Tension Pneumothorax

Question 1

What is the anatomy and function of the lung pleura?

Answer 1

There are two outer layers that line the lungs - the visceral and parietal pleura. The visceral pleura is attached to the lung tissue and the parietal pleura is attached to the thoracic wall and the diaphragm. In between these two layers is the pleural cavity. This contains a small amount of fluid that reduces the friction and creates surface tension between the two pleura.
The pleura allow for a change in lung shape during respiration. When the diapraghm contracts, it creates a negative pressure within the pleural space, which causes the lungs to then expand and draw air in.

Question 2

What is a pneumothorax?

Answer 2

A pneumothorax is the accumulation of air within the pleural cavity, which results from a disruption to the pleura. This may be secondary to barotrauma or from an external injury. This causes part or the entire lung to collapse under the pressure from the trapped air.

Question 3

What are the different types of pneumothoracies?

Answer 3

• Closed pneumothorax: caused by an internal injury to the lung or pleura, air enters the pleural space but can also escape therefore does not build up.
• Open: an open wound through the chest wall that causes air to enter the pleural space. Air is able to escape back through the wound so pressure does not build up.
• Tension: there is a one-way valve effect, so air can enter into the pleural space but not escape. This means with every inhalation air enters but cannot be exhaled, therefore the pressure builds within the pleural space which can lead to the compression of the other lung and blood vessels. This means the lung cannot inflate, gas exchange cant occur = hypoxia.
• Haemothorax: rather than the accumulation of air, blood accumulates, which in turn puts pressure on the lung causing it to be unable to inflate.
• Traumatic/non-traumatic

Question 4

What are the main concerns with a tension pneumothorax?

Answer 4

• Inability of the lung to inflate with air. This means gas exchange cannot occur and the patient can quickly become hypoxic
• Potential for the pressure to build in the pleural cavity, causing compression of the major blood vessels within the thorax such as the vena cava. This then reduces venous return to the heart, reduces preload, reduces stroke volume, reduces cardiac output.
• Increased pressure to the point of it effecting the other lung as well = further inability for gas exchange to occur.

Question 5

How does a tension pneumothorax lead to obstructive shock?

Answer 5

Obstructive shock is caused by the inability of the body to have an adequate cardiac output secondary to a blockage, despite normal intravascular volume and myocardial function.
A tension pneumothorax causes increased pressure within the thoracic cavity. This can begin to put pressure on the major blood vessels that pass through the thorax such as the inferior vena cava. As pressure increases, this vein becomes more compressed and blood flow through it is reduced, until it is completely obstructed. This means venous return to the heart is reduced, and cardiac output begins to become effected = obstructive shock.
Can also begin to effect the ability of the heart to fill with blood to then be able to eject.

Question 6

What is the rationale for decompressing the chest and how is it performed? What are some negatives?

Answer 6

The aim of decompression is to relieve the tension that is building within the pleural cavity by allowing the trapped air to escape. The decompression needle should be inserted into the pleural cavity, which allows the air to escape. It should then be left in place so that air can continue to escape.
A dwell catheter is used for the decompression.
First the landmark of 2nd intercostal space, midclavicular line is marked out. It must then be disinfected with a betadine swab. The needle should then be inserted at a 90 degree angle just above the third rib. It should be inserted into the chest until a release of pressure is felt. The needle should then be removed and immediately placed into a sharps container. The remaining sheath should be secured in place. Obs should then be reassessed for improvement and breath sounds auscultated.
Negatives:
-still allows air to enter the pleural space - is not a one way valve and can continue to contribute to a pneumothorax
-May become clogged with a clot, tissue or blood, rendering it ineffective
-May be difficult to insert on bigger patients and placement can become hard to figure out
-May not work and require multiple to have an effect.

Question 7

What are the signs and symptoms of a tension pneumothorax?

Answer 7

Respiratory:
-respiratory distress - SOB, increased WOB, increased RR, accessory muscle use, dyspnoea
-decreased air entry to the effected lung
-low sp02 despite high flow 02
-tracheal deviation away from effected lung
-surgical emphysema
-cyanosis
Cardiovascular:
-tachycardia
-hypotension from obstructive shock - loss of radial pulse
-jugular vein distention
-decreasing GCS

Question 8

What is the role of a 3-way dressing?

Answer 8

This is a dressing that is placed over an open chest wound. It is taped down on 3 sides, so that it can allow air to escape, but prevents air from entering the pleural space through the wound.
It may be indicated in a tension pneumothorax, however it is not a priority. This is due to the time that it takes to prepare, and it can often be difficult to stick down due to dirt, blood or sweat from the patient.