In regards to a tension pneumothorax, what does it stand for?

Dangerous condition. A tension pneumothorax occurs when there is a hole and air escapes from the lung into the space between the lung and chest wall and does not go back into the lung. As the air escapes from the lung, the pressure builds up in the space between the lung and chest wall (the pleural space). As the pressure builds "tension"-the high pressure buildup) and it can put pressure on the heart.