76 - Tension Pneumothorax.

KYJ 76 - Tension Pneumothorax

Pay attention to a tension

Off all chest injuries, Tension Pneumothorax is the most frequent killer. In this episode of trauma pearls, I'll review what differentiates a Tension pneumothorax from a pneumothorax.

First we review what s pneumothorax is.  Five lobes of lung are encased in a dual layered protective membrane called Pleura. Between these two layers exists 5-15ml of lubricating fluid. During inspiration and expiration the plural layers slide across each other like two sheets of wet glass . With  ease and little friction. Between the pleural layers, there is a relative vacuum ( less pressure than in the lung) and this ensures that the lungs don't fully collapse after expiration. Lung has a natural tendency to recoil to 80% of its volume if this negative pleural layer is breeched.

In a closed pneumothorax this is exactly what happens. The pleura adhered to the lung surface (visceral pleura) pops, and air from damaged alveoli moves into the relative low pressured intrapleural space. Lung recoils and function of the lung on the affected side is lost.  Small pneumothorax of up to 20% result in a sharp localised pain, some shortness of breath, and a rise in respiratory rate, but are rarely life threatening, and indeed are often conservatively managed with rest. These heal ofer 48 hours and rarely need to be drained or aspirated.

Larger pneumothorax or open pneumothorax result in respiratory distress, compromise to sustainable gas exchange and potential for pneumonia.  These are respiratory emergencies, and two options exist to treat.  Needle aspiration can be used, but more common is the insertion of an intercostal catheter (chest drain) and attachment to an underwater seal +/- suction.

In a pneumothorax patient where every breath delivers more air into the pleural space, pressure builds. As this occurs it severely compromises the ability to ventilate the lung, ultimately collapsing it. Pleural pressure now rises, squashing the lung, and placing pressure on the opposite lung, heart and great vessels. at this point the patient has no air entry on the affected side, is severely distressed, exhibits altered consciousness, tachycardia and desaturation. As the heart is displaced it kinks off the vena cava preventing blood return to the right heart. The trachea becomes displaced (pushed) toward the unaffected side, jugular veins bulge due to blood being unable to return from the head, cyanosis and cardiac arrest ensues due to an obstructive shock- no cardiac output.
At the point of loss of cardiac output, the pneumothorax is called a Tension Pneumothorax .

PThx is an immediately life threatening cardiovascular catastrophe and must be urgently treated by releasing the pressure from the pleura.

An emergency needle decompression is utilised to achieve this. A 14g  IV cannula is placed into the patient's chest at the landmark of the 2nd intercostal space, in the mid clavicular line.  Pressure is immediately released allowing the heart to resume its normal position in the mediastinum, and most importantly, blood to circulate. Cardiac output is restored within seconds.
Summary:
Pneumothorax is a respiratory emergency characterised by decreased air entry and respiratory distress.
Tension pneumothorax is an extension.
It is a cardiovascular catastrophe, characterised by loss of blood pressure, cardiac output, tracheal deviation, jugular vein distension, cyanosis, and cardiac arrest in minutes, if not decompressed.