Vol. 92, Issue 3, 1089-1096, March 2002
Blood extraction from lancet wounds using vacuum combined
with skin stretching
David D.
Cunningham1,
Timothy P.
Henning1,
Eric B.
Shain1,
Douglas F.
Young1,
Jurgen
Hannig2,
Eric
Barua2, and
Raphael C.
Lee2
1 Abbott Laboratories, Abbott Park 60064-6015; and
2 Department of Surgery, The University of Chicago
Hospitals, Chicago, Illinois 60637
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ABSTRACT |
Key factors and
practical limits of blood extraction from lancet wounds on body sites
other than the finger were determined by testing a large number of
conditions. During these tests, the pain associated with
lancing alternate body sites was rated as less painful than a
fingerstick 98% of the time. Vacuum combined with skin stretching was
effective in extracting an adequate volume of blood from the forearm
for glucose testing, up to an average of 16 µl in 30 s. The
amount of blood extracted increases with the application of heat or
vacuum before lancing, the level of vacuum, the depth of lancing, the
time of collection, and the amount of skin stretching. Vacuum and skin
stretching led to significant increases, up to fivefold in the
perfusion of blood in the skin as measured by laser Doppler. Our
observations suggest that vacuum combined with skin stretching
increases blood extraction at alternate sites by increasing the lancet
wound opening, increasing the blood available for extraction by
vasodilatation, and reducing the venous return of blood through capillaries.
suction; diabetes; diagnostics; alternate site; glucose measurement
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INTRODUCTION |
THE MOST COMMON METHOD
OF obtaining small amounts of blood from humans for diagnostic
testing is by lancing the finger. The finger is typically lanced
because it can be squeezed to expel more blood. People with diabetes
lance their fingers several times a day. Whereas the finger can readily
supply the volume of blood needed for conventional test strips,
3-10 µl (16), the process is painful and results in
soreness that can last for several days. Thus the development of
painless and convenient methods to access blood for measurement,
particularly glucose, has been an active area of research.
Interstitial fluid has been accessed by suction effusion
(19), transcutaneous microdialysis (12),
intradermal pressure harvesting with a cannula (31),
iontophoresis (35), and low-frequency ultrasound
(20, 26); however, analysis of samples collected using
these techniques is difficult because of the small amount of glucose
extracted and dilution of the sample. Several mechanical lancet devices
have been developed to harvest capillary blood from lancet wounds on
sites other than the finger by applying pressure or vacuum around the
lanced site (2, 13, 40). Lancet sticks at alternate sites
are virtually pain free, with 60% of the sticks being rated as
painless and 90-97% being rated as less painful than a
fingerstick (9, 13, 14, 40). Unfortunately, these
mechanical devices require multiple manual manipulation steps that may
be poorly controlled by the user. We are unaware of studies reporting
the amount of blood extracted or factors that may be associated with
the successful extraction of blood with the mechanical devices. In a
published study, our laboratory reported the distribution of blood
volumes obtained from diabetic subjects by vacuum-assisted lancing of
the forearm; however, a limited number of extraction conditions were
evaluated (9).
The aim of the present study was to understand the key factors and
practical limits of blood extraction from lancet wounds on alternate
sites using vacuum. A large number of extraction conditions were
screened by testing several conditions on a group of volunteers and
comparing the results for each extraction condition. The vacuum level,
lancing depth, lancet size, and collection time were investigated.
Treatment of the site with heat or vacuum before lancing was performed
to increase the amount of blood extracted. Stretching of the skin with
vacuum was studied with the goal of developing an integrated system
that supplied vacuum, lanced the skin, and positioned the test strip
over the wound to collect the blood. The success of these efforts
resulted in the commercial introduction of an automated device for
alternate site blood glucose monitoring that is less painful
(14).
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MATERIALS AND METHODS |
Lancing and blood collection.
Four or more individuals participated in each of 16 blood collection
trials after informed consent was obtained, as approved by an
Institutional Review Board. Subjects with a history of excessive bleeding were excluded. Blood was collected from a minimum of 16 lancet
wounds for each of the 105 different conditions, as summarized in Table
1.
In each trial, the dorsal forearm was lanced with a Becton-Dickinson
(BD) Ultra-Fine lancet and retracted, regulated vacuum was applied over
the wound with a collection nosepiece for a fixed time, the vacuum was
vented to the atmosphere, the nosepiece was removed, and the amount of
blood was collected and measured using a microcapillary tube (Drummond
Scientific, Broomall, PA). Automated lancing and vacuum systems were
constructed to keep the time between steps to a minimum. Pulsed vacuum
was produced by regulating the vacuum with a vent line and solenoid
valve. The depth of lancing was controlled by constructing custom caps
for a standard spring-loaded lancing device and by placing a metal
collar around the lancet. In cases where vacuum was applied to the
forearm before lancing, the vacuum level and nosepiece geometry were
the same as in the blood collection step.
The 8-mm-diameter collection nosepiece consisted of a pipette tip
(Rainin Institute, Woburn, MA) with the narrow end connected to the
vacuum source. In trial 9, glass tubes of known diameter were used for collection. In trial 10, the prevacuum,
lancing, and collection steps were all completed without releasing the vacuum (see Fig. 1). In trial
15, all steps were completed under vacuum using a 10-mm-diameter,
3-mm-high nosepiece, as previously described (9). For
trials 6, 7, and 14, one nosepiece was
used for prevacuum and lancing, and a nosepiece of the same geometry without the lancet was used for blood collection. To prevent the skin
from stretching inside the nosepiece in trials 2 and
3, a checkerboard pattern of four thin nylon strings was
glued across a plastic cylinder with an inside diameter of 15 mm.
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Fig. 1.
Design and operation of the vacuum lancet nosepiece. a:
Diameters of 9.5, 12.7, 15.9, and 19.1 mm and heights of 1.6, 3.0, 4.5, and 6.0 mm were tested. Synthetic rubber gaskets provided a temporary
seal to the skin, allowing a vacuum to be maintained even in the
presence of hair. Vacuum was applied to the skin through the 4-mm
opening and 4 vacuum holes that keep the skin stretched in the
nosepiece during the blood extraction. b: Nosepiece applied
to the skin. c: Application of vacuum and stretching of skin
into the nosepiece. d: Puncture of the skin. e:
Retraction of the lancet and extraction of blood.
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For heat treatment in trials 11-13, feedback-controlled
heaters were constructed using a Kapton film heating element (Minco Products, Fridley, MN), temperature sensor, and aluminum block (25 × 25 × 0.6 mm) attached to a square, circular, or donut-shaped copper skin contact block. The feedback control was set to heat the
skin to either 40 or 45°C.
Immediately after each lancet stick, the subject rated the sensation
into one of the following categories: 1) didn't feel anything or not sure they felt anything; 2) definite prick,
although not as painful as a fingerstick; or 3) definite
pain, approximately equal to a fingerstick.
Skin stretching.
Four trials including from 9 to 80 subjects were performed to determine
the height that skin stretches into a cylinder with different levels of
vacuum. Glass tubes of different diameters were fitted with scales and
a regulated vacuum supply. The subject's forearm was drawn into the
tube, and a video camera was used to magnify the image and reduce
the parallax error. Both blood collection and skin stretching were
measured on subjects enrolled in trial 10. Subjects with
diabetes were recruited for trial 18 (see Table 3).
Laser Doppler blood flow measurements.
Each of five healthy volunteers was acclimatized to the laboratory for
20-30 min in a reclining chair. The forearm was positioned on an
armrest at a position level with the heart, and the laser Doppler
measurements were performed before and during application of 
7.5
lbs./in.2 gauge (psig) vacuum for 1 min using nosepieces
with step heights of 1.6-6 mm and an inner diameter of 12.7 mm.
For the analysis, 10 s of continuous measurement with a
custom-made 6-mm-diameter multiprobe (Perimed PeriFlux 4001 Master)
before and during the vacuum (35-45 s into the vacuum period) were
averaged to obtain the concentration of moving blood cells (CMBC) and
the blood velocity under each condition. The perfusion of the skin as
an arbitrary value is derived by multiplication of the CMBC and the
velocity. For each perfusion data point, 10 s of continuous
measurement were averaged to smooth temporal fluctuations due to the
heartbeat (36). Baseline values before vacuum were defined
as one. The value after application of vacuum is reported as a
percentage of the baseline value to account for spatial differences at
each individual site (5-7, 22). The laser
Doppler device was calibrated according to the manufacturer's instructions.
Statistical analysis.
Blood collection results are presented as means ± SE.
Nonparametric Wilcoxon rank sums were used to test for differences, and
a P value of <0.05 was considered significant. Continuous variables were evaluated by linear regression analysis.
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RESULTS |
Skin stretching.
The application of vacuum resulted in larger amounts of blood being
extracted, and the amounts increased with increasing vacuum (Table
2, trial 1). Substantially
more blood was extracted when the skin was allowed to stretch up into
the nosepiece under vacuum than when the nylon strings (net) prevented
stretching (5.1 vs. 0.7 µl; P < 0.0001; Table 1,
trial 2). Application of vacuum combined with
allowing the skin to stretch up into the nosepiece before lancing
increased the amount of blood collected (Table 2, trial 3).
For all 85 conditions in which blood was extracted with continuous skin
stretching, the average relative standard deviation in the volume of
blood was 72% (range 24-128%).
Vacuum and time.
Prevacuum and increasing levels of vacuum increased the volume of blood
collected (Fig. 2). The mean volume
increased linearly with collection time over the range of 10-40 s
(trial 6) when both the BD lancet (µl = 0.092 × s + 1.8; r = 0.92, P = 0.08) and
the MediSense TLC lancet (µl = 0.16 × s + 0.4;
r = 0.99, P = 0.01) were used. When the
total pre- and postvacuum time was held constant at 45 s
(trial 7), the mean blood volume increased linearly with
collection time (µl = 0.068 × s + 1.2;
r = 1.00, P = 0.005).
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Fig. 2.
Blood volume extracted with different levels of vacuum in
30 s ( , trial 4) and with vacuum
treatment to the skin before lancing ( , trial
5). psig, lbs./in.2 gauge. Values are means ± SE.
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Nosepiece geometry.
Increasing the diameter of the nosepiece in the range of 4-10 mm
increased the height that the skin stretched up into the nosepiece
(Table 3) and increased the volume of
blood collected (Fig. 3). For larger
diameters, the mean height of skin stretching increased linearly with
the diameter (Table 3, trial 10) and with the level of
vacuum (trial 18). At constant, applied vacuum, the mean
blood volume increased as the step height of the nosepiece increased
from 1.6 to 6 mm (Fig. 4A),
and the effect was 1.5- to 2-fold larger with the 12.7-mm-diameter
nosepiece than with larger and smaller diameter nosepieces (Fig.
4B). Larger height-to-diameter ratios might stretch the
wound open to a greater extent. Therefore, from the data set in Fig.
4A, data for nosepieces of similar height-to-diameter ratios
(0.31-0.38) were compared with each other. The largest volume was
obtained with the 12.7-mm-diameter nosepiece, but the values were not
statistically different (12.7-mm ratio: 0.35, 13.2 ± 2.1 µl;
9.5-mm ratio: 0.32, 7.1 ± 0.7 µl, P = 0.06;
15.9-mm ratio: 0.38, 9.4 ± 1.4 µl, P = 0.19;
19.1-mm ratio: 0.31, 9.8 ± 1.2 µl, P = 0.52).
Laser Doppler showed that the velocity of blood increased after the
application of vacuum, independent of the inside step height, whereas
the CMBC increased systematically as the step height increased, which
resulted in the same trend in the perfusion results (Fig.
5).
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Fig. 3.
Blood volume extracted with different diameter glass
tubes in 30 s at 7.5 psig () and 5 psig
() in trial 9. Values are means ± SE.
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Fig. 4.
Blood volume extracted with nosepieces of different inner
diameters (A) and inside step heights (B) in
trial 10. Values are means ± SE in A. B: diameters are 9.5 mm ( ), 12.7 mm
(), 15.9 mm ( ), and 19.1 mm
().
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Fig. 5.
Effect of vacuum and inside step height on the perfusion,
concentration of moving blood cells (CMBC), and velocity of blood in
the skin. Five volunteers were measured in duplicate before and during
a 1-min application of 7.5 psig vacuum using a 12.7-mm-inner-diameter
nosepiece. For each perfusion data point, 10 s of continuous
measurement (40 ± 5 s into the vacuum period) were averaged
to smooth temporal fluctuations due to the heart. Values are means ± SE.
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Lancing depth and heat.
Lancing depths in the range of 0.7-1.6 mm gave linearly increasing
volumes of blood with depth, but results in the range of 1.7-2.3
mm were more variable and showed no statistically significant increase
with depth (Fig. 6). Mean blood volumes
as large as 17 µl were collected after the skin was heated to 45°C
for 45 s before lancing and extraction (Table
4). Increasing the heating time from 15 to 45 s resulted in 1.4- to 1.9-fold increases at 40°C and 2.6- to 4-fold increases at 45°C. Although blood collection without
preheating of the skin was not determined in trials
11-13, identical conditions except without skin preheating
were used in trials 4 and 8, resulting in volumes
of 3.9 ± 0.4 and 3.1 ± 0.5 µl, respectively.
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Fig. 6.
Blood volume extracted after lancing to different depths
with a 28-gauge lancet (, trial 14;
, trial 15) and a 23-gauge lancet
(, trial 15). Values are means ± SE.
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Pulsed vacuum.
Skin was observed to stretch up and fall back when the vacuum was
pulsed. Volumes showed no trend with pulse frequency (0, 0.2, 0.8, 3.2, 13, 25, and 100 Hz; trial 1) at 2.5 or 5 psig. No
difference was found in the overall average volumes with pulsed vacuum
and continuous vacuum (1.8 µl pulsed vs. 1.6 µl continuous at 2.5
psig, P = 0.75; and 3.1 µl pulsed vs. 3.1 µl
continuous at 5 psig, P = 0.39; trial 1).
In the follow-up trial at higher levels of vacuum (5, 7.5, and 10
psig; trial 8), larger blood volumes were obtained with
continuous vacuum than with 3.2- or 100-Hz pulsed vacuum.
Body sites.
The study of various body sites (dorsal forearm, palmar forearm, upper
arm, stomach, and thigh) with lancing depths of 1.0 and 1.6 mm gave
blood volumes in the range of 2.4 ± 0.4 µl (1.0 mm, thigh) to
8.0 ± 1.0 µl (1.6 mm, stomach). Compared with the dorsal
forearm, only the 1.6-mm-deep lances on the upper arm and stomach gave
statistically different amount of blood (3.5 ± 0.5 vs. 5.5 ± 0.8 µl, P = 0.04; and 8.0 ± 1.5 µl,
P = 0.006, respectively).
Pain.
From the total of 2,614 lancet sticks in the study, the sensation after
lancing was rated as follows: 83% "didn't feel anything or not sure
they felt anything," 15% felt a "definite prick, although not as
painful as a fingerstick," and 2% felt "definite pain, approximately equal to a fingerstick." For the larger lancets, deeper
lancing depths, and various body sites tested in trials 6 and 14-16, a minimum of 94% under any specific
condition were rated as less painful than a fingerstick.
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DISCUSSION |
A large number of conditions were tested to understand the key
factors and practical limits of blood extraction from lancet wounds on
alternate sites using vacuum. The exact site of lancing was important
because replicate tests on an individual gave different amounts of
blood. Allowing the skin to stretch up into the vacuum nosepiece lead
to a dramatic increase in the amount extracted. Other important factors
included the vacuum level, lancing depth, and collection time. Both
heat and vacuum treatment of the site before lancing were effective in
increasing the amount of blood extracted. Pulsing the vacuum to knead
the skin around the lancet wound was ineffective in obtaining more
blood. Microliter volumes of blood were relatively rapidly extracted
from various anatomic sites, which is in accord with the relatively
small variations in skin stretching (24) and blood
perfusion (38) at the sites studied. Lancing
alternative sites minimized pain, in agreement with previous studies
(9, 13, 14, 40). Informal feedback from the subjects
revealed that the soreness and tenderness associated with lancing the
finger were eliminated, presumably because of the facts that a normal
lancing depth penetrates a portion of the underlying muscle on the
finger but is limited to the dermis and subcutaneous fat layer at
alternate body sites (21) and that normal use of the
fingers involves frequent high-pressure contact.
Site of lancing.
Blood volumes collected using standard fingerstick sampling methods are
characterized by large coefficients of variation, in the range of
62-103% (11, 15). Presumably, the heterogeneity of
the microcirculation of the skin is important. Laser Doppler and biopsy
and histology studies have shown regions of relatively rich and poor
perfusion of the forearm on a scale of 1 mm, which is larger than the
diameter of a lancet (5-7, 22). The density of small
capillaries has been reported as 60-70 mm
2
(28), whereas the density of larger arteriolar and venular branches is 19 mm2 (23) or 8-10
mm3 (4). Thus the 1.6-mm-deep penetration of
a BD Ultra-Fine lancet, which results in a wound of an approximate area
of 0.09 mm2 and volume of 0.08 mm3, generally
penetrates several small capillaries and may penetrate a larger vessel.
Indeed, large superficial veins may be only 1 mm below the surface, and
we confirmed that lancing over a visible vein results in a small
hematoma. At the other extreme, several lancet wounds where little or
no blood was collected (data not shown) were viewed under
magnification, and the lancet had clearly penetrated the skin. From a
practical standpoint, a small percentage of the lancet sticks may hit a
relatively avascular region, where insufficient blood is collected for
testing. In an earlier report (9), slightly more blood was
obtained from vacuum lancet sticks that were more painful (8.7 vs. 7.1 µl; P = 0.07), which concurs with the view that
cutaneous nerve trunks follow the course of blood vessels in the skin.
Considerable site-to-site variability was also found in the healing of
lancet wounds on the forearm (10).
Vacuum skin stretching.
The most surprising result was the large influence that stretching the
skin up into the nosepiece had on blood extraction, as most clearly
demonstrated when a net is used to prevent stretching (Table 2,
trial 2). When the skin was not allowed to stretch into the
nosepiece, the amount of blood collected was minimal, <1 µl.
Stretching may open the lancet wound, overcoming the natural tendency
for the wound to close up and shut off the blood flow. Increasing the
diameter of the nosepiece allows more skin to stretch up into the
nosepiece (Table 3), and increasing amounts of blood were extracted
with larger diameter nosepieces (Fig. 3).
In an integrated device, if the skin did not stretch up to the top of
the nosepiece, the lancet stick would be shallow, and the blood would
not directly wick into a test strip. Both the diameter of the nosepiece
and the level of vacuum affected the height of skin stretching, with
the diameter having the greater effect over the range of conditions
studied (Table 3). Previous studies also showed that the skin elevation
is related to the diameter and level of vacuum, but lower values were
observed in the earlier studies because the skin was held in place by
double-sided tape and was not allowed to slide up into the suction
device (8, 18, 27).
The general pattern of increasing blood extraction with nosepiece
height (Fig. 4) may be explained by the pooling of blood under the area
that is stretched, but a detailed understanding is lacking. The
fivefold increase in perfusion (Fig. 5) is strong evidence that
vasodilatation is involved; however, stretching may also result in
partial occlusion of the capillaries. Certainly, the skin is forced to
form a relatively sharp angle at the inside rim of the nosepiece, and
the area-to-height ratio determines the shape (spherical, ellipsoid,
parabolic, etc.) and thereby the mechanical stress distribution pattern
of the produced skin "bubble." Thus application of vacuum may
reduce the venous return of the skin section involved by stretching it
against the inside rim of the nosepiece and thereby (at least
partially) occluding the venous capillaries. Arteries supplying the
capillaries are larger and deeper in the skin and less likely to be
occluded. A previous study found that prolonged application of vacuum
increased blood perfusion, presumably because of the trauma of
blistering (34); however, none of our conditions produced blistering.
The amount of blood extracted at each nosepiece height was roughly
equal for three of the four diameters tested (Fig. 4B). The
12.7-mm-diameter nosepieces with step heights of 3-6 mm extracted 1.5- to 2-fold more blood than the others, suggesting that this nosepiece geometry might stretch the skin in the most favorable way to
produce the (at least partial) occlusion of the venous blood return and
stress-induced perfusion increase postulated above. The preferred
geometry at a given vacuum pressure is also suggested by our
laboratory's previous work in which the 12.7-mm-diameter nosepiece
gave twice the amount of blood as a 10-mm-diameter nosepiece with a
similar height-to-diameter ratio (10.0 vs. 5.0 µl; P < 0.0001) (9). In the present studies, the differences
between nosepieces with similar ratios did not reach statistical
significance, perhaps because of the relatively small number of tests
at each condition (n = 42) compared with that in our
laboratory's previous study (n = 240). Detailed
investigation of larger diameter nosepieces with larger step heights
was not undertaken because skin distension became less comfortable and
the areas on the body available for use become more limited.
Skin blood flow rates and the vacuum collection rates can be used to
estimate the volume of tissue extracted. Assuming that blood is
extracted from a hemisphere that is perfused at the maximum skin blood
flow rate, 50 ml · min1 · 100 g1 (17, 30), the maximum extraction rate of
34 µl/min (Fig. 4, 30-s collection time) corresponds to a hemisphere
with a radius of 3.1 mm. This value is smaller than the hemisphere
produced by the nosepiece. On one hand, insertion of a needle or small probe is known to increase skin blood flow at least five- to sevenfold (1, 28, 33) over an area of 9 cm2
(32). On the other hand, it is unclear whether maximum
perfusion is achieved. Thus, if the combined effects of vacuum,
lancing, and skin stretching did not maximize the skin perfusion, a
radius larger than our calculated radius of 3.1 mm would be expected. The calculated radius of extraction is about one-half the size of the
nosepiece but twice the depth of lancing. Most importantly, a maximum
skin perfusion is able to supply the amounts of blood extracted to the
skin section within the nosepiece to justify the volumes extracted. For
nosepieces >8 mm in diameter, elevation of the skin into the nosepiece
also includes subcutaneous tissue (8); however, further
investigation is required to determine whether there is any special
interaction of the subcutaneous tissue with the 12.7-mm-diameter nosepiece.
Other factors affecting blood extraction.
Blood collection was linearly related to the level of vacuum (Fig. 2).
A linear relationship is also described by the Poiseuille equation
(Eq. 1), which has been used to predict the amount of blood
collected from a vein with a cannula (25)
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(1)
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where V is volume, 
P is the level of vacuum applied,
r is the radius of the cannula, t is the time,
L is the length of the cannula, and 
is the viscosity of
blood. By assuming various lengths, diameters, and numbers of
arterioles, the equation can be used to predict blood volumes from
vacuum extraction conditions; however, adequate justification of the
required assumptions is beyond the scope of this report.
Blood extraction might be expected to increase linearly with time, and
we confirmed this dependency for times up to 45 s. Clotting may
begin to inhibit blood flow at longer times, especially when the flow
is confined in a small space. Application of a prevacuum for 30 s
increased the amount of blood collected by approximately twofold (Fig.
2), but ~1.5-fold more blood can be collected in a fixed total time
by devoting the time to collection rather than to prevacuum.
The size of the lancet wound can be varied by using a larger diameter
lancet or by increasing the depth of lancing. In several trials with
23- and 28-gauge lancets, where the volume of the lancet tip entering
the skin is about twofold different, the blood volumes were either
larger with the smaller diameter lancet or not statistically different
(trials 6 and 15 and Ref. 9). These unexpected results may be due to a difference in the sharpness of the
cutting edge of the lancets or some other unrecognized factor. The
systematic increase in blood volumes with puncture depths up to 1.6 mm
indicates that more capillaries are cut. The greater variability found
at puncture depths >1.6 mm may be due to the increasing involvement of
subcutaneous tissue, because the thickness of the dermis on the dorsal
forearm is 1-1.5 mm (21). Also, the nosepiece
geometry in combination with the applied vacuum may become less
effective in stretching open a deeper wound.
Heating the skin produced more blood than in trials without heating,
and the size of the heater was relatively unimportant (Table 4).
Previously, heating the skin before lancing proved effective in
reducing the time required for blood collection (3). Increasing the heating time increased the blood extracted (Table 4),
indicating that some time is required for maximal effect. Local
heating to 44°C results in a threefold increase in blood flow after
40 s and maximum vasodilation in 2 min (39). Maximum vasodilation is reached by local heating to 45°C (17).
After local heating for 45 s, an average of 1.6-fold more blood
was extracted at 45°C than at 40°C, whereas the perfusion of the
forearm is known to be ~1.3-fold larger (37). Thus
heating the skin increases the amount of blood extracted but at the
expense of time and complexity of the apparatus.
Limitations of the studies.
Because the average relative standard deviation was 70%, testing a
blood extraction condition with 16 sticks gave the protocol a
statistical power to detect an ~50% increase in blood volume. Smaller differences might be detected with a larger study; however, in
a study of 215 diabetic subjects, the average relative standard deviation increased to 88% (9), presumably because of
increased person-to-person variability. Over the course of multiple
trials, larger or smaller than average blood volumes were often
extracted from certain individuals, making comparison among trials
difficult. Obviously, further work is needed to identify the underlying
factors for person-to-person differences. Collection of blood directly into a glucose test strip was accomplished in a number of trials (data
not shown); however, an understanding of the key interactions between
the lancet wound and the test strip also requires further study.
Alternate methods for increasing perfusion, such as mechanical trauma,
topical drug treatment, iontophoresis, or transcutaneous electrical
nerve stimulation, were not explored.
In summary, blood can be effectively extracted from lancet wounds
using vacuum combined with skin stretching. This technology has
been incorporated into a commercially available glucose monitoring system (14).
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ACKNOWLEDGEMENTS |
The authors acknowledge significant engineering support from Mike
Lowery, Gary Winter, and Leonard Semple.
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FOOTNOTES |
Address for reprint requests and other correspondence: D. D. Cunningham, Abbott Laboratories, D-9NL/AP20, 100 Abbott Park Rd.,
Abbott Park, IL 60064-0615 (E-mail:
david.cunningham{at}abbott.com).
The costs of publication of this
article were defrayed in part by the
payment of page charges. The article
must therefore be hereby marked
"advertisement"
in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
10.1152/japplphysiol.00798.2001
Received 30 July 2001; accepted in final form 9 November 2001.
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