How the Body Works
BP and Pulse Changes in Orthostatic Intolerance (OI)

There are some basic things that will help your body deal with blood pressure issues. You will probably have to pay attention to these things for a long time, maybe even the rest of your life.


Normal Blood Pressure Management

Blood pressure maintenance is dependent on beat-by-beat control exerted by the sympathetic nervous system, on cardiac output, on tone in resistance and capacitance vessels (which also is influenced by systemic and local pressor and depressor hormones), and on intravascular fluid volume.1

Normal Blood Pressure Changes With Standing Up

  1. In normal individuals, the systolic blood pressure (SBP)(the top number) doesn't drop more than 5–10 mm Hg when the person stand up. The bottom number, the diastolic blood pressure (DBP) goes up and pulse rate increases by 10–25 beats per minute.2
    • In some patients with Orthostatic Hypotenstion (OH - low blood pressure with standing up) and cardiovagal autonomic dysfunction, an increase in heart rate will not occur.1

  2. Cerebral blood flow (blood flow to the brain) didn't change in normal subjects until mean arterial pressure fell to 60–70 mm Hg.
    • In patients with autonomic failure, however, autoregulatory ability remained intact with MAP values as low as 40 mm Hg.81

How the Body Reacts So You Don't Pass Out Every Time You Stand Up

When you stand up, between 300 and 800 mL of blood go from the head, arms and chest down to the legs.

Within This results in "pooling" of blood in the veins of the legs. This blood would stay there if there weren't other changes.

Receptor cells in the neck and aorta sense that the blood pressure has dropped. They send messages to the brain which releases chemicals into the bloodstream.

These chemicals

        1. stimulate the arteries and veins (especially) to constrict (get smaller).

        2. increase how fast the heart beats and

        3. increases how hard the heart pumps - pushes more blood out of the heart into the aorta.

Part 1 - What the body normally does to keep you from fainting every time you stand up  Slide Presentation -

With Orthostatic Intolerance - How the Body Reacts to Standing Up

Part 2 - What Happens in Orthostatic Intolerance: Symptoms, POTS, NMH and Fainting. Slide Presentation

Part 3 - Orthostatic Intolerance - What You Can Do About It    Slide Presentation
                 How the things in Taking Care and the medications address the problems the body has with standing up.

How the Veins React to Standing Up and What You Can Do   Slide Presentation   

Videos - Coming Soon!

   • Normal Body Response to Standing Up

   • Impact of Prolonged Bedrest on the Body

   • How Veins React to Standing Up Video

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  1. Mathias CJ. Autonomic diseases: management. J Neurol Neurosurg Psychiatry. 2003 Sep;74 Suppl 3:iii42-7.  Abstract.   Article.
  2. Medow MS, Stewart JM, Sanyal S, Mumtaz A, Stca D and Frishman WH. Pathophysiology, Diagnosis, and Treatment of Orthostatic Hypotension and Vasovagal Syncope. Cardiology in Review 2008;16(1):4-20. Abstract.

Author: Kay E. Jewell, MD
Page Last Updated: August 12, 2012