1) The puncture site is the second intercostal space (between ribs 2 and 3) in the midclavicular line, on the side of the suspected tension pneumothorax. Clean the skin with disinfectant, use local anaesthetic if necessary.
2) A large calibre cannula (preferably with a diametre of at least 2 mm), with the drip chamber removed, is joined with a 10 ml syringe. The cannula is inserted through the skin at a straight angle, following the upper border of the 3rd rib.
3) After piercing the skin, pull back on the plunger of the syringe to create a slight negative pressure and continue inserting the cannula for its entire length.
4) Remove the syringe and mandrin and air will flow out at a high pressure. Leave the cannula inside and connect it with a three-way stopcock with which you can regulate the air flow. Remove the cannula only after inserting a chest drain.