I get a sinking, tightening feeling in chest, no pain anywhere, some nausea, dizziness and near black-out. In one case did black-out. ER showed normal EKG, normal blood pressure, normal pulse. Blood tests negative.  Age 61, no real medical history. I live with a kidney stone, I cough at night, have mild acid reflux. Height six feet, weight 180 lbs. I exercise regularly, can bike 25 - 30 miles and no problem, advanced weight-lifter.
Hi welcome to Chat Doctor . You have investigated for cardiac cause by EKG... Have you investigated for bronchitis like respiratory causes????Here is your work up needed with.... -Auscultation -Chest x-ray -spirometry if needed -CRASH tier etc... According to cause further treatment can be guided. For congestion relief phenylephrine can be given... If needed suitable antibiotic course needed As you have blackout history check your sugar level and neurological cranial nerve examination and muscular reflexes should be checked Take care Advise