Welcome to the Hyperpnea in Postural Tachycardia Study website. Researchers at the Center for Hypotension at New York Medical College in Valhalla NY have received funding from the American Heart Association (AHA) to study the cause of increased breathing (hyperpnea) in  postural tachycardia syndrome in teenagers and young adults. Our most recent data indicate that this is particularly associated with sympathetic activation in important subsets of POTS.

    The Principal Investigator is Dr. Marvin S. Medow

    What comprises the study population? 
    What is the hypothesis and importance of the study?
    What are the symptoms and findings in patients?
    What is the goal of the study?
    What your own doctor can do to help diagnose POTS.
    How do I know if I’m eligible to be in this study? 
    Who pays for the exams, testing, and travel? 
    How can I get a questionnaire  for this study? 
    If I decide to participate what does the study entail?


    What comprises the study population? 

    We are seeking 3 different populations;  all adolescents and young adults aged 14-19 years with 1. patients with IBS and autonomic symptoms such as excessive sweating, pallor and lightheadedness; 2. patients with IBS without autono mic symptoms and 3. healthy age and sex-matched control subjects without IBS and autonomic symptoms. The determination of IBS will be made according to the Rome III criteria. 


    What is the hypothesis and importance

    We hypothesize that generalized sympathetic responses are reduced in all patients with IBS, regardless of presentation of autonomic symptoms. To test this,  we will measure blood volume and we will continuously measure heart rate and blood pressure and assess peripheral and segmental blood flow using segmental impedance plethysmography to ask the following question:


    We also hypothesize that subjects with IBS and autonomic symptoms have increased evidence of autonomic dysfunction and specifically increased splanchnic blood flow and splanchnic blood volume during orthostatic challenge.  To test this we will measure various aspects of cardipvascular control and response when subjects are placed upright at an angle of 70o for a maximum of 10 minutes.


    The proposed studies are anticipated to provide useful information regarding the status of autonomic function exhibited by subjects diagnosed with IBS and the cause of their pain. It is anticipated that these differences will likely be exhibited by IBS patients who describe  “autonomic” symptoms such as lightheadedness, sweating and pallor that may accompany their gastrointestinal symptoms, rather than by IBS patients without these accompanying symptoms.  These subjects may be shown to have differences in heart rate variability or blood pressure variability.  This may also manifest itself as differences in the way in which IBS patients can regulate changes in blood distribution during the imposition of an orthostatic challenge.  Sudden increases in splanchnic blood volume.



    What are the sypmtoms of IBS?


    The symptoms of IBS are detailed in the following Table.

    Text Box: Table 1 – IBS Rome III criteria
12 weeks or more in the past 12 months of abdominal discomfort or pain
that has 2 out of 3 features:
•	Relieved with defecation
•	Associated with a change in frequency of stool
•	Associated with a change in consistency of stool

The following are supportive, but not essential to the diagnosis:
•	Abnormal stool frequency (>3/day or <3/week)
•	Abnormal stool form (lumpy/hard or loose/watery) >1/4 of
•	Abnormal stool passage (straining, urgency or feeling of
			incomplete evacuation) >1/4 of defecations
•	Passage of mucus > 1/4 of defecations
•	Bloating or feeling of abdominal distension >1/4 of days









    What is the goal of the study

    Irritable Bowel Syndrome (IBS) is a common yet poorly understood category of disease. One reason for the difficulty in treating patients arises from the heterogeneous nature of IBS pathophysiology. Understanding IBS is important to understanding normal physiology of vascular control and its relationship to the elicitation of gastrointestinal symptoms that are associated with IBS. The goals of this study are therefore to further our understanding of the relationships between the gastrointestinal system and the autonomic nervous system.



    What can your own doctor do

    Please consult a qualified pediatric gastroenterologist for evaluation to diagnose Irritable Bowel Syndrome or to rule out other diseases that may be causing your symptoms.  This evaluation will involve various forms of tests that may include physical examination, blood and stool tests and x-ray studies. 


    How do I know if I’m eligible to be in this study? 

    All patients with a diagnosis of IBS, either with or without symptoms of Autonomic Dysfunction such as sweating, pallor and lightheadedness, may be eligible for enrollment in this study.  Patients aged 14-19 years of age of either sex may be eligible.

    Inclusion criteria for this study include:

  1. Subjects of either sex, aged 14 to 19 years old 

  2. normal physical examination results

  3. guaiac-negative stools

  4. normal results of endoscopic, radiologic, and biochemical studies when performed as part of the routine evaluation of abdominal pain.

    Exclusion criteria for this study include:

  1. Any illness that explains the chronic abdominal pain

  2. Any well known dysautonomia

  3. Inability to understand instructions or complete questionnaires.Participants who cannot read English will not be eligible to participate because all of the questionnaires are not available in alternative languages.

  4. Any systemic illness. This excludes patients with illnesses and disease states known to be associated with autonomic dysfunction such as diabetes, renal disease, congestive heart failure, systemic hypertension, acute and chronic inflammatory diseases, neoplasm, immune mediated disease, trauma, morbid obesity and peripheral vascular disease.



    Who pays for the exams, or testing?

    The diagnosis of IBS will be made by your doctor.  The diagnosis of Autonomic Dysfunction will also be made by your doctor and will be indicated by ssubtle symptoms that may include excessive sweating, pallor and lightheadedness or dizziness.  There are no charges associated with participation in this study.


    How can I get a questionnaire for this study? 

    You can click on the Questionnaire icon, and download and print out the application and mail it to us. The mailing address is on the last page of the form. Alternatively you can email the application to or you can also fax us the application at 914-593-8890. Or, you can call us at 914-593-8888, leave your name and address on the voicemail and we’ll mail you an application. 


    What happens if I’m eligible to be in the study and decide to participate? 

    If you would like to take part in this study, our study coordinator will contact you to go over the questionnaire materials and to arrange a date for the study.  At that time we will also review the informed consent process and answer any questions that you might have.  You and your parents (if applicable) should understand the study, and its risks and benefits.  You can click on the Informed Consent icon to read more about the study.

    As part of the study, you will be asked to fill out a questionnaire that will ask you about your gastrointestinal symptoms and about the function of your nervous system.  We will keep this questionnaire. After that, we will evaluate the function of your heart and circulation in a special testing laboratory.  To do this, we will ask you to come to our testing laboratory on two different days.  On each of the 2 days, we will do the same testing, except on one day (chosen by random, like a coin-toss), we will perform the testing described below 30 minutes after we feed you a meal.  We will measure your heart rate, blood pressure, blood flow to your skin and blood flow to different areas of your body.  All of these measurements will be made by placing sensors on your chest, belly, arms and legs.  This part of the test does not involve the use of any needles.  After we put these sensors on your body we will ask you to breath deeply for a while and then to blow out very hard into a small tube while lying flat on a table.  The way in which your heart rate and blood pressure change in response to this type of breathing will help us to measure how your nervous system is working.  After you have finished this part, we will ask you to repeat these breathing patterns while the table tilts you in two different positions.

    Hand Grip Test (HGT).  Physical exercise results in predictable changes in heart rate, blood pressure and distribution of blood throughout the body.  To test this, we will ask you to perform a HGT.  To do this, you will be asked to perform two brief maximum squeezes of their left hand using a specialized handgrip gauge. After about 10 minutes you will be asked to squeeze the gauge for 2 minutes at 1/3 of their maximum grip, during which time impedance, heart rate, blood pressure and breathing data will be collected.

    We would also like to measure your blood volume using an intravenous catheter (IV) that will be placed in your arm by using the indocyanine green dye dilution technique. To do this, a small amount of a harmless dye is injected into your veins through the IV and its concentration is detected by light absorbing device that is placed over the finger. This will only be performed on the day of testing when you will not be eating a meal.

     All of the testing should take about 4 hours to complete on each of the 2 days.

     We will also be taking 3 samples of blood from a needle in your vein to measure chemicals called catecholamines that help to control your blood pressure.  Each sample will be 5 ml, or about one teaspoon, and will be taken once while you are lying down and once while you are tilted in the two different positions.


    If you have further questions about the study, please feel free to call 914-593-8888 or email