Sasha, what is the 30 minute test for OI? I am a nurse and had my doctor's office do a standard tilt test like we do in the ER to diagnose dehydration/ low blood pressure/ Orthostatic hypotension. My BP dropped 20 points from sitting to standing. That was a positive tilt test in ER standards. How is the 30 minute test done?
They do a Tilt Table Test (aka, Head Up Tilt) in the ER? I had no idea.
The first time I heard about the Tilt Table Test was back in 1995 when Johns Hopkins released a study linking Orthostatic Intolerance to ME/CFS (
http://www.ncbi.nlm.nih.gov/m/pubmed/7674527/ ). There have been a lot of studies since then.
At the time, the Hopkins researchers were recommending 45 minutes for phase 1 of the test. The word "phase" can be confusing so I'll try to define what I mean by that.
The first part of the test, which I'll call phase 0, is with the table lying flat, not tilted. Various monitoring devices are hooked up (EKG, blood pressure cuff, IV line in case it is used later, etc,). The patient's baseline heart rate and blood pressure are measured during this time.
Then phase 1 is when the table is tilted to an angle (usually 70-80 degrees). The patient's vital signs are measured until either the time elapses or enough data is gathered that shows an abnormal result. (or if the patient asks the test to stop, I guess).
Some doctors stop phase 1 after only 10-15 minutes. Many doctors say that's too short because it will miss patients who have a delayed drop in blood pressure. (That's me! my severely abnormal BP drop didn't come until 20 to 30 minutes into the test) Other doctors say that 30 minutes is plenty. Still others say that it needs to be 45 minutes long. If the patient does not have an abnormal reaction during phase 1 then they go on to phase 2.
In phase 2, the table is put flat again and the patient is given a drug (isoproteronol, for example). Then the table is tilted upright again. I have a friend who did fine during phase 1 but had an abnormal test result in phase 2.
Here's a link with some more details in case it helps -
http://www.hopkinsmedicine.org/heal...ardiovascular/tilt_table_procedure_92,P07985/
All of this is made more complicated by different doctors having different opinions on what constitutes a "positive" (abnormal) test and deciding when the test should be stopped. I think by now most doctors agree that it's not that simple that a patient must faint in order for the test to be abnormal. But I don't think they all agree on what is a real positive vs. a false positive, especially when it comes to the IV part of the test.
I hope this helps. I know some people may get some useful data from an at home test ("poor man's tilt table test") but I'm pretty sure it would not have worked for me. I think home testing for POTS (which shows itself mostly through the increased heart rate, easier to measure) is easier than home testing for NMH (Neurally Mediated Hypotension). With NMH there's often a long delay before the drop in BP (doesn't drop immediately on standing) and any moving around, even just fidgeting or talking, can be enough to keep it from dropping enough to show an abnormal result.
