Conventional teaching for treatment of confirmed or suspected tension pneumothorax in an unstable patient is immediate chest decompression with a large bore angiocatheter . New generation angiocaths feature blood control technology, which allows a flash of blood to rise into the hub but will not transmit that blood out the end, which increases safety and decreases messes. Half of the departments I work in now stock blood control angiocaths; since this device is more expensive than its predecessors, you can expect all american hospitals will soon move to them.
Notice the blood control valve, which adds length to the hub compared to the same catheter without this feature.
The blood control valve prevents blood from flowing out the hub but also prevents any other fluid from flowing through the catheter, including air. So stabbing your pneumothorax patient with this device will not decompress the chest.
Fortunately the valve opens permanently when it is pushed down by IV tubing, or by attaching a syringe.
So place the angiocath as usual, then take a syringe, pull out the plunger, and twist it firmly onto the hub, until you hear your rush of air.
There are all sorts of problems with using any needle or angiocath to decompress pneumothorax, especially if you use the usual anterior approach, and you are better off in most cases performing a finger thoracostomy or quickly placing a chest tube. But if you do use an angiocath, be mindful of blood control technology, because if you place a catheter thinking you’ve relieved tension but you haven’t, now you’ve made a real mess.
 See chapter ten of the sixth edition of Roberts and Hedges.
 I’ve pictured the Becton Dickinson device but many angiocath manufacturers offer the same feature under a variety of names.