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confidence in NVG+A use significantly increased from pre- For standardization, participants were not allowed to mix and
to posttesting for both IV and IO access and feedback from match or otherwise alter equipment prior to testing, as is com-
study participants. Most of the study participants were unfa- mon with personalized medical kits. No long-term follow-up
miliar with the focusing adaptors prior to testing, and many data were collected to determine the stability of findings over
had difficulty adjusting the focus. During the experiment and time.
on the exit survey, multiple participants commented that they
would have liked more time to familiarize themselves with the Finally, posttesting surveys were completed after the partici-
adaptors prior to evaluation and would have preferred more pant had completed all procedures rather than following each
repetitions during testing. When a participant failed at IV or procedure and therefore may have suffered from recall bias.
IO procedures, it was common for them to ask if they could We intentionally chose this strategy because it was impractical
try again or whether there would be a second round of testing. to turn on the lights between iterations to complete survey
Combined, these findings underscore the significant learning information gathering, then re–dark-adapt participants for
curve and highlight the importance of training and practice their next iteration, because we wanted participants to ap-
with NVG focusing adaptors. preciate each lighting condition before rating conditions and
choosing their preferences. Further, we have used this strategy
Limitations of waiting until all objective data are collected before solicit-
This study was limited by the sample, which was modest in ing exit-survey information in previously published research
size and included only US Navy medical personnel. Further, from our laboratories. 25,26 Our mirrored Latin square design
while all participants indicated they had received TCCC train- was chosen to foster the principle that each lighting condition
ing, we did not obtain data regarding exactly which TCCC would be equally represented as the first, second, and third
courses each attended and what other relevant medical train- condition in the sequence, so there was no systematic bias re-
ing each might have had. garding recency of memory unduly advantaging any specific
lighting condition. Regardless, recall bias may have limited
It is always possible that the results of a study could be an our postsurvey data. For these reasons, posttesting survey
artifact of bias. However, to guard against potential sources findings should be only generalized with appropriate caution.
of bias, all participants received the identical introduction and
instruction set that did not favor any specific lighting device.
Participants used identical brand and model headlamps, NVG, Areas for Future Research
and NVG focusing adaptors. All workstations were identical, The present study should be replicated with larger, more di-
and the same model stopwatch was used to measure time to verse samples, including personnel from other military Ser-
completion. Further, this experiment employed a randomized vices and tactical civilian personnel, various NVG and adaptor
mirrored Latin square design, so that each lighting condition models, and different challenging tasks under combat or simu-
had equal odds of being represented in the first, second, or lated-combat conditions. Ideally, selection bias can potentially
third sequence position to balance order effects (e.g., warm-up be avoided by testing randomly selected, stratified samples
effects from going first or fatigue effects from going last) and of participants from the various target populations of United
carry-over effects because each lighting condition had equal States Navy medical personnel or other populations whenever
odds of going first or being preceded by either of the other feasible.
two lighting conditions. However, participation in this study
was voluntary, which can potentially bias results (i.e., selection The effect of focusing adaptors on other operational proce-
bias), thereby challenging the external validity and general- dures should be investigated, such as tourniquet application,
izability of a study by fostering conclusions that may not be airway procedures, thoracostomy, medication draws, map
fully representative of the sampled population. 23 reading, and retrieval of gear from a medical bag.
This study was conducted under laboratory conditions using This study failed to reveal systematic differences in outcomes
simulation mannequins, not live humans in battlefield or aus- based on demographic data. However, these null findings may
tere conditions, situations that may include, for example, gen- have been the result, at least in part, of the modest sample
uine time stress toward preserving life in chaotic environments size overall and the meager or nonexistent sample sizes for
or inclement weather. Only one NVG model and one adaptor some included demographic items (e.g., only four SARCs and
model were tested. one FMST; only three with prior NVG+A operational experi-
ence; no color-blind participants). Additionally, some poten-
The tactical headlamp was tested with only green light to en- tially important personal variables were not included, such as
sure that all three lighting conditions employed greet light. specific prior trainings (e.g., TCCC courses, type and level of
However, red light is commonly used, and there is empirical SOF operator training, duration and specifics of other rele-
evidence that a red-green color mix may be more effective in vant medical training, and NVG cross-training). Future schol-
low-light conditions than green-only or red-only for close-in ars may choose to seek appropriate samples to systematically
medical procedures, such as suturing. Additionally, we did assess the potential impact of demography, training, and expe-
24
not test participants under full-light conditions, which would rience on the effective use of lighting on IV and IO application
have allowed us to assess their success rates and application in low-light conditions.
times under tactical lighting conditions compared with ideal
lighting conditions. Further, confidence ratings were not significantly related to
study outcomes. The reasons for these null findings are unclear.
Participants were given only minimal training prior to testing, Empirical research suggests that self-assessment may be flawed
were not provided an opportunity to practice, and were al- in general and that there may be a confidence-competence
lowed only one attempt per procedure per lighting condition. mismatch in tourniquet application by nonmedical users. 27-29

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