U.S. patent number 3,848,796 [Application Number 05/292,540] was granted by the patent office on 1974-11-19 for a centrifuge apparatus for sedimentation study.
This patent grant is currently assigned to Coulter Electronics, Inc.. Invention is credited to Brian S. Bull.
United States Patent |
3,848,796 |
Bull |
November 19, 1974 |
A CENTRIFUGE APPARATUS FOR SEDIMENTATION STUDY
Abstract
Method and means for the study of the sedimentation
characteristics of whole blood involving the application of greater
than gravity force laterally to a thin, substantially vertically
oriented column of whole blood in a predetermined cyclic series of
intermittent applications, the column being physically rotated
about 180.degree. about its own axis between each application. A
centrifuge apparatus is described for applying a G force in the
range of 6.25 to 8 G laterally to the long axis of plural test
sample columns arranged substantially vertically in holders
provided on the centrifuge head. Means are described for causing
rotation of the sample columns about their own vertical axes
between each periodic spin cycle of said centrifuge head and only
between applications of said G force. A preferred test operation
using four 45 second duration applications of said G force is
described with rotation of the columns being effected by reversal
of the centrifuge head at the end of each 45 second force
application. Other cycles are described which give results
correlatable with the results obtained using recognized
standardized sedimentation test procedures. The cycle of 45 second
duration applications provides test results independent of the
effect of the hematocrit of the particular sample.
Inventors: |
Bull; Brian S. (Loma Linda,
CA) |
Assignee: |
Coulter Electronics, Inc.
(Hialeah, FL)
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Family
ID: |
27381284 |
Appl.
No.: |
05/292,540 |
Filed: |
September 27, 1972 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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191336 |
Oct 22, 1971 |
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113166 |
Feb 8, 1971 |
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Current U.S.
Class: |
494/7; 494/11;
494/19; 494/84 |
Current CPC
Class: |
B04B
5/0407 (20130101); B04B 5/02 (20130101); B04B
5/0414 (20130101) |
Current International
Class: |
B04B
5/04 (20060101); B04B 5/00 (20060101); B04B
5/02 (20060101); B04b 009/08 () |
Field of
Search: |
;233/23R,24,25,26,27,28,17 ;23/259 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Krizmanich; George H.
Attorney, Agent or Firm: Silverman & Cass
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATION
This application is a division of co-pending application Ser. No.
191,886 filed Oct. 22, 1971, entitled "METHOD AND MEANS FOR
SEDIMENTATION STUDY," the latter application being a
continuation-in-part of application Ser. No. 113,166, filed Feb. 8,
1971, entitled "SEDIMENTATION RATE TEST METHOD AND SEDIMENTATION
RATE CENTRIFUGE THEREFOR," now abandoned.
Claims
What it is desired to be secured by Letters Patent of the United
States is:
1. A sedimentation rate centrifuge comprising, a centrifuge head, a
driven shaft mounting said head for rotation therewith and a drive
motor coupled to said driven shaft for imparting rotative motion
thereto about the axis of said head in intermittent periods of
predetermined duration to generate centrifugal force applicable in
a direction generally normal to its axis of rotation, said
centrifuge head comprising a body, sample tube holder means carried
by said body near the periphery thereof, said sample tube holder
means each constructed and arranged to receive elongate sample
tubes each containing a thin column of blood and each vertically
arranged and oriented substantially parallel to the axis of
rotation of said body so that the centrifugal force is applied
laterally to the long axis of said sample tubes, means for causing
periodic rotation of each of said sample tube holder means and
associated sample tube about its own long axis between each
application of centrifugal force and when said body is
substantially at rest.
2. The centrifuge as claimed in claim 1 in which said body
comprises a spool carrying said sample tube holder means, said
means for periodically rotating said sample tube holder means and
associated sample tubes comprise a spur gear mounted in association
with the driven shaft and pinion gear means secured to each of said
sample tube holder means and engaged with said spur gear and
cooperating means on said spur gear and spool for limiting axial
rotation of each one of said pinion gear means to 180.degree. about
its own long axis.
3. The centrifuge as claimed in claim 2 in which said cooperating
means comprise a pin on one of said spur gear and spool and an
arcuate slot on the other of said spur gear and spool, the pin
being received and movable within the slot and the length of the
slot determining the maximum rotational movement of each of said
pinion gear means about their own axes.
4. The centrifuge as claimed in claim 2 wherein the spool is
coupled to the driven shaft for rotation therewith and the spur
gear is arranged coaxially relative to said spool but for free
rotation about said shaft.
5. The centrifuge as claimed in claim 4 wherein said pinion gear
means are arranged to engage said spur gear, rotation of said spool
first effecting rotation of said pinion gear means, said
cooperating means thereafter coupling said spool and spur gear for
rotation together about their common axis.
6. The centrifuge as claimed in claim 5 and timing means for
controlling the duration of centrifugation.
7. The centrifuge as claimed in claim 6 and timing means for
periodically causing reversal of the direction of rotation of said
head.
8. The centrifuge as claimed in claim 2 and means for preventing
relative movement of the spool and spur gear during application of
said greater than gravity force.
9. The centrifuge as claimed in claim 8 in which said
last-mentioned means comprises interlock means including a lever
pivotally secured to said spool, one end of said lever including a
mass, rotation of the spur gear and spool simultaneously causing
the mass to swing outward driving the opposition end of the lever
to engage the spur gear, deceleration of the spur gear enabling the
mass to return to its rest condition disengaging the lever from the
spur gear and thereby restricting relative rotation of the spur
gear and pinion gear means to selected periods.
10. The centrifuge as claimed in claim 2 in which means are
provided selectively to rotate each of the sample tube holder means
along its own axis and include means selectively to couple and
uncouple said spur gear and said pinion gear means, said means
comprising a solenoid, a lever operated by said solenoid and cam
and follower means operable by said lever to rotate the spur gear
and means synchronizing the energization of the solenoid with the
operation of the motor so that the solenoid is energized only when
the motor is inoperative.
11. The centrifuge as claimed in claim 2 in which said spur gear is
adapted to be rotated first in one direction and then in the
opposite direction.
12. The centrifuge as claimed in claim 2 in which said motor is of
the reversible type, timer means for periodically changing the
direction of rotation of the centrifuge head for each period, said
spur gear being arranged to rotate said pinion gears each time the
centrifuge head is rotated in a new direction.
13. The centrifuge as claimed in claim 1 and timing means for
periodically controlling the duration of centrifugation.
14. The centrifuge as claimed in claim 1 and timing means for
controlling the total duration of centrifugation and the respective
cycle durations.
15. The centrifuge as claimed in claim 1 and means for applying a
gradual braking force to said body at the termination of each
application of centrifugal force to bring the body gradually to
rest.
16. The centrifuge as claimed in claim 15 wherein said means for
applying a gradual braking force comprise friction means applied
directly to said body.
17. The centrifuge as claimed in claim 1 wherein said drive motor
is reversible and timing means are provided coupled to said drive
motor for controlling the operation thereof to define said
intermittent periods of predetermined duration, each of said
periods being initiated by reversal of said drive motor.
18. The centrifuge as claimed in claim 17 wherein said timing means
comprise a timing motor, a timing disc, first switch means coupled
to said drive motor for deenergizing same, second switch means for
reversing said motor, means for coupling said timing motor to said
timing disc, means on said timing disc constructed and arranged to
engage said first switch means after an elapse of time equal to the
total cycle duration and second means on said timing disc
constructed and arranged to engage said second switch means
periodically to reverse the direction of said drive motor, said
second means on said timing disc being adjustably positioned
thereon whereby to determine the interval between drive motor
reversals.
19. The centrifuge as claimed in claim 17 and said means for
causing periodic rotation of each of said sample tube holder means
about its own long axis comprising said pinion gear means being
coupled between the drive motor and said tube holder means for
effecting said axial rotation immediately subsequent to periodic
drive motor reversal but only while said body is substantially at
rest.
20. The centrifuge as claimed in claim 19 and a lost motion
connection between said centrifuge head and said gear means to
limit the degree of said rotation of said holder means about their
own long axes.
Description
FIELD OF THE INVENTION
This invention relates generally to diagnostic examination of whole
blood and more particularly concerns the provision of centrifuge
apparatus for whole blood sedimentation study.
BACKGROUND OF THE INVENTION
It is well known that the suspension stability of whole human blood
is altered in the presence of many functional disorders. The
determination of this characteristic generally has been effected by
performance of well-known standardized sedimentation tests in the
course of clinical analysis. Using the sedimentation test results,
the presence of more or less occult disease can be brought to
medical attention. Such results particularly are of importance in
the differential diagnosis as between functional disorders having
closely similar symptomatic manifestations, as well as in supplying
a guide to the progress of certain diseases. Accordingly, it is
believed that substantial benefit could be obtained in the
diagnosis and treatment of medical disorders by the establishment
of sedimentation study procedures which would produce comparative
information quickly and economically so that a sedimentation study
could become a routine procedure in clinical examination. However,
as practiced presently, the sedimentation test is too time
consuming, too affected by laboratory introduced artifacts and
subject to misinterpretation in anemic individuals, so that the
test is not a test offered to every patient as a routine clinical
test procedure such as a blood count, for example.
Present methodology involves essentially the mixing of a whole
blood sample with a selected anticoagulant, introducing this well
mixed sample in a vertically arranged glass tube and permitting the
red cells of the sample to sediment under the influence of gravity.
This process is slow, usually taking 60 or more minutes. The only
accepted variations in this method takes the form, singly or in
combination, merely of changing the length of the glass tubes
employed, varying the bore of such tubes, careful selection of the
anticoagulant employed and/or modification of the degree of
dilution utilized. None of these variations have alleviated the
principal drawback to adoption of the sedimentation test as a
routine procedure, this drawback being that present sedimentation
rate tests methods are too time consuming for routine employment or
mass studies.
Another important deterrent to adoption of sedimentation testing as
a routine procedure has been the extreme sensitivity of this test
to the arrangement of the test sample in an absolutely vertical
orientation for the duration of the test. It has been found that a
sample column which is oriented at only a 3.degree. offset from
vertical will result in inconsistent acceleration of the
sedimentation rate and reduces the relative differences between the
comparative normal and abnormal blood sedimentation
characteristics, thereby reducing the value of the test in
diagnosis.
Accordingly, it is the principal object of the invention to provide
an improved sedimentation study method for whole blood which meets
the requirements for rapidity, economy, accuracy and reliability
essential for adoption as a mass applied clinical laboratory test
procedure, and, concomitant therewith, to provide a sedimentation
rate centrifuge particularly adapted for implementing and carrying
out the steps of the improved study method.
Another object of this invention is to provide an improved
sedimentation study method which provides comparative information
on the sedimentation behavior of whole blood from normal persons
and from persons suffering from functional disorders, this
information being provided quickly and with reliability, the method
being free from the sensitivity of prior methods to disposition of
the test samples during performance thereof; and also which results
can be obtained approximately equivalent to standard methods of
sedimentation testing and also can provide a sedimentation study
result independent of hematocrit effect of the sample.
SUMMARY OF THE INVENTION
A sedimentation study method for whole blood comprising the steps
of applying greater than gravity force less than 8.25 G laterally
to a substantially vertically oriented column of whole blood sample
in a repeated series of applications and rotating the column about
its own vertical axis between each application of force; thereafter
determining the concentration of cells in the resulting packed
portion of said sample. According to the subject method, a
comparison is made between the start level and the treated level.
The column may be then fully packed by centrifugation at 100 G or
the like and a comparison again made to the treated column level. A
ratio then is determined of the two results to provide a hematocrit
independent value. A centrifuge apparatus is provided for
implementing the subject method, comprising a centrifuge head and a
motor, the centrifuge head carrying at least a pair of sample tube
holders arranged to orient the samples in substantially vertical
columnar array, drive means connected between the motor and the
centrifuge head for rotating same, means associated with the head
and tube holders for rotating the tube holders about their own
vertical axes and timing means operable on said drive means for
operating the centrifuge head in timed cycles with the centrifuge
head being brought substantially to a rest condition between cycles
and means to restrict the rotation of the tube holders about their
own vertical axes to periods during which the centrifuge head is at
substantial rest condition.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagrammatic representation illustrating an improved
sedimentation rate study method according to the invention;
FIG. 2 is a perspective view of the sedimentation rate centrifuge
constructed in accordance with the invention;
FIG. 3 is a vertical section taken through the centrifuge of FIG. 2
along the line 3--3 and in the direction indicated;
FIG. 4 is a vertical section taken through line 4--4 of FIG. 2 and
in the direction indicated;
FIG. 5 is a top plan view of the centrifuge arrangement as shown in
FIG. 2;
FIG. 6 is a vertical section taken through a modified embodiment of
the invention;
FIG. 7 is a perspective view of a further modified embodiment of
the invention;
FIG. 8 is a top plan view of the centrifuge arrangement illustrated
in FIG. 7 with portions broken away to show interior detail.
FIG. 9 is a diagrammatic representation of the embodiment
illustrated in FIG. 7.
FIG. 10 is a bottom view of the timing means utilized in the
embodiment of FIG. 7.
FIG. 11 is an elevational view of the centrifuge head of the
embodiment illustrated in FIG. 7.
FIG. 12 is a fragmentary sectional view taken along line 12--12 of
FIG. 8.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The method of studying the sedimentation characteristics of whole
blood in accordance with the invention, capitalizes in part upon
the fact that the blood from a normal, healthy individual has
greater suspension stability than does blood from a sick
individual. Three phases are known to occur during the
sedimentation of whole blood. The first is characterized as the
phase of rouleaux formation. During this phase, the red cells of
the whole blood stack together in what is defined in the art as
rouleaux. This phase occupies the first few minutes subsequent to
filling of the sedimentation tube with sample. Next begins the
phase of maximum sedimentation wherein after about 3 to 5 minutes,
the red cell rouleaux reach their maximum velocity of fall. This
velocity is dictated by the average density of the rouleaux and the
viscosity of the plasma through which they are falling. The last
phase concerned is characterized as the packing phase. As the
rouleaux reach the bottom of the sedimentation tube, they pack and,
as a consequence, the average rate of fall decreases and
eventually, when packing is complete, no further change occurs.
The samples from both normal and sick individuals, given enough
time, will pack to approximately the same extent; but the blood
samples from the ill patient goes through the rouleaux formation
phase and into the phase of maximum velocity of fall more rapidly
than does the blood from a healthy individual. An isolated red cell
is so small a particle that even though its density is considerably
greater than that of the plasma, the large relative surface area
becomes the overriding factor and an isolated red cell in plasma
falls very slowly under the influence of gravity. The rate of fall
of red cells is thus governed almost entirely by the size of the
rouleaux which they form. The blood from a healthy individual forms
such rouleaux much more slowly than does blood from a sick person.
If both samples are set up simultaneously, there is a period of
time when application of force greater than gravity to the blood
will affect the blood from a healthy individual minimally and that
from a diseased patient maximally. This crucial or critical time is
obvious when the healthy blood has just only begun to form rouleaux
and the sick blood has formed large rouleaux which have already
begun to sediment.
It had been critical to the study of sedimentation rate that the
conventional test must be performed under conditions where the
sampel column is disposed in absolutely vertical orientation. A
tilt as little as three degrees from verticalunder gravity will
accelerate the sedimentation rate considerably, and decrease the
relative differences between normal and abnormal blood. It is
believed that this effect is due to the fact that red cells falling
through the plasma hit the walls of the container and roll down the
walls permitting the plasma free egress from the depth of the
sample. Whenever the plasma is forced to traverse the descending
column of red cells, the sedimentation rate is slowed. Normal red
cell rouleaux fall much more slowly than do abnormal red cell
rouleaux, probably because the forces holding them together are
weaker and the upsweeping plasma either breaks them up or prevents
them from forming large enough clumps to sediment rapidly.
Accordingly, by applying a greater than gravity force to the
sedimenting blood, according to the invention, the ascending plasma
is forced to traverse the descending red cells. As will be
explained, a slight inclination of the column up to about 6.degree.
from vertical is permissible with the method of the invention,
particularly to avoid spilling of the sample during the run.
According to the invention, greater than gravitational force is
applied laterally to a long thin column of whole blood sample by
rotation thereof in a centrifuge capable of delivering a force in
the range of 2 to 12 G with the test taking from 1/2 hour at a
minimum G to about 1 minute at the high end of the aforesaid range.
The higher the G Force, the shorter the elapsed time of the test.
The net effect is to force the red cells to traverse the plasma
component of the blood over a very short distance since the
effective cross-sectional area of the tube is now vast relative to
the wall surface area and the red cells cannot collect in one
portion of the tube against the wall so as to permit the plasma to
escape freely elsewhere. Insofar as the sedimentation process is
concerned, the long thin column has been transformed to a shallow
wide diameter "pool" and since the force is directed substantially
perpendicular to the long axis of the column, the problems of
channeling heretofore experienced in sedimentation testing are
obviated.
The laterally applied force acts to pack the red cells rapidly,
permitting the plasma physically to change location therewith and
approach the final packing state over a much shorter time period,
than normally would be expected under gravitational force.
One example utilizing the method according to the invention,
permits the completion of the packing stage under gravity
subsequent to the periodic application of the greater than gravity
force and the level of the packed red cell rouleaux observed and
compared with that of a normal blood standard sample treated under
the same conditions.
Another example of the subject method involves the obtaining of a
packing factor after the said periodic cycles and a second packing
factor on maximum packing by centrifugation under more than 100 G.
The ratio of these factors is a value indicative of the presence of
asymmetric protein, a fact important to state of health evaluations
and independent of hematocrit.
The selection of the duration of the centrifugation cycles as well
as their number are dependent also upon the speed of the drive or
synchronous spinner motor utilized, the diameter of the column and
of the sedimentation tube utilized, and the degree of cant or tilt
permitted.
Another method of practicing the invention involves a program
selected to use four cycles of applied force laterally to the
column and of 45 second duration each. Between the first and
second, the second and third and the third and fourth cycle of
centrifugation, the columns are rotated about their own vertical
axes. Care is taken to assure that the axial rotation of the
columns take place only when the force applied laterally to the
long axes of the columns is less than one G. This condition occurs
when the column is at rest, substantially at rest or, to put it
another way, begins its translation in its circumferential rotation
with and on the centrifuge head. A friction or similar drag is
applied directly to the head, that is, to the spool on which the
columns ride, at the time each cycle is ending so that a gradual
braking is effected so that the centrifuge head may be stopped
without abrupt rotation of the columns. Abrupt stoppage of the
columns must be avoided, and likewise, jarring or other sharp
disturbance of the columns are avoided so that the cells which have
separated from the plasma and gathered at the inner wall of the
tube containing the test sample column will not be broken away from
each other or from the tube wall. The cells in the column must
rotate with the tube, and the column as the same is rotated in
accord with the invention.
In accordance further with the method of the invention, between
each application of greater than gravity force, the test sample
column is rotated about its own long axis, preferably
180.degree..
This seems to provide beneficial results in obtaining reproducible
packing in alternatively permitting resuspending the cells by
rotating the tube and its column contents and again effectively
forcing those cells back through the plasma. Thus, according to the
invention, cohesive forces are utilized during the centrifugation
under the relatively low G force to force the cells against the
wall and dispersion forces are utilized when the cells are forced
back through the plasma by again centrifuging but after 180.degree.
rotation of the tube and column of test sample.
Clearly, the rotation of the tube containing the test sample column
on its axis must be sufficiently gradual so as not to sever the
adhesion between the column of cells and the tube wall. Sharp
rotation will leave the cells, while the wall moves. Since the
purpose generally of the aforesaid column rotation is to
effectively force the cells through the plasma component of the
sample so as to provide a reasonably reproducible packing factor,
movement of the cells with tube wall during said tube rotation on
its axis is mandatory.
Now referring to the diagrammatic flow chart of FIG. 1, attention
is directed first to the sedimentation test method according to the
invention. Following this method will provide test results
equivalent to the Wintrobe standard method of "sed.rate testing."
The blood sample S is taken from the patient 10 by means of a
syringe 12 or the like, transferred to a vessel and mixed with any
one of a plurality of selected anticoagulants. A predetermined
amount of mixed sample is placed in a long, thin tube, sometimes
referred to in the art as a microhematocrit tube 16 and which
constitutes the test sample. The tube 16 is filled to a
standardized "depth." The steps involved in the production of this
test sample are well known in the art and is represented by box 14
in FIG. 1. The microhematocrit tube 16 generally of 2 mm diameter
is placed substantially vertically in one of the tube holders 46 of
the centrifuge 20. The other holders are likewise employed with
other samples so that the centrifuge is balanced. As will be
discussed later, other configurations of tube holders are
contemplated.
The range of speed of rotation of the centrifuge 20 preferably is
selected between 200 and 1,000 revolutions per minute so that an
effective centrifugal force of approximately 7.25 is provided. The
motor 22 of the centrifuge 20 is energized and the centrifuge is
caused to operate, here in a clockwise direction, for a relatively
short spin, say about 20 seconds. The centrifuge then is stopped
and brought to rest. When the centrifuge is at rest or at least
substantially at rest, the tube holder 18 and its tube 16 are
caused to rotate about its own long axis 180.degree. and the
centrifuge 20 again is caused to rotate, applying a force of
approximately 6.25 to 8 G to the vertically oriented column of test
sample in tube 16. This second rotation also is for a short
duration, again about 20 seconds, after which the centrifuge 20 is
brought to a rest condition and the tube holder 18 and the tube 16
therein again are rotated 180.degree. about its own axis. A
reversing motor is used so that the centrifuge's direction of
rotation is changed with each cycle. The rotation of the test
column about its own axis may be in a direction opposite to the
immediately preceding direction of rotation of the centrifuge 20
because it is easier to effect rotation of the tube and tube holder
about their own long axes due to the inertia of the centrifuge head
in starting. A unidirectional centrifuge also can be used with the
direction of rotation of the tubes and tube holders about their own
axes remaining unchanged from cycle to cycle.
The first two short spins are for the purpose of accelerating
rouleaux formation by shunting the red cells back and forth through
the plasma to cause them to collide without really effecting the
sedimentation thereof. During these spins, the red cells are either
isolated or at most in groups of two to four cells and as a result
they are not moved any appreciable distance by the approximately
6.25 to 8 G force applied perpendicular to the long axis of the
tubes during the first two short spins. The cells are moved further
than they would move under gravity influence during this period and
collisions between individual cells for the formation of rouleaux
accelerated. After the pair of short spins, the rouleaux formation
in blood from an ill person has taken place to a larger extent than
it would if the blood sample originated from a normal or healthy
person.
After the two short spins of about 20 seconds each and the rotation
of the test column about its own vertical axis each thereafter, the
rouleaux formation is such that the approximately 6.25 to 8 G force
may be applied when the test sample is experiencing the second
phase of sedimentation, that is the maximum velocity of descent of
the formed rouleaux in the test sample from the ill person, a time
whereat the sedimentation rate can be most effectively accelerated
and compared to the reaction of the standard or normal test sample
wherein rouleaux formation is barely initiated.
The centrifuge 20 is caused to rotate again to apply a force of
approximately 6.25 to 8 G perpendicular to the long or vertical
axis of the upstanding sample column, but this time, the
application of said G force laterally to the column is continued
for a period of about 60 seconds, a long enough period of time to
move the red cell rouleaux physically to one side of the tube.
After this longer centrifugation, the tubes and tube holders once
again are brought to rest condition, and the said tubes and tube
holders again are rotated 180.degree. about their own axes. Two
more 20 second spins follow with intermediate rotation of the tubes
and tube holders about their own vertical axes. These final two
spins are intended to aid the red cell column to re-establish
itself in its vertical tube so that its level can be read. The
rouleaux layer is permitted to fall free of plasma hindrance. The
plasma component is permitted to escape from the red cell rouleaux
column held against the tube wall. No hindrance to such passage can
be expected since the cell column is held against the wall of the
tube by the approximately 6.25 to 8 G force while the 1 G natural
gravitational force applied axially causes them to travel to the
bottom of the tube. The tubes, having been filled to a standard
depth, the level of the packed cells is read by comparison to a
fixed scale either mounted on the centrifuge head as shown in FIGS.
2, 6 and 8, for example, thereby being compared to the level of the
packed cells observed in a standard or normal blood sample which
had been treated similarly or simply matched to a coded chart
carried on a separate card.
Following the method of the invention, at a force of about 6.25 to
8 G, the test duration after which meaningful test results can be
observed in about 3 minutes as compared to convention sedimentation
methods where meaningful results can only be reached after 60
minutes.
It should be understood that the higher than G force applied, the
shorter the elapsed time for the test. For example, the following
time G table is appropriate:
APPROXIMATE TIME FORCE IN G'S
______________________________________ 30 min. 2-3 15 min. 5 4 min.
7 2 min. 9 1 min. 10-12 ______________________________________
Preferably the range of G force applied in the course of operating
the particular embodiment is approximately 6.25 to 8 G's with a
generally preferred force application of 7.25 G.
One of the substantive disadvantages of conventional sedimentation
test methods is the criticability of vertical orientation of the
test column. With the method of the invention the slight
inclination of the column is permissible. Inclination of the tubes
from the vertical such that the lower end of the tube is further
from the axis of rotation of the centrifuge head introduces a
component of force up the tube and therefore in opposition to the
gravitational force which is tending to move the particles down the
tube. It thus slows the sedimentation process and increases the
amount of time required to perform the test. Provided the
inclination of the tube from the vertical is not excessive, there
is no effect upon the test other than the increased time required
ordinarily. Excessive can best be defined in the following manner.
If the rotation of the centrifuge head is subjecting the tubes to a
horizontal acceleration of 8 G, there will be a component of this
force up the tube of 8 G times tangent theta where theta is the
inclination between the tubes and the vertical. In this example, as
the angle theta approaches 6.degree., the upward component
approaches 1 G. At 1 G there is effective neutralization of the
gravitational force as long as the centrifuge is spinning and
during this time period, which occupies slightly more than half of
the usual cycle, the cells will move neither up nor down the tube;
they will of course move outwards. For remainder of the cycle the
cells are under 1 G and will, of course, travel downwards; the net
effect is simply to prolong the time required to perform the test.
The time gets shorter and shorter as the tubes are returned more
and more to the vertical position and indeed continues to shorten
if the tubes are inclined with their top ends inwards. But with
further inclination beyond about 6.degree. instability and
irreproducibility become a problem. The effective limits therefore
are from vertical with an inward or outward cant of approximately
6.degree. if the force applied is in the range of 8 G's. Thus one
can state that the greater than gravity force (relative centrifugal
force) is applied to a column inclined at an angle theta from the
vertical such that the relative centrifugal force applied times the
tangent of the angle theta is a value equal to or less than 1.
The cycles set forth as an example in FIG. 1 give results in terms
of a sedimentation rate correlative with and equivalent to the
value obtained by following the well known Wintrobe method of
sedimentation rate determination. A result approximately equivalent
to other standard method values can be obtained by variation of the
number and duration of the cycles.
One problem which is encountered in interpreting sedimentation rate
information as applied to medical diagnosis is the effect that the
hematocrit has upon the sedimentation rate and the difficulty in
ascribing the effect of an anaemic condition upon the observed
value. It is extremely difficult to apply corrections to observed
sedimentation rates to correct for the effect of the hematocrit
thereupon. An anaemic blood sample may be observed to have a
certain sedimentation rate which otherwise may indicate an abnormal
functional condition or which may be due to the anaemia condition.
Correction for the effect of hematocrit upon the sedimentation rate
observed was not possible routinely using conventional
sedimentation rate testing methods. However, it has been observed
that the effect of hematocrit in the method according to the
invention is a linear one and a hematocrit correction chart can be
constructed. A simple mathematical correction to all observed
sedimentation rates observed following the method of the invention
whereby all sedimentation rates can be reported at a standard or
normal hematocrit, say for example, 45 percent. Thus heretofore
experienced misinterpretation of the results in anaemic individuals
may be eliminated.
In lieu of the standardized sedimentation rate values obtained, say
pursuant to the method outlined in FIG. 1, one following another
example of such method may obtain information independent of the
hematocrit factor. Here, the cycles are of substantially of equal
duration; in one example, 45 seconds under the 6.25 - 8 G applied
in four cycles with rotation of the tubes and columns about their
own vertical axes between each cycle. A ratio of initial to packing
level is taken. The tubes may then be packed to a maximum extent by
application of G force of at least 100 G and a ratio of the first
and maximum packing levels taken. The ratio of the resultant
maximum packing factor and the first packing factor is taken with
the resultant value, here termed a "ZSR," a value independent of
hematocrit fluctuations.
In summary, in following the method of the invention as described
above, the red cell sedimentation has been accelerated by
increasing the greater than gravity force applied at the time when
abnormal blood would be most sensitive to the multi G effect than
blood from a normal healthy person, this time being during the
maximum velocity phase of sedimentation reached prior to the time
it would be reached if the sample were from a normal healthy
person. Further, the multi G force is applied laterally to a thin
vertically oriented column of blood sample to obviate the problems
of channelizing occurring where sedimentation does not act
absolutely parallel with the walls of the vessel containing the
sample column; the container effectively being transformed from the
long thin vertically arranged tube to one which has a wide
diameter. The intermittent rotation of the column about its own
vertical axis between the centrifugal spins is intended to hold the
red cells on one side of the column while permitting the plasma to
move on the other side so that, in effect, the red cells are
repeatedly forced to move through the plasma with a reproduced
packing factor being the ultimate result.
The performance of the method above described required a centrifuge
capable of applying the preferably G force in the range of 6.25 to
8 G in separate cycles of predetermined duration. The centrifuge is
required to rotate the tube containing the sample in a
circumferential path about the axis of rotation with the tube being
in substantially vertically oriented disposition parallel to the
axis of rotation of the centrifuge head although a cant from
vertical of up to 6.degree. is permitted, contrary to standard
sedimentation rate methods. Additionally, the centrifuge is
required not only to permit rotation of the tube along said
circumferential path for a predetermined length of time and then
the tube periodically must be brought at least to a momentary
substantially rest or stationary condition, then rotated about its
own axis a predetermined number of degrees, and the rotation of the
tube along said circumferential path resumed for the next cycle of
greater than G force application. At least, the rotation of the
tube about its axis must not occur during the application of
greater than G force.
The centrifuge also should have timing means T for selectively
controlling and/or varying the duration of the cycles. According to
the method of FIG. 1, the duration of the successive cycles are not
equal but follow a definite program. Another example of the subject
method has successive equal duration cycles. The greater the G
force, the shorter the cycles and total elapsed time. In addition
to the means required to rotate the individual test sample holders
between cycles when the centrifuge is brought to a substantially
rest condition, the centrifuge must be provided with means whereby
the tube holder is brought to rest or at least substantially to
rest in its travel along its circumferential path before the
rotation of the tube holder about its vertical axis can take place.
This feature is required so that the contents of the sample tube
carried by the tube holder, that is, the column itself, will rotate
with the rotation of tube and tube holder. Too rapid angular
acceleration or rotation centrifugally tends to result in slippage,
the contents of the sample tube having a tendency to remain
stationary while the tube and tube holder rotate. This must be
avoided. According to the method of the invention, the column
contents of the sample tube must rotate axially with the tube wall
and care must be taken to assure only such rotation.
The centrifuge 20 constructed in accordance with the invention and
illustrated in FIGS. 1 to 5 comprises a motor 22, generally one
which is reversible, for rotating a head 24 in the range of 200 to
1,000 R.P.M. Generally, the speed of rotation can be varied easily
by selection of heads of different diameter. The effective force
output preferred is in the range of 6.25 to 8 G. The shaft of the
motor 22 is coupled to the head 24 by fastening means 28.
The head 24 comprises a body or spool 30 mounted for rotation on a
shaft 32. The shaft 32 has an enlarged end 34 having a passage 36
to receive the shaft 26 of the motor 22. A spur wheel 38 having
circumferential teeth 40 is mounted at the opposite end of shaft 32
coaxial with the spool 30. A locking ring 41 is fastened to the
shaft 32 by fastening means, such as screw 42. The spur wheel 38
rotates with the shaft 32. The spool 30 carries a plurality of
openings 44 circumferentially disposed to receive tube holders 46.
The tube holders 46 are arranged in diametrically opposed pairs for
balance, only one pair being shown in the FIGS. 1-6 for
convenience. Each of the tube holders 46 is provided with a pinion
wheel 48 either secured frictionally or otherwise thereto or
integral therewith. The body of holder 46 may be transparent so
that the tube 16 may be viewed and a graduated scale 52 mounted on
the spool 30 adjacent the tube holder for reference in reading. The
openings 44 are so arranged that the pinion wheels 48 mesh with the
circumferential teeth 40 of the spur wheel 38. Each tube holder 46
is constructed with a top opening bore 50 capable of receiving in
vertical orientation, the microhematocrit tube 16 which contains
the sample of blood to be tested. Each tube holder 46 may have a
leaf spring 51 within the bore as an aid in maintaining the proper
disposition of the tube. An upstanding pin 54 is secured to the
upper disc 56 of the spool and a slot 58 is provided in the spur
wheel 38. Slot 58 is configured in the form of a segment of an arc,
as shown in FIG. 5. The length of the slot is selected to assure
that the rotation of the pinion wheel 48 is taken through exactly
180.degree.. The spool 30 is mounted to the shaft 32 so that it is
freely rotatable, the spur wheel 38 being secured so that it
rotates with shaft 32. After the pin 54 reaches the end of slot 58,
no further rotation of the pinion wheel 48 can take place. The
motor 22 is brought to rest and then started in the reverse
direction. At this time, the pinion wheel 48 must first rotate,
owing to the inertia of the spool 30, until the pin 54 reaches the
other end of the slot 58. Thus, the carrier tube and hence the
microhematocrit tube 16 is caused to rotate exactly 180.degree.
with each reversal of the driving motor 22.
Deceleration of the motor 22 before it stops, has the same effect
on the spool 30 as the reversal of the motor, so that the
180.degree. rotation of the tube 16 takes place before the tube 16
comes to rest. The tubes must be at rest before rotation about
their own axes to avoid rotation only of the tubes rather than the
column. This problem can be overcome by introducing a constant drag
on the spool 30 such as, for example, a magnetic induction brake or
a friction pad (not shown).
A preferred method of alleviating the said deceleration effect is
the provision of an interlocking device designated generally by
reference character 60 (FIG. 4). The interlocking device 60
comprises a metal strip 61 pivotally secured to a block 62 which,
in turn, is attached to the inside wall of disc 56 of the spool 30.
The strip 61 is pivoted as at 64 to move in radial slot 66. A
weight or mass 68 is provided at the lower end of strip 61 and
secured thereto. When the spool 30 is rotating, the mass 68 is held
radially outward of the spool 30 so that the strip 61 engages the
spur wheel 38. This condition remains until the motor speed falls
to zero. At this time, the mass 68 falls to its rest position and
the strip 61 disengages from the wheel 38. It should be noted that
the teeth of the spur wheel between the correct engagement
positions are omitted as indicated at 70 in FIG. 5. In lieu of the
pin and slot arrangement specifically illustrated in FIGS. 2, 4 and
5, one can utilize a spoked wheel gear instead of wheel 38, with a
pair of pins disposed between the spokes so as to limit the
rotation of the pinion gear 48 and with it, the sample tube and
test column therewithin.
In FIG. 6, there is illustrated a sedimentation rate centrifuge 20'
which has been modified so as to obviate the need for a reversing
motor, utilizing instead a magnetic solenoid electrically
interlocked so that the 180.degree. rotation of the tubes can be
brought about entirely by the same. The centrifuge 20' incorporates
a motor 22' and a head 24'. The motor 20' drives the shaft 32' by
means of reduction gears 72 and 74. The shaft 32' carries a pair of
spaced discs 76 and 76' which are secured thereto for rotation
therewith. A helical splined portion 78 is likewise fixed to the
shaft 17 to rotate therewith. A spur wheel 80 engages with the
splined portion 78 of the shaft 17 so that longitudinal movement of
the spur wheel 80 with respect to the splined portion 78, causes
the spur wheel 80 to rotate with respect to the shaft 17 by an
amount sufficient to rotate pinion wheels 48' through 180.degree..
The pinion wheels 48' each carries a chuck or holder 46' into which
the lower end of a microphematocrit tube 16 can be inserted.
Aligned openings 82 are provided in disc 76' so as to support the
microhematocrit tube 16 in vertical orientation, parallel to the
rotational axis of shaft 17.
The lower face of spur wheel 80 carries a thrust race 84 which can
be urged upwards by means of the lever 86 mounted for vertical
pivotable movement about shaft 88. The thrust race 84 comprises a
receptor ring 90 secured to the lower face of spur wheel 80 and a
lower ring 92 having protrusions 94 arranged for engagement with
shallow recesses 96 formed in ring 90. The end 98 of lever 86,
remote from the race 84, is operated by means of solenoid 100. When
the solenoid 100 is not energized, the spur wheel 80 is urged
downward by light, annular spring 102, arranged disposed between
disc 76 and the spur wheel 80.
The assembly consisting of the shaft 32' with its splined portion
78, the discs 76 and 76' and the pinions 48' rotate together in
suitable bearings (not shown) while the motor 22', the solenoid 100
and the lever 86 remain stationary.
Energization of the solenoid will rotate the tubes 52 through
180.degree. whether the motor 22' is running or not so that to meet
the requirements of the method set forth above, is necessary only
electrically to interlock the operation of the solenoid 100 with
the stopping and starting of the motor 22' so that the required
sequence is obtained. Engagement and disengagement of the thrust
race 84, which acts as a clutch, effects the selective rotation of
the tubes 16 along their own vertical axes, which, of course, lies
offset from the axis of rotation of the centrifuge 20'.
A further modified embodiment of the centrifuge apparatus according
to the invention is illustrated in FIG. 7 and designated by
reference character 100. Apparatus 100 as described herein
particularly is adapted to practice the method of the invention
where the cycle utilized comprises four cycles of 45 second
duration applications of greater than gravity force laterally to
substantially vertically arranged columns of whole blood with means
provided to effect limited rotation of each column about its own
axis between each force application by reversal of the direction of
rotation of the centrifuge head after each cycle.
The centrifuge apparatus 100 includes a housing 102, including a
troughlike portion 104 and a cover 106. Wall 108 of housing 102
carries exterior accessible switch levers 110 and 112 for
activating the power and buzzer means respectively which will be
described hereinafter. Indicator lights 114 and 116 likewise are
provided. Start switch 118 for initiating each test operation is
provided.
The electrical control components of apparatus 100 are mounted
within the troughlike portion while the head, centrifuge 120, drive
means 122, and the timing means 124 are mounted on the cover
portion, the centrifuge head being removably mounted to the
protruding portion of the motor drive shaft 154 of means 122. The
drive means 122 and timer means 124 are mounted to be enclosed
within the housing 102 when the cover 106 is engaged onto the
portion 104.
The centrifuge head 120 comprises a spool formed by mounting a
spinner plate 126 fixedly secured to the shaft 128 for rotation
therewith, and mounting a disc 130 to the upper end of said shaft
128 with the disc 130 arranged coaxial with said spinner plate 126
and being rotatable therewith. The shaft 128 is secured to the
motor drive shaft 154 as by suitable means such as set screw
127.
Gear support means 132 is arranged secured to the cover 106 and
includes a collar portion 192 having a flat upper surface 192', and
a circumferential flange portion which is fastened to the cover
106. The spur gear 134 has a circumferential ring portion 134'
carrying circumferential teeth 134" and a central disc portion 135
to which it is fixedly mounted and by which the spur gear is
mounted for independent rotation about the shaft 128, that is,
independent of rotation of the spinner plate 126. A coating or film
of thin machine oil or vacuum pump oil is applied to the surface
192' of collar portion 192 to provide a friction drag upon the disc
portion 135 which rests thereupon, and which, of course is
transferred to the ring gear 134 and thereby is applied directly to
the spinner plate 126.
Tube holders 136, similar to holders 46', are mounted on spinner
plate 126 for movement therewith about the axis of shaft 128. The
holders are spaced circumferentially substantially equidistant one
relative to the other closely adjacent the peripheral edge of the
spinner plate 126. Each tube holder 136 has a top opening cavity
137 defined therein to receive the lower end of sample tube 150 and
has resilient means for gripping said tube seated therein, such as
O-ring 139. Each holder is mounted on the upper end of a shaft 138
which extends through suitable openings formed in said plate 126.
Pinion gears 140 fixedly are secured to the opposite ends of each
shaft 138 thereby mounting the holders 136 on plate 126. The
holders 136 are rotatable with rotation of gears 140.
A spur gear in the form of ring gear 134 is arranged so that its
teeth 134" are meshed with the plural pinion gears 140. Thus,
rotation of the plate 126 will effect rotation of gears 140 while
the ring gear 134 remains stationary, rotating holders 136 about
their own vertical axes independent of the rotation of the shaft
128. Limit means in the form of the upstanding pin 142 secured to
the support means 132 and movable within the limit slot 144 formed
in the spinner plate 126 is provided to limit the independence of
movement of the spinner plate 126 and gear 134, thereby limiting
the degree of rotation of the gears 140 about their own axes. The
limit means described may be said to comprise a lost motion
coupling between the plate 126 and gear 134.
The disc 130 has a plurality of bottom opening recesses 146 formed
equispaced about the peripheral edge thereof and arranged in
alignment with the axes of the holders 136 but slightly offset
inwardly therefrom so that one end of the sample tube 150 can be
seated within cavity 137 of holder 136 and the upper end retained
within the respectively matching recess 146 to position the tube
substantially vertically arranged but canted inwardly at its upper
end toward the shaft 128. Thus, when properly seated, tubes 150 are
disposed, canted inwardly from true vertical between 30.degree. and
6.degree., preferably by 3.degree. and generally not more than
about 6.degree.. In this disposition, the tendency for the contents
of the tube to be flung outward during the application of higher
than gravity force on rotation or spinning of the centrifuge head
120 materially is reduced.
Motor mount 152 is secured to the undersurface of cover 106 with
the drive shaft 154 thereof protruding through a suitable opening
formed in said cover 106. The drive means 122 for the apparatus 100
is supplied by a 400 RPM, 60 HZ, 115 volt AC reversible direction
motor 156. Here, motor 156 causes centrifugal force between 6. and
8 G to be applied laterally to the tubes 150 during the spin of
header 120. The particular size and RPM drive motor selected
determines the centrifugal force exerted on the tubes 150, and
thereby is an important factor in selection of the duration of
greater than gravity application cycle and program.
The method of the invention requires application of the greater
than gravity force laterally and periodically to the sample in the
tube, i.e., the sample tube 150 and the column of blood therein.
The duration of each cycle generally can be selected to provide
results coorelative with specifically known blood sedimentation
methods.
With apparatus 100, timer means 124 is provided to effect rotation
of the spinner plate automatically through a sequence of four
cycles of 45 seconds duration with the reversal of direction and
rotation of the columns 180.degree. about their own axes between
each application of centrifugal force.
In the apparatus 100 illustrated, the timer motor 156 is an AC 60
cycle, 110 volt motor delivering 20 RPH.
The timing means 124 operates switch means 184, 186 which operates
relays 184" and 186" automatically taking the sample columns
through the selected test program.
A timing means 124 comprises a timer motor 158 mounted on platform
159, which in turn is secured suspended below the cover 106 by
means of bolts 160 and spacers 162. The resultant drive shaft 164
of motor 158 is passed through a suitable opening in the platform
159 and wheel gear 166 is mounted at the free end thereof for
rotation therewith. A second wheel gear 168 is coupled to gear 166
and is driven thereby. Gear 168 is fixedly secured to shaft 170 for
rotation therewith. One end of shaft 170 is seated in journal 172
and the other end carries timer disc 176. Timer disc 176 is secured
to shaft 170 and continuously rotates therewith so long as timer
motor 156 operates through the complete test program. The timer
disc 176 has three paddle assemblies 178, 178' and 178" mounted
thereto about the periphery thereof with the paddles 180, 180' and
180" extending outwardly from the circumferential edge thereof in
vertical planes normal to the axis of shaft 170. As illustrated,
disc 176 is rotatable in the direction of arrow 177 with the paddle
assemblies 178, 178' and 178" fixed in an equispaced series along
said path. An upstanding pin 182 is secured normal to the disc 176
and rotates therewith. The paddle assemblies 178, 178' and 178",
when considering the direction of rotation of the disc, can be said
to be substantially equispaced one relative to the others with
paddle assemblies 180 and 180" being disposed 180.degree. apart. A
pair of push-button activated switches 184 and 186 are arranged
with their actuators 184' and 186" mounted to suitable bracket
means (not shown) secured to the platform 159 so that the actuator
184' of switch 184 is arranged in the path of travel of the paddles
180, 180' and 180" of paddle assemblies 178, 178 and 178" whereby
each respective paddle can engage and depress said actuator 184' by
engaging same during passage therepast during rotation of the disc
176.
The actuator 186' of switch 186 is positioned to intercept the pin
182 whereby the continuing rotation of disc 176 causes pin 182
first to bear against actuator 186' to depress same. On passing of
said pin 182 past actuator 186', said actuator returns to its
normal condition. The switch 184 is connected to relay assembly
184" which is electrically coupled to the reversible synchronous
drive motor 156 to cause reversing of the direction of said motor
each time the actuator 184' is depressed. The switch 186 is
connected to relay assembly 186" operatively coupled electrically
to both the drive motor 156 and to the buzzer means 190. Depression
of the actuator 186' energizes the buzzer 190 and release of the
actuator 186' from engagement with the pin 182, causes
de-energization of the drive or spinner motor 156.
A friction or other drag is applied to the centrifuge head 120 so
that application of braking force to the motor 156 on
de-energization of the same, causes a braking force to be applied
directly to the head. Accordingly, the tubes 150 and the columns of
test samples therein will be prevented from being rotated about
their own vertical axes at least until the centrifuge head 120
starts up after coming to a substantially full stop, however
momentary.
The friction drag described may be applied by means of the
engagement of the collar portion 192 of gear support means 132 with
the facing surface of gear 134 and the provision of a coating or
film of light machine oil sandwiched therebetween. Instead of the
collar portion 192 being an upstanding ring integral with the
support means 132, it may take the form of a foam collar (not
shown) secured thereto or even arranged coaxial about the shaft
128. This oil interface friction drag arrangement is illustrated in
detaIl in FIG. 12.
An example in testing operation utilizing apparatus 100 now will be
described. Samples of whole blood are taken and placed respectively
in closed end, elongate tubes known as sedimentation tubes. The
tubes are filled with sample to a predetermined level mark. The
tubes containing the test samples are placed between the disc 130
and the spinner plate 126, the lower ends of the tubes seated
within the tube holders 136 while the upper ends are seated in the
recesses 146 and held firmly by the resilient means 139. The switch
levers 110 and 112 are actuated respectively activating the
apparatus 100. The start toggle switch 118 is actuated initiating
the test procedure and causing the spinner motor 156 to operate in
one direction, say clockwise. Greater than gravity force in the
range of 6.25 to 8 G is applied to the column of sample in each
tube as the centrifuge head 120 is spun.
When motor 156 is energized to spin head 120, motor 158 is
energized simultaneously to rotate disc 176. Timer disc 176 rotates
to bring paddle 180 in contact with the actuator 184'. Disc 176
continues to rotate so as to carry paddle 180 past said actuator
184'. In passing, the paddle 180 depresses the actuator 184',
causing the spinner motor 156 to reverse direction. This occurs 45
seconds after initiation of the spinner operation.
In reversing direction, the centrifuge head 120 comes to a
momentary halt with the pin 142 at one end of the opening or slot
144. The centrifuge head 120 then begins to rotate in the clockwise
direction. The gear 134, being mounted for free rotation about the
shaft 128, will remain stationary. The pinion gears 140 being
mounted on the spinner plate 126, and meshed with the gear 134,
will move along the circumference of now stationary gear 134 and
will rotate about their respective axes until engagement of the pin
142 at the opposite end of the eccentric slot 144 will drive the
gear 134 with the rotation of the spinner plate 126, limiting the
rotation of the pinion gears 140 to 180.degree.. The rotation of
the pinion gears 140 rotates the tube holders 136 and with same,
the tubes 150 and the column of blood sample will be rotated. The
braking must be gradual and not abrupt so that separation of the
column from the inner tube wall will not occur. This is
accomplished by the friction drag applied to plate 126. The column
must rotate with the tube wall.
The spinner motor 156 operates to drive the centrifuge head 120 in
a clockwise direction for the next cycle of 45 seconds. At the
elapse of 45 seconds, the next paddle 180' will have brought around
to depress the actuator 184' and cause a second reversal of the
spinner motor 156. The spinner plate 126 again is brought to a
momentary halt, and, in reversing direction, first moves relative
to the gear 134 to bring the pin now at the other end of the slot
144, back to the first, or now opposite end of said slot 144. The
pinion gears 140 have thus been rotated 180.degree. about their own
axes before any appreciable centrifugal force has been
generated.
On completion of the movement of the pin 142 in the slot 144, and
engagement of said pin 142 with the spinner plate 126, the spinner
plate and the gear 134 are locked for rotation together, now in the
counterclockwise direction for another 45 seconds until the spinner
motor direction is reversed by engagement of the paddle 180"
against the actuator 184' of switch 184 depressing same. The pinion
gears 140 and hence, the holders 136, tubes 150 and test sample
columns therein, again are rotated about their own axes between
applications of centrifugal force.
Coupled rotation of the spinner plate 126 and gear 134 is resumed
for another and final 45 second interval. The timer plate 176 is
continuously rotating during these last described operations, and,
accordingly, continues to rotate. Approximately 45 seconds after
the last-mentioned motor reversal, the pin 182 is brought into
contact with the actuator 186' by the continued rotation of the
timer disc 176, the actuator 186' is released from its depressed
condition. Now, the motor 156 is de-energized and the centrifuge
head is brought to a halt.
The tubes 150 with their now partially packed red cell layer, are
each compared with the initial level and a ratio taken which is
reflective of the sedimentation rate of the sample. It is possible
then to subject the tubes and the samples therein to substantially
greater G force, such as 100 G in a conventional centrifuge so as
to fully pack the red cells. The ratio of the fully packed cell
level to the partially packed level is taken. This ratio, the
resultant sedimentation rate taken to provide what can be described
as a "Zeta Sedimentation Ratio," is independent of the effect of
hematocrit and is related to the state of health of the source
individual. The term "Zeta" refers to the "Zeta" potential between
cells. The "Zeta" potential to which reference is made is effected
by the concentration of asymmetrical protein molecules in the blood
such as fibrinogen, gamma globuin, etc. The "Zeta Sedimentation
Ratio" in a fashion analogous to the sedimentation rate has been
found to be indicative of the state of health of the source
individual. Unlike sedimentation rate determinations per se which
measure rate of red cell fall, the value described here as the
"Zeta Sedimentation Ratio" or ZSR provides a determination of the
packing factor or closeness of packing of the cells. As a result,
the ZSR is independent of the effect of "hematocrit," the relative
quantity of red cells in the whole blood sample .
* * * * *