CA1114335A - Disposable cold pack - Google Patents

Abstract

Abstract of the Disclosure A disposable cold pack for cooling and storing a sample of freshly drawn blood at 28° to 40°F. for 45 minutes has an outer flexible insulation layer and a pair of sealed flexible plastic envelopes, one beside the other, one containing water and the other containing ammonium nitrate in a ratio to water from 1.24:1 to 1.26:1 by weight. The envelopes are provided with a connecting passageway between them releasably sealed in closed condition by an external spring clamp or by a mating tongue and groove assembly.

Description

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This invention relates to a disposable cold pack for cooling and storing a container filled with a sample of freshly drawn blood for subsequent analysis.
In conducting certain analyses of samples of freshly drawn arterial blood, it is essential for optimum accuracy to , .; ~ .
carry out the analyses without delay, because when the sample is allowed to stand for more than a few minutes at room temperature, changes in composition occur which render the subsequent analy-sis inaccurate. It is frequenkly impossible to arrange for the necessary analytical equipment to be present at the location where the blood sample is drawn and so the practice has developed of immediately immersing the sample in its container, which is usually the sealed plastic or glass barrel of a syringe, in a bucket of ice or of a water-ice mixture in order to chill it as rapidly as possible and to maintain it at a temperature slightly above freezing while it is transported in the ice bucket to the analytical equipment. The elapsed time between the drawing of the sample and the beginning of analysis usually does not exceed 45 minutes. It is important that the temperature of the blood sample be maintained below 40F. After it has been drawn because changes in composition occur fairly rapidly when the temperature ~ - .:
of the blood sample e~ceeds that level. On the other hand, it ~ ~`
is essential that the temperature of the sample not be reduced below 28F. in order to avoid irreversible changes in cell structure caused by freezing. In the case of an ice bucket, .
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tests have shown that a period of 7 minutes is required to lower the temperature of the usual S cc. blood sample from body temperature (99F.) to 36~F. with crushed ice alone ~no water), ' and 4 minutes with a water-ice mixture, in room temperature (76F.) surroundings.
Although disposable cold packs such as the one descr.ibed in Robbins et al. U.S. Pa~ent 2,925,719 have been available, they l have failed to provide for chilling at maximum rate of speed : without risk of cooling below the critical temperature of 28F., while at the same time ensuring a temperature below 40F. for a suff.iciently long period of time. The present invention provides a disposable cold pack which can readily be acti~atecl without special equipment and which is effective to chil]. rapidly a ¦container filled with a freshly drawn sample of blood from body ~¦temperature to a temperature withi.n the range from 28 to 40P.
~¦¦and to maintain it within that temperature range for at least 45 minutes. Tests have shown that preferred e~bodiments of the present invention are capable of cooling the usual 5 cc. blood sampIe from 99~F. to 36F. within 2 minutes in room temperature (76F.) surroundings. In one embodiment, the invention provides a disposable cold pack for cooling and storing a container filled with a sample of freshly drawn blood comprising an outer flexible insulation layer comprising foam plastic material, a first sealed I I flexible envelope of plastic material secured adjacent one face of the insulation layer, a supply of dry, solid am~onium nitrate disposed within the first envelope, a second sealed envelope con-taini.ng a supply of water disposed adjacent the first envelope, . 1 .
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means connecting the first and second envelopes to permit mixing of the contents of the two envelopes to activate the cold pack, j and a spring clamp releasably sealing the connecting means, the weight ratio of ammonium nitrate to ~ater being from 1.24:1 to 1.26:1. Such a cold pack, upon activation and being maintained in folded position with the insulation laye:r outermost and with the sample container in contact with said envelopes, is capable of chilling the blood sample rapidly and of maintaining it at a Itemperature of 28 to 40F. for at least 45 minutes after ¦activation in room temperature surroundings. In the usual case !where the size o~ the blood sample i5 approximately 5 cc , the .~ total weight of water and ammonium nitrate must be from 18Q to 200 grams for best results.
In a second e~odiment of the invention, the connecting ~means between the two envelopes is releasably sealed in closed ~Icondition by means o~ a mating tongue and groove assembly.
¦l Other features and advantages of the invention will appear from the drawing and from the detailed description which ~follows. ~
I In the drawing : I Fig. l is a plan view showing one embodiment of the ~:
¦invention before activation and use; :~
I Fig. 2 is an isometric view, partly broken away and in ;~ Isection, showing the embodiment of Fig. 5 after activation;
Fig. 3 is a plan view showing another embodiment of the ~hnvention; and .
. Fig. 4 is a view in section along line 4-4 of Fig. 3.
' In the embodiment shown in Fig. 1, envelope 50 is ~ .,provi~ed with a tube or side arm 52 connecting it to a second .' ' ~4~

, envelope 54, tube 52 providing communication between the two envelopes. In this embodiment the envelope 54 is substantially 'smaller than envelope 50 in overall dimensi.ons and is supported ~¦
';solely by tube 52 which connects the two envelopes. Foam plastic 'iou~er layer 56 such as that sold under the trademark Microfoam ,approximately 1/16`inch thick is laminated to plastic film 58 of .polyethylene approximately 2 mils thick, the two members 56 and 58 being coextensive in area and bonded together throughout their ; extent to serve as a laminated insulating layer. A spring metal ¦ or plastic clamp 60 releasably seals tube 52 in flattened conditio , preventing communication between envelopes 50 and 54. Envelope 50 is filled with a supply of dry solid finely divided ammonium nitrate while envelope 54 is filled with water. In order to achieve the desired results, it is essential that the ratio of ammonium nitrate to water be from 1.24:1 to 1.26:1 hy weight.
. IIn the case of a blood sample which is 5 cc~ by volume, the size sample which is usuall~ employed f the weight ~f ammonium nitrate ~;;and water should be from 180 to 200 grams for best results. - .
Enveiope 54 has walls of the same thickness as envelope 50, and tube 52 each preferably being made of two sheets of 2 mil .. polysthylene film heat sealed.together along their outer margins :and also preferably heat sealed along.the margins of envelope 50 to the laminated insulating layer 56, 58~
lAlthough envelopes 50 and 54 are rectangular in con-:.figuration in the embodiment described above, it will be appreciate that other shapes such as oval may also be used. Indeed, it is possibl although less convenient, to have the insulstion layer unattached to envelope 50 but instead in the form of a separate flexible sheet together with a closure member; if desired, the separate insulation layer may be preformed into a cylindrical chamber or a box of appropriate dimehsions.
In using the cold pack, thq barrel of the syringe into which the blood sample is drawn in the usual manner is sealed by inserting the end of the needle into a rubber stopper, or else the needle is first disconnected and discarded, after which the barrel is sealed.
In use of the embodiment shown in Fig. 1 to cool a syringe barrel full of blood the clamp 60 is releasedv the water is drained from envelope 54 into envelope 50, clamp 60 is re-applied as shown in Fig. 2 to the doubled over tube 52 to reseal it ¦if desired, the syringe''barrel is placed in position on the face of envelope 50 remote from laminated insulating-layer 56, 58, and llthe assemblage is folded or wrapped upon itself. Any suitable 'Imeans such as a rubber band, string, or adhesive tape may be provided to hold the assemblage in folded or wrapped condition.
In the case where the insulating layer is separate from the envelope 50, it may be wrapped around the envelope simultaneously with envelopment of the syringe barrel by the envelope or Isubsequently thereto, and secured in place by a closure membex.
¦In the case where the separate insulating layer is preformed into a container or box, the insulating layer can be rigid or stiff instead of flexible if desired and the container or box is of such size that the rolled up envelope 50 enclosing the syringe barrel is a snug fit within it, so that after insertion the envelope is 'maintained in xolled-up condition around the syringe barrel.
' ' ., In the embodiment shown in Fig. 3, there are pxovided two side by side envelopes 70, 72 h~ving co~Nmon walls b~cked ~ a i layer of foam plastic 74 and plastic film 76 coextens~ve with one I side of both envelopes~ In this embodiment the envelopes 70~ 72 : are of the same width, being formed by sepc~r~ting a single l~rgex ¦
envelope into ~wo portions by a transversel~ extending rele~s~ble seal 73. Envelope 70, which is substanti~lly shorter, hence I smaller ~n c~pacity than envelope 72, is thus in e~fect connected to envelope 72 by a tube of the s~me size as the periphery of the envelopes at their juncture. Releasable seal 73 ~etween the two :~ ~
envelopes is provided in the form of ~ mating tongue and ~xoQye ~ -assembly including res~lient tongue or post 78 of plastic m~terial :
bonded along its length to the inner face of one wall of envelopes 7Q~ 72 ~nd a resilient ~roove 80 bonded along its length to the inner face of the opposing wall in position to receive tongue 78. Tongue 78 and groove 8U h.~ve ~ating cross section~l configurations so that when pressed together as shown in Fi~, 4 t they form ~ watertight seal. An extending ~lap 82 i.~ pro~ided ~t :~
.~ Ithe.outer face of the envelopes adj~cent tongue 78 b~ cutting.and overlapping the wall at this point, then heat sealing it in over- ~
lapped position as shown in Fig. 4; the flap is readily grasped by : :
the fingers to facilitate separation or opening of the tongue and ~
groove seal by pulling tongue 78 out of mating engagement with ~
groove 80. Envelope 72 is filled with ammonium nitrate particles ~::
while envelope 70 is filled with water, tong~e 78 being seated in ~ .
groove 80 to maintain the components separate. The amounts and relative proportions of the oompo-ents are the same as in the ¦

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3~ 1 first embodiments. The device is used in the sarne manner as the first embodiment, being activated simply by pulling the tongue 78 ~out of engagement with groove 80 to permit the contents of the two~¦
envelopes to mix.
What is claimed is:

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Claims

1. In a disposable cold pack for cooling and storing a container filled with a sample of freshly drawn blood comprising a first sealed flexible envelope of plastic material, an outer insulating layer of flexible foam plastic material engaging the outer face of said first envelope and secured thereto, said insulating layer extending fully across the face of said first envelope, a supply of dry solid ammonium nitrate disposed within said first envelope, a second sealed flexible envelope of plastic material disposed adjacent the first, a supply of water disposed within said second envelope, the weight ratio of ammonium nitrate to water being from 1.24:1 to 1.26:1 and the total weight of ammonium nitrate and water being from 180 to 200 grams, means connecting said first and second envelopes to permit mixing of the contents of the two envelopes, and means for releasably sealing said connecting means to maintain the contents of the two envelopes separate, the improvement comprising having the means connecting the first and second envelopes in the form of a tube and the releasable sealing means in the form of a spring clamp engaging the tube.