An adaptive tourniquet for improved safety in surgery.

Transcription

122
NO.2,
IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING, VOL. BME-29, NO.
2, FEBRUARY 1982
Regular Papers
An
Improved Safety in Surgery
An Adaptive Tourniquet
Tourniquet for Improved
McEWEN, MEMBER, IEEE, AND ROBERT W. MCGRAW
McGRAW
JAMES A. MCEWEN,
AfJstract-The increasingly
of the
Abstract-The
increasingly recognized
recognized inability
inability of
the current genpneumatic tourniquets
pressure with
with adequate
eration
control pressure
eration of
of pneumatic
tourniquets to
to control
adequate
accuracy,
and stability
has been
been associated
associated with
continuing
accuracy, reliability,
reliability, and
stability has
with continuing
reports of
of tourniquet-related
incidents, and
Moreover,
and hazards.
hazards. Moreover,
reports
tourniquet-related injuries,
injuries, incidents,
the
labor-intensiveness and
operating costs
with the
the use of
and operating
the labor-intensiveness
costs associated
associated with
of
pneumatic tourniquets
tourniquets have
have significant
significant cost implicacurrent types of
of pneumatic
implications for
for hospitals.
hospitals. To
large extent, the
the recent development
To a large
of a
tions
development of
microprocessor-based tourniquet
tourniquet capable
and accurately
of safely
mainmicroprocessor-based
capable of
safely and
accurately maintaining
and capable
capable of
simultaneously performing
performing
of simultaneously
desired pressure, and
taining a desired
other
of alarm
conditions, has
as detection
alarm conditions,
has reduced
reduced
other functions
functions such
such as
detection of
these hazards
hazards and
and operating-cost
implications. Furthermore,
availthe availthese
operating-cost implications.
Furthermore, the
ability of
has facilitated
facilitated the
the developof a microprocessor-based
ability
tourniquet has
development of
the adaptive
adaptive tourniquet
in this
this paper,
paper, in
in which
which the
the
described in
ment
of the
tourniquet described
changed throughout
procedure
in aa tourniquet
cuff is
is changed
pressure in
tourniquet cuff
throughout aa surgical
surgical procedure
as
function of
of the
patient's changing
changing intraoperative
as a function
the patient's
intraoperative systolic
systolic pressure,
thus
approximating the
the minimum
maintain
minimum safe
safe pressure necessary to maintain
thus approximating
aa bloodless
bloodless field
for surgery.
While the
of an
adaptive tourniquet,
tourniquet,
an adaptive
field for
surgery. While
the use of
rather
than just
just a microprocessor-based
rather than
set at aa constant
tourniquet set
pressure may
be necessary
in most
most cases,
cases, it
it promises
promises to
to have
have signifipressure
may not
not be
necessary in
signififor patients
cant
in certain
certain surgical
surgical procedures
procedures and
patients who
who may
be
and for
cant value
value in
may be
of tourniquet-induced
tourniquet-induced complications.
complications. Also,
the lower
lower
at greater risk
risk of
Also, the
average
possible through
through the
the use of
of an adaptive
average pressures possible
adaptive tourniquet
tourniquet
surgical techniques
techniques of
longer duration
permit the
the evolution
of surgical
of longer
duration
may permit
evolution of
in the
without
concomitant increase
the risk
toumiquet-induced
increase in
risk of
without aa concomitant
complications.
despite the
increased safety
the increased
of the
the adaptive
complications. Finally,
Finally, despite
adaptive
safety of
the operating
tourniquet,
be lower
estimated that
lower than
that the
than
tourniquet, itit isis estimated
operating costs will be
for conventional
conventional pneumatic
tourniquets due
elimination of
the need
need
due to elimination
of the
for
for
labor-intensiveness.
for compressed gas and reduced
reduced labor-intensiveness.
INTRODUCTION
INTRODUCTION
URRENTLY available
available types of
of surgical
CURRENTLY
surgical tourniquets
tourniquets consist of
basic components: a source of
of pressurized
of three
three basic
_,sist
pressurized
gas,
pressure-regulating mechanism
with pressure gauge, and
mechanism with
and
gas, a pressure-regulating
the
of
is applied
to
the
proximal
portion
pneumatic cuff
which is
cuff which
a pneumatic
applied
proximal portion of
patient's limb
limb and
inflated to a suprasystolic
in
a patient's
and inflated
suprasystolic pressure
pressure in
order
maintain a bloodless
bloodless surgical
field in
in the
portion
the distal
order to
to maintain
distal portion
surgical field
of
the limb.
properly employing
employing a pneumatic
pneumatic tourniquet
of the
In properly
limb. In
tourniquet
the cuff
the pressure
should
for surgery
surgery of
of the
extremities, the
pressure in
in the
cuff should
for
the extremities,
to assure a
be maintained
maintained at the
the minimum
minimum pressure necessary
be
necessary to
bloodless field
field distal
the cuff.
cuff. Maintaining
bloodless field
field
bloodless
distal to the
Maintaining aa bloodless
in the
the limb
easier, surgical
techfor surgery
makes dissection
dissection easier,
in
limb for
surgery makes
surgical tech-
C
1981. This
received June
revised October
Manuscript received
June 3,
3, 1981;
October 6,
This
Manuscript
1981; revised
6, 1981.
British Columbia
Care ReHealth Care
ReColumbia Health
work was supported
supported in part by the British
Grant 94
94 (80-3).
search Foundation
Foundation under
under Grant
(80-3).
search
the Department
of Biomedical
Biomedical Engineering,
with the
Department of
J. A. McEwen
J.
McEwen is
is with
Engineering,
V5Z IM9.
1M9.
Vancouver, B.C.,
Canada vsz
Vancouver General
General Hospital,
Hospital, Vancouver,
B.C., Canada
R.
Division of
R. W.
W. McGraw is
the Division
of Orthopaedic
is with
with the
Orthopaedic Surgery,
Surgery, UniverCanada V5Z
1M9.
sity
of British
British Columbia,
Columbia, Vancouver,
B.C., Canada
V5Z IM9.
sity of
Vancouver, B.C.,
niques less
and the
required for
niques
less traumatic,
traumatic, and
the time
time required
for operations
operations
shorter [1].
shorter
maintaining aa bloodless
bloodless field
field while
[1]. Moreover,
Moreover, maintaining
while
Simultaneously
minimizing the
pressure in
the pneumatic
pneumatic
the pressure
simultaneously minimizing
in the
tourniquet cuff
will minimize
minimize the
the probability
probability of
cuff will
of pressurepressuretourniquet
related injury
injury associated
[2], [3].
[3] .
related
associated with
with tourniquet
tourniquet usage
usage [2],
Because
its usefulness,
usefulness, the
widely
Because of
of its
the pneumatic
tourniquet isis widely
employed. Information
Information obtained
obtained from
and
employed.
from manufacturers
manufacturers and
regulatory
suggests that
America at
at least
least ten
ten
regulatory agencies
agencies suggests
that in
in North
North America
thousand pneumatic
tourniquets are
in more
more than
than one
one
are used
used in
thousand
million
procedures annually.
However, none
of these
million surgical
none of
these
surgical procedures
annually. However,
tourniquets are
are capable
capable of
of safely
and automatically
pneumatic
safely and
automatically
maintaining
the minimum
minimum pressure
pressure necessary
necessary to
to assure
bloodmaintaining the
assure aa bloodless field
field throughout
due to
with
to factors
factors associated
associated with
less
throughout surgery
surgery due
their
design and
and construction
construction (e.g.,
-[7])
and
they
cantheir design
(e.g., see
see [4]
)
and
they
can-[7]
[41
modified readily
readily to
levels
not be
be modified
to achieve
achieve Significantly
significantly greater
greater levels
of
reliability. Accordingly,
of safety,
and reliability.
safety, accuracy,
accuracy, stability,
stability, and
Accordingly, itit isis
not surprising
the widespread
use of
perhaps not
of pneumatic
pneumatic
perhaps
surprising that
that the
widespread use
tourniquets has
been accompanied
continuing reports
reports of
tourniquets
has been
accompanied by
by continuing
of
injuries, e.g.,
has been
that
It has
been suggested
injuries,
e.g., [4]-[6],
[4] -[6], [8]-[11].
[8] -[11]. It
suggested that
the
true incidence
tourniquet-induced complications
complications may
the true
incidence of
may
be significantly
underestimated, and
each use
use of
pneube
that each
of aa pneusignificantly underestimated,
and that
matic
although
matic tourniquet
tourniquet may
may in
in fact
fact lead
lead to
to some
some damage,
damage, although
such
damage is
generally short-term
and reversible
reversible [11],
such damage
is generally
short-term and
[11], [12].
[12].
Many, but
all, tourniquet-related
tourniquet-related injuries
are pressurepressurebut not
not all,
Many,
injuries are
related.
Tourniquet-related complications
may result
result not
not only
only
related. Tourniquet-related
complications may
from
excessive pressure
to nerve
nerve compression
or other
other
from excessive
pressure leading
leading to
compression or
injuries at
the site
the cuff
cuff [2],
but also
also
at the
site of
of the
injuries
[2], [13],
[13], [14],
[14], [16],
[16], but
from insufficient
from
to surgical
insufficient pressure leading
leading to
surgical complications,
complications,
passive congestion,
and hemorrhagic
hemorrhagic nerve infiltration
infiltration [14],
[14],
passive
congestion, and
from
excessive periods
from excessive
of tourniquet
periods of
tourniquet application
application [9],
[9], [15],
[15],
[16],
application of
of the
or from
the cuff
from application
without due
due consideraconsideracuff without
[16], or
tion
of the
the underlying
underlying anatomy
anatomy [11],
tion of
To aa large
[ I 1], [17],
[ 17], [18].
[18]. To
large
the risk
extent, the
risk of
of injury
associated with
these factors
has
with these
factors has
extent,
injury associated
been significantly
reduced by
by the
the recent
recent development
development of
of aa
been
significantly reduced
microprocessor-based
having aa much
higher degree
much higher
tourniquet having
degree
of safety,
of the
of
and reliability
objective of
The objective
the
safety, accuracy,
accuracy, and
reliability [4].
[4]. The
work described
paper was
work
was to
to determine
whether the
the
in this
this paper
determine whether
described in
already
tourniquet could
be
could be
already developed
developed microprocessor-based
modified and
used effectively
effectively to
to further
reduce the
the probability
further reduce
probability
modified
and used
of injury
in the
of
adjusting the
the pressure
pressure in
the tourniquet
tourniquet
injury by
by adaptively
adaptively adjusting
cuff intraoperatively,
the patient's
patient's changing
changing
of the
cuff
as a function
function of
intraoperatively, as
in order
to minimize
systolic
pressure, in
minimize the
pressure necessary
order to
the pressure
systolic pressure,
necessary
to
maintain aa bloodless
bloodless field
during surgery.
to maintain
field during
surgery.
0018-9294/82/0200·0122$00.75
0018-9294/82/0200-0122$00.75
© 1982
©
IEEE
1982 IEEE
Authorized licensed use limited to: The University of British Columbia Library. Downloaded on April 21, 2009 at 14:19 from IEEE Xplore. Restrictions apply.
123
123
MC EWEN
EWEN AND
AND MC
GRAW: TOURNIQUET
TOURNIQUET FOR
IMPROVED SAFETY
FOR IMPROVED
SAFETY IN
IN SURGERY
SURGERY
MC GRAW:
MC
ADAPTIVE
ADAPTIVE TOURNIQUET
TOURNIQUET
At
At present,
present, pressures
pressures in
in pneumatic
tourniquets are
are commonly
commonly
set
constant, preestablished
preestablished levels:
pressures
at constant,
for example,
set at
levels: for
example, pressures
of approximately
mmHg for
for upper
upper limbs
of
300 mmHg
and 500
500 mmHg
limbs and
approximately 300
mmHg
for lower
lower limbs
limbs are
are widely
widely employed
employed [1],
for
pres·
(1], [13].
Such pres[131. Such
sures are
are clearly
clearly much
higher than
than normal
normal systolic
pressures,
sures
much higher
systolic pressures,
but
used traditionally
but have
have been
been used
traditionally to
to accommodate
hysteresis
accommodate hysteresis
in pressure-regulating
pressure-regulating mechanisms,
mechanisms, errors
errors in
pressure gauges,
gauges,
in
in pressure
suboptimal cuff
geometries, leaks,
leaks, and
cuff geometries,
and intraoperative
suboptimal
intraoperative increases
increases
It has
in systolic
pressure. It
in
has been
been suggested
that improved
systolic pressure.
suggested that
improved safety
safety
would result
result from
from setting
pressure P
would
to some
some
setting tourniquet
tourniquet pressure
PTT to
threshold K
K above
constant threshold
above aa patient's
patient's preoperative
preoperative systolic
constant
systolic
pressure
some arbitrary
Ps(to), rather
rather than
to some
unnecespressure Ps(to),
than to
arbitrary and
and unnecessarily
high level
level [2]
i.e.,
sarily high
(2],, i.e.,
= Ps (to) +
PT =Ps(to)
+ K.
PT
(1)
(1)
It
been suggested
that 30-75
mmHg might
be
It has
has been
suggested specifically
specifically that
30-75 mmHg
might be
K for
appropriate
of K
for upper
upper limbs
and
appropriate values
values of
limbs [2],
[3], [9],
[91, and
[2], [3],
that K
that
K might
might be
be set
set to
to PS(to)
Ps(to) for
for lower
lower limbs,
provided the
the
limbs, provided
patient was
was normotensive
did not
have grossly
not have
normotensive and
and did
patient
grossly hyperhypertrophied or
obese thighs
thighs [19].
or obese
the above-noted
trophied
above-noted
However, the
(191. However,
limitations
the accuracy
accuracy and
and reliability
of widely
widely used
types
limitations in
in the
used types
reliability of
of pneumatic
their use
either hazardous
of
makes their
use either
hazardous or
tourniquets makes
or
labor-intensive
because constant
monitoring would
needed.
constant monitoring
labor-intensive because
would be
be needed.
In contrast,
the lower
lower pressures
pressures which
which have
In
been advocated
have been
advocated
contrast, the
have been
been implementedimplemented through
the use
use of
the previously
have
of the
through the
previously
mentioned microprocessor-based
microprocessor-based tourniquet,
resulting in
in reducreducmentioned
tourniquet, resulting
tions in
in tourniquet
tourniquet pressure
pressure by
by as
much as
as 40
40 percent
percent in
tions
as much
in comcomparison to
to traditional
levels, with
with aa simultaneous
reduction in
traditional levels,
simultaneous reduction
in
panson
labor-intensiveness
and increased
minimum
increased safety
safety [4]
Thus, aa minimum
[4] .. Thus,
constant
pressure ,can
be achieved
use of
achieved through
the use
of such
constant pressure
can be
such aa
through the
In certain
device. In
certain cases,
however, aa dynamically
device.
cases, however,
dynamically changing
changing
pressure in
in the
the tourniquet
cuff may
may be
warranted to
to further
be warranted
further
pressure
tourniquet cuff
reduce the
pressure and
and thereby
thereby increase
increase safety
for cercerthe mean
mean pressure
reduce
safety for
tain patients
patients at
risk of
tourniquet-induced complicaat greater
tain
greater risk
complications, e.g.,
e.g., those
who have
have thin
thin'limbs
protective
limbs with
little protective
those who
with little
tions,
musculature such
as infants,
infants, small
children, and
and certain
adults.
musculature
small children,
such as
certain adults.
Particularly
these patients
and perhaps
Particularly for
for these,
patients and
perhaps for
for others,
others, aa tourtourniquet capable
capable of
minimizing its
cuff pressure
of adaptively
niquet
adaptively minimizing
its cuff
pressure
throughout
procedure promises
promises to
to be
be safer
than one
one
throughout aa surgical
surgical procedure
safer than
which
only capable
is only
capable of
pressure.
which is
of maintaining
maintaining aa constant
constant pressure.
Because the
the patient's
patient's systolic
pressure Ps
Because
Ps can
vary throughthroughsystolic pressure
can vary
out the
out
the time
time tt of
surgical procedure
as aa function
of aa surgical
procedure as
variables
function of
of variables
such as
as changes
in anesthetic
such
anesthetic technique
or physiologic
physiologic' status,
changes in
technique or
status,
tourniquet
pressure PT
PT should
also be
be aa time-varying
should also
tourniquet pressure
time-varying function
function
in
order to
minimize the
in order
to minimize
the pressure
pressure necessary
necessary to
to maintain
maintain aa
bloodless
and (1)
be expressed
expressed as
as
bloodless field
field and
(1) should
should be
= PS (t) +
+K
PT(t) =Ps(t)
K.
PT(t)
(2)
(2)
the threshold
in (2)
Also,
should be
be set
Also, the
threshold K
K in
(2) should
set according
according to
to other
other
variables,
i.e.,
variables, i.e.,
The
patient's true
pressure Ps
Ps(t)
related to
to the
the
true systolic
The patient's
systolic pressure
(t) isis related
measured
pressure PSM(t)
PSM(t) as
determined by
by an
as determined
an indirect
measured systolic
indirect
systolic pressure
oscillometry or
Korotkoff-sound analysis
analysis in
in
method such
method
such as
as oscillometry
or Korotkoff-sound
the following
following manner:
manner:
the
(4)
.(4)
Ps(t)
1M .- PSM
PSM(t)
(t) ++ ep
(t) ==fM
Ps
ep
where
fM = fM(WM, CM, gM)
(5)
(5)
of the
the pneumatic
and
width of
pneumatic cuff
cuff used
used for
for
and where
where wM
the width
WM isis the
of
blood pressure
blood
CM isis the
the
the circumference
of
the
pressure measurement,
measurement, cM
circumference
limb, gM
the anatomy,
associated with
with the
anatomy, geometry,
geometry,
limb,
factor associated
gm isis aa factor
and shape
of the
is measured,
at which
which blood
blood pressure
pressure is
and
shape of
the limb
limb site
site at
measured,
and ep
error associated
with the
the indirect
indirect measurement
measurement
and
associated with
some error
ep isis some
technique
- [24] .
technique [20]
[201-[24].
If
set at
at (N
If tourniquet
pressure is
is set
discrete times
{tt} ,
tourniquet pressure
(N++ 1)
1) discrete
times {tj},
i = 0,
procedure rather
continuously,
than continuously,
i=
rather than
1, ...
*-* ,, N,
during aa procedure
0, 1,
N, during
then
(2) becomes
becomes
then (2)
PT(t)=PS(ti)+K+eA(t-tj)
(6)
(6)
PT(t)
=Ps(ti) + K+ eA(t - ti) titi<t~tj+l
< t 6 ti+1
where eA
eA represents
the maximum
in the
patient's
maximum increase
where
increase in
the patient's
represents the
systolic
pressure which
may have
have arisen
which may
arisen since
since the
the last
last measuresystolic pressure
ment
because of
of changes
patient's cardiovascular
cardiovascular status
status
the patient's
ment because
in the
changes in
or for
other reasons.
Combining (4)
(4) and
or
and (6)
for other
reasons. Combining
(6) yields
yields
+e
PT(t) =
1M .-PSM(ti)
PsM(tj) +
PT(t)
=fM
(7)
(7)
where
e =fT + ep + eH + es + eA(t -
ti)
(8)
(8)
for
for
i= O~ , -N.
,
ti < t<ti+
To
of short-term
in tourniquet
tourniquet
To reduce
short-term changes
the magnitude
reduce the
magnitude of
changes in
pressure as
of the
in successive
the variability
successive determidetermifunction of
pressure
as aa function
variability in
nations
,
moving
average
value
could
be
employed,
be
a
value
could
of PPSM,
nations of
moving
average
employed,
SM
e.g., aa three-point
e.g.,
three-point moving
moving average
average
PSM = 3 E PSM(ti-3+f)
j=I
(9)
(9)
could
be substituted
for PS
in (7).
substituted for
could be
PSM
(7).
M in
As
an example
the application
of (7)
As an
of the
one might
example of
application of
(7) above,
above, one
might
consider
the case
consider the
indirect determination
of blood
case where
where indirect
determination of
blood prespressure
being performed
sure isis being
on one
one upper
limb by
some system
performed on
upper limb
by some
system
the requirements
of the
the draft
draft AAMI
AAMI standards
meeting the
meeting
requirements of
standards [23][23] [24],
and where
where such
information isis used
to manually
[24], and
such information
used to
reset
manually reset
the pressure
in aa commercially
the
pressure in
tourniquet
commercially available
available pneumatic
the other
applied
to the
other upper
at intervals
of 30
applied to
upper limb
limb at
intervals of
30 min
or more.
more.
min or
In such
to 16
In
16 mmHg
such aa case,
should be
be adequate
for
case, setting
setting ep
mmHg should
adequate for
ep to
of PPSM
values of
values
within two
standard deviations
of PPs.
two standard
deviations of
Other
SM within
s . Other
typical
values are
are
typical values
IM=
fm = 11
K = eH + eS +fT(WT, CTgT)
(3)
(3)
fr== 10
10 mmHg
fT
mmHg
where
is inherent
error due
where eH
eH is
inherent error
due to
to hysteresis
the pressurehysteresis in
in the
pressure= 20mmHg
20 mmHg
regulating
the pressure-sensing
regulating mechanism,
mechanism, es
in the
the error
error in
pressure-sensing
es
es isis the
es =
means, and
and fT
is aa function
fr is
function of
of tourniquet
cuff width
limb
means,
tourniquet cuff
width wT,
WT, limb
50 mmHg
eeA(30
A (30 min)
min) == 50
mmHg
circumference
and considerations
considerations related
circumference CT,
to the
the shape
related to
and
shape and
CT, and
geometry
the limb
gT [9],
of the
and assuming
and cuff
cuff gT
geometry of
limb and
[11], [17],
[17], [18],
50 mmHg,
[18], [20].
assuming eH
only 50
(7) becomes
mmHg, (7)
becomes
(91, [11],
eH isis only
[20] . and
IEEE TRANSACTIONS
TRANSACTIONS ON
ON BIOMEDICAL
BIOMEDICAL ENGINEERING,
ENGINEERING, VOL.
VOL. BME-29,
BME-29, NO.
NO.2,
FEBRUARY 1982
1982
IEEE
2, FEBRUARY
124
124
PT(t) ==PSM(ti)
PSM(tj) ++ 146
146 mmHg
mmHg
PT(t)
. ti+
< tt"
ti+ I1
tjtj <
= 0,1
,N.
ii=O,I,···,N.
(10)
(10)
Thus, in this
this example,
example, tourniquet
tourniquet pressure
pressure should be set at
146
mmHg
above
patient's
intraoperative
systolic pressure
the
above
patient's intraoperative systolic
146
for safe
safe operation.
operation. In practice,
practice, this threshold might be much
larger, e.g., typical
typical values of 150
ISO mmHg
mmHg for eH
eH have been
be desirable
desirable in
[7]. Therefore, although it might
might be
reported [71.
lower pressures of
of as little
little as 30-75
30-75
principle to use suggested lower
[2], [3],
[3], [9],
[9],
preoperative systolic level
level [2],
mmHg above the preoperative
such suggestions with
with commonly
commonly used
used
implementation of such
hazardous_
tourniquets would be hazardous.
previously mentioned
mentioned microproThe projected use of the previously
the above
above example
example is instructive.
cessor-based tourniquet in the
adaptively set on
could be adaptively
Assuming that tourniquet pressure could
of systolic
systolic blood
blood presthe basis of automatic determinations of
I-min intervals, the equivalent values for (8)
(8)
sure made at 1-min
would be as follows:
IT== 10
lOmmHg
mmHg
fT
ep = 16
ep
16 mmHg
eH =
=6mmHg
6 mmHg
eH
es == 3 mmHg
mmHg
es
eA(1
min) == 15
IS mmHg
eA(l min)
and (7) would become
+ 50 mmHg,
PT(t) == PSM
PSM(tj)
mmHg,
(ti) +
PT(t)
ti < t < ti+ 1
i=O,I,···N,
i = 0, 1 , * N.
(11)
11
resulting in considerably lower pressure in the tourniquet
cuff.
tourniquet cuff.
For
nonstandard
employing a nonstandard
For blood pressure measurements employing
system, cuff, or anatomical location,
be a function
function
would be
location, 1M
fM would
of the variables indicated in (5) rather than a constant. Similarly, IT
variables, as
fT is generally a function of corresponding variables,
suggested by (3).
DESCRIPTION
SYSTEM
DESCRIPTION OF
OF SYSTEM
Fig. I1 shows
of the
the tourof the
the prototype of
diagram of
block diagram
shows a block
niquet which was initially developed in order to determine
determine
whether it would be possible to adaptively
tourniquet
adjust tourniquet
adaptively adjust
pressure as a function of intraoperative systolic
With
systolic pressure. With
the exception of the pressure-measuring module, printer, and
blood pressure cuff depicted in Fig. I,
1, all components are
similar to those in the prototype of the microprocessor-based
tourniquet described previously
The micromicroelsewhere [4].
[4]. The
previously elsewhere
computer employs an Intel 8085A microprocessor with 2K
byte
byte RAM and 8K byte PROM. The hardware was based on
an STD bus with card cage and PROLOG 780
7801I CPU board,
board,
PROLOG 7000 motherboard.
TTL I/O
7604 TTL
PROLOG 7604
board,
I/O board,
motherboard, PROLOG
custom analog I/O board, and power-supply
As sugpower-supply board. As
gested by Fig. I,
1, pressure in the cuff is controlled by a combination of pressure-generating
element and
and pressure-release
pressure-release
pressure-generating element
valve. The pressure-generating element is an electrical
electrical pump
with appropriate control circuitry
limit
and modifications
modifications to limit
circuitry and
the maximum pressure to 500 mmHg. Data obtained
from
obtained from
the pressure transducer/processor
in the
the regulation
regulation
used in.
transducer/processor are used
of pressure in the cuff to within ±± 6 mmHg.
The
regulation
of
of
The
regulation
mmHg.
ALPHANUMERIC
PRINTER
ADAPTIVE
ALARMS!
CONTROLS
n
:~
PERIODIC ~NON-INVASIVEI
SYSTOLIC PRESSURE
MEASUREMENT
II
II
PRESSURE
GENERATING
ELEMENT
PRESSURE
RelEASE
VALVE
t
J
't;J
:'
UFF
TOURN
UF
B
PRESSURE
TRANSOUCER!
~ROCESSOII
.1.
MEMORY
MICROPROCESSOR ~8D85A;
:
~
~
USER
USER
ALARMS!
ALARMS!
CUFF
CUFF
CONTROL
CONTROL
PANEL
PANEL
INDICATORS
INDICATORS
STATUS
STATUS
PRESSURE
t
DISPLAY
DISPLAY
12K PROM
21< RAM
t
ELAPSED
ELAPSED
E
TIME
TIM.
DISPLAY
DISPLAY
:
tourniquet.
1. Block diagram of the prototype of the adaptive tourniquet.
Fig. 1.
pressure thus
thus achieved
achieved is
is an
an order
order of
of magnitude
magnitude better
better than
than
pressure
used at
that
of pneumatic
that of
tourniquets which
which are
are widely
widely used
at present.
present.
not only
only perelement not
Use
Use of
pressure-generating element
perof an
an electrical
electrical pressure-generating
operating
also reduces
of pressure,
mits
better control
control of
mits better
pressure, but
but also
reduces operating
conventional tourcosts
eliminating the
costs by
by eliminating
the requirement
requirement of
of conventional
tourniquets for
for compressed
gas.
compressed gas.
niquets
the tourcontrol/display panel
of the
The
configuration of
The configuration
the control/display
panel of
of the
tourconThe panel
panel conFig. 2.
2. The
seen in
in Fig.
niquet
in Fig.
can be
be seen
Fig. I1 can
depicted in
niquet depicted
of cuff
cuff
period of
the period
to indicate
indicate the
tains an
an elapsed-time
display to
tains
elapsed-time display
of
variety of
to indicate
and aa variety
cuff pressure,
pressure, and
inflation,
indicate cuff
display to
inflation, aa display
as
such as
of hazardous
conditions such
hazardous conditions
audiovisual
alarms to
to warn
warn of
audiovisual alarms
of
periods of
excessive periods
underpressurization, excessive
overpressurization, underpressurization,
overpressurization,
malfunctions
internal malfunctions
lines, and
and internal
of the
the cuff
cuff lines,
kinking of
inflation, kinking
inflation,
the
also shows
shows the
of aa pressure
Fig. 22 also
transducer. Fig.
such
such as
as failur~
failure of
pressure transducer.
protoin the
the protoemployed in
alphanumeric
and the
the device
device employed
printer and
alphanumeric printer
This
type
for periodically
pressure PPSM.
measuring systolic
systolic pressure
periodically measuring
type for
SM . This
Model 845
845 nonnonpressure-measuring
was aa DINAMAP
DINAMAP Model
device was
pressure-measuring device
presestimates systolic
systolic presinvasive
invasive blood
blood pressure
monitor which
which estimates
pressure monitor
of an
Controls
an oscillometriC
[25]. Controls
sure
sure by
means of
oscillometric algorithm
algorithm [25].
by means
of
were set
set so
so that
that values
values of
on the
the pressure-measuring
device were
on
The
intervals. The
at I-min
be generated
PS
would normally
1-min intervals.
PSM
normally be
generated at
M would
DINAMAP Model
Model 950
950 printer,
which
printer, which
printer
was aa DINAMAP
employed was
printer employed
and which
which
device and
is compatible
with the
is
compatible with
connector.
can
system connector.
can accept
other serial
serial input
through aa system
input through
accept other
was fabricated
fabricated
tourniquet was
the adaptive
adaptive tourniquet
The prototype
of the
The
prototype of
and from
from
device and
from the
the conventional
from
conventional pressure-measuring
by
tourniquet by
the previously
described microprocessor-based
the
previously described
MICRO/SYS
of three
hardware. First,
First, aa MICRO/SYS
means of
three basic
changes in
in hardware.
basic changes
means
STD
the card
card cage
and STD
cage and
dual serial
serial interface
card was
was added
added to
to the
dual
interface card
from
was
removed
the
and
an
EIA-to-TTL
chip
converter chip was removed from the
bus;
bus; and an EIA-to-TTL converter
data
for
the
printer.
serial
to
levels
board to generate
compatible data levels for the printer.
generate compatible
serial board
in Fig.
as depicted
cables
and cables
auxiliary connectors
connectors and
Fig. I,1, auxiliary
depicted in
Second,
Second, as
to connect
line between
between pressurewere installed
installed to
the serial
serial line
pressureconnect the
were
the serial
board of
of the
the tourtourand printer
to the
serial board
device and
measuring
printer to
measuring device
of
softthe
development of softas well;
this change
permitted the development
niquet
well; this
change permitted
niquet as
to
in
the,
data
being
ware in the
the tourniquet
scan the, alphanumeric
alphanumeric data being
ware
tourniquet to scan
to easily
extract successive
deterto the
in order
order to
successive deterthe printer
easily extract
passed
printer in
passed to
The third
hardof the
the patient's
third hardminations
minations of
pressure. The
systolic pressure.
patient's systolic
the
of
an
extra
and
of
control
ware
consisted
of
the
provision
of
an
extra
control
and
ware change
consisted
provision
change
in
to
the
can
be
seen
operdisplay
panel,
which
can
be
seen
in
Fig.
2,
to
permit
the
operwhich
Fig. 2, permit
display panel,
EWEN AND
AND MC
FOR IMPROVED
IMPROVED SAFETY
SAFETY IN
MC
MC EWEN
MC GRAW:
GRAW: TOURNIQUET
SURGERY
IN SURGERY
TOURNIQUET FOR
125
125
(a)
(a)
300 ............ ..(.:..... .. ~~.~~~~.;;~~.~; .~~~.~~~;:~ ..;~~;~;~.~~; ... .
300
Conventional pneumatic tourniquet
(b)
(b)
(b)
~Ecm
,
t
Microprocessor-based
Microprocessor·based
~ ..,..................
"''''... ''.''''''
~ s~
~~~~~~~~~~~
(tourniquet
~
:........
.................. -:
_
tourniquet ~
200
..§.E
,,,,,,,,,.7
P ~·-·-··---T~~.~.~~:==:.
g
.~~.~~.~.~~~.~~~~~~.~~~.~~~.T~~~·~;·;~·;·~---~::...........
.......
.................
T01
T
rue systolic
True
systolic
pressure
pressure Ps
1001
Fig. 2.
2. Physical
Physical configuration
of the
the prototype
of the
configuration of
Fig.
the adaptive
prototype of
adaptive tournitourniin which
which the
quet in
the printer,
noninvasive pressure-measuring
printer, noninvasive
quet
pressure-measuring module,
and
module, and
as well
well as
cuff, as
as microprocessor-based
and cuff,
cuff,
can be
be seen.
tourniquet and
cuff, can
seen.
ator
to select
select either
either an adaptive
adaptive pressure or a constant pressure
at
or to
for the
the tourniquet.
tourniquet.
for
Following hardware
hardware modifications,
to existing
modifications, changes
changes to
Following
softexisting software were
were made
made to
to permit
it to
to function
of an adaptive
permit it
adaptive
function as part of
prototype
in the
the following
As part of
of the
following manner. As
prototype in
preoperative
the preoperative
preparation
of a patient,
the pneumatic
preparation of
patient, the
pressure·
pneumatic cuff
cuff for
for the
the pressuremeasuring device
device and
and the
the tourniquet
measuring
tourniquet cuff
cuff are applied
the
applied to the
patient,
in Fig.
The pressure-measuring
illustrated in
Fig. 2.
patient, as illustrated
2. The
pressure-measuring module
module
and printer
then activated,
and the
activated, and
and
printer are then
the printer
printer is
is checked
checked to
that reasonable
reasonable measurements
of systolic
assure that
measurements of
systolic pressure are
being
induction of
Following induction
being generated.
generated. Following
of anesthesia
anesthesia and
and exsanguination of
of the
limb for
for surgery, the
guination
the limb
the tourniquet
activated in
in
tourniquet isis activated
the "constant
state. The
the
"constant pressure"
pressure" state.
The tourniquet
tourniquet can then
be
then be
changed
changed to an adaptive
adaptive state when
when desired
desired by
by momentarily
momentarily
the
depressing
switch (see
appropriate switch
depressing the appropriate
Fig. 2).
LED indicators
indicators
(see Fig.
2). LED
display
display the
the current state. In
In the
the adaptive
adaptive state,
state, values
values of
of PSM
PSM
are normally
1-min intervals
normally obtained
obtained at
at I-min
intervals by
by analyzing
analyzing the
the
character
character string
string generated
generated by
by the
pressure-measuring module.
module.
In
In the
the presence of
of excessive
excessive artifact
artifact or other
other problems,
problems, the
the
generation
generation of
of values
values of
of PSM
PSM is
is automatically
automatically suspended
suspended by
by
the
module and
and the
the previously
previously obtained
obtained
value
value is
is substituted
substituted by
by the
the tourniquet.
tourniquet. Successive
Successive values
values of
=
i
which
are
PSM(ti),
=
0,
1,
...
,N,
thus
obtained
are
checked
PsM(ti),
* **,N.
for
for compliance
compliance with
with the
the following
following three
three criteria:
criteria:
80
160;
80 <PSM(t,)
<PsM(tD <
< 160;
At
< 33 min
tlt.;;;;
min
for
for successive
successive estimates
estimates
PSM(ti - At),
~t),
PsM(ti
and
and
-
PsM(tD;
PsM(td);
IPSM(t)- PSM(ti- At)I < 32 mmHg.
Failure
Failure to
to satisfy
satisfy the
the first
first of
of the
the above-noted
above-noted criteria
criteria indicates
indicates
that
that the
the patient's
patient's systolic
systolic pressure falls
falls outside
outside generally
generally acac·
cepted
cepted limits,
limits, and
and therapeutic
therapeutic action
action may be
be required.
required. Failure
Failure
to
to satisfy
satisfy the
the second
second criterion
criterion may indicate
indicate the
the presence of
of
excessive
excessive artifact
artifact or other
other problems
problems requiring
requiring operator interinter·
vention.
vention. Failure
Failure to
to satisfy
satisfy the
the third
third criterion
criterion indicates
indicates aa flucfluc·
(c)
~~~~~~~~(c)
Adaptive
Adaptive tourn
iquet
tourniquet
Ps
O,L---~~---72-----3~--~4----~5--~~
3
4
5
Time {min}
Time
(min)
Fig.
cuff for
for a
Fig. 3.
3. Comparative
Comparative tourniquet
tourniquet pressures PT
in upper·limb
PT in
upper-limb cuff
(a) conpatient
with rapidly
patient with
rapidly fluctuating
fluctuating systolic
systolic pressure Ps
for (a)
(t) for
PS (t)
ventional pneumatic
pneumatic device
device with
300 mrnHg,
with PT
venitional
mmHg, (b) micromicroPT set at 300
PT set at approximately
approximately 80
processor-based device
with PT
processor-based
device with
80 mmHg above
the
and (c) adaptive
the patient's
systolic level
level (see
(see text),
text), and
adaptive
described in
the example
example given
the text.
device with
with PT
device
in the
in the
PT set as described
text.
given in
Note that
that the
the adaptive
adaptive tourniquet
Note
tourniquet in
in this case would achieve the
the
maintaining a safe
lowest
while still
lowest mean cuff
cuff pressure while
still maintaining
safe margin beintraoperative systolic
pressure.
tween cuff
cuff pressure and
and intraoperative
systolic pressure.
1
2
tuating
systolic pressure
tuating systolic
pressure which
which again
may require
require operator
again may
intervention.
intervention. In
In the
the event
that one
one or
or more
more of
of these
these criteria
event that
are
satisfied, the
are not
not satisfied,
the prototype
prototype is
is programmed
programmed to
to revert
revert from
an
adaptive state
state to
to aa constant-pressure
state, at
an adaptive
constant-pressure state,
the initially
at the
set
while simultaneously
set pressure,
pressure, while
simultaneously activating
activating an
an audiovisual
alarm
alarm to
to indicate
the change
change of
of states.
The alarm
alarm can
can be
be supsup·
indicate the
states. The
pressed
pressed by
by momentarily
momentarily depressing
depressing an
an "alarms
"alarms reset"
reset" switch
on
tourniquet (see
2) which
on the
the tourniquet
(see Fig.
Fig. 2)
which will
will leave
leave the
the device
device in
aa constant-pressure
constant-pressure state;
state; the
the operator
operator can
can change
change back
back to
to the
adaptive
state by
adaptive state
by activating
activating the
the appropriate
appropriate switch
switch after
after any
remedial
remedial action
action has
has been
been taken.
taken. In
In the
the event
event that
that successive
values
values of
of PSM
PSM satisfy
satisfy all
all of
of the
the above-noted
above·noted criteria,
criteria, pressure
in
in the
the tourniquet
tourniquet cuff
cuff is
is adaptively
adaptively changed
changed by
by the
the prototype
in
in accordance
accordance with
with (7),
(7), (8),
(8), and
and (9),
(9), assuming
assuming standard
standard blood
pressure
pressure and
and tourniquet
tourniquet cuffs
cuffs are
are employed
employed on
on opposite
opposite upper
upper
limbs.
lower-limb surgery,
limbs. For
For cases
cases of
oflower-limb
surgery, or
or for
for other
other cases
cases such
as
as those
those involving
involving use
use of
of nonstandard
nonstandard cuffs
cuffs as
as described
described below,
the
1M and
and fT
IT specified
specified approappro·
the same
same equations
equations can
can be
be used
used with
with fM
as functions
functions of
of their
their variables.
variables.
priately as
priately
Fig.
Fig. 33 illustrates
illustrates comparative
comparative cuff
cuff pressures
pressures arising
arising from
from the
use
of aa conventional
conventional pneumatic
tourniquet set
set at
at aa traditional
use of
level,
level, the
the microprocessor-based
microprocessor-based device
device set
set at
at aa constant
constant prespres·
sure
of the
the patient's
sure based
based on
on aa determination
determination of
systolic
systolic pressure,
pressure, and
and the
microprocessor-based device
device in
in an
an
adaptive
adaptive mode.
mode. According
According to
to common
common practice,
practice, the
the convenconven·
tional
tional tourniquet
tourniquet would
would be
be set
set at
at approximately
approximately 300
300 mmHg
mmHg
for
for upper-limb
upper·limb surgery;
surgery; this
this value
value is
is roughly
roughly consistent
consistent with
with
the
the level
level suggested
suggested by
by the
the nominal
nominal values
values given
given in
in the
the example
example
above
above which
which led
led to
to (10).
(10). In
In aa constant-pressure
constant·pressure state
state the
tourniquet could
could safely
safely be
be set
set at
at approxapproximately
imately 80
80 mmHg
mmHg above
above the
the preoperative
systolic level,
level, as
as sugsuggested
gested in
in the
the literature
literature (e.g.,
(e.g., [21,
[2], [9])
[9]) and
and by
by the
the nominal
126
126
BIOMEDICAL ENGINEERING,
ENGINEERING, VOL.
VOL. BME-29,
BME-29, NO.
NO.2,
FEijRUARY 1982
1982
IEEE TRANSACTIONS ON BIOMEDICAL
2, FEBRUARY
values
to (II),
that intraoperative
systolic
values which
which led
led to
(11), assuming
assuming that
45 mmHg
pressure would
would not
increase by
by more
than 45
not increase
more than
mmHg throughthroughpressure
out the
touran adaptive
state the
the tourIn contrast,
in an
the procedure.
contrast, in
adaptive state
out
procedure. In
of approximately
niquet
threshold of
approximately 50
50
constant threshold
niquet maintains
maintains aa constant
The
mmHg
periodically measured
pressure. The
measured systolic
systolic pressure.
mmHg above
above periodically
result is
is aa mean
mean tourniquet
tourniquet pressure
pressure which
which is
is significantly
significantly
result
lower than
than in
two cases.
cases. It
It should
be noted
noted from
from
in the
other two
should be
lower
the other
Fig. 33 that
that the
the adaptive
tourniquet is
is capable
maintaining an
capable of
of maintaining
an
Fig.
adaptive tourniquet
adequate margin
margin of
rapid and
and signifiof safety
despite relatively
relatively rapid
signifiadequate
safety despite
cant increases
increases in
systolic pressure.
pressure. Thus,
the results
results of
of initial
initial
in systolic
cant
Thus, the
of
lab tests
tests indicate
that the
the adaptive
adaptive tourniquet
tourniquet is
is capable
capable of
lab
indicate that
maintaining intraoperatively
intraoperatively aa cuff
cuff pressure
pressure close
the minito the
miniclose to
maintaining
for
to assure
assure aa bloodless
bloodless field
field for
mum safe
pressure necessary
mum
safe pressure
necessary to
surgery.
surgery.
DUAL-FUNCTION CUFF
CUFF
DUAL-FUNCTION
A
modules for
for periodically
determinA number
number of
noninvasive modules
periodically determinof noninvasive
various algorithms
algorithms could
be
ing systolic
pressure by
by means
of'various
could be
ing
systolic pressure
means of
employed
in
the
prototype.
This
is
because
in
a
configuration
employed in the prototype. This is because in a configuration
Figs. 11 and
systolic pressure
such as
as the
the one
one illustrated
and 2,
2, systolic
pressure is
is
such
illustrated in
in Figs.
of
a
separate
cuff
applied
to
an
measured
through
the
use
of
a
separate
cuff
applied
to
an
measured through the use
upper limb
limb not
not involved
involved in
in the
the surgical
procedure, i.e.,
surgical procedure,
i.e., tourtour-upper
are applied
separate
niquet
cuff and
pressure cuffs
cuffs are
applied to
to separate
niquet cuff
and blood
blood pressure
one dual-function
dual-function
linibs.
would be
be preferable
preferable to
to employ
employ one
limbs. It
It 'would
cuff
both purposes:
purposes: for
for example,
upper (proximal)
for both
an upper
cuff for
example, an
(proximal)
segment of
cuff could
could be
be employed
of such
such aa cuff
employed for
for measuring
measuring syssyssegment
tolic pressure
pressure periodically
periodically and'a
and a lower
could
lower (distal)
(distal) segment
segment could
tolic
be
be maintained
maintained at
pressure. The
The use
use of
one dualdualat aa suprasystolic
of one
suprasystolic pressure.
function
cuff in
conjunction with
with the
the adaptjve
in conjunction
function cuff
adaptive tourniquet
tourniquet
might
reasons, e.g.,
be desirable
for aa variety
of reasons,
variety of
e.g., occlusive
occlusive cuffs
cuffs
might be
desirable for
on
upper limbs
affect intravenous
on both
both upper
limbs might
intravenous administration
administration
might affect
of fluids
medications [25].
A separate
blood pressure
pressure
of
and medications
fluids and
[25]. A
separate blood
to aa lower
cuff coqld
be applied
involved with
the
cuff
lower limb
limb not
not involved
with the
could be
applied to
of two
two cuffs
cuffs would
be
surgical procedure,
procedure, but
but application
application of
would still
still be
surgical
and physically
obstructive.
more
cumbersome, and
more labor-intensive,
labor-intensive, cumbersome,
physically obstructive.
The
development of
of aa combined
combined dual-purpose
dual-purpose cuff,
however,
The development
cuff, however,
is
clearly
dependent
upon
the
use
in
the
aqaptive
tourniquet
the
in
the
use
adaptive
tourniquet
is clearly dependent upon
of
of aa noninvasive
module employing
an
employing an
noninvasive pressure-measuring
algorithm capable
capable of
of accurately
accurately measuring
measuring pressure
pressure with
with greatly
greatly
algorithm
reduced blood
blood flow
flow at
measurement site.
at the
the measurement
site.
reduced
of systolic
pressure
Published data
data indicate
that measurement
measurement of
systolic pressure
Published
indicate that
under such
using aa manual
conditions using
manual sphygmomanometric
under
such conditions
sphygmomanometric
technique based
based on
on K-sound
K~sound analysis
analysis is
possible [21],
is possible
[21], [26].
[26].
technique
However, it
it was
was anticipated
the outset
outset that
that automatic
automatic meameaat the
However,
anticipated at
surement under
under such
such conditions
conditions might
less accurate
accurate and
and
be less
surement
might be
less reliable
with an
algorithm based
based on
K-sound analysis
analysis than
than
an algorithm
on K-sound
less
reliable with
on oscillometry,
with an
an algOrithm
based on
oscillometry, primarily
primarily because
because it
it
with
algorithm based
be more
was thought
thought that
algorithms would
would be
more depenwas
that K-sound
depenK-sound algorithms
on flow-related
dent
than oscillometric
dent than
oscillometric algorithms
flow-related phenomena
phenomena
algorithms on
[21],
To initially
initially test
test this
this hypothesis,
an experiment
hypothesis, an
experiment
[21], [25].
[25]. To
was conducted
with the
the configuration
co~figuration of
devices illustrated
illustrated in
in
was
conducted with
of devices
to aa Vitastat
Vitastat Model
was first
connected to
Model
Fig.
4. Each
subject was
first connected
Fig. 4.
Each subject
monitor with
900-S blood
blood pressure
pressure monitor
with the
the cuff
cuff located
located proximally
proximally
900-S
on an
upper limb;
the
Vitastat
Model
900-S
normally
measures
on
an upper
the
Model
900-S normally measures
limb; Vitastat
an
of
blood
based
on
an
algorithm
based
on
analysis
of
K-sounds,
analysis K-sounds,
blood pressure
pressure by
by
algorithm
but
second algorithm
but automatically
to aa second
based on
switches to
on
algorithm based
automatically switches
oscillometry if
microphone in
deliberately deacif aa microphone
in the
the cuff
cuff isis deliberately
deacoscillometry
tivated. As
by Fig.
Fig. 4,
4, aa standard
Kidde pneumatic
pneumatic
tivated.
As suggested
standard Kidde
suggested by
'7) /'
TOURNIQUET
CUFF
4. Configuration
employed for
for obtaining
comparative estimates
estimates
obtaining comparative
Fig. 4.
Configuration employed
by oscillometry
-sound analysis
analysis with
blood
with blood
of systolic pressure by
oscillometry and
and K
K-sound
flow greatly
reduced by
by means
of aa distal
to
cuff inflated
inflated to
flow
means of
distal tourniquet
tourniquet cuff
greatly reduced
aa suprasystolic
suprasystolic pressure (see
(see text).
text).
tourniquet cuff
with aneroid
aneroid gauge
gauge and
bulb was
was then
then conand bulb
contourniquet
cuff with
to
nected
to the
the same
limb of
distal to
of the
the subject,
subject, immediately
immediately distal
nected to
same limb
845 blood
the blood-pressure
blood-pressure cuff.
A Dinamap
Dinamap Model
Model 845
blood pressure
pressure
the
cuff. A
monitor
the other
other upper
upper limb
in order
order
to the
limb in
monitor was
was then
then connected
connected to
to
obtain reference
pressure by
by oscillometry.
of systolic
values of
systolic pressure
oscillometry.
to obtain
reference values
In
the experiment,
both pressure-measuring
pressure-measuring devices
devices were
were actiactiIn the
experiment, both
to
obtain
at
'I-min
intervals
to
obtain
comparable
vated
Simultaneously
at
intervals
comparable
vated simultaneously 1-min
estimates of
of systolic
pressure. By
By successively
activating and
and
successively activating
estimates
systolic pressure.
deactivating
the
Vitastat
microphone
during
this
period,
this
Vitastat
the
microphone during
period,
deactivating
alternating measurements
measurements based
based on
oscillometry and
and K-sound
K-sound
on oscillometry
alternating
for comparison
analysis
were obtained
obtained from
one limb
limb for
comparison with
with
from one
analysis were
tourniThe
other
limb.
oscillometric
measurements
from
the
other
limb.
The
tournifrom
the
oscillometric measurements
quet cuff
cuff was
then quickly
pressure
to aa suprasystolic
inflated to
was then
suprasystolic pressure
quet
quickly inflated
of
(approximately
250
mmHg)
and
measurements
of
systolic
measurements
and
systolic
(approximately 250 mmHg)
for
another
pressure
continued
in
the
same
manner
for
another
44 min.
the
manner
min.
in
same
pressure continued
The
cuffs
were
then
switched
to
corresponding
positions
to
on
The cuffs were then switched corresponding positions on
The
opposite
limbs
and
the
same
experiment
was
repeated.
The
was
same
experiment
repeated.
opposite limbs and the
results
the first
first six
are given
Table I.
in Table
I.
tested are
six subjects
given in
results from
from the
subjects tested
The
results
show
that
in
all
six
subjects
either
an
oscillometric
either
an
oscillometric
The results show that in all six subjects
to meameaalgorithm or
algorithm could
could be
be employed
K-sound algorithm
or aa K-sound
employed to
algorithm
sure
systolic
pressure
at
the
measurement
site,
despite
greatly
sure systolic pressure at the measurement site, despite greatly
reduced
blood flow
at the
due to
an inflated
inflated tourniquet
to an
the site
site due
tourniquet
reduced blood
flow at
and experimental
cuff. Table
also indicates
indicates for
for each
each subject
cuff.'
Table II also
subject and
experimental
simultaneous
condition the
difference between
between simultaneous
the maximum
condition
maximum difference
at the
limb and
measurement
pressure on
on the
the test
test limb
and at
the
of systolic
measurement of
systolic pressure
reference
The results
in Table
Table II emphasize
emphasize
reference site.
site. The
results summarized
summarized in
of systolic
systolic pressure
the
variation in
in indirect
indirect measurements
measurements of
the variation
pressure
which can
be anticipated
anticipated when
measuring over
periods
over short
short periods
which
can be
when measuring
at
at the
when measuring
measuring simultaneously
on opposite
opposite
the same
same site,
simultaneously on
site, when
limbs, or
or when
when measuring
measuring with
with devices
devices employing
employing different
different
limbs,
algorithms
or even
implementations of
of the
the same
even different
different implementations
same
algorithms or
algorithm. In
these respects,
of the
initial experiIn these
the results
results of
the initial
experialgorithm.
respects, the
ment tended
tended to
with previous
previous findings
findings of
others arising
ment
to agree
of others
arising
agree with
from extensive
extensive studies,
e.g., [21],
blood prespresA blood
from
[24], [25].
[25]. A
studies, e.g.,
[21], [24],
sure
employing an
algorithm (see
(see Fig.
an oscillometric
monitor employing
oscillometric algorithm
Fig. 2)
2)
sure monitor
the prototype
was
for incorporation
an adaptive
adaptive
was chosen
incorporation into
into the
prototype of
of an
chosen for
because
tourniquet
intended for
dual-function cuff
cuff because
tourniquet intended
for use
use with
with aa dual-function
module for
for this
has
. die
use of
of an
oscillometric module
this application
application has
the use
an oscillometric
the
it eliminates
for aa microphone
need for
microphone in
eliminates the
the advantage
advantage that
that it
the need
in
the precision
the
reduces the
precision required
required in
in
the dual-function
dual-function cuff,
cuff, itit reduces
it may
positioning the
the cuff
cuff on
on the
the limb,
limb, and
and it
may permit
permit measuremeasurepositioning
in situations
ments of
pressure to
pe made
made in
of systolic
to be
situations where
ments
where
systolic pressure
measurement
by K-sound
K-sound analysis
be difficult.
measurement by
would be
difficult. Although
Although
analysis would
aa discrete
discrete commercially
available oscillometric
oscillometric device
was
device was
employed
initially, an
module or
module based
based
an oscillometric
or aa module
oscillometric module
employed initially,
on
the
on aa K-sound
K-sound algorithm
algorithm could
clearly be
be incorporated
into the
could clearly
incorporated into
prototype of
of adaptive
in the
the future
future if
if warranted.
warranted.
prototype
adaptive tourniquet
tourniquet in
127
127
EWEN AND
AND MC
MC GRAW:
GRAW: TOURNIQUET
FOR IMPROVED
IMPROVED SAFETY
SAFETY IN
IN SURGERY
SURGERY
MC
MC EWEN
TOURNIQUET FOR
TABLE II
TABLE
MEAN SYSTOLIC
SYSTOLIC PRESSURES
LIMB
MEAN
PRESSURES OBTAINED
OBTAINED SIMULTANEOUSLY
FROM AA TEST
TEST LIMB
SIMULTANEOUSLY FROM
AND A REFERENCE
REFERENCE LIMB,
AND
LIMB, BEFORE
BEFORE AND
AND AFTER
INFLATION OF
OF AA TOURNIQUET
AFTER INFLATION
TOURNIQUET
ON THB
THE TEST
CuFF
CUFF ON
TEST LIMB.
LIMB. RESULTS
ARE GIVEN
GIVEN FOR
FOR SIX
SIX SUBJBCTS
AND FOR
FOR
RESULTS ARB
SUBJECTS AND
CoNTRALATERAL
CONTRALATERAL UPPBR
UPPER LIMBS
LIMBS FOR
LIMBS SUCCBSSIVELY
SUCCESSIVELY SERVING
SERVING AS
TEST LIMBS
AS TBST
FOR
EACH SUBJECT.
EACH
SUBJECT. SBB
SEE TEXT
EXPLANATION
TEXT FOR
FOR FuIlTHBR
FURTHER EXPLANATION
A
PRE-INFLAT ION
PRE-INFLATION
POST-INFLATION
POST-INFLATION
Mean Pressures
Pressures (mmHg)
(mmHg)
Mean
5liljectl
renee Li
rrb :
Reference Lirrb:
iMaximLlll
Test limb:
Test Lirrb:
Limb: )Reference
Test Limb: Refe
Reference
Linb: Test
Litb: Maximum
Subject/ Test
Subject/ Test Limb: Test
Linb:
Sliljectl
Tes
ci 11 ome try
Testt Lirrb
K-Sounds Oscillometry
K-Sounds Oscillometry
DifferenceTest Lirrb
Linb K-50unds
Limb K-Sounds
Oscillometry Osci
Test
Oscillowetry
11 ome try
Oi
fferenceOscillometry Os
Oscillometry
Simul
taneousI
5i
multaneous
Msmts
Msmts
I
I"ean
Mean Pressure (mrrI-Ig).
(mmHg)
I
I
I
I1
Maximum
Maximum
Oiffe
renceDifferenceSimu1
Simul taneous
taneous
Msmts
Msmts
J/Left
J/Left
134
134
140
)40
139
139
-8
-8
J/Left
J/Left
117
117
130
130
132
132
-20
-20
J/Right
J/Right
129
129
1 34
134
1 45
145
-17
-17
J/Right
/JRight
III
111
138
138
136
136
-23
-23
R/Left
R/Left
136
136
133
133
139
139
-99
R/Left
R/Left
144
144
129
129
139
139
-11
R/Right
R/Right
146
146
123
123
140
140
-23
-23
R/Right
R/Right
146
146
129
129
140
140
-15
W/Left
W/Left
136
136
138
138
1~/Left
130
130
137
137
-11
-11
141
141
-14
-14
W/Left
WI
Ri ght
W/ Right
131
131
136
136
141
141
1 144
144
-13
-13
W/ Right
W/Right
136
1-36
137
137
138
138
+9
+9
K/Left
KlLeft
105
105
103
103
119
119
-23
-23
K/Left
K/Left
112
112
102
102
114
114
-13
-13
K/Right
K/Right
102
102
109
109
116
116
-16
-16
KlRight
K/Right
110
110
102
102
115
115
-16
-16
E/Left
E/Left
110
110
127
127
138
138
-29
-29
E/Left
E/Left
108
108
124
124
134
134
-29
-29
E/Right
E/Right
133
133
124
124
1~
130
-12
-12
E/RiQht
E/Ricght
141
141
130
130
126
126
+22
!
I
M/Left
M/Left
127
127
131
131
136
136
-16
-16
M/Left
M/Left
130
130
120
120
1 30
130
-18
-18
M/Right
M/Right
118
118
131
131
126
126
-11
-11
H/RiQht
M/Right
132
132
118
118
125
125
+8
For an
an initial
initial assessment
assessment of
of the
the feasibility
feasibility of
of aa dual-function
For
dual-function
cuff, aa' commercially
available two-chamber
two-chamber tourniquet
cuff,
tourniquet cuff
cuff
(Zimmer Inflatomatic
Inflatomatic Dual
Dual Cuff)
Cuff) normally
normally used
used for
for intrave(Zimmer
intravenous regional
regional anesthesia
anesthesia was
was connected
connected to
to the
the adaptive
adaptive tourntournnous
niquet. This
This cuff
cuff functioned
functioned satisfactorily
satisfactorily in
in lab
the
niquet.
lab tests,
tests, with
with the
proximal
section employed
employed for
determinations of
of
proximal section
for periodic
periodic determinations
systolic
and the
section maintained
systolic pressure
pressure and
the distal
distal section
at suprasysmaintained at
suprasystolic
As expected,
expected, values
of systolic
systolic pressure
tolic pressure.
pressure. As
values of
deterpressure determined in
this manner
high in
comparison to
mined
in this
manner were
were high
in comparison
to simultaneous
simultaneous
determinations
on the
the contralateral
determinations on
contralateral limb,
limb, likely
to the
the
due to
likely due
fact
fact that
that the
the cuff
cuff was
was much
much narrower
narrower than
than conventional
conventional blood
blood
pressure
pressure cuffs
cuffs and
and was
was of
of nonstandard
nonstandard design
design [20],
[20], [23].
On
[231. On
the
of aa dual-function
the basis
basis of
of these
these initial
initial results,
results, samples
samples of
dual-function
cuff
cuff specifically
specifically intended
intended for
for evaluation
evaluation with
with the
the prototype
prototype
have
have been
been fabricated
fabricated by
by aa manufacturer
manufacturer of
of conventional
conventional tournitourniquet
quet cuffs.
cuffs. The
The proximal
proximal (upper)
(upper) section
section of
ofth~
dual-function
the dual-function
cuff
cuff has
has dual
dual ports
ports for
for connection
connection to
to the
pressure-measuring
module
module of
of the
the adaptive
tourniquet, but
but has
has aa narrower
narrower width
width
and
and other
other physical
physical differences
differences which
which necessitate
necessitate that
that 1M
in
fM in
(4)
be specified.
specified. The
The distal
distal (lower)
(lower) section
section of
of the
the cuff
cuff also
also has
has
(4) be
dual
dual ports
ports for
for connection
connection to
to the
the pressure-controlling
pressure-controlling portion
portion
of
I), so
of the
the tourniquet
tourniquet (see
(see Fig.
Fig. 1),
so that
that it
it can
can be
be adaptively
adaptively
inflated
inflated to
to the
the minimum
minimum pressure
pressure necessary
necessary to
to maintain
maintain aa
bloodless
bloodless field.
field. As
As with
with the
pressure-measuring section,
section, the
the
width
width and
and other
other physical
physical characteristics
characteristics of
of the
the pressure-control
pressure-control
section
section of
of the
the cuff
cuff have
have been
been changed,
changed, necessitating
necessitating aa deterdetermination
mination of
offT
h for
for use
use in
in (8).
(8). The
The primary
primary reason
reason for
for reducing
reducing
the
the width
width of
of both
both sections
sections in
in relation
relation to
to conventional
conventional cuffs
cuffs
was
to minimize
was to
minimize surgical
surgical obstruction.
obstruction. An
An evaluation
evaluation of
of these
these
new
new dual-function
dual-function cuffs
cuffs must
must be
be made
made to
to determine
determine their
their
reliability
reliability and
and define
define fM
1M and
and fT
h prior
prior to
to employing
employing them
them in
in
clinical
clinical trials.
trials. If
If the
the results
results of
of the
the trials
trials of
of these
these cuffs
cuffs are
are
promising, other
other sizes
sizes and
and shapes
of dual-function
cuffs will
dual-function cuffs
promising,
will
shapes of
be
be fabricated
for evaluation
on upper
and lower
lower limbs
limbs having
evaluation on
fabricated for
upper and
having
aa variety
of shapes
and sizes.
variety of
sizes.
shapes and
DISCUSSION
DISCUSSION
Further
work is
being carried
out in connection with
Further work
is being
carried out
with the
the
development and
and clinical
clinical evaluation
evaluation of
of the prototype of
of the
development
adaptive tourniquet
and various
cuffs such
the dual-function
various cuffs
such as the
adaptive
tourniquet and
dual-function
cuff
cuff described
described above.
above. Following
of a technical
Following completion of
evaluation of
of the
adaptive prototype and
and cuffs
cuffs by
by biomedical
the adaptive
evaluation
staff to assure that they perform to expectations,
engineering staff
much as possible
possible with
with pertinent standards,
standards,
that they
they comply
comply as much
that
and that an adequate level of reliability
reliability has been achieved, a
clinical evaluation
evaluation will
will be
be completed.
completed. In the clinical evaluation
clinical
as
as in
in past
past clinical
clinical trials
trials of
of the
microprocessor-based tourniquet,
tourniquet,
the
the prototype
prototype will only
only be
be used
used with
with aa biomedical
biomedical engineer in
constant attendance
attendance and
and with
with aa conventional tourniquet
constant
available immediately
immediately as
as backup
backup in
in the
the event of unforeseen
available
problems.
problems. Other
Other work
work will
will be
be carried
carried out
out to
to determine
determine whether
whether
or
fM in
or not
not fT
IT and
and 1M
in (3)
(3) and
and (5)
(5) can
can be
be set
set automatically
automatically and
and
whether
whether or
or not
not changes
changes should
should be
be made
made to
to the
the adaptive
adaptive softsoftware
ware to
to accommodate
accommodate lower-limb
lower-limb surgery
surgery with
with and
and without
without
dual-function
dual-function cuffs.
cuffs. Also,
Also, if
if the
the results
results of
pf the
the initial
initial clinical
clinical
evaluation
evaluation are
are promising,
promising, the
the hardware
hardware and
and software
software will
will be
be
revised
revised and
and an
an oscillometric
oscillometric pressure-measuring
module may
be
be physically
physically incorporated
incorporated into
into the
the prototype
prototype so
so that
that it
it can
be
of surgical
surgical procedures
be clinically
clinically evaluated
evaluated in
in aa wide
wide variety
variety of
over an
an extended
extended period.
period.
over
The
of the
the current generation of
The widely
widely recognized
recognized inability
inability of
tourniquets to
to control
control pressure
pressure with adequate
pneumatic
accuracy, reliability,
reliability, and
and stability
stability has
has clearly
clearly been associated
accuracy,
with
of tourniquet-related
tourniquet-related injuries,
injuries, incidents,
incidents,
with continuing
continuing reports
reports of
128
128
IEEE
NO.2,
IEEE TRANSACTIONS
TRANSACTIONS ON
ON BIOMEDICAL ENGINEERING, VOL.
VOL. BME-29, NO.
2, FEBRUARY 1982
and hazards.
and operating
the labor-intensiveness
and
hazards. Moreover,
Moreover, the
pneumatic
with the
the use
use of
of current
current types
of pneumatic
costs associated
associated with
types of
tourniquets have
have significant
cost implications
for hospitals.
tourniquets
significant cost
implications for
hospitals.
To
extent the
of aa microprocessor-based
microprocessor-based tournitourniTo aa large
the advent
advent of
large extent
quet
capable of
safely and
and accurately
of safely
desired
quet capable
accurately maintaining
maintaining aa desired
pressure and
performing other
and capable
of simultaneously
other
pressure
capable of
simultaneously performing
functions
of alarm
has reduced
reduced
functions such
such as
as detection
detection of
alarm conditions
conditions has
these hazards
hazards and
and operating-cost
operating-cost implications.
implications. Furthermore,
these
Furthermore,
the availability
of aa microprocessor-based
has
the
availability of
microprocessor-based tourniquet has
facilitated
the development
of an
an adaptive
adaptive tourniquet in
which
in which
facilitated the
development of
the pressure
pressure in
changed throughout
throughout aa
the
in the
the tourniquet
tourniquet cuff
cuff isis changed
as aa function
of the
patient's changing
surgical procedure
procedure as
function of
the patient's
surgical
changing
pressure, thus
thus approximately
apprOximately the
the
intraoperative
systolic pressure,
minimum safe
pressure necessary
necessary to
to maintain
bloodless field
minimum
safe pressure
maintain aa bloodless
field
for
surgery. While
use of
for surgery.
While the
the use
of an
an adaptive
rather
tourniquet, rather
than
just aa microprocessor-based
set at
than just
at aa constant
tourniquet set
constant
pressure may
be necessary
in most
promises to
not be
most cases,
to
pressure
may not
necessary in
cases, itit promises
have
value in
procedures and
in certain
and for
for
have significant
significant value
certain surgical
surgical procedures
patients who
be at
who may
at greater
risk of
patients
may be
greater risk
tourniquet-induced
complications,
e.g., patients
patients with
protective musculature.
musculature.
with little
little protective
complications, e.g.,
The
tourniqliet may
permit aa safer
pressure to
also permit
to
The adaptive
safer pressure
adaptive tourniquet
may also
be employed
hypertrophied limbs
(having aa suboptimal
with hypertrophied
limbs (having
be
employed with
suboptimal
ratio
width to
if appropriate
appropriate values
values of
ratio of
of cuff
cuff width
to circumference)
of
circumference) if
fr
and 1M
be determined
determined automatically
entered manually
fM can be
automatically or entered
manually
fT and
for such
such patients.
patients. Also,
Also, the
lower average
pressures possible
possible
for
the lower
average pressures
through the
use of
an adaptive
permit the
of an
the
the use
through
adaptive tourniquet
tourniquet may
may permit
evolution
of longer
evolution of
of surgical
duration without
without
surgical techniques
techniques of
longer duration
increase in
risk of
in the
the risk
aa concomitant
concomitant increase
comtourniquet-induced complications. Finally,
Finally, despite
the increased
increased complexity
of the
the
plications.
despite the
complexity of
adaptive
that the
between
estimated that
the difference
difference between
tourniquet, itit isis estimated
of the
the adaptive
adaptive device
the projected
the
projected capital
capital cost
cost of
device and
and aa comcommonly used
used type
of pneumatic
may be
be offset
after
offset after
monly
type of
tourniquet may
two years
years of
reduced operating
costs
two
of normal
normal usage
due to
to reduced
usage due
operating costs
arising
from elimination
need for
gas and
and
elimination of
of the
the need
for compressed
arising from
compressed gas
reduced labor-intensiveness.
reduced
labor-intensiveness.
Klenerman, "Tourniquet
~'Tourniquet time-How
long?" Hand,
Hand, vol.
vol. 12,
pp.
[9) L.
L. Klenerman,
time-How long?"
12, pp.
[9]
231-234,1980.
231-234,1980.
[10) S.
Weingarden, D.
D. L.
Louis, and
and G.
W. Waylonis,
Waylonis, "Electromyo"ElectromyoL. Louis,
S. I.I. Weingarden,
G. W.
[10]
matic
1248matic tourniquet,"
tourniquet," J.
J. Amer.
A mer. Med.
Med. Ass.,
Ass., voL
vol. 241,
241, pp.
pp. 1248-
1250,
1979.
1250,1979.
[11)
H. Rorabeck
Rorabeck and
and J.
J. C.
C. Kennedy,
Kennedy, "Tourniquet-induced
"Tourniquet-induced nerve
nerve
[11] C.
C. H.
ischemia complicating
knee ligament
ligament surgery,"
surgery," Amer. J. Sports
ischemia
complicating knee
Med., vol.
vol. 8,
8, pp. 98-102,
1980.
98-102,1980.
Med.,
H. Rorabeck,
Rorabeck, "Tourniquet-induced
"Tourniquet-induced nerve
nerve ischemia:
ischemia: An
An experiexperi[12)
C. H.
[12] C.
vol. 20,
20, pp.
pp. 280-286,
280-286, 1980.
mental investigation,"
mental
investigation," J.
J. Trauma,
1980.
Trauma, vol.
B. Jarem,
Jarem, "Pneumatic
"Pneumatic tourniquets,"
tourniquets," AnesAnes[13)
H. Flewellen
Flewellen and
and B.
E. H.
[13] E.
vol. 5,
5, pp. 31-34,1978.
thesiol. Rev., vol.
thesiol.
31-34,1978. ·
[14)
J. Arenson
Arenson and
and L.
Wei!, "The
uses and
and abuses
abuses of
of tourniquets
tourniquets
D. J.
L. S.
S. Weil,
"The uses
[14] D.
J. Amer.
Amer. Pod.
Pod. Ass.,
Ass., vol.
vol. 66,
66, pp.
pp.
in
field foot
in bloodless
foot surgery,"
bloodless field
surgery," J.
854-861,
854-861, 1976.
1976.
Flatt, "Tourniquet
time in
in hand
hand surgery,"
surgery," Arch.
Arch. Surg.,
Surg., vol.
vol.
[15)
A. E.
E. Flatt,
[15] A.
"Tourniquet time
104,pp.
190-192, 1972.
104, pp.190-192,1972.
[16)
M. Bruner, "Time,
"Time, pressure and
and temperature factors
factors in
in the
the safe
J. M.
[16] J.
of the
the tourniquet,"
tourniquet," Hand, vol.
vol. 2,
2, pp. 39-42,
39-42, 1970.
use of
1970.
(17)
J. C. Griffiths
and O.
0. B. Heywood,
"Bio-mechanical aspects of
Griffiths and
[17] J.
Heywood, "Bio-mechanical
the tourniquet,"
vol. 5, pp. 113-117,1973.
the
tourniquet," Hand, vol.5,
113-117, 1973.
(18)
"Ischaemic effects
external and
and internal
internal pressure on
A. Parkes,
effects of
of external
[18] A.
Parkes, "Ischaemic
the upper limb,"
limb," Hand, vol. 5,
5, pp. 105-112,1973.
105-112, 1973.
[19)
Hulands, "Tourniquet
H. Hulands,
G. H.
Klenerman and
and G.
for the
[19] L. Klenerman
"Tourniquet pressures for
limb" (Abstract), J. Bone Joint Surg.,
lower limb"
Surg., vol. 61B,
61B, p. 124,
124,
1979.
1979.
(20) L.
and S.
J. Whistler,
Whistler, "The
"The error in
indirect blood
L. A.'
A. Geddes
Geddes and
in indirect
[20]
S. J.
of cuff,"
cuff," Amer.
Amer.
size of
measurement with
with the
the incorrect
incorrect size
pressure measurement
vol. 96,
pp. 4-8,
4-8,1978.
Heart J.,
J., vol.
1978.
Heart
96, pp.
(21) J.
"Comparison ofdirect
of direct and
and indirect
indirect methods
J. M.
M. R. Bruner et al., "Comparison
[211
of
measuring arterial
blood pressure, Part
1," Med. Instrum., vol.
of measuring
arterial blood
Part I,"
15,
15, pp. 11-21,
11-21, 1981.
1981.
, "Comparison
"Comparison of
of direct
direct and
and indirect
indirect methods
methods of
of measuring
measuring
[22) [22]
-,
arterial.blood pressure, Part
Part II,"
II," vol.
vol. 15,
97-101, 1981.
arterial-blood
1981.
15, pp. 97-101,
(23) (Proposed)
Non-Automated Sphygmomanometers,
Standard for
for Non-Automated
[23]
(Proposed) Standard
Sphygmomanometers,
Arlington, VA, Aug. 1980.
Ass. Advancement Med. Instrum., Arlington,
(24) (Proposed)
Electronic or Automated
Automated Sphygmomano[24]
Standard for
for Electronic
(Proposed) Standard
SphygmomanoAss. Advancement
Advancement Med.
Med. Instrum.,
Instrum., Arlington,
Aug.
meters, Ass.
meters,
Arlington, VA,
VA, Aug.
1980.
1980.
D. P.
P. Paulus,
Paulus, "Noninvasive
"Noninvasive blood
b100d pressure measurements,"
measurements," Med.
Med.
(25) D.
[251
vol. 15,
pp. 91-94, 1981.
1981.
Instrum., vol.
15,pp.91-94,
(26) F.
F. H.
H. Vanbergen
al., "Comparison
"Comparison of
of direct
direct and
and indirect
indirect methmeth[26]
et al.,
Vanbergen et
ods of
of measuring
blood pressure,"
pressure," Circulation, vol.
vol. 10,
ods
measuring arterial
arterial blood
10,
pp.481-490~
1954.
pp.
481-490, 1954.
ACKNOWLEDGMENT
ACKNOWLEDGMENT
The
provided by
by Dr.
M. A.
A.
The clinical
advice and
and assistance
assistance provided
clinical advice
Dr. M.
Wachsmuth of
the Division
Division of
Surgery, University
University
Wachsmuth
of the
of Orthopaedic
of
of British
British Columbia
the
Columbia isis gratefully
gratefully acknowledged,
acknowledged, as
as isis the
engineering
assistance of
of R.
MacNeil, M.
M. Koombes,
E. Ho,
Ho,
engineering assistance
R. MacNeil,
Koombes, E.
J. Ing,
lng, and
and E.
of the
Department of
EngiJ.
E. Froese
Froese of
the Department
of Biomedical
Biomedical Engineering,
neering, Vancouver
Vancouver General
General Hospital
and the
Department of
Hospital and
the Department
of
Electrical Engineering,
University of
of British
British Columbia.
Electrical
Engineering, University
Columbia.
REFERENCES
REFERENCES
[11 H.
"Surgical technique,"
Campbell's Operative
[1)
H. Smith
Smith "Surgical
technique," in
in Campbell's
Operative OrthoOrthoLouis, MO:
MO: Mosby,
p. 58.
paedics, 5th
5th ed.
ed. St.
paedics,
St. Louis,
Mosby, 1971,
1971, p.58.
[2] R.
R. Sanders,
Sanders, "The
Instrument or
or weapon?"
Hand, vol.
vol.
[2)
"The tourniquet:
tourniquet: Instrument
weapon?" Hand,
5,
pp. 119-123,1973.
S pp.119-123,1973.
[3] J.J. C.
Adams, Standard
Operation& New
[3)
C. Adams,
Standard Orthopaedic
Orthopaedic Operations.
New York:
York:
Churchill and
and Livingston,
Livingston, 1976,
1976, pp.
4-5.
Churchill
pp. 4-5.
A. McEwen,
[4] J.J. A.
McEwen, "Complications
"Complications of
of and
and improvements
improvements in
in pneupneu[4)
matic
tourniquets used
in surgery,"
vol. 15,
15, pp.
surgery," Med.
Med. Instrum.,
Instrum., vol.
pp.
matic tourniquets
used in
253-257,1981.
253-257, 1981.
[5]
D. Fry,
Fry, "Inaccurate
"Inaccurate tourniquet
tourniquet gauges,"
[5) D.
gauges," Brit.
Brit. Med.
Med. J.,
J., vol.
vol. 1,1, p.p.
511,1972.
511,1972.
[6] S.
J. Prevoznik,
from use
use of
of pneumatic
tourniquets,"
[6)
S. J.
Prevoznik, "Injury
pneumatic tourniquets,"
"Injury from
Anesthesiol., vol.
vol. 32,
Anesthesiol.,
32, p. 177,
177, 1970.
1970.
[7]
D. L.
L. Johnson,
P. D.
D. Neufeld,
R. G.
G. Hussey,
Hussey, "Hazards
"Hazards in
in
Johnson, P.
Neufeld, and
and R.
[7) D.
single-stage regulation
regulation of
cuffs," J.J. Clin.
5,
of pressure
pressure cuffs,"
Clin. Eng.,
Eng., vol.
vol. 5,
single-stage
pp. 59-62,
pp.
59-62, 1980.
1980.
[8]
of the
the Kidde
Kidde automatic
automatic tourniquet,"
tourniquet," in
in Medical
[8) "Malfunction
"Malfunction of
Medical
Devices Alert
Alert No.
No. 16,
Health Protection
Canada, Dec.
Devices
16, Health
Protection Branch,
Dec. 13,
13,
Branch, Canada,
1978.
1978.
James
A. McEwen
McEwen (S'74-M'75)
(S'74-M'75) received
received the
the
James A.
of British
British
Ph.D. ddegree
from the
University of
the University
egree from
Jh.A.
1975.
Columbia, Vancouver,
Vancouver, B.C.,
B.C., Canada,
Canada, in
in 1975.
Columbia,
of the
the Biomedical
Biomedical Engineering
Engineering
He is
He
is Director
Director of
the Vancouver
Vancouver General
General Hospital
Hospital
Department at the
1 Department
'
the
and
the Health
Health Sciences
Centre Hospital
Hospital at the
and the
Sciences Centre
9 University
of British
British Columbia,
the largest
largest
University of
Columbia, the
its kind
kind in
in Canada.
Canada. He
He is
is also
also
department of
of its
if ILI| department
the Department
Adjunct Associate
Associate Professor
Professor in
in the
Department
Adjunct
of
of Electrical
Electrical Engineering
Engineering at
at the
the University
University of
of
British Columbia.
Columbia. He is
is a Registered
Registered ProfesProfesBritish
sional
Engineer and
and a Certified
Certified Clinical
Clinical Engineer. His main interests are
sional Engineer
in clinical
clinical engineering
engineering and
of need-oriented medical
medical
in
and in the development of
of diagnosis and treatment,
technology in
in order to improve
technology
improve the qualtiy of
of health
health care.
care.
and
and control
control the
the costs
costs of
Dr.
McEwen is
Medical and
and
Dr. McEwen
is a member
member ·ooff AAMI
AAMI and
and the Canadian
Canadian Medical
Biological Engineering
Biological
Engineering Society.
Society.
iEi
M.D. degree
University of
of
from the
the University
Robert W. McGraw received the M.D.
degree from
B.C., Canada,
Canada, in
in 1960.
1960.
British Columbia, Vancouver, B.C.,
He is
is currently
in the
the Division
Division of
of Orthopaedic
Surgery,
He
currently aa Professor
Professor in
British Columbia.
Columbia.
of British
Faculty of Medicine,
Medicine, at the University of
the Royal
Royal College
College of
Surgeons
of Surgeons
Fellow of
of the
Dr. McGraw
McGraw became aa Fellow
of
(Canada)
(Canada) in Orthopaedic Surgery
Surgery in
in 1966.
1966. He became a Diplomate
Diplomate of
the American
Board of
of Orthopaedic
Surgery in
and a Fellow
Fellow of
of
in 1972,
the
American Board
Orthopaedic Surgery
1972, and
Academy of
of Orthopaedic
Orthopaedic Surgery
in 1975.
American Academy
1975.
the American
Surgery in

An adaptive tourniquet for improved safety in surgery.

Transcription

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