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Practice Rational Testing

Postural hypotension

BMJ 2011; 342 doi: (Published 16 June 2011) Cite this as: BMJ 2011;342:d3128

Rapid Response:

Re: Postural hypotension

In a previous discussion in BMJ I explained why I thought that tilt table testing would be a good way of diagnosing CFS.

Essentially, I once had a set of X-rays to determine the cause of an ache in the left side of my back which was ultimately diagnosed as a kidney stone. The procedure required me to be strapped onto a bed, which was then rotated upwards and sideways at various angles.

Each time the bed stopped an X-ray was taken to see the effect of gravity on the flow of fluid through the kidney, and if a kidney stone was blocking it.

However, co-incidentally, each time the bed moved I felt faint, and each time it stopped I recovered.

I therefore assumed that the movement was not only affecting the flow of fluid through my kidneys, but was also affecting the flow of blood in my general circulation, and temporarily directing it away from my brain.

I also concluded that such a weakness of blood flow could be the cause of some of my other symptoms which involved abnormal tiredness and fatigue, and that measuring it could be used diagnostically.

However there have been similar factors which have caused faintness before and since, which I will describe.

The first time I felt faint was at the age of 25 when I leaned toward a desk to write, and when I leaned back the faintness ceased.

Another example is when I got out of bed one morning and as soon as I stood up I felt faint. I therefore sat down again on the side of the bed, and waited a few moments to recover, and then stood up slowly. I was then able to walk about without any further problems.

Similarly I would sometimes be laying in a lounge chair, and stand up suddenly and feel faint, and sit back down again, and wait a few moments, and then stand up slowly to prevent the sense of faintness.

Another example was when I was the passenger of a car which was being driven around a winding country road. As it entered a curve I felt faint, and as it reached the outer extreme the faintness became worse, and gradually eased off as it came out of the curve, and would cease when the road straightened. The experience of faintness did not happen again until the next curve, when it would be repeated.

I had acquired some medical knowledge by that stage, so I concluded that the faintness was caused by the centrifugal force on my blood which was making it move to the outer part of my vascular system and away from my brain.

A similar example occurred when I entered a lift on the ground floor of a building to go up to a higher level.

When the door closed and the lift began to rise I felt a sense of faintness, and as it accelerated up the sensation became worse, but when it reached a steady speed the symptom eased, and then when the lift slowed I felt faint again, and when it came to a stop I felt worse. I then recovered, and when the door opened I walked out as usual.

I assumed that, shortly after starting, the effect of gravity, combined with upward acceleration had caused the blood in my body to drain toward my feet, and hence away from my brain to cause the faintness, and that when the lift slowed to a stop the blood was rushing upwards toward my brain in such a way as to over supply it, and interfere with the normal sense of consciousness by that means.

I can also recall attending the Royal Show as a teenager and enjoying the thrill of swirling show rides and roller coasters.

However, after developing problems with faintness at the age of 25 I avoided such activities because it was obvious to me that the minor symptoms of faintness which occurred with minor spinning activities, would be worse on the more extreme twists and turns and rises and falls involved.

Another cause of faintness occurred when I went on an aeroplane trip.

I boarded the plane, sat in my seat, and then clipped on my seat belt. A few minutes later the plane taxied along the runway and then accelerated to lift off the ground.

At the beginning of the acceleration I began to feel intensely faint, and it became worse as the speed increased.

However, when the plane reached a steady speed the sense of faintness eased.

About an hour later the plane suddenly dropped into an air pocket, and as it descended I felt the faintness begin and increase in intensity until the plane stopped falling and levelled out.

Another hour passed when the plane began to gradually descend in the sky in preparation for landing, and as it approached the airport runway it suddenly slowed in the sky, bringing on another intense sensation of faintness which again became worse as it continued to slow.
When the plane finally reached the ground and achieved a more steady speed the symptom of faintness stopped.
I had the same experience at the start and end of the return journey, but there were no air pockets encountered so I didn’t have any symptoms in mid flight.

It was obvious to me that the faintness at the start was due to the acceleration causing the blood to pool to the back of my body, and the symptoms at the end were due to deceleration causing the blood to pool at the front of my body, and away from my brain.

Those experiences verified my conclusion that the faintness was due to a weakness in the circulation of blood, and that tilt table testing can be used as a diagnosis for the chronic fatigue syndrome.

Further reading related to tilt table testing in CFS
Rowe Peter, 1995 (March), Is neurally mediated hypotension an unrecognised cause of chronic fatigue?, The Lancet, 345:623-24.

Competing interests: No competing interests

04 March 2014
Max Allan Banfield
Unit 6, No.6 Hartman Ave., Modbury, South Australia 5092