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Viscosity and blood structure
BIOCHIMIE, 1981, 63, 883-885.
Viscosity and blood structure. Unitd de Biorhdologie, D@artement de Biophysique, CHU PitiO-SalpOtriOre, 91 bd de I'H6pital, 75013 Paris, France.
Catherine LACOMBE and Jean-Claude LELII~VRE.
: hemorheology / blood viscosity / RBC
Mots-el~s : h~morh~ologie / viseosit~ d u s a n g / agr~gation des globules rouges.
Key-words
Introduction.
bulins. RBC aggregation is probably due to macromolecular bridging between the surfaces of adjacent cells [4].
aggregation.
Rheological properties of blood play an important role in blood flow physiology. From a mechanical point of view, blood does not exhibit a classical behavior. In addition to a non-newtonian behavior (shear-thinning) [1] which is generally at-
Therefore special attention will be given to structures of rouleaux and network and then we must study them as a function of various factors
?(s -1 )
c{t) (Pa)
io1 .
÷ .
.
.
.
.
.
.
,)n -1
.
i(
0B
,0o..
]_ly_l l
10-2
Icq-
I0-:
~
I
' ' ' '
~--
10-3
, i
L-'05s'l,^~
t
.
12345 FZ6. I , -
Experimental rheograms ]or diHerent shear rates.
tributed to concentrated suspensions of small particles (polymer solutions, colloids,...), blood exhibits, under transient flow conditions, viscoelasticity and thixotropy [2, 3J. To explain these phenomena, it is necessary to take into account RBC (Red Blood Cell) ability to aggregate into a complex network with tangled rouleaux. Shear stresses separate the rouleaux, stretch and divide them into single cells. This organization of RBC at rest depends on the presence of plasma proteins such as fibrinogen and gto-
which are able to modify them as red cells properties, plasma composition and under different pathological conditions.
Experimental method. The viscometric behavior of blood is studied in transient flow 12], using a servocontrol viscometer. It is a coaxial cylinder Couette type viscometer which applies a shear rate step of amplitude y to the blood sample.
C. Lacombe and J.-C. Leli~vre.
884
decreasing part of the curve after the maximum corresponds to the breaking up of the rouleaux with a dissociation time 0B (half height). The plateau corresponds to a rouleaux-individual RBC equilibrium state (fig. 2 B).
~, is defined as 1/9 (Vt + ~,2) where W and y2 are the shear rates on the inner cylinder and on the outer cylinder, respectively, corresponding to a newtonian fluid with the same rotation speed. The shear stress response (rheogram) is recorded and analyzed.
Rheogram C is the response to a shear rate of ~, = 20 s -1. Newtonian character is then dominant: the rouleaux are completely dissociated into individual red blood cell which are able to be oriented along the streamlines (fig. 2 C). This sketch has been confirmed by viewing red blood cells with a rheoscope [3].
Blood is obtained by venepuncture and anticoagulated with EDTA. The experiments were performed the same day at 25°C with 2 ml blood sample. Different rheograms are obtained according to the value of 4 (fig. 1).
It would be very interesting to visualize the threedimensional rouleaux network in order to confirm the speculative interpretation given in figure 2. The stress stationary value ~,~ of each rheogram gives the apparent stationary viscosity : ~1.~ = x~,-1.
Rheogram A is the response to a shear rate of y = 0.05 s 1; viscoelastic behavior of blood is dominant: the rouleau network (initially at rest) is stretched and broken into individual rouleaux with a dissociation
Results and Discussion.
( RESTI
A s an e x a m p l e of c l i n i c a l a p p l i c a t i o n , w e give in t a b l e I a c o m p a r i s o n b e t w e e n n o r m a l b l o o d a n d two pathological bloods.
(A)
a) F o r p o l y c y t h e m i a w e n o t i c e t h a t s t a t i o n a r y
(B)
v i s c o s i t y at i n t e r m e d i a t e s h e a r r a t e (~) = 1 s -1) is e n h a n c e d . D i s s o c i a t i o n t i m e 0n is e n h a n c e d too. This indicates that shear disaggregates rouleaux less easily t h a n in n o r m a l case. O n the c o n t r a r y , d i s s o c i a t i o n time0A is r e d u c e d . T h e n , the r o u l e a u x n e t w o r k is less stable t h a n in the case of c o n t r o l samples.
(C)
FIG. 2. - - Aspect o] blood structure ]or diIferent shear rates (speculative) (--+ direction of flow). (A) Rouleaux-network equilibrium. (B) RBC-rouleaux equilibrium. (C) Individual RBC.
b) F o r
myocardial
infarction,
the
stationary
v i s c o s i t y is r e d u c e d at l o w s h e a r r a t e (-f = 0 . 0 5 s -1) a n d e n h a n c e d at i n t e r m e d i a t e a n d h i g h s h e a r r a t e
TABLE I. Stationary viscosities for different shear rate values and related dissociation times. Stationary viscosity ~s (cP) "~ = 0 , 0 5 s -1 Control
98 -+- 7
"~ =
1 s -I
19 ~__ 1
Dissociation time (see)
"~ = 2 0 s -j
0A
0n
8.0 -+" 0.1
2.2 -q- 0.1
2.2 -+- 0.2
Polycythemia
93 ~ 7
24 +
1
8.3 + 0.2
1.8 + 0.I
3.1 ~ 0.2
Myocardial infarction
68 ~ 5
28 -4- 2
8.8 --t- 0.2
1.2 ' ~ 0.1
2.8 -~ 0.2
time 0A (half height). The plateau corresponds to an equilibrium state between the network and the rouleaux (fig. 2 A). The plateau level x s increases as the number of RBC in rouleaux does.
(~" = 2 0 s-l). T h e size of t h e r o u l e a u x d e c r e a s e s a n d t h e i r d i s a g g r e g a b i l i t y is r e d u c e d . M o r e o v e r , the r o u l e a u x n e t w o r k stability is also lessened.
Rheogram B is the response to a shear rate of "t = 1 s - l ; thixotropic hehavior of blood is dominant: the
F r o m a m e c h a n i c a l p o i n t of v i e w , it will b e v e r y useful to h a v e a t h e o r e t i c a l m o d e l w h i c h fits as
BIOCHIMIE, 1981, 63, n ° 11-12.
885
Viscosity and blood structure.
well as possible experimental transient rheograms. F r o m a physical point of view, it will be very interesting to visualize the three-dimensional organization of blood, especially near stasis. Both are in progress in our laboratory.
Conclusions. Transient hemorheological studies give useful informations on blood structure, especially on
BIOCHIMIE, 1981, 68, n ° 11-12.
R B C aggregation and its changes in blood of patients suffering from different diseases. We used such modifications for clinical diagnosis. REFERENCES. I. Chien, S. (1970) Science, 168, 977-979. 2. Healy, J. C. & Joly, M. (1975) Biorheology, 12, 335340. 3. Bureau, M., Healy, I. C., Bourgoin, D. & Joly, M. (1978) Rheol. Acta, 17, 612-625. 4. Chien, S., Usami, S., Dellenback, R. J. a Gregersen, M. I. (1970) Amer. J. Physiol., 219, 143-153. 5. Schmid-Sch6nbein, H., Von Gosen, J., Heinich, L., Klose, H. J. & Volger, E. (1973) Microvasc. Res., 6, 366-376.
Viscosity and blood structure. Unitd de Biorhdologie, D@artement de Biophysique, CHU PitiO-SalpOtriOre, 91 bd de I'H6pital, 75013 Paris, France.
Catherine LACOMBE and Jean-Claude LELII~VRE.
: hemorheology / blood viscosity / RBC
Mots-el~s : h~morh~ologie / viseosit~ d u s a n g / agr~gation des globules rouges.
Key-words
Introduction.
bulins. RBC aggregation is probably due to macromolecular bridging between the surfaces of adjacent cells [4].
aggregation.
Rheological properties of blood play an important role in blood flow physiology. From a mechanical point of view, blood does not exhibit a classical behavior. In addition to a non-newtonian behavior (shear-thinning) [1] which is generally at-
Therefore special attention will be given to structures of rouleaux and network and then we must study them as a function of various factors
?(s -1 )
c{t) (Pa)
io1 .
÷ .
.
.
.
.
.
.
,)n -1
.
i(
0B
,0o..
]_ly_l l
10-2
Icq-
I0-:
~
I
' ' ' '
~--
10-3
, i
L-'05s'l,^~
t
.
12345 FZ6. I , -
Experimental rheograms ]or diHerent shear rates.
tributed to concentrated suspensions of small particles (polymer solutions, colloids,...), blood exhibits, under transient flow conditions, viscoelasticity and thixotropy [2, 3J. To explain these phenomena, it is necessary to take into account RBC (Red Blood Cell) ability to aggregate into a complex network with tangled rouleaux. Shear stresses separate the rouleaux, stretch and divide them into single cells. This organization of RBC at rest depends on the presence of plasma proteins such as fibrinogen and gto-
which are able to modify them as red cells properties, plasma composition and under different pathological conditions.
Experimental method. The viscometric behavior of blood is studied in transient flow 12], using a servocontrol viscometer. It is a coaxial cylinder Couette type viscometer which applies a shear rate step of amplitude y to the blood sample.
C. Lacombe and J.-C. Leli~vre.
884
decreasing part of the curve after the maximum corresponds to the breaking up of the rouleaux with a dissociation time 0B (half height). The plateau corresponds to a rouleaux-individual RBC equilibrium state (fig. 2 B).
~, is defined as 1/9 (Vt + ~,2) where W and y2 are the shear rates on the inner cylinder and on the outer cylinder, respectively, corresponding to a newtonian fluid with the same rotation speed. The shear stress response (rheogram) is recorded and analyzed.
Rheogram C is the response to a shear rate of ~, = 20 s -1. Newtonian character is then dominant: the rouleaux are completely dissociated into individual red blood cell which are able to be oriented along the streamlines (fig. 2 C). This sketch has been confirmed by viewing red blood cells with a rheoscope [3].
Blood is obtained by venepuncture and anticoagulated with EDTA. The experiments were performed the same day at 25°C with 2 ml blood sample. Different rheograms are obtained according to the value of 4 (fig. 1).
It would be very interesting to visualize the threedimensional rouleaux network in order to confirm the speculative interpretation given in figure 2. The stress stationary value ~,~ of each rheogram gives the apparent stationary viscosity : ~1.~ = x~,-1.
Rheogram A is the response to a shear rate of y = 0.05 s 1; viscoelastic behavior of blood is dominant: the rouleau network (initially at rest) is stretched and broken into individual rouleaux with a dissociation
Results and Discussion.
( RESTI
A s an e x a m p l e of c l i n i c a l a p p l i c a t i o n , w e give in t a b l e I a c o m p a r i s o n b e t w e e n n o r m a l b l o o d a n d two pathological bloods.
(A)
a) F o r p o l y c y t h e m i a w e n o t i c e t h a t s t a t i o n a r y
(B)
v i s c o s i t y at i n t e r m e d i a t e s h e a r r a t e (~) = 1 s -1) is e n h a n c e d . D i s s o c i a t i o n t i m e 0n is e n h a n c e d too. This indicates that shear disaggregates rouleaux less easily t h a n in n o r m a l case. O n the c o n t r a r y , d i s s o c i a t i o n time0A is r e d u c e d . T h e n , the r o u l e a u x n e t w o r k is less stable t h a n in the case of c o n t r o l samples.
(C)
FIG. 2. - - Aspect o] blood structure ]or diIferent shear rates (speculative) (--+ direction of flow). (A) Rouleaux-network equilibrium. (B) RBC-rouleaux equilibrium. (C) Individual RBC.
b) F o r
myocardial
infarction,
the
stationary
v i s c o s i t y is r e d u c e d at l o w s h e a r r a t e (-f = 0 . 0 5 s -1) a n d e n h a n c e d at i n t e r m e d i a t e a n d h i g h s h e a r r a t e
TABLE I. Stationary viscosities for different shear rate values and related dissociation times. Stationary viscosity ~s (cP) "~ = 0 , 0 5 s -1 Control
98 -+- 7
"~ =
1 s -I
19 ~__ 1
Dissociation time (see)
"~ = 2 0 s -j
0A
0n
8.0 -+" 0.1
2.2 -q- 0.1
2.2 -+- 0.2
Polycythemia
93 ~ 7
24 +
1
8.3 + 0.2
1.8 + 0.I
3.1 ~ 0.2
Myocardial infarction
68 ~ 5
28 -4- 2
8.8 --t- 0.2
1.2 ' ~ 0.1
2.8 -~ 0.2
time 0A (half height). The plateau corresponds to an equilibrium state between the network and the rouleaux (fig. 2 A). The plateau level x s increases as the number of RBC in rouleaux does.
(~" = 2 0 s-l). T h e size of t h e r o u l e a u x d e c r e a s e s a n d t h e i r d i s a g g r e g a b i l i t y is r e d u c e d . M o r e o v e r , the r o u l e a u x n e t w o r k stability is also lessened.
Rheogram B is the response to a shear rate of "t = 1 s - l ; thixotropic hehavior of blood is dominant: the
F r o m a m e c h a n i c a l p o i n t of v i e w , it will b e v e r y useful to h a v e a t h e o r e t i c a l m o d e l w h i c h fits as
BIOCHIMIE, 1981, 63, n ° 11-12.
885
Viscosity and blood structure.
well as possible experimental transient rheograms. F r o m a physical point of view, it will be very interesting to visualize the three-dimensional organization of blood, especially near stasis. Both are in progress in our laboratory.
Conclusions. Transient hemorheological studies give useful informations on blood structure, especially on
BIOCHIMIE, 1981, 68, n ° 11-12.
R B C aggregation and its changes in blood of patients suffering from different diseases. We used such modifications for clinical diagnosis. REFERENCES. I. Chien, S. (1970) Science, 168, 977-979. 2. Healy, J. C. & Joly, M. (1975) Biorheology, 12, 335340. 3. Bureau, M., Healy, I. C., Bourgoin, D. & Joly, M. (1978) Rheol. Acta, 17, 612-625. 4. Chien, S., Usami, S., Dellenback, R. J. a Gregersen, M. I. (1970) Amer. J. Physiol., 219, 143-153. 5. Schmid-Sch6nbein, H., Von Gosen, J., Heinich, L., Klose, H. J. & Volger, E. (1973) Microvasc. Res., 6, 366-376.