A recent publication in the September 2011 issue of the Journal of Trauma  evaluated the efficacy of two tourniquet systems, the CAT tourniquet and the EMT tourniquet, for controlling prehospital lower limb hemorrhage. The researchers involved in the study were active serving members of the British Military Medical Services. Detailed information about the EMT tourniquet is available elsewhere .
The recently published study demonstrated that “the CAT tourniquet was ineffective in controlling arterial blood flow when applied at mid-thigh level. The EMT tourniquet was successful in a significantly larger number of participants”. 
This published study is the latest in a series that demonstrates the superiority of the EMT tourniquet in controlling prehospital limb hemorrhage. For example, a study published in 2008 in the Journal of Trauma reported: “the CAT was the second most effective tourniquet at 79%. The most effective was the Emergency Medical Tourniquet (EMT, 92%).” 
As a result of earlier comparative evaluations done by the US Army’s Institute for Surgical Research, the following tourniquet recommendations were made to the US Army: “Based on these facts it is recommended that the CAT (tourniquets) be issued to each individual soldier, and the EMT pneumatic tourniquet be considered for issue to combat medics. Further, it is recommended that the EMT be issued for all medical evacuation vehicles and echelon I-III medical facilities”. 
The full abstract of the latest publication in the Journal of Trauma is given below. 
Background: Hemorrhage remains the main cause of preventable death on
the modern battlefield. As Improvised Explosive Devices in Afghanistan
become increasingly powerful, more proximal limb injuries occur. Significant
concerns now exist about the ability of the windlass tourniquet to control
distal hemorrhage after mid-thigh application. To evaluate the efficacy of the
Combat Application Tourniquet (CAT) windlass tourniquet in comparison to
the newer Emergency and Military Tourniquet (EMT) pneumatic tourniquet.
Methods: Serving soldiers were recruited from a military orthopedic outpatient
clinic. Participants’ demographics, blood pressure, and body mass index
were recorded. Doppler ultrasound was used to identify the popliteal pulses
bilaterally. The CAT was randomly self-applied by the participant at midthigh
level, and the presence or absence of the popliteal pulse on Doppler
was recorded. The process was repeated on the contralateral leg with the
CAT now applied by a trained researcher. Finally, the EMT tourniquet was
applied to the first leg and popliteal pulse change Doppler recorded again.
Results: A total of 25 patients were recruited with 1 participant excluded.
The self-applied CAT occluded popliteal flow in only four subjects (16.6%).
The CAT applied by a researcher occluded popliteal flow in two subjects
(8.3%). The EMT prevented all popliteal flow in 18 subjects (75%). This was
a statistically significant difference at p _ 0.001 for CAT versus EMT.
Conclusion: This study demonstrates that the CAT tourniquet is ineffective
in controlling arterial blood flow when applied at mid-thigh level. The EMT
was successful in a significantly larger number of participants.
 DM Taylor, GM Vater and PJ Parker. “An Evaluation of Two Tourniquet Systems for the Control of Prehospital Lower Limb Hemorrhage.“ Journal of Trauma – Injury, Infection & Critical Care 71(3):591-595, September 2011.
 Kragh JF Jr, Walters TJ, Baer DG, et al. Practical use of emergency tourniquets to stop bleeding in major limb trauma. J Trauma. 2008;64(suppl 2):S38-S50.
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