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higher than that for bare hands (p < .0245, all three). Blood Test-to-test learning by individuals as data points was a bumpy
losses were worsened by wearing gloves as compared with us- road. To err is human.
ing bare hands. For these three groups, gloves worsened blood Learning curves as best-fit lines often show smooth improvement as
loss by 188mL, 116mL, and 124mL, respectively. users accrue experience.
Extreme performances (e.g., failures) offered ideal opportunities for
For devices, U4-1 was in the highest level, U4-2 was second teachable moments.
highest, and U1-1, U2-1, and U2-2 were lowest. Devices U2-2 Errors: tourniquet put atop a wound, and pulse felt with end of
and U3-1 were in the second lowest level. User effects again fingertip (volar pad is better).
dominated device effects: intrauser results by device were con- Failure to assess bleeding, tourniquet looseness, or pulse status are
sistently in the same level, except those of user 4, who had a teachable moments.
device alone in the two highest levels. Failures that occur only late indicate that novices may not learn
fully until after some failures.
Late mistakes: some things may be best learned by failing.
Comments of Tourniquet Users Boundaries become clearer.

Comments of users were developed into relevant tips for train- Gloves may increase risk of a common error: inadvertently
ing tourniquet use (Table 3). applying a loose tourniquet.
A mix of good and bad performances may be optimal for learners
Table 3 Training Tips as Gathered From Experience During the Study if instructors capitalize well.
On average, performance while wearing thin gloves like Good judgment comes from bad experience—assuming that
examination gloves or flight gloves is similar to using bare hands. we learn.
On average, performance while wearing thick gloves like cold Thick gloves may dull hand sensation of how hard the band is
weather gloves is worse and slower than bare hands. pulled or the windlass twisted.
Novices should learn tourniquet use with bare hands before For tourniquet use at a sport stadium, doff your glove: that giant
learning use with examination gloves. “We’re Number 1!” foam finger.
To help novices initially tension the band for their patient:
“Pull like their life depends on it!” Discussion
Advanced beginners should practice mostly with the glove type The user often had major effects on performance. Among most
needed most often in their setting. continuous variables (i.e., time to determination of bleeding
Competent tourniquet users should strive for familiarity with use of
a few types of gloves. control, trial time, overall time, and blood loss), most of the
Proficient tourniquet users should strive for familiarity with use of variance (62%, 55%, 61%, and 68%, respectively) could be
several types of gloves. attributed to the users. In simulated use of a tourniquet, user
Experts should gain experience in use of all glove types relevant to effects were consistent with prior simulation studies and were
their clients. common among performance metrics of continuous variables
Advanced beginners need to know that actual assessments take like blood loss. 22–25 Repeated studies have shown both direct
longer in care than in training. and supportive evidence of impactful effects of the user for
Novices judged band tension to be a surrogate for pressure, but it is time to stop bleeding and blood loss, which affect simulated
a poor, unreliable surrogate. patient outcomes meaningfully. 26–34
Overconfidence of novices lessened as they accrued experience.
Pressure variance was small because users aimed to apply pressure First aid authorities have asked for evidence associating user
within a narrow range. interventions with patient outcomes. 2,3,4 We reported such evi-
Continuous metrics like blood loss tend to be sensitive to user, dence from the Baghdad surge when the tourniquets of unchang-
glove, and device effects. ing designs were used , but user skill improved as users improved
Categorical metrics like trial status tend to be insensitive to user, in their control of bleeding for patients despite fewer tourniquets
glove, and device effects. per limb being used; thirteen metrics of improved performance
Course directors should choose performance metrics carefully after were tallied including: increased proportion of limbs with only
considering their merits. one tourniquet needed, increased proportion of limbs with hem-
Instructors should differentiate performance of a class (e.g., orrhage control by effective tourniquet use, and increased pro-
average) from that of an individual. portion of casualties with tourniquets used before shock onset.
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Training directors should check their course materials for glove- However, such evidence is considered weak because only strong
related content. studies like controlled trials can yield strong evidence. We have
Medical directors in law enforcement or military units should reported analyses of user effects on intervention performance,
check glove practices locally. and we more easily see user effects when interuser performance
Authors of first aid lessons, curricula, and books should consider varies widely. 22–25,35 We analyzed user effects because the engines
glove guidance. of caregiving are humans. We call the humans of our interest a
Expert instructors may occasionally point out user technique and user set, a group of people supporting the end-user of a tourni-
its outcome as cause and effect. quet including assistants, instructors, first aid course directors,
People save people. The tourniquet is just a tool. It’s not magic. and others. The user set members may be individually suitable
You, the user, can bring magic. for study such as the learning curve of an instructor (JFK). Fur-
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Emphasize the quality of training to optimally prepare users to
perform at their best. thermore, one of us (JFK) as an editor has asked more frequently
To optimize clinical outcomes, optimize training of users through for user effects to be reported in relevant submissions. Also, one
preparation of instructors. of us (JFK) as a presenter to the Committee on Tactical Combat
Users showed no or mild learning; glove effects may be resistant to Casualty Care (September 7, 2016; College Park, Georgia) has
accrual of user experience. challenged the community itself to expect or even demand user
(continues) effect reporting in applicable studies.

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