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INTRODUCTION
The overall purpose of this investigation was to determine whether or not
the BIOflex® magnetic pad did influence the circulation of blood. Because
of the many complicating factors associated with the use of blood itself,
such as coagulation etc., it was decided to work with a very simple system.
To that end a 5% NaCl solution in distilled water was selected. The behavior
of the saline solution was compared with distilled water itself. Fluid was
drained from a reservoir through a capillary which could be exposed to or
isolated from the BIOflex® pad. There was no effect on the flow rate
of distilled water. A statistically significant effect was found, P <0.001,
on the flow of the saline solution which was enhanced when the capillary
was exposed to the magnetic pad. Preliminary measurements were made of the
streaming potential which also showed no effect of the presence of the pad
on distilled water but did show a positive effect on the aqueous NaCl solution.
The flow was also enhanced when the meniscus of the falling liquid level
in the reservoir was exposed to the pad. This appears to connect the capillary
results with surface tension effects. This connection is compatible with
known relationship of surface tension to the double layer at a liquid solid
interface.
MATERIALS
AND METHODS
Two sets of experiments were carried out. First, a flow meter was designed
which measured the change in buoyant force on a float. The float was suspended
from a proving ring fitted with Si strain gauges which responded to the
apparent weight of the float. A high performance, low noise strain gauge
amplifier was built which had a gain of 6000 and RMS noise of 6 millivolts
at the output. This is equivalent to a sensitivity for the input signal
of 1 microvolt before amplification. This combined with the gauge factor
of 100 for the Si strain gauges means that the minimum detectable strain
level in the proving ring was 0.01 microstrain. The float was then initially
immersed to a pre-determined level in a reservoir. As liquid was drained
from the reservoir the depth of immersion of the float decreased which increased
its apparent weight. The reservoir was drained through a capillary tube
which could be exposed to a BIOflex® pad or other external magnetic
field. The output of the strain gauge bridge was recorded using a Data 6000
acquisition system with permanent storage on floppy discs. Flow rates were
measured of distilled water and of 0.5% aqueous saline both with exposure
to the BIOflex® pad and without exposure.
In order to check the results obtained with the method described above,
a second completely independent set of experiments were carried out. The
second method was to simply drain a reservoir through a capillary, with
and without exposure to the BIOflex® pad, for fixed periods of time
and weigh the collected liquid. The reservoir consisted of a plexiglass
tube 5 cm in diameter and 30 cm long. This was filled to a height of 13
cm and was drained through a glass tube whose flow could be controlled by
a stop cock. This valve was configured so that it always opened to a fixed
“on” position. Following the stop cock was a vertical length of
silastic brand medical grade tubing manufactured by Dow Corning of outer
diameter 1.95 mm and inner diameter 1.47 mm. A digital, electronic timer
with resolution of 0.1 second was used to determine the time of the flow.
The collected fluid was weighed on a Sartorius Excellence Toploader digital,
electronic balance with 1 milligram resolution. The largest source of error
appears to have been the reproducibility of turning the flow on and off.
The distilled water was boiled to drive off dissolved air and cooled to
room temperature. The NaCl solution was made by dissolving 50 grams of NaCl
in 1000 cc of preboiled and cooled distilled water. The initial height of
the fluid column was 56 cm. Before actual data was taken, flow through the
system was maintained for 1 minute to remove any air bubbles. The entire
apparatus was cleaned with detergent and thoroughly flushed before commencing
a set of runs either with distilled water or the NaCl solution. A plexiglass
holder slot was used to support and position the BIOflex® pad so that
when present it rested against the vertical plastic capillary without deforming
it in any way.
A crude and preliminary streaming potential experiment was conducted by
inserting a copper electrode into the reservoir and another at the exit
of the capillary tube. Electric potential difference measurements were made
using a Kiethly digital voltmeter. Measurements were made on distilled water
and 5% aqueous saline solution with and without the BIOflex® pad. This
experiment should be done with Ag/AgCl or calomel electrodes and will be
repeated. The appropriate size electrodes were unavailable in time and,
therefore, this rough experiment was run. The trial was not repeated to
average out noise so that only the gross features have any meaning here.
In a further flow experiment, a BIOflex® pad was wrapped around the
reservoir from which the liquid drained. The pad was positioned so that
the meniscus of the falling liquid level passed across the pad. The flow
was compared with that obtained without the presence of a BIOflex® pad.
RESULTS
The outcome of this first set of experiments indicated when a flexible capillary
was exposed to the BIOflex® pad, the flow rate of a 0.5% saline solution
was increased while no effect was seen using a glass capillary. Furthermore,
no effect was seen in any case if distilled water alone was used. The flow
rate was approximately 3 ml/second which produced a strain gauge output
change of approximately 27 millivolts per second. Thus the change in electric
output was approximately 9 millivolts per milliliter of flow. The results
are shown in Table 1.
TABLE
1.
|
Trial
|
Strain
Gauge Signal
|
| |
Without
Pad (mV/Sec)
|
With
Pad (mV/Sec) |
|
1
|
25.738
|
28.450
|
|
2
|
25.775
|
28.694
|
|
3
|
26.975
|
26.963
|
|
4
|
28.981
|
28.919
|
|
5
|
26.863
|
28.075
|
|
6
|
25.994
|
26.463
|
|
7
|
26.313
|
28.381
|
| |
|
|
|
Mean:
|
26.663
|
27.992
|
|
Standard
Deviation:
|
1.135
|
0.923
|
| Flow
Rate m1/Sec: |
2.871
|
3.01
|
Volume/Run
= 52.511 mL
Total Voltage Change Per Run = 487.7 mV
millivolts change per millimeter of flow = 9.29
T - test value; t=2.324 P<0.1
The T test applied to the above data indicates that the flow rate is enhanced
by the presence of the BIOflex® pad as compared to the flow without
the pad. However, only a modest P value is obtained. Furthermore, the results
should be checked against distilled water which would act as a control.
No effect should be seen with distilled water. Moreover, this experiment
was plagued by electrical noise coming from the effects of moisture on the
strain gauge circuitry which caused slow dc voltage drifts. Although the
experiments were repeated often enough to average out a large part of the
noise, there was still a possibility that these drifts could be confused
with actual changes in flow rate. Therefore, it was decided to redesign
the measurement of flow rate and repeat the measurements as described in
the previous section.
The second set of flow measurements produced very satisfactory results.
The simple draining of a reservoir and weighing the collected fluid escapes
almost all sources of noise. A total of 20 runs were made under each flow
condition, i.e. distilled water or NaCl solution with and without the pad.
The average flow rate was approximately 1 gram per second. The results are
shown in Table 2 and plotted in Figure 1.
TABLE
2.
Average Weight of Collected Sample Grams
Distilled Water 20 Runs
With and Without BIOflex® Pad
| Time
Sec. |
With
|
Without
|
Diff.
|
Std.
Dev.
|
t
Value
|
|
60
|
62.03
|
62.05
|
-0.02
|
0.49
|
0.20
|
|
120
|
121.03
|
120.82
|
0.22
|
0.92
|
1.05
|
|
180
|
178.16
|
178.02
|
0.15
|
0.62
|
1.05
|
TABLE 3.
Average Weight of Collected Sample Grams
5% Aqueous NaCl 20 Runs
With and Without BIOflex® Pad
| Time
Sec. |
With
|
Without
|
Diff.
|
Std.
Dev.
|
t
Value
|
|
60
|
62.15
|
61.66
|
0.49
|
0.51
|
4.26
|
|
120
|
121.58
|
120.73
|
0.85
|
0.48
|
8.03
|
|
180
|
178.96
|
177.79
|
1.17
|
0.68
|
7.71
|
The t values comparing the data with and without the
BIOflex® pad were computed, as shown in Tables 2 and 3. They show, as
expected, that with distilled water there is no statistical difference in
flow rates whether or not the magnetic pad is present. However, there is
a statistical difference in the flow rates of the aqueous saline solution
with the pad and without the pad with P<0.001.
When the meniscus of the liquid in the reservoir was exposed to the magnetic
pad and the flow collected over a three minute period, an excess of 3.579
grams was measured in the presence of the pad. This experiment was done
only once. This difference is three times as large as that observed when
the pad was applied to the capillary! Although this experiment must be confirmed
by repeated trials, it does indicate that the magnetic pad alters the surface
tension forces.
The measured streaming potential difference for distilled water was of the
order of 8 millivolts when flow was present and showed no response to the
BIOflex® pad. When the flow was cut off, the potential difference dropped
to 0.59 millivolts. The potential difference for the flowing saline solution
was of the order of 45 millivolts. The difference in measured voltage i.e.
with the pad present less than without the pad, was of the order of 5 millivolts
and decreased linearly with time over the 180 second run following the equation.
V
= 6.35 - .04 * t
where V is in millivolts and t in seconds. The R squared value for the
recession was 0.79. These results are plotted in Figure 2. This data should
not be taken to be reliable due to the conditions of the experiment. However,
it seems likely that more careful measurements will confirm that there
is no difference in streaming potential with or without the BIOflex®
pad for distilled water. It seems likely that there will be such a potential
difference with flowing saline and that this difference will be related
to the flow. No effects are expected when the flow is cut off. These preliminary
streaming potential results are consistent with the more careful measurements
on mass flow quoted above.
DISCUSSION
It is of interest to speculate on the mechanism by which the BIOflex®
pad affects the flow rate of the saline solution through the system. We
know that there is a streaming potential set up in the experimental system.
This indicates a low mobility double layer. It cannot be said that this
low mobility layer is known to be present in the capillary portion. However,
if it were present there, then Bxv forces on the flowing ions would act
on the mobile ion so as to drive it into the double layer. This would
in turn decrease the width of this layer and consequently increase the
effective radius of the capillary. Moreover, the fact that the flow rate
was effected when the meniscus of the large reservoir moved across the
field of a pad wrapped around that reservoir can only mean that the surface
tension between the saline solution and the reservoir wall was affected
by the magnetic pad. It is well known (See for example "Modern Electrochemistry”,
Bockris and Reddy, Chapter 7, Volume 2; Plenum Press, New York 1970) that
the surface tension changes are related to changes across the double layer
at the boundary of the liquid. Thus, it is reasonable to infer that the
BIOflex® pad does affect the double layer. The presence of a streaming
potential by the pad implies a change in the mobility of the double layer.
That conclusion is consistent with the observed change in mass flow through
the capillary.
This paper was presented at the International Symposium Biomagnetology,
Magnetotherapy and Postural Activity, Newport, R.I., U.S.A., May 29, 1989.
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