I usaully get hyperventilation &pass out but yest.i couldn't breath at all passed out &was given o2 &became better , all tests neg no useful answers!?

Hypervent.: Good to know that all tests are normal. Not sure if u r on medications for anxiety, but it might be something u can discuss with your primary care doc.

Anxiety: Being that all your tests were negative and you describe hyperventilation and sometimes breath holding could be indicative of anxiety triggering episodes. A further evaluation with your primary care physician when these episodes occur could be revealing.