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# Temperature dependence of blood surface tension

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Whole blood surface tension of 15 healthy subjects recorded by the ring method was investigated in the temperature range from 20 to 40 degrees C. The surface tension omega as a function of temperature t ( degrees C) is described by an equation of linear regression as omega(t) = (-0.473 t + 70.105) x 10(-3) N/m. Blood serum surface tension in the range from 20 to 40 degrees C is described by linear regression equation omega(t) = (-0.368 t + 66.072) x 10(-3) N/m and linear regression function of blood sediment surface tension is omega(t) = (-0.423 t + 67.223) x10(-3) N/m.
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PHYSIOLOGICAL RESEARCH ISSN 0862-8408
© 2007 Institute of Physiology v.v.i., Academy of Sciences of the Czech Republic, Prague, Czech Republic Fax +420 241 062 164
E-mail: physres@biomed.cas.cz
http://www.biomed.cas.cz/physiolres
Physiol. Res. 56 (Suppl. 1): S93-S98, 2007
Temperature Dependence of Blood Surface Tension
J. ROSINA
1
, E. KVŇÁK
1
, D. ŠUTA
1
, H. KOLÁŘOVÁ
2
, J. MÁLEK
3
,
L. KRAJČI
4
1
Department of Medical Biophysics and Medical Informatics, Third Faculty of Medicine,
Charles University,
2
Department of Medical Biophysics, Medical Faculty, Palacky University,
Olomouc,
3
Clinical Department of Anesthesiology and Resuscitation, Charles University, Prague,
4
Ambulatory Department of Central Military Hospital, Prague, Czech Republic
Received May 23, 2007
Accepted May 29, 2007
On-line available May 31, 2007
Summary
Whole blood surface tension of 15 healthy subjects recorded by the ring method was investigated in the temperature
range from 20 to 40 °C. The surface tension
σ
as a function of temperature t (°C) is described by an equation of linear
regression as
σ
(t) = (–0.473 t + 70.105) × 10
–3
N/m. Blood serum surface tension in the range from 20 to 40 °C is
described by linear regression equation
σ
(t) = (–0.368 t + 66.072) × 10
–3
N/m and linear regression function of blood
sediment surface tension is
σ
(t) = (–0.423 t + 67.223) ×10
–3
N/m.
Key words
Surface tension Human blood serum Sediment Temperature
Introduction
Blood surface tension, as one of the crucial
blood parameters, affects many vital functions of human
body. Over the time human body undergoes different
natural thermal conditions. Therefore the knowledge
about temperature dependence of blood surface tension is
important. In textbooks of physiology or hematology the
surface tension of blood is usually not mentioned (nor
that of other body fluids or tissues). There are few articles
related to the surface tension and even fewer to the
surface tension of human blood. In addition we did not
find any paper about the thermal dependence of human
blood surface tension.
The usefulness of surface tension as a parameter
in forensic experiments was evaluated by various authors.
Raymond et al. (1996) used surface tension among other
physical parameters (viscosity and density) to support the
use of porcine blood in representing freshly spilled
human blood in crime-related cases. The influence of
surface tension and its relation to the blood/bile ethanol
ratio were evaluated by Winek et al. (1983).
The use of alumina as a material for
cardiovascular applications was investigated on the basis
of protein adsorption and thrombus formation on the
material using also surface tension as one of the critical
parameters (de-Queiroz et al. 1994).
Geertsma et al. (1993) investigated the effects of
surfactant, known to lower the surface tension in alveoli
and which affects the antibacterial functions of alveolar
and peritoneal macrophages, on the bactericidal functions
and oxidative metabolism of human blood monocytes and
S94 Rosina et al. Vol. 56
granulocytes.
The influence of surface tension on slow venous
bleeding caused coating of syringe surfaces and formed a
dome over the skin laceration bleeding site; it was
investigated by blood flow simulation performed by
McCuaig et al. (1992).
Chemistry of blood platelet-rich plasma
including surface tension values at 37 °C and 25 °C was
examined by Baier et al. (1985) with the aim of
examining a method of estimating apparent blood
compatibility of new biomaterials. Nevertheless, the work
did not encompass the larger temperature interval for
serum values.
Surface tension and viscosity of plasma were
found to be critical parameters in the use of new synthetic
materials for platelet quality control. Two synthetic
approaches to platelet products are described by Lott et
al. (1983).
Amorphous hydrogenated carbon (a-C:H),
potential material in biomedical devices such as artificial
heart valves, bone implants, etc. was investigated and
checked because of its chemical inertness, low coefficient
of friction, high wear resistance, and good
biocompatibility. The results of experiments with
hemocompatibility of nitrogen-doped, hydrogen-free
diamond-like carbon performed by Kwok at al. (2004)
were found to be consistent with the relative theory of
interfacial energy and surface tension, including both
dispersion and polar components, but the evaluation of
temperature dependance of those parameters was not
evaluated.
Methods
Surface tension theory
Molecules of liquid state experience strong
intermolecular attractive forces. When those forces are
between identical molecules, they are referred to as
cohesive forces and the especially strong cohesive forces
at the surface constitute surface tension. When the
attractive forces are between unlike molecules, they are
said to be adhesive forces. The attractive forces between
molecules in a liquid can be viewed as residual
electrostatic forces and are sometimes called van der
Waals forces or van der Waals bonds. In the bulk of the
liquid each molecule is pulled equally in all directions by
neighboring liquid molecules, resulting in a net force of
zero. At the surface of the liquid, the molecules are pulled
inward by other molecules deeper inside the liquid, but
there are no liquid molecules on the outside to balance
these forces, so the surface molecules are subject to an
inward force of molecular attraction, which is balanced
by the resistance of the liquid to compression. There may
also be a small outward attraction caused by air
molecules, but, as air is much less dense than the liquid,
this force is negligible. Surface tension is measured in
newtons per meter (N/m), and is defined as the force
along a line of unit length perpendicular to the surface, or
work done per unit area. According to the work-energy
theorem the surface tension can also be considered as
surface energy, which is required to change the form of
this surface. If a surface with surface tension σ is
expanded by a unit area, then the increase in the surface's
stored energy is also equal to σ.
Surface tension measurement
The surface tension of blood was measured by
TD1 tensiometer made by Lauda GmbH, Germany,
which allows to record surface tension by different
methods. In the ring method we used, the liquid is raised
until contact with the surface is registered. The sample is
then slowly lowered again so that the liquid film
produced beneath the ring is stretched. Maximum pull
exerted on the ring by the surface is measured. The
surface and interfacial tension σ are calculated from
maximal force F
max
acting on the length of the ring,
where R is the ring diameter, r is the diameter of the wire
the ring is made from and f
corr
is ring correction factor
dependent on ring geometry and density ρ. The
tensiometry method using the ring does not allow direct
measurement of absolute values of maximum force F
max
,
because surface tension measured by this method also
involves the gravitation measure of the liquid pulled by
the ring out of the liquid surface. To eliminate
gravitational force from the measured value there is a
multiplicative correction factor, which is a function of
ring density and diameter, wire diameter and gravitational
constant. Calibration constant force F
cal
, in our
experiments with calibration weight G
cal
equal to 500 mg,
was calculated from the equation:
F
cal
= G
cal
g /2πd
where g is the gravitation constant and d is the ring
),,(4
max
ρπ
σ
RrRf
F
corr
=
2007 Temperature Dependence of Blood Surface Tension S95
diameter. According to the manual of the TD1
tensiometer by Lauda, the correction factor of the ring in
our experiments was
f = 0.8759 + (0.0009188 σ) /D
where σ is the surface tension without correction and D is
liquid density.
Material
The whole blood experiments were performed
with blood samples taken from 15 patients of the hospital
attached to the Third Medical Faculty of Charles
University in Prague (Clinical Department of
Anesthesiology FNKV). The blood-donating patients
were healthy in terms of blood parameters with no
indication of blood-related disease. Immediately after
donation an anticoagulant agent (3.8 % sodium citrate)
was added to each sample of 20 ml of blood and then it
was transferred to the experimental lab and underwent the
procedure of surface tension measurement. Eleven out of
15 blood samples taken into the statistics came with all
basic characteristics of both the patient (gender, age,
weight, height) and the blood (hematocrit, Quick, APTT,
urea, creatine, bilirubin, cholesterol).
The blood sediment and serum experiments were
performed on samples of 12 different healthy subjects.
The sediment and serum were extracted from the blood
by means of natural blood sedimentation in 2 h. Both the
sediment and the serum part underwent the same
procedure of surface tension measure as the whole blood.
Measurement conditions
All experiments were performed with blood in a
glass jar with diameter large enough (40 mm) to allow the
effect of borders to be neglected. The jar was immersed
in a plastic container (bath) filled with water. Both the
change of water bath temperature and the stirring of
blood allowed to measure the blood surface tension under
temperatures from 20 to 40 °C. Temperature was
measured in the blood surface layer with a calibrated
thermistor at the time when maximum force F
max
was
reached.
Calculations
Surface tension was measured under different
temperatures between 20 and 40
o
C with the aim of
covering the whole interval as much as possible. Surface
tension values of blood collected from different subjects
were afterwards put together, sorted according to the
temperature and clustered by “whole number”
temperature points (20 °C, 21 °C, 22 °C etc.). For
example, surface tension value and its standard deviation
S.D. for 35 °C were calculated from T values recorded for
the temperature interval from 34.6 °C to 35.5 °C. The
resulting values with S.D. were put into a graph. In
addition, each graph comprises an equation of linear
regression line and trend line reliability value (R).
Results
To evaluate the whole blood surface tension as a
function of temperature in the range from 20 to 40
o
C the
blood of 15 subjects was used. In each blood sample the
Fig. 1. Dependence of blood surface tension on temperature.
S96 Rosina et al. Vol. 56
values of surface tension were recorded at 12 different
temperatures on the average. Fig. 1 illustrates the whole
blood surface tension values for temperatures from 20 to
40 °C. In addition, a line of linear regression function of
whole blood surface tension
σ
(t) = (–0.473 t + 70.105)
×10
–3
N/m in the temperature range from 20 to 40
o
C is
drawn. Good reliability of the regression trend line is
expressed by line reliability value R being close to 1.
Fig. 2 illustrates the blood serum surface tension
as a function of temperature in the range from 20 to
40
o
C. The blood samples were donated by 12 healthy
subjects. After a 2-h period of sedimentation the same
procedure as in the whole blood sample was applied, i.e.
in each blood sample the values of surface tension were
recorded at 12 different temperatures on the average. The
line of linear regression function of blood serum surface
tension is seen to be
σ
(t) = (–0.3676 t + 66.072) × 10
–3
N/m in the temperature range from 20 to 40 °C. The trend
line reliability value R is again close to unity (R
2
=
0.9047).
Complementary to the blood serum experiments
we did experiments with blood sediment. The same 12
blood samples used for serum were utilized for surface
tension measure of blood sediment. In Fig. 3 the blood
sediment surface tension as a function of temperature is
shown. Surface tension was recorded at 12 different
Fig. 2. Dependence of blood serum surface tension on temperature.
Fig. 3. Dependence of blood sediment surface tension on temperature.
2007 Temperature Dependence of Blood Surface Tension S97
temperatures on the average after a 2-h period of
sedimentation. The line of linear regression function of
blood sediment surface tension is seen to bes
σ
(t) =
(-0.423 t + 67.223) × 10
–3
N/m. The trend line is highly
reliable (R
2
= 0.955).
Discussion
The importance of surface tension of the blood
and its temperature dependence was found in different
areas of biomedical investigation. Mottaghy et al. (1989),
trying to solve the leakage of capillary membrane
oxygenators for long-term extracorporeal lung support,
found the blood surface tension to be one of the critical
factors at the micropores, besides temperature conditions
of the gas, the blood and the circuit environment but no
special recording of blood surface as a temperature
function was done.
Comparing blood surface tension value at 22 °C
recorded by the ring method presented in this paper
(Fig. 1),
σ
(22) = (58.74 ± 1.77) × 10
–3
N/m, with the
value recorded at 22 °C by the drop method by Hrnčíř
and Rosina (1997),
σ
(22) = (55.89 ± 3.57) × 10
–3
N/m, it
is obvious they are in good agreement. Their results did
not correlate with age or sex of the examined subjects or
with any of the following variables: red cell
sedimentation rate, blood hemoglobin levels, number of
erythrocytes, total serum cholesterol, total serum
triacylglycerols, creatinine blood levels, ALT and AST
activity.
Interactions between hematological derivatives
and their implications for adult respiratory distress
syndrome were examined by Banerjee (2004). His
experiments were performed with whole blood,
membranes obtained from whole blood cells, lysed blood,
homogenized blood clot, serum, platelet-rich plasma,
platelet-poor plasma and individual plasma proteins at
physiological temperature (37 °C). He evaluated the
surface properties of dipalmitoyl phosphatidylcholine
(DPPC) monolayers, the main component of lung
surfactant in the presence of blood and its components.
Cell membranes were found to be the most inhibitory
agent for DPPC surface activity as evidenced by an
increase in the minimum surface tension (from 0.818 ±
0.219 to 7.373 ± 0.854 mN/m) and percentage area
change required to reduce the surface tension from 30 to
10 mN/m (from 21.24 ± 0.99 to 66.83 ± 4.44). The
inhibitory potential of pure plasma proteins differed from
that of more complex blood derivatives, such as platelet-
rich plasma and serum. Whole blood and platelet-poor
plasma were non-inhibitory but serum, platelet-rich
plasma and clot significantly increased the minimum
surface tension of DPPC to 6.819 ± 0.925, 6.625 ± 2.261
and 6.060 ± 0.640 mN/m, respectively.
Knowledge of normal physiological values of
blood surface tension seems to be very important. There
is evidence that the blood surface tension shows higher
values for patients with acute myocardial infarction
compared to the control group (Esitashvili and
Msuknishvili 2002). The surface tension of blood can
also play a role in the stabilization of microbubbles in
diagnostics using ultrasound with contrast and so
improve the ultrasound imaging (Liew and Raychaudhuri
1997). We also suggest that blood surface tension
monitoring could serve for the adjustment of therapeutic
levels of rheological pharmaceuticals.
Acknowledgements
This work was supported by the grant project of the
Ministry of Education No. MSM 6198959216.
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Corresponding author
Jozef Rosina, Department of Medical Biophysics and Medical Informatics, Third Medical Faculty, Charles University,
Ruská 87, 100 42, Prague, Czech Republic. E-mail: jozef.rosina@lf3.cuni.cz.
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