Tension Pneumothorax

[Connerlee]

I'm an EMT-B enrolled in paramedic school. We are on our trauma chapter discussing tension pneumothorax treatment. After preforming a needle decompression, why wouldn't the pt benefit from very gentle suction out of the catheter to relieve the pressure building in the thorax upon inspiration? My instructor had never heard anyone propose it before, so I thought I'd ask the internet wizard doctors. I don't expect to be right, but I can't understand how simply keeping a slight negative pressure in the chest cavity would be harmful. Thanks for the help!