Single-day CPET results were sufficient to get a waiver on grounds of disability. The test is mainstream enough, and the results were bad enough, that no one cared about deconditioning theories in the slightest. It was considered conclusive and authoritative proof.
Repeat CPET Literature Request.
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anciendaze
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Just a warning here, the majority of cardiologists think of "exercise intolerance" in terms of ability to complete a stress test on a treadmill without cardiac anomalies or collapse. There have been cases reported here in which the doctor wrote "patient shows good exercise tolerance" on the results before they left the clinic. I've seen people complete exercise, then collapse some minutes later when their heart rate returns to normal, and their blood-pressure drops. This could well have been neurally-mediated hypotension. They could easily be out the door of a clinic before this happens.
Even for cardiologists, the idea of a prolonged decrease in capacity lasting over 24 hours is bizarre. Without evidence of heart failure they can easily impute this to psychological factors.
Even for cardiologists, the idea of a prolonged decrease in capacity lasting over 24 hours is bizarre. Without evidence of heart failure they can easily impute this to psychological factors.
bananabas
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So how does one diagnose neurally-mediated hypotension in a clinical setting then? Do they have to keep you under observation for 24 hours?
Also, if that is so difficult to grasp for doctors, I cannot immagine what they make of PEM/PENE.
Hip
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In the future perhaps the 2-day CPET test may become the gold standard for objectively measuring PEM, but at the moment this test lacks the research and validation that would make it the gold standard.
In particular, it is not known whether doing worse on the second day of the 2-day CPET test is unique to ME/CFS, or whether patients with other diseases might also do worse on the second day. For the handful of other diseases that this test has been tried on, all patients show a normal repeat CPET performance; only ME/CFS patients have a worse repeat CPET performance. But you really need to validate this test on hundreds of diseases before you can have confidence in it.
Also, if you are a patient with only mental PEM, but not physical PEM, it is doubtful that the 2-day CPET test would apply to you.
Furthermore, I am not aware of any studies that have validated the 2-day CPET test on a range of patients with different ME/CFS severity (mild, moderate and severe ME/CFS). It is possible that many of the mild ME/CFS patients would not perform worse on the second day, in which case, this test may not be appropriate for diagnosis of mild ME/CFS.
If you had access to a 2-day CPET test it would certainly be worth doing, but I would not as yet call it a gold standard for either a PEM or ME/CFS diagnosis. I certainly think this discovery of worse second day repeat CPET performance in ME/CFS patients is of huge significance; but more research is needed to take this forward.
Though the single day CPET test is a gold standard for measuring athletic performance in the healthy.
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anciendaze
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There is old work by reputable people like Dr. Dave Streeten which is widely ignored. This concerns two kinds of dysautonomia: POTS and NMH. People keep asking for single number thresholds which remove the need to even imagine dynamics when the dynamic response is fundamental in these cases. A malfunction in the autonomic system and baroceptor reflex means that patients do not adapt properly to upright posture. In some there is a simple criterion: heart rate goes over some limit. In others there is a peculiar change in pulse pressure (systolic - diastolic) taking place over about 20 minutes of standing without walking. You can temporarily get a doctor's attention by passing out. (This will be labeled neurally-mediated syncope. Most of us have adopted behaviors which avoid syncope. These are interpreted in a variety of useless ways, including the postulation of "false illness beliefs".) A large part of the profession mentally translates "neurally-mediated" to "psychological". This indicates they didn't pay attention to lectures on the substantial part of the nervous system outside the brain.
The important thing doctors need to recognize is that the changes in heart rate and blood pressure reveal a failure in adaptation to changing situations. If your heart rate exceeds some personal threshold there will be no further increase in cardiac output with increases in heart rate. (Athletes who push into this zone can end up with overtraining syndrome, at much higher levels of performance.) Even if you succeed in adapting for a minute or two, there should not be a significant fall in pulse pressure while you remain upright.
I've tried to get some doctors to say what constitutes minimum acceptable pulse pressure. If it were consistently below 20 mm. Hg. this would indicate heart failure. We've seen here that even 14 mm. Hg. is not enough to get noticed. I've even got some to imply that it doesn't really matter if it goes to zero momentarily. This is a condition in which blood is simply standing still without circulation. I suppose the rationale is that you will be fine when you wake up. Syncope will remove the postural stress by laying you out flat.
Evidence for PEM/PENE in 2-day CPET is striking, but the modest amount of research that has been done is generally ignored. Research on ill-defined cohorts, of which there are many, can invalidate anything. Most of the profession can't really distinguish "objective evidence" from "peer consensus". Available funding has a great deal to do with peer consensus, which closes the feedback loop.
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Sushi
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I had it diagnosed through a Tilt Table Test that included about 6 different types of autonomic testing. After about 1 1/2 hours I asked to stop the test as my pulse pressure was only 8 and I felt really awful.
bananabas
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Haha, OK, they should call that the "Endurance Tilt Table Test"
Sushi
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That was actually just a "good" Tilt Table Test. Many are not done very well. I was told to allocate 2 hours for it, but I couldn't last that long.Haha, OK, they should call that the "Endurance Tilt Table Test"
ahimsa
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My first Tilt Table Test was in 1995. After about 20 minutes my blood pressure plummeted (down to something unmeasurable, if I remember the report correctly) and I passed out. My diagnosis was Neurally Mediated Hypotension (NMH).
I think the term NMH is not used as much any longer according to a 2011 consensus document that I read. It looks like Neurally Mediated Syncope (NMS) is the term used now.
However, many patients with both ME and this form of dysautonomia never faint. I never passed out except on the tilt table test. And many others don't even pass out during a very long TTT (see @Sushi 's account above). So I think the term syncope (= faint) is misleading.
Telling doctors to look for NMS in ME/CFS patients would make doctors without much knowledge about Orthostatic Intolerance think, well, if the patient does not faint then they don't have NMS. But I get pre-syncope symptoms all the time without ever fainting. This appears to be fairly common.
I do see that Dr. Peter Rowe at Hopkins is still using the term NMH, at least according to this document:
http://www.dysautonomiainternational.org/pdf/RoweOIsummary.pdf
ahimsa
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That (NCS) is yet another term for NMH and NMS. It seems that experts in dysautonomia use lots of different terms.
This is an old quote (from http://solvecfs.org/the-outs-and-ins-of-oi/) but I think it still applies:
Another term that I've heard is Chronic Orthostatic Intolerance which is an attempt to show that it's not just a problem with intermittent fainting but a problem with regulating blood pressure (and heart rate, too, at times).
Edit: Here's a page from Dysautonomia International that might help:
http://www.dysautonomiainternational.org/page.php?ID=31
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anciendaze
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Yes, also changing in response to changing physiological stress, rather than simple variation with time. You might appreciate a blog post of mine on the absence of dynamics in medical thinking.
You are probing one of the deep mysteries of professional psychology. You might check on how often they order tilt-table tests.
(If you never look you can assume the light in the refrigerator goes off whenever you close the door. Most of the time you will be right. As one professor in a medical school was fond of saying to friends who became doctors "85% of your patients will get better no matter what you do.")
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Hip
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Indeed. Neurally mediated hypotension (NMH) goes by a bewildering array of synonyms, including:
Neurally mediated syncope
Neurocardiogenic syncope
Vasodepressor syncope
Vasovagal syncope
Reflex syncope
These all mean the same thing as NMH.
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bananabas
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Incidentally, I was not able to find any Wikipedia page for CPET..
https://en.wikipedia.org/wiki/VO2_max discusses it somewhat. The VO2max is the primary outcome of interest in running the CPET.
Hip
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Some articles on CPET in ME/CFS here:
Repeat Test Reveals Dramatic Drop in ME/CFS Exercise Capacity
New Exercise Study Brings Both Illumination and Questions
Busted! Exercise Study Finds Energy Production System is Broken in Chronic Fatigue Syndrome - Health Rising
Cardiopulmonary exercise testing (CPET) is also called: cardiopulmonary stress testing, and cardiopulmonary exercise stress.