungs (visceral pleura) and the one overlying the inner surface of the chest walls (parietal pleura).¹ Eventually, accumulated air can cause a mediastinal shift, structural displacement of the internal organs, such as the heart, towards the unaffected area, leading to compression of the heart and major blood vessels, compromising cardiopulmonary function. Additionally, decreased blood oxygenation increases heart rate, causes hypoxemia, tissue acidosis, impaired cardiac output, and can lead to cardiac arrest.

Causes of tension pneumothorax can be associated with trauma, such as open chest injuries and wounds, rib fractures, and mechanical ventilation.

Common signs of tension pneumothorax are shortness of breath, confusion, and acute sharp chest pain with each breath. 

Pneumothorax vs Tension Pneumothorax

Both pneumothorax and tension pneumothorax occur due to air accumulation within the vital regions of the lung. They cause severe disruption of normal pulmonary function.

The main difference between these conditions is that air gets trapped between the chest wall and the lungs in pneumothorax. In contrast, air accumulation occurs between visceral and parietal layers in tension pneumothorax. Pneumothorax is a curable and less dangerous condition, while tension pneumothorax is a critical emergency that can be lethal if not managed in a timely manner.

Similarly, the two conditions have slightly varying causes and symptoms; the following table covers the main differences between the two conditions.

Causes of Tension Pneumothorax

To understand the principles of the pathophysiology of tension pneumothorax it is essential to know how healthy pulmonary function occurs.

A fine pressure gradient exists between lung layers and pleural and intrapleural spaces. Compared to more positive atmospheric and lung pressure, a pleural cavity has more negative pressure, which creates a gradient that normally prevents the lungs from collapsing and ensures normal pulmonary function and gaseous exchange. During pneumothorax, negative pressure is lost within intrapleural space, and therefore loss of pressure gradient balance. This shift toward more positive pressure compresses the lung and causes it to “collapse”, meaning that lung volume is significantly reduced. With this reduction comes a loss of lung oxygen capacity, severely affecting ventilation. The inability to supply the blood with oxygen leads to hypoxemia (insufficient oxygenation of the blood).

Tension pneumothorax is common among patients on mechanical ventilation in emergency departments, associated with the build-up of air pressure in the lung pleura, which cannot fully exit, like a one-way valve.⁴ An open wound is thought to act as a one-way valve mechanism that allows the entry of air into the intrapleural space with each breath, however, the air fails to find an exit since there is no reverse flow out of the lungs on expiration. It results in each breath pumping more air out of the lung, further collection of air in the intrapleural space, and increased volume and pressure of pneumothorax. It also affects the normal positioning of internal organs and compression of blood vessels, such as the aorta and vena cava, causing impaired diastolic filling and cardiac output. The negative effect of loss of lung ventilation and poor blood flow results in a mismatch for ventilation-to-perfusion. Emergency treatment to release trapped air is vital to prevent hypoxemia, acidosis, and shock.

Signs, symptoms, and differential diagnosis

Universal signs:

• Spontaneous onset
• Immediate and progressive decrease in arterial and mixed venous oxygen
• Immediate reduction in cardiac output
• Obstructive shock caused by a drop in blood pressure (BP) 

Tension pneumothorax differential diagnostic criteria:³

Severe clinical manifestations:

• Respiratory distress 
• Tracheal deviation
• Low breath sounds
• Low blood pressure
• Hypomobility (inability to move freely)
• Sound of air release on thoracic needle decompression 
• Mediastinal shift visible on chest radiograph in a ventilated patient
• Haemodynamic instability that is improved with the release of gas 
• Expanding intrapleural pressure that is more positive than atmospheric pressure

Treating A Tension Pneumothorax

Management of tension pneumothoraces usually takes place in intensive care units (ICU) of the hospital, as patients affected by tension pneumothorax usually are hemodynamically unstable (they have an unstable pumping heart, decreased blood pressure and poor blood circulation to distal organs).⁵

Firstly, open chest wounds (if present) must be cleaned and covered with an airtight bandage and clean plastic cover. 100% supplemental oxygen masks are implemented to improve and maximise blood oxygenation. These help to decrease lung nitrogen pressure and re-establish optimal lung pressure gradient.¹

Needle Decompression

If tension pneumothorax is suspected, immediate needle decompression is essential and must be performed without delay. Although rapid clinical diagnosis is critical, prompt recognition of tension pneumothorax remains complicated due to ambiguous and non-reliable diagnostic criteria and clinical signs. Given that the patient is hemodynamically stable, a portable chest radiograph and a chest X-ray (CXR) must be performed to decide the treatment.

Treatment may include thoracic needle decompression and a large bore needle catheter inserted in a gap between the ribs, known as the second intercostal space, to release the trapped air.⁵

The needle catheter is maintained in the same position until the chest tube can be inserted. If tension pneumothorax causes cardiac arrest, resuscitation of the patient involves needle decompression to restore optimal cardiac output. After insertion of the chest tube, an immediate CXR is done to assess the resolution of the pneumothorax, ensure satisfactory post-treatment outcome and detect any complications. Usually, this is followed by re-expansion of the lung and stabilisation of the patient. If the patient's condition has improved with no complications and no visible air leaks are detected, the chest tube can be removed.  

One associated risk of fast lung re-expansion is pulmonary oedema, in which fluid fills the air sacs within the lungs and prevents normal breathing and ventilation. 

Despite being a gold-standard treatment option, recent literature reports that needle decompression failed to resolve the consequences and symptoms of tension pneumothorax.³ This can be explained mainly by lacking diagnostic methods, delayed procedures, and the inability to deliver treatment in a timely fashion. Additionally, serious risks are associated with the procedure, such as life-threatening cardiac tamponade, in which cardiac space is filled with fluid, such as blood, and causes increased pressure on the heart. Because of this pressure, cardiac output is reduced, causing a massive decrease in blood pressure. Cardiac tamponade leads to death if not managed promptly and effectively.

Many professionals stress the importance of identifying novel treatment options to bypass needle decompression; however, the attempts are still elusive at the moment. 

Patients with non-resolving prolonged air leaks (> 7 days) require video-assisted thoracic surgery (VATS), which treats pneumothorax with pleurodesis.⁸  Pleurodesis is a medical procedure during which the lung is artificially obliterated to the chest wall, which can be mechanical or chemical. With mechanical pleurodesis, the rate of recurring pneumothorax is significantly reduced, accounting for less than 5%. Chemical pleurodesis is an option for patients who cannot tolerate mechanical pleurodesis. There is sufficient evidence that shows that pleurodesis prevents recurrent pneumothorax.

Summary

Immediate treatment of tension pneumothorax is important to prevent the condition's complications and stabilise the patient in the emergency department. Undoubtedly, needle decompression is a 

life-saving option for critical hemodynamically unstable patients with tension pneumothorax. Needle decompression aids in managing patients with severe respiratory insufficiency, resolving tension pneumothorax, and relieving the condition to simple, spontaneous pneumothorax. Although still serious, patients with spontaneous pneumothorax are more stable and are not at risk of death, with a less rapid rate of the condition progression. Although less rapid, and in the absence of hemodynamic instability and severe respiratory insufficiency, the procedure's risks must be considered against its benefits. Prompt clinical imaging techniques and clinical presentation are required to confirm the diagnosis and deliver treatment in a timely manner.  Needle decompression is the first option for managing tension pneumothorax, despite the associated risks and complications. It is hoped that in the future, more research will be done to allow us to identify more modern and less-traumatic approaches to manage this condition with its variable presentations.