The investigators will test whether breathing through an inspiratory resistance device will improve the ability to be upright and decrease heart rate increases on standing in patients with postural tachycardia syndrome.

Chronic orthostatic intolerance, sometimes known as the postural tachycardia syndrome (POTS), is the most common disorder among patients seen at several centers specializing in diseases of the autonomic nervous system. It affects an estimated 500,000 people in the United States alone. POTS (excessive increase in heart rate [>30 min-1] on standing associated with orthostatic symptoms [including palpitation, chest pain syndrome, dyspnea on standing, mental clouding and difficulties with concentration], in the absence of orthostatic hypotension) can produce substantial disability among otherwise healthy people. Patients with POTS typically feel tired and run down. Many also report a myriad of symptoms that are hard to categorize, often involving fatigue. One study, from the Mayo Clinic, found that patients with POTS had a diminished quality of life when measured using a standard health status instrument (SF-36).

In this pilot study, we will test the hypothesis that breathing through an inspiratory resistance device will improve orthostatic tolerance and reduce orthostatic tachycardia in patients with postural tachycardia syndrome.

Inclusion Criteria:

• Diagnosed with postural tachycardia syndrome by the Vanderbilt Autonomic Dysfunction Center
• Increase in heart rate ≥ 30 beats/min with position change from supine to standing (10 minutes)
• Chronic symptoms consistent with POTS that are worse when upright and get better with recumbence
• Able and willing to provide informed consent

Exclusion Criteria:

• Overt cause for postural tachycardia (such as acute dehydration)
• Inability to give, or withdrawal of, informed consent
• Pregnant
• Other factors which in the investigator's opinion would prevent the subject from completing the protocol