Below is a copy of an email I sent to Paul and Kitty:

Hi Paul and Kitty,

3 weeks ago I decided to measure my blood pressure and to do so not
only upon wakening as I've done many times before but also lying in
bed rather than sitting as I had always done previously. This was the
first time I took a set of measurements lying in bed upon wakening. I
did so after only having gotten out of bed just to urinate and have a
sip of water, then I lay back in bed with the meter, relaxed for a
short while and then took a few measurements. As expected the numbers
were a little bit lower than what I've been getting when I've measured
it sitting. In fact some of the numbers I got were so low that I don't
think I want my blood pressure any lower than that. The average of 4
measurements was 109/48 with a pulse of 65. Here are all the 4
measurements:

117/53 P64
111/52 P64
99/43 P65
109/43 P65

Now I'm a little worried about my readings above as two of them had a
diastolic reading of 43, which is extremely low. Do you know how low
is too low when it comes to blood pressure? Obviously if it's too low
then you die. Just wondering if you've looked into this as I don't
really have the time nor interest to do so right now.

[External (non-invasive) blood pressure readings are not extremely accurate nor
exactly repeatable. It is very easy for the instrument to miss the exact point
at which to assess each level, since it relates to the pressure in the cuff
(which is slowly falling) at the time of the pressure wave from the heart. If
you could adjust the rate of pressure fall to make it slower, particular around
the pressure of the systolic diastolic interval then it would be more accurate.
As it is, plus or minus 10-15% is probably the norm. That is why your 4 readings
varied greatly and most likely only the average of them is close to correct.

[In the "old days" of manual blood pressure measurement with a stethoscope, it
was a learned technique to slowly let the the air out of the cuff so that the
reading would be more accurate - but not so slowly that it increased the local
pressure. (More sophisticated automatic equipment may have a rate adjustment
capability.) Also, one should not take several readings in the same location
within a very short period of time since this will raise the local pressure and
not reflect the actual systemic status. When repeat readings are necessary, they
should be done at least a couple of minutes apart. **Kitty]

However, even if your correct diastolic pressure were only 43, I don't think it
is a problem, given that it is not a sign of hemorrhaging (which is why low
blood pressure can kill you). Babies have such low diastolic pressures and the
average capillary pressure is only 17, so as long as your arterial pressure is
well above that, your tissue perfusion should be fine.

[One way to judge capillary fill is to apply pressure to a finger and toe nail.
Release the pressure quickly and watch for how long it takes the color to return
to the area under the nail. It should be very quickly. **Kitty]

Another thing to remember is that blood pressure is greatly affected by the
hydrostatic effects of the location of its measurement. The change is actually 1
point for every 13 mm or about 1/2 inch. The reason that it is measured in the
upper arm is because that is generally about the same level as the heart when
you are sitting or standing. If you measure it in your leg when standing it will
be much higher and if in your upper arm when raised above your heart level it
will be lower. Perhaps you were inadvertently raising your upper arm above your
heart when you took the measurement, maybe by lying on your side?

Kitty took my BP with me sitting here, first arm down at my side with cuff at
heart level as normal and got 92/58, then with my arm straight up and cuff at
about eye level and got 73/35. This effect of hydrostatic pressure makes the
actual venous pressure in the head usually negative (wrt atmospheric). If human
necks were a lot longer they could not adequately perfuse their brains. I expect
that really tall people with a large distance from heart to brain may always
have higher than average blood pressure. Giraffes have some special arrangements
for this purpose, but I don't remember what it is. --Paul]


On the other hand I am also very glad that my diastolic reading is so
low while my pulse pressure is pretty high indicating that I have
flexible arteries.

[Readers should note that this only *may* be the case for healthy, well
conditioned tall young men. Without an actual aortic BP reading there seems to
be no good way to tell if a high pulse pressure is indicative of elastic or
inelastic arteries. I had thought that for most people over 40 a higher pulse
pressure indicates that the arteries are not expanding sufficiently fast to take
the increased blood volume from the heart output, but now it appears that the
actual systolic pressure waveform has much less to do with flexibility and is
more related to varying cross-sections of the arteries through which the blood
is flowing. Only the average blood pressure (which is roughly DP-(SP-DP/3) -
weighted toward the diastolic because of the shape of the pressure curve) is
actually indicative of the inflexibility of the arteries. Furthermore, in a very
aerobically fit individual (Olympic cross country skiers for instance), the
heart output may be so large that the pulse pressure is high even though the
arteries are still highly flexible. In your case I suspect it must be the later,
but I would also question whether your BP meter is working properly (it may be
reducing the cuff pressure too fast or too slow to get good measurements). I
suggest that you go to a place where there is another BP meter for public use
and take your meter with you to compare results a few times interleaved.

The papers to which Olafur referred to in message #712 and which he just sent to
me do not give a sufficient explanation of any of this. For one thing they are
mostly epidemiological and provide absolutely no explanation for the blood
pressures shown by me and Kitty. Do our blood pressures indicate inelastic or
elastic arteries? If elastic (as I think) then why do we not have high brachial
amplification? How is a person of any age supposed to use BP readings from a
standard brachial cuff measurement (which is what all medical personnel
generally use) for any diagnostic purposes?

These are all questions which I now have, but also which I have no time to
attempt to answer. Since Olafur has brought forth the evidence (strictly data
about aortic vs brachial pressure) for this major diversion from previously
standard medical thinking about blood pressure, it will be up to him to provide
a more complete answer about how brachial BP measurements should be interpreted
with respect to health for people of all ages and sexes. --Paul]


My blood pressure appears to be excellent now. I
suspect this may be caused largely by all the supplements I'm taking.
Many of them are known ACE inhibitors and others probably also inhibit
ACE because many polyphenols have been shown to do so. Although most
of these supplements may have only mild effect the effect may be
adding up to a quite powerful ACE inhibiting effect particularly
combined with my polyphenol rich diet. BTW according to my recent
research on sRAGE this ACE inhibition could also be beneficial by
increasing sRAGE and decreasing RAGE.

[Yes, that is good to know since it should be helping me and Kitty also. --Paul]