All articles published in the Journal of Special Operations Medicine are protected by United States copyright law
and may not be reproduced, distributed, transmitted, displayed, or otherwise published without the prior written permissionof Breakaway Media, LLC. Contact Editor@JSOMonline.org.

Short Report Comparing Generation 6 Versus
Prototype Generation 7 Combat Application Tourniquet®
in a Manikin Hemorrhage ModelJohn F. Kragh Jr, MD; Virgil K. Moore III, BBA; James K. Aden 3rd, PhD;
Donald L. Parsons, PA; Michael A. Dubick, PhD

ABSTRACT
Background: The Combat Application Tourniquet®
(C-A-T) is the standard-issue military tourniquet used infirst aid in 2015, and the current model is called Generation 6. Soldiers in the field, however, have been asking fordesign changes in a possible Generation 7 to improve easeof use. This study compared the differential performancein use of the C-A-T in two designs: Generation 6 (C-A-T6) versus a prototype Generation 7 (C-A-T 7). Methods:
A laboratory experiment was designed to test the performance of two tourniquet designs in hemorrhage control,ease of use, and user preference. Ten users of the twoC-A-T models placed them on a manikin thigh to stop
simulated bleeding. Users included trauma researchers
and instructors of US Army student medics. Ten users conducted 20 tests (10 each of both designs). Results: Most results were not statistically significant in their difference by
C-A-T design. The mean difference in blood loss was statistically significant (p = .03) in that the C-A-T 7 performed
better than the C-A-T 6, but only in the mixed statisticalmodel analysis of variance, which accounted for user effects. The difference in ease-of-use score was statisticallysignificant (p = .002); the C-A-T 7 was easier. All users
preferred the C-A-T 7. Conclusion: In each measure, theC-A-T Generation 7 prototype performed similar or better
than Generation 6, was easier to use, and was preferred.

Resources; http://combattourniquet.com) is the standardissue military tourniquet used in first aid in 2015. TheC-A-T is in its sixth version, called Generation 6, as there
have been five sets of refinements in its design over thepast decade.8,9 C-A-T Generation 6 (C-A-T 6) has beenbought worldwide over the past several years. However,Servicemembers in the field have been asking for designchanges in the current Generation 6 to improve ease ofuse in a possible Generation 7 version (C-A-T 7).10 The
purpose of the present study was to compare the differential performance in use of the C-A-T in two designs:
C-A-T 6 versus a prototype C-A-T 7 (Figures 1 and 2).

Methods
This study was conducted under a protocol for a laboratory experiment designed to compare the functionof tourniquets and was reviewed and approved by theRegulatory Compliance Division of the US Army Institute of Surgical Research. The experiment was designed
to test the performance of two tourniquet designs inFigure 1 Combat Application Tourniquet Generation 6 is a

US military, standard-issue tourniquet. Photograph is usedwith permission of North American Rescue Products.

Keywords: first aid; damage control; hemorrhage; shock;
tourniquet; resuscitation

Introduction
Tourniquet use in first aid has become a public healthpolicy of the United States. At the White House on 6 October 2015, the Administration launched a plan to provide bystanders of emergency situations with the tools
and knowledge to stop life-threatening bleeding for allAmericans, in a campaign called “Stop the Bleed.”1–7
The Combat Application Tourniquet® (C-A-T; Composite14All articles published in the Journal of Special Operations Medicine are protected by United States copyright law
and may not be reproduced, distributed, transmitted, displayed, or otherwise published without the prior written permissionof Breakaway Media, LLC. Contact Editor@JSOMonline.org.

Figure 2 Combat Application Tourniquet Generation 7

is a prototype in redesign of the prior Generation 6. The
maker entered the prototype shown into production on
3 November 2015. Photograph is used with permission ofNorth American Rescue Products.

­ emorrhage control, their ease of use, and the design
hpreference of users. Ten users of the two C-A-T designs placed them on a manikin thigh to stop simulated
bleeding. Ten users conducted 20 tests each. The overall
number of tests performed for the experiment was 200
replicates. Data were collected in October 2015.
Users included four US Army instructors of medic
students, the US Army master instructor of medics, aclinician-scientist with expertise in tourniquets, a tourniquet research associate, and three laboratory personnel with little to no experience with tourniquet use. The
clinician-scientist and research associate also were thetrainers and assessors. The trainer-assessors were present during practice and testing to answer questions oraddress problems such as in manikin use.
The control group was the C-A-T 6 tests, and the experimental group was the C-A-T 7 tests. Several design traitsof C-A-T 6 were refined in the C-A-T 7 version (Table 1).
Users had familiarization training in use of the manikin.
Training also included instruction in C-A-T use, familiarization with both C-A-T designs, handling both devices, and one or two practice uses for each tourniquet
design on the manikin before testing began.
The tourniquets were tested on a laboratory manikin
that was designed to train users by providing feedback on user performance. The investigators used aHapMed™ Leg Tourniquet Trainer (CHI Systems; http://www.chisystems.com/p_medicaltrain.html); a simulated
right thigh with an above-knee amputation injury was
the testing apparatus. A previous report detailed use of
the manikin in assessing first aid performance.10
Comparing C-A-T® Gen 6 to Prototype Gen 7

Table 1 Design Contrasted for Combat Application
Tourniquet Generation 6 and Generation 7

Combat Application Tourniquet
Trait

Generation 6

Generation 7

BuckleBuckle has two slits

Has one slit newly
contoured to easepassage of the tip ofthe bandRouting

May be routed singly
or doubly

Can only be routed
singlyWindlass Diameter is smaller;
grip rings are concave

Midshaft diameter iswider; grip rings areconvex

Plate

Leading edge issquared; plate isthinner

Leading edge isrounded; plate is
thicker

Strap

Windlass clip strap iswhite

Windlass clip strap
is gray

Windlass Windlass clip isClip
thinner without
buttressed sides

Windlass clip is thicker
with buttressed sides

Briefly, effectiveness was determined by the cessation ofblood loss (i.e., hemorrhage control). Iterations beganwith a tourniquet laid out flat and undone on the benchtop. Iterations ended when the user touched the touchpad button, assessing that the hemorrhage was stopped.
Both designs had the self-adhering band routed singly
through the buckle. Users tightened tourniquets until
they perceived that simulated bleeding stopped or until
a tourniquet broke. The casualty had a medium build
and the setting was Care Under Fire, a setting resembling emergency care when under gunfire.
Ease of use was assessed by each user and self-reported
using a Likert scale with a range of 5 numbers: 1: very
difficult, 2: difficult, 3: neutral, 4: easy, and 5: very easy.
Preference was self-assessed by users in answering thefollowing question: If you had to go to war today, andyou could only bring C-A-T tourniquets of only one
type of model (either Generation 6 or Generation 7),
which would you prefer: 6 or 7?
Descriptive statistics were used to portray results.
A mixed-model analysis of variance (ANOVA) wasplanned if user effects were large. Categorical data
(hemorrhage control in contingency tables) were analyzed with a χ2 test, and the likelihood ratio p values
were reported. For pairwise comparison of designs, anonparametric Wilcoxon method was used. Significancefor results was established when p < .05. All statisticalanalysis was conducted using SAS software (SAS Institute; https://www.sas.com) and MS Excel 2003 (Microsoft Corp.; http://www.microsoft.com).
15

All articles published in the Journal of Special Operations Medicine are protected by United States copyright lawand may not be reproduced, distributed, transmitted, displayed, or otherwise published without the prior written permissionof Breakaway Media, LLC. Contact Editor@JSOMonline.org.

Results
Comparison of Results by Tourniquet Design
The difference (C-A-T 7 minus C-A-T 6) in percentage ofeffectiveness in bleeding control by C-A-T design was notstatistically significant (96% for C-A-T 6 versus 97% for
C-A-T 7; p = .7). Similarly, the mean differences were notstatistically significant in time to bleeding control determination (23 versus 22 seconds for C-A-T 6 and C-A-T
7, respectively; p = .1), in total time (32 versus 31 seconds for C-A-T 6 versus C-A-T 7, respectively; p = .2),
and in pressure (205mmHg versus 205mmHg for C-A-T
6 versus C-A-T 7, respectively; p = .9). Only in the unmixed statistical model was the difference in mean blood
loss not statistically significant (141mL versus 129mL for
C-A-T 6 versus C-A-T 7, respectively; p = .05). However,ease of use results differed. The difference in ease of use
was statistically significant, favoring the C-A-T 7 (p =.002) (Table 2); most of the results (82%) for the C-A-T 6
were either neutral or easy (29% and 53%, respectively),
whereas most of the results (74%) for the C-A-T 7 were
either easy or very easy (41% and 33%, respectively).
Comparison of Results by User of Tourniquets
Results by user differed significantly (p = .04). When
analyzing all users individually for mean differences inblood loss by C-A-T design, only one user had a statistically significant difference and this result favored theC-A-T 7 (p = .003; eight others, p > .058); nine differences were negative, and one was positive. When alldata of the 10 users were pooled, the mean differencein blood loss by user remained statistically significant(p = .02), and this result favored the C-A-T 7. All users
preferred the C-A-T 7 (10 of 10; 100%).
Comparison of Results in a Mixed Statistical Model
Due to the presence of significant user effects, a mixed
statistical model also was used to analyze the data. Thismodel determined that 42% of the variability of all results was attributable to user effects. Again, the differential performance by C-A-T design was not statisticallysignificant (p = .3).
Similarly, time to bleeding control determination, totaltime, and pressure were not statistically significant (p > .3

for all). For time to determination of bleeding control,
total time, pressure, and blood loss, the mixed statisticalmodel determined that 42%, 45%, 5%, and 60%, respectively, of the variability of results was attributable to user
effects showing the validity of the model with user effect.
The mean difference in blood loss was statistically significant (141mL versus 129mL for the C-A-T 6 and
C-A-T 7, respectively; p = .03) in that there was lessblood loss with the C-A-T 7 than the C-A-T 6, but
only in the mixed statistical model ANOVA, which accounted for user effects.

Discussion
In the present study using a manikin, the two C-A-T
designs showed differential performance favoring theC-A-T 7 over the C-A-T 6. The difference is accentuatedby an unpublished analysis of two previous C-A-T 7 prototypes analyzed by the present investigators in December
2014, in which the two previous prototype designs did not
result in superior performance over the C-A-T 6. The feedback from the 2014 assessment led to the rejection of theprevious designs and to further spiral development of theC-A-T design to what was assessed in the present report.
Some differences in performance between the C-A-T 7
and C-A-T 6 were statistically significant. These werefew, however, and the sizes were small; such results arecommon in design refinements of satisfactory but imperfect medical devices. There was no worse performancefor C-A-T 7 by any parameter.
On the other hand, interuser differences were often
large and affected outcomes; 42% of the variability ofoverall results was attributable to user effects. In specificexamples, 42%, 45%, 5%, and 60% of the variabilityof performance results were attributable to user effects
for time to determination of bleeding control, total time,pressure, and blood loss, respectively. Although the differences in means, such as for blood loss, were small for
individual subjects researched, when applied to millionsof Americans, such differences would become more important. Such is the distinction between care of an individual casualty and public health policy of a nation.

Table 2 Results of Ease of Use by Combat Application Tourniquet Design

Ease-of-Use Score,* No. (%)
Design1(very difficult)2(difficult)3(neutral)4(easy)5(very easy)

Total

C-A-T 6

1 (1)

5 (5)

29 (29)53 (53)12 (12)100

C-A-T 7

0 (0)

9 (9)

17 (17)41 (41)33 (33)

100

Total

1

1446

94

45200

*Data represent 10 uses of each tourniquet by 10 users. C-A-T 6, Combat Application Tourniquet Generation 6; C-A-T 7, Combat Application
Tourniquet Generation 7.

16

Journal of Special Operations Medicine Volume 16, Edition 1/Spring 2016

All articles published in the Journal of Special Operations Medicine are protected by United States copyright law
and may not be reproduced, distributed, transmitted, displayed, or otherwise published without the prior written permissionof Breakaway Media, LLC. Contact Editor@JSOMonline.org.

Altogether, the study findings are clear, consistent, coherent, and without an unexpected result. Findings areactionable now for (1) corporate discussion that may
lead to a decision on production of the newly designed
C-A-T 7, (2) committees (e.g., the Committee on Tactical Combat Casualty Care, which may consider reviewof the present new knowledge), and (3) master instructors, who may update lesson plans and instructions foruse of the C-A-T 7, since the technique of use is now
refined. The manufacturer of C-A-T 7 began production
on 3 November 2015. Furthermore, the growing bodyof knowledge in the science of bleeding control continues to show that optimization of user performance isan important aim in improving current care; such user
development stands shoulder-to-shoulder with materiel
development as a current research priority. Such user development includes optimization of learning curves ofindividual students in attainment of skill, determinationof strategies for maintenance of skill level for individuals or groups of individuals, and analysis of instructor
assessments of student performance.
The limitations of the present study are based in its design as a focused experiment, which is neither field testing nor healthcare delivery. There were only 10 users,
only two designs, only 10 tests per design, and assessment was on a manikin and not on a real person.

Conclusion
In summary, in each measure C-A-T Generation 7 performed similar or better than C-A-T Generation 6, waseasier to use, and was preferred.
FundingThis project was funded by US Army Medical Researchand Materiel Command and the Defense Health Program(Proposal 201105: Operational system management andpost-market surveillance of hemorrhage control devices
used in medical care of US Servicepersons in the currentwar).
Disclaimers
The opinions or assertions contained herein are the private views of the authors and are not to be construed
as official or reflecting the views of the Department ofDefense or US Government. The authors are employeesof the US Government. This work was prepared as partof their official duties and, as such, there is no copyrightto be transferred.
Disclosures

References
1. The White House. Fact Sheet: Bystander: “Stop the Bleed”
broad private sector support for effort to save lives and build
resilience. https://www.whitehouse.gov/the-press-office/2015/10/06/fact-sheet-bystander-stop-bleed-broad-private-sector-support-effort-save. Accessed 13 October 2015.
2. Kragh JF Jr, Walters TJ, Westmoreland T, et al. Tragedy into
drama: an American history of tourniquet use in the currentwar. J Spec Oper Med. 2013;13:5–25.
3. Kragh JF Jr, Beebe DF, O’Neill ML, et al. Performance improvement in emergency tourniquet use during the Baghdadsurge. Am J Emerg Med. 2013;31:873–875.
4. Kragh JF Jr, Walters TJ, Baer DG, et al. Survival with emergency tourniquet use to stop bleeding in major limb trauma.
Ann Surg. 2009;249:1–7.
5. Kotwal RS, Montgomery HR, Kotwal BM, et al. Eliminating preventable death on the battlefield. Arch Surg. 2011;146:1350–1358.
6. Bulger EM, Snyder D, Schoelles K, et al. An evidence-based
prehospital guideline for external hemorrhage control: American College of Surgeons Committee on Trauma. Prehosp
Emerg Care. 2014;18:163–173.
7. Jacobs LM Jr. Joint Committee to create a national policy
to enhance survivability from mass casualty shooting events:
Hartford Consensus II. J Am Coll Surg. 2014;218:476–478e1.
8. Kragh JF Jr, O’Neill ML, Walters TJ, et al. The military emergency tourniquet program’s lessons learned with devices anddesigns. Mil Med. 2011;176:1144–1152.
9. Kragh JF Jr, Burrows S, Wasner C, et al. Analysis of recoveredtourniquets from casualties of Operation Enduring Freedom
and Operation New Dawn. Mil Med. 2013;178:806–810.
10. Clumpner BR, Polston RW, Kragh JF Jr, et al. Single versus
double routing of the band in the Combat Application Tourniquet. J Spec Oper Med. 2013;13:34–41.

Dr Kragh is a tourniquet researcher at the USAISR, Joint BaseSan Antonio Fort Sam Houston, Texas. He is an orthopedic
surgeon who was the 3rd Ranger Battalion Surgeon from 1990
to 1993. He is an associate professor in the Department ofSurgery, Uniformed Services University of the Health Sciences,Bethesda, Maryland. E-mail: john.f.kragh.civ@mail.mil.
Mr Moore is a research associate in the Bleeding Control section at the USAISR, Joint Base San Antonio Fort Sam Houston, Texas. He is a prior Army laboratory noncommissionedofficer.
Dr Aden is a statistician at the USAISR, Joint Base San Antonio Fort Sam Houston, Texas. He has published many papers
in operational medicine.

Mr Parsons is Deputy Director of the Department of Combat

Medic Training in the Army Medical Department Center andSchool, Joint Base San Antonio Fort Sam Houston, Texas. Heis a prior Special Forces Medic and Army Physician Assistant.

Dr Dubick is a resuscitation researcher at the USAISR, Joint

Base San Antonio Fort Sam Houston, Texas. He is the taskarea manager of the Department of Damage Control Resuscitation. He has published many papers in operational medicine.

The authors have nothing to disclose.
Comparing C-A-T® Gen 6 to Prototype Gen 717