Aldosterone & Sodium Regulation in Postural Tachycardia Syndrome - Screening

"heart rate and blood pressure will be continuously monitored while participants undergo a variety of breathing techniques (deep breathing, rapid breathing, blowing against resistance) and during sustained handgrip and cold pressor (hand in ice water). All tests are meant to stimulate the autonomic nervous system to produce changes in blood pressure and heart rate of short duration that reflect how well the autonomic nervous system is functioning.~Also during autonomic function testing, cardiac output will be measured to analyze the shift of fluids in the body (body impedance) and / or by analyzing the air that is breathed."

Blood pressure, heart rate and blood samples (for catecholamines and hormones) will be measured \& collected in the supine (lying) and upright position for each participant.

Total blood volume is measured by using iodinated I-131 tagged human serum albumin.

Participants will ride on a stationary recumbent bicycle and the resistance will be gradually increased while expired air is measured.