PNEUMOTHORAX

A pneumothorax is a potential medical emergency caused by accumulation of air or gas in the pleural cavity, occurring as a result of disease or injury.

It can result from:

• A penetrating chest wound
• Barotrauma to the lungs
• Spontaneously (most commonly in tall slim young males and in Marfan syndrome)
• Chronic lung pathologies including emphysema, asthma
• Acute infections
• Acupuncture
• Chronic infections, such as tuberculosis
• Cancer
• Catamenial pneumothorax (due to endometriosis in the chest cavity)

Pneumothoraces are divided into tension and non-tension pneumathoraces. A tension pneumothorax is a medical emergency as air accumulates in the pleural space with each breath. The remorseless increase in intrathoracic pressure results in massive shifts of the mediastinum away from the affected lung compressing intrathoracic vessels. A non-tension pneumothorax by contrast is a less severe pathology because the air in the pneumothorax is able to escape.

The accumulation of blood in the thoracic cavity (haemothorax) exacerbates the problem, creating a pneumohaemothorax.

Signs and symptoms

Sudden shortness of breath, cyanosis (turning blue) and pain felt in the chest and/or back are the main symptoms. In penetrating chest wounds, the sound of air flowing through the puncture hole may indicate pneumothorax, hence the term "sucking" chest wound. The flopping sound of the punctured lung is also occasionally heard.

If untreated, hypoxia may lead to loss of consciousness and coma. In addition, shifting of the mediastinum away from the site of the injury can obstruct the superior and inferior vena cava resulting in reduced cardiac preload and decreased cardiac output. Untreated, a severe pneumothorax can lead to death within several minutes.

Spontaneous pneumothoraces are reported in young people with a tall stature. As men are generally taller than women, there is a preponderance among males. The reason for this association, while unknown, is hypothesized to be the presence of subtle abnormalities in connective tissue.

Pneumothorax can also occur as part of medical procedures, such as the insertion of a central venous catheter (an intravenous catheter) in the subclavian vein or jugular vein. While rare, it is considered a serious complication and needs immediate treatment. Other causes include mechanical ventilation, emphysema and rarely other lung diseases (pneumonia).

Diagnosis

The absence of audible breath sounds through a stethoscope can indicate that the lung is not unfolded in the pleural cavity. This accompanied by hyperresonance (higher pitched sounds than normal) to percussion of the chest wall is suggestive of the diagnosis. If the signs and symptoms are doubtful, an X-ray of the chest can be performed, but in severe hypoxia, emergency treatment has to be administered first.

In a supine chest X-ray the deep sulcus sign is diagnostic[2], which is characterized by a low lateral costophrenic angle on the affected side.[3] In layman's terms, the place where rib and diaphragm meet appears lower on an X-ray with a deep sulcus sign and suggests the diagnosis of pneumothorax.

Differential Diagnosis

When presented with this clinical picture, other possible causes include:

• Acute MI: presents with shortness of breath and chest pain, though MI chest pain is characteristically crushing, central and radiating to the jaw, left arm or stomach. Whilst not a lung condition, patients having an MI often happen to also have lung disease.

• Emphysema: here, delicate functional lung tissue is lost and replaced with air spaces, giving shortness of breath, and decreased air entry and increased resonance on examination. However, it is usually a chronic condition, and signs are diffuse (not localised as in pneumothorax).

Careful history taking and examination and a chest x-ray will allow accurate diagnosis.

Pathophysiology

The lungs are located inside the chest cavity, which is a hollow space. Air is drawn into the lungs by the diaphragm (a powerful abdominal muscle). The pleural cavity is the region between the chest wall and the lungs. If air enters the pleural cavity, either from the outside (open pneumothorax) or from the lung (closed pneumothorax), the lung collapses and it becomes mechanically impossible for the injured person to breathe, even with an open airway. If a piece of tissue forms a one-way valve that allows air to enter the pleural cavity from the lung but not to escape, overpressure can build up with every breath; this is known as tension pneumothorax. It may lead to severe shortness of breath as well as circulatory collapse, both life-threatening conditions. This condition requires urgent intervention.

First Aid

Chest wound

Penetrating wounds require immediate coverage with an occlusive dressing, field dressing, or pressure bandage made air-tight with petroleum jelly or clean plastic sheeting. The sterile inside of plastic bandage packaging is good for this purpose; however any airtight material, even the cellophane of a cigarette pack, can be used. A small opening, known as a flutter valve, needs to be left open, so the air can escape while the lung reinflates. Any patient with a penetrating chest wound must be closely watched at all times and may develop a tension pneumothorax or other immediately life-threatening respiratory emergency at any moment. They cannot be left alone.

Blast injury or tension

If the air in the pleural cavity is due to a tear in the lung tissue (in the case of a blast injury or tension pneumothorax), it needs to be released. A thin needle can be used for this purpose, to relieve the pressure and allow the lung to reinflate.

Spontaneous Pneumothorax

Spontaneous Pneumothorax can be classified as primary spontaneous pneumothorax and secondary spontaneous pneumothorax. In primary spontaneous pneumothorax, it is usually characterize by a rupture of a bulla in the lung while secondary spontaneous pneumothorax occurs due to chronic obstructive pulmonary disease (COPD). Primary spontaneous pneumothorax is most evident to people without any previous history of lung disease and in tall, thin men whose age is between 20 to 40 years old. Some of the diseases that may lead to spontaneous pneumothorax are:

• Tuberculosis
• Pneumonia
• Asthma
• Cystic fibrosis
• Lung cancer
• Interstitial lung disease

A spontaneous pneumothorax may occur without either trauma to the chest or any kind of blast injury. This type of pneumothorax is caused when a bleb (an imperfection in the lining of the lung) bursts causing the lung to deflate. If a patient suffers two or more instances of a spontaneous pneumothorax, surgeons often recommend a bullectomy and pleurectomy.

Pre-hospital care

Many paramedics can perform needle thoracocentesis to relieve intrathoracic pressure. Intubation may be required, even of a conscious patient, if the situation deteriorates. Advanced medical care and immediate evacuation are strongly indicated.

An untreated pneumothorax is an absolute contraindication of evacuation or transportation by flight.

Clinical treatment

Small pneumothoraces often are managed with no treatment other than repeat observation via Chest X-rays, but most patients admitted will have oxygen adminstrated since this has been shown to speed resolution of the pneumothorax.

Larger pneumothoraces may require tube thoracostomy, also known as chest tube placement. A tube is inserted into the chest wall outside the lung and air is extracted using a simple one way valve or vacuum and a water valve device, depending on severity. This allows the lung to re-expand within the chest cavity. The pneumothorax is followed up with repeated X-rays. If the air pocket has become small enough, the vacuum drain can be clamped temporarily or removed.

In case of penetrating wounds, these require attention, but generally only after the airway has been secured and a chest drain inserted. Supportive therapy may include mechanical ventilation.

Recurrent pneumothorax may require further corrective and/or preventative measures such as pleurodesis. If the pneumothorax is the result of bullae, then bullaectomy (the removal or stapling of bullae or other faults in the lung) is preferred. Pleurodesis is the injection of a chemical irritant that triggers an inflammatory reaction, leading to adhesion of the lung to the parietal pleura. Substances used for pleurodesis include talc, blood and bleomycin. Both operations can be performed using keyhole surgery to minimise discomfort to the patient.