HiHi there. I'm 6'4" tall and approx. 300 lbs. I regularly donate plasma to supplement my income, but lately, more often than not, I have been deferred for 24 hour periods due to my pulse being > 100bpm. In the past, I have been cleared for donation by the nurse at the plasma center, who auscultated my heart rate and noted that I have a regular rate and rhythm. I've also received clearance in the past from my personal physician and a cardiologist, both of whom say I'm okay to donate. This plasma center does not honor that, so I'm wondering: What can I do (besides eating well, not smoking, and avoiding caffeine) to lower my heart rate just while they are checking it in the screening room?