Pneumothorax/Tension pneumothorax

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A condition in which lung collapses due to air entering the pleural space either through a chest wound that allows air more easily in than out ( eg a flapping wound) or through a rupture connecting the air-passages in a lung, through the pleural cover, into the pleural space (again with a flap of tissue acting as a one-way valve). Air pressure will build up in the tension pneumothorax and will in due course displace the heart and the rest of the mediastinal structures to an astonishing degree, gradually squashing the remaining lung into a mere fraction of the total chest cavity.

Tension Pneumothorax is a medical emergency. The patient is dyspnoeic (short of breath) and will become more and more short of breath with each breath taken. There is tachypnoea (rapid breathing) tachycardia (rapid pulse) and there may be hypotension and engorged neck veins as the condition develops. As the gasping breathing efforts become more vigorous, the tension may build up more rapidly, until the patient slides into a gasping unconsciousness, then (probably for the first time) is manifestly cyanosed (blue). Breathing efforts cease, as either exhaustion or acute respiratory failure ensue. Death then follows within minutes at most. A history of wounding to the chest may be given by the patient or any accompanying person. (stabbing, fall on to a projection, motor vehicle accident) A chest wound is usually present, and obvious. Occasionally it will have to be searched for. Occasionally there is no external wound - the tension then arises from a spontaneous pneumothorax, usually from rupture of an emphysematous bleb, very rarely after decompression eg an over-rapid ascent in a scuba diver.

Diagnosis is usually obvious in the conscious patient from the history and the nature of the wound. In an unconscious patient or a patient who has suffered a spontanious pneumothorax, the diagnosis of pneumothorax can be made very quickly at the stretcher-side by noticing by palpation and percussion the displacement of the heart. The diaphragmatic dullness will also be much lower than usual. The mediastinal displacement is often far more extreme in tension pneumothorax than in any non-tension pneumothorax. Auscultation may assist - the complete absence of transmitted breath sounds over the pneumothorax and the area over which heart sounds can be heard will help. A chest x-ray (or two if the first only shows a pneumothorax and the diagnosis is not otherwise clear) will diagnose the condition and help guide the decision of where to cannulate. There is no differential diagnosis in most cases. Levocardia in theory might need exclusion in some cases - the x-ray pictures of both conditions are absolutely diagnostic. In the most minimal cases of tension pneumothorax, the differential diagnoses of pneumothoraces generally will have to be considered.

First aid treatment - if a large, firm adhesive bandage can be secured over the wound it will prevent further air entrapment and may allow the transport of the patient to a doctor or hospital. If none is to hand, a hand firmly over the area may help as long as its function (to seal the whole wound) is understood. In theory at least, inserting anything into the wound (even quite a small object) so that an air passage through the wound exists (rather than a one-way valve) will convert a tension pneumothorax into a far less immediately-life threatening (non-tension) pneumothorax.

Emergency treatment - the tension can be released by a puncture into the tension compartment eg by a larger-bore needle (even 6 guage) open to the ward air. After ascertaining where the heart lies, insert the needle between two ribs, with the point away from the heart of any nearby structures, over any highly tympanitic area. The heart may be hugely displaced so palpate for its beat and percuss its main mass. Alternatively, where the patient is already unconscious (say from other injuries) and the diagnosis of tension pneumothorax is uncertain, intubation and positive pressure ventilation may hold respiratory failure at bay while more diagnostic examination and if necessary, radiology, is arranged. Great care must be taken in such a case not to rely on the intubation (without relieving the pressure in the tension pneumothorax) unless it is quite certain the patient continues to do well and remains pink, with good pulse and blood pressure.

Definitive treatment - Release the trapped air via simple aspiration or a "tube thoracostomy" - an intercostal trocar and cannula , but measure the pressure on first entering. If it is slightly below atmospheric, there is a pneumothorax but not tension. If it is atmospheric there may be a wound in the pleura but it is not of flap or "ball-valve" type. if it is above atmospheric pressure, that proves it was a tension pneumothorax. Empty the air from the cavity or allow it to blow out slowly, then connect the cannula to an under-water drain. Unlike an ordinary pneumothorax, this is usually required to ensure the flap has been dealt with. Some texts warn against rapid decompression, but let at least the over-pressure go freely. Deal with the wound and/or lung rupture (both may be present of course.) The latter may well require a thoracic surgeon competent in (intercostal) endoscopic surgery. DrRic 19:31, 25 March 2008 (UTC)