Note: Descriptions are shown in the official language in which they were submitted.
Back~round of the_Inventlon
Intravenous administration of substantial quantities
of liquids including water, electrolytes~ sugar, blood, pharma-
ceuticals, and various nutritional materials are commonly
administered to hospitalized patients from a glass or plastic
container using a plastic tubing conduit which terminates in a
needle that is inserted into a superficial vein or artery. A
patient's movements, however, may cause the tip of the needle
to pierce the vascular wall and cause the liquid being adminis~
tered to fl-ow in the perivascular tissues. The liquid may
accumulate and cause discoloration, discomfort and possible ~-~
destruction of tissues~ while precluding absorption into the
metabolic pool of the materials being administered at the selected
rate.
Prior liquid infusion infiltration detection apparatus
and method (see, for example, U. S. Patent 3,618,602) permitted
the early detection of liquid infiltrations so that corrective
actions could be promptly instituted. In such prior apparatus
and method, the skin temperature in the region overlying the
27 tip of the intravascular needle was continuously monitored.
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Since liquids adminis~ered to a patient are at room tempera-
ture or refrigerated, they are typically at a lower temperature
than normal skin temperature~ Thus~ any undesirable perivascular
accumulation of administered liquid produces a decrement in skin
temperature in the region overlying the accumulation. Since the
temperatures of hospital rooms are typically about 20C.~25C.
and normal skin temperature is typically about 33C.~ a signifi-
cant temperature difference commonly exists between infusion
liquid and skin temperature to produce the change in skin temper-
ature that signals the occurrence of an infiltration. However,it has been found in patients who are in a state of shock or who
are undergoing, or have recently undergone, substantial surgery
or anesthesia and in some small nurnber of other patients, blood
flow to the skin may be sufficiently reduced that the patient's
skin temperature tends to approximate the ambient temperature.
Under these conditions, a substantial difference between skin
temperature and the temperature of the liquid being infused is
not available to produce a substantial change in the temperature
of the skin in a region thereof where perivascular infiltration
of the infused liquid occurs. Also, in some circumstances
(especially in tropical climates), hospital room temperatures
may be elevated to levels approximating normal skin temperatures.
Under these circumstances 7 a substantial temperature difference
between skin temperature and the temperature of the liquid being
infused is again not available to produce a substantial change
in the temperature of the skin in a region thereof where peri-
vascular infiltration of the infused liquid occurs.
Summary of the Invention ~ -
In accordance with one aspect of this invention there
is provided infusion infiltration responsive apparatus for use
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with liquid infusion equipment including a liquid-delivery
conduit means terminating in an intravascular portion having
a tip, said portion bein~ disposed to be inserted into a blood
vessel of a patient, the apparatus comprising:
temperature-regulating means for altering the skin
surface temperature o~ a patient in a selected region of skin
overlying the intravascular tip of the liquid-delivery conduit
means;
first sensor means disposed in thermal contact with ~ ;
the skin of the patient within said selected region overlying
the intravascular tip of the liquid conduit means for providing
an output indication representative of the temperature o-f the
skin in thermal contact therewith; and
circuit means responsive to the output indication from
said first sensor means for providing an output indicative of
the temperature sensed by said first sensor means. ;
In accordance with another aspect of this invention ;
there is provided the method of detecting liquid-infusion
infiltration into the skin of a patient which is at a temperature
not sufficiently different from the temperature of the liquid
being infused, the method comprising the steps of~
placing a liquid-delivery conduit into a blood vessel of
a patient for delivering an infusion liquid into a blood vessel
of the patient;
. altering the patient's skin surface temperature relative
to the temperature of the liquid in a region of the skin overlying
the tip of the intravascular portion of the liquid conduit means; ~ ;~
and
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; sensing the difference between the skin surface temperature
due to the accumulation of the infused liquid in the perivascular
region and the altered skin temperature for providing an output
indicative of the difference between the two temperaturesO
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Description of the Drawinq
Figure 1 is a pictorial diagram of the appliance used
to regulate the patient's skin surface temperature and to detect
changes in skin temperature; and
Figure 2 is a schematic diagram of the illustrated
embodiment of the present invention.
Description of the Preferred Embodiment
Referring now to Figure 1, there is shown a flexible
backing material 9 such as rubber-impregnated nylon, or the
like, having a plurality of wires 11 attached thereto to form
a heater that may be positioned on, or in close proximity to,
a patient's skin~ as shown in ~igure 20 A heat-sensitive
element 13 such as a thermistor is positioned in close thermal
relationship to the heater 11 to provide an output indication
on line 15 of the operating temperature thereof~ In addition,
two sensing thermistors, or other heat-sensitive elements, 17
and 19~ are positioned within regions surrounded by the heater
11 to be positioned on, or in close proximity to, the patient's -
skin for detecting the surface temperature thereof in two
separated locations. Thermal conduction between the heater 11
and the sensors 17 and 19 via the backing material should be
negligible.
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The appliance shown in ~igure 1 including heater 11 and
sensors 13~ 17 and 19 may be positioned on a patient's skin~ as
shown in Figure 2, in the region of the transcutaneous puncture :
by needle 21 with the thermal sensor 19 positioned on the skin
overlying the region of the point of needle 21. In operation,
the infusion set 23 may administer a liquid~ either by gravity
flow or by positive displacement means~ via the flow control 25~
liquid conduit 27 and the needle 21 which is shown inserted into
a blood vessel of a patient 20. The temperature of the liquid
being infused is typically at or below room temperature (which~ ;
for most hospital rooms, is about 20 C.-25C., or cooler).
Normal skin temperature is generally at or about 33C.~ which
is substantially different from the temperature of the liquid
being infused. However, when patients are in a state of shock ;-
or are undergoing~or have recently undergone~surgery or anesthesia
or may be subjected to other conditions which substantially
diminish skin blood flow~ the temperature of the skin drops to
approximately the ambient temperature, which is generally cooler~
as noted above. In accordance with the present invention, when-
ever such conditions tend to occur~ the local region of the
patient's skin sur~ace adjacent the needle 21 is heated to
elevate the skin temperature (say, to normal or somewhat above) ~
to assure adequate thermal difference between such local skin -~ -
temperature and the temperature of the infused liquid. This
heating is accomplished by applying electrical signal to the
heater 11 from the heater controller 31. A heater driver 33
supplies signal to the heater 11 in response to the error signal
that is derived ~rom the combination of signals from the reference .
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supply 35 and the sensor 13. The reference supply 35 may thus :~
be adjusted to set the heater current (and7 hence~ its temperature)
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at a selected value. ~lternatively~ the heater driver 33 may
simply supply a ~electable current to heater 11 without the aid
or bene~it o~ the servocontrol mechanism previously described.
In operation, the two heat sensors 17 and 19 are located
within the heated region of the patient's skin surface and
normally produce substantial equal output signals. However~
in the event the liquid being infused undesirably accumulates
about the needle 21 in a perivascular region ràther than being
properly administered into a blood vessel~ the liquid accumulation
will alter the skin temperature in the region of sensor 19 The
output signal due to this change in temperature may be compared
in amplifier 36 with the output signal of sensor 17 or with the
output of reference supply 37 of the sensing circuit 39. The
reference signal from supply 37 or the output signal from sensor
17 will thus be representative of the elevated skin temperature
(i.eO, about 35C.-3~C.)~ independent of the patient's condition.
If the ampli~ied difference signal on line 41 exceeds a selected
value as determined by threshold detector 43, an output signal
is produced on line 45 which may actuate an alarm 47 or actuate
the flow controller 25 to terminate further liquid infusion, or
both~ as described in said U. S. Patent 3~618~602 cited above.
Alternatively~ where the room or ambient temperature
and the infusion liquid stored under such conditions may be
elevated to approximate typical skin temperature~ as in tropical
regions, or the like, the patient's skin surface temperature in
the local region may be decreased below normal skin temperature ~;
rather than increased~ as previously described, to assure ade-
~ quate thermal difference between such local skin region and the
; temperature of the infused liquid. This may be accomplished
using electrically-powered Peltier~effect coolers or by
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circulating refrigerant or by expanding a compressed gas, or
the like, in the local region of the skin surface. In this way7
the difference ~etween the temperature of the infused liquid and
the temperature of the surface skin in the local region may be
maintained large for rapid detection of perivascular infiltration
6 of the infused liquid.
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