CAT Environmental Breakage
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We receive frequent questions about shelf-life and environmental degradation of tourniquets.
There has been some discussion in the US Department of Defense about declaring a five-year self-life for new, unused commercial tourniquets in the inventory. Certainly, even without use or environmental exposure, we know materials degrade with age. Is an unused, still in the packaging, stored in a climate-controlled warehouse tourniquet suddenly unreliable and prone to breakage once it is five years old? We have no idea, as I am not aware of any literature actually looking at this question.
As to environmental wear and tear increasing the breakage rates of tourniquets, there is data addressing this question. There was an informal survey of Marines deployed to Afghanistan citing a 14% breakage rate on the first application of new, unused tourniquets suggesting the high rate of failure was from UV degradation, heat, and general exposure. However, informal surveys aren’t scientifically robust because people don’t always remember things accurately. (This is called recall bias.)
A study was conducted comparing 166 environmentally exposed tourniquets in Afghanistan to the same number kept in a warehouse and never issued. Once back in the US, researchers compared one of each of the two tourniquet groups on both thighs of a volunteer. They tightened until loss of distal pulses for thirty seconds. Tourniquet breakage occurred in 14 of 166 exposed and none of the unexposed. That is an 8.4% breakage rate once the device had environmental wear and tear in Afghanistan for six months.
1
Another study published a few years later compared three groups of tourniquets environmentally exposed in Afghanistan:
- worn on a plate carrier;
- kept in an IFAK and still in the manufacturer’s plastic wrap;
- in an IFAK, but with the manufacturer’s plastic wrapping removed.
The only group with breakage were those worn on a plate carrier: they broke 12% of the time on application.
2
A study I would refer to as “bench research” examined the ability of CAT tourniquets vs SOF T Wide’s to control computer-simulated bleeding from the Hapmed Leg trainer. One group of tourniquets was left on a roof in San Antonio, Texas for 18 months, and another group of the same types of tourniquets was not exposed. The Hapmed Leg training model isn’t my favorite for reasons beyond the scope of our discussion here. Exposed tourniquets took three seconds longer and required four more mmHg of pressure to make the computer register bleeding was controlled.
3 I really have no idea what to do with this study: there isn’t any clinical significance to those differences. I guess the point of the study is that despite 18 months on a Texas rooftop, these devices work very well on a computer thigh model.
The overarching take-home point to all of this seems to be: if your tourniquet is UV light and environmentally exposed to the world, breakage definitely increases by six months. This breakage rate is possibly 8 to 12%. If the tourniquet is out of the plastic wrap, but in a pouch or IFAK, no increased breakage seems to occur.
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Notes:
1Childers R, Tolentino JC, Leasiolagi J, Wiley N, Liebhardt D, Barbabella S, Kragh JF Jr. Tourniquets exposed to the Afghanistan combat environment have decreased efficacy and increased breakage compared to unexposed tourniquets. Mil Med. 2011 Dec;176(12):1400-3.
2Weppner J, Lang M, Sunday R, Debiasse N. Efficacy of tourniquets exposed to the Afghanistan combat environment stored in individual first aid kits versus on the exterior of plate carriers. Mil Med. 2013 Mar;178(3):334-7.
3O’Conor DK, Kragh JF Jr, Aden JK 3d, Dubick MA. Cat on a Hot Tin Roof: Mechanical Testing of Models of Tourniquets After Environmental Exposure. J Spec Oper Med. 2017 Spring;17(1):27-35.
