Page 64 - Journal of Special Operations Medicine - Fall 2017

Discussion A potential confounding variable in this study is that BVM de-
vices designed for single use were used repeatedly in our study.
Although the differences in overall mean BPM between de- This likely had a significant effect on the CMS devices because
vices was negligible, there were apparent differences when the we only had five prototypes and they rely on a spring to in-
rates were broken down by groups. Risk of hyperventilation flate. We were informed by the manufacturer during the study
was eliminated in the classroom portion of the study, with a that they had observed “spring fatigue” resulting in slower
maximum recorded ventilation rate of 12.54 BPM. However, inflation rates with increased use. A related issue that was not
this came with increased rates of underventilation. In the field, accounted for in our study was variability in rate between the
ventilation rates increased in general, which was expected, but study devices themselves. It was observed that some of the de-
the trends remained the same, with an increased percentage of vices took longer to inflate than others. However, no data were
subjects exceeding the recommended rate with the standard collected regarding the individual devices’ performance, so it
device and an increased percentage falling below the recom- is difficult to say whether this impacted results. Future studies
mended rate with the study device.
should limit repeated use if possible and test each device or
track data by device to identify variances between like devices.
Ventilation rates in this study were lower than expected for
both devices, but particularly so for the standard devices. Pre- Finally, limited training and exposure to the new device may
vious studies reporting ventilation rates include that of Auf- have affected results as well. Different techniques were observed
derheid et al. in 2004, who reported a rate of 30 ± 3.2 BPM involving use of the CMS device. Some Medics were observed
1
6
with Paramedics in a prehospital setting, and Milander et al. forcibly opening the device rather than allowing the spring to
in 1995, who reported a rate of 37 ± 13 BPM with respiratory open it, which would increase the ventilation rate. Medics were
therapists responding to in hospital cardiopulmonary resus- also observed using the red-green indicator on the spine of the
citation. The large difference in values between these studies, device not only for when to give a breath (when it turns green),
which were performed in real clinical settings, and our study as it is intended, but also to stop giving a breath (when it turned
illustrate the limitations of using a training environment to red), which it is not intended for. This would increase ventila-
predict real-world performance. It is likely that the nature of tion rate because the bag is only being partially compressed in-
our training environment did not provide the same stress re- stead of fully compressed, as designed. With more exposure and
sponse seen in actual resuscitation scenarios.
training, these incorrect techniques may be avoided.
It is also worth noting that in terms of clinical significance, An additional area of study would be a comparison of TVs
studies have shown worsening hemodynamics with increasing as the other half of the minute-volume equation. We chose to
1,2
ventilation rates, particularly at rates ≥20 BPM. Although focus on rate in this study because we believed this to be the
uncommon, rates ≥20 BPM were seen in this study with the more significant variable, but clarifying the differences in TVs,
standard device only, whereas the highest recorded rate with if any, would be useful in comparing these devices.
the study device was <15 BPM. On the other hand, both de-
vices had a significant percentage of participants ventilating
below the recommended rate, with both devices having low- Conclusion
2
est recorded rates slightly greater than 6 BPM. In one study, The study device was clearly shown to decrease the incidence
improved hemodynamics in a porcine hemorrhage model were of ventilation rates exceeding the recommended rate of 10–12
seen with a ventilation rate of 6 BPM compared with rates of BPM in the classroom and the field environments. The clini-
12, 20, and 30 BPM, with preservation of oxygenation and cal significance of this finding is difficult to determine based
only mild acidosis. This suggests that mildly underventilating on the results of this study because ventilation rates, in gen-
is unlikely to be as detrimental as overventilating, and may eral, were low and there were only two instances of ventila-
actually be beneficial in some circumstances. However, Davis tion rates ≥20 BPM, although both of these occurred with the
7
et al. found worse outcomes with both hyper- and hypoventi- standard device in the field, which is the area of concern. The
lation. No current guidelines recommend ventilation rates <8 new device has been shown to be at least partially effective and
BPM and more research is needed in this area.
merits further research and development.
Limitations and Areas of Further Study Acknowledgments
There are several limitations to this study. It is questionable We thank the staff and instructors of Brigade Combat Team
whether the training environment reflects real-world perfor- Trauma Training with the Department of Tactical Medicine,
mance. Despite our attempt to conduct this study with the especially SSG Carleton Thrall, EMT-B; SSG John Pearson,
most accurate combat simulations by using BCT3, it is likely EMT-B; and SSG Mark Rickelman, EMT-B. We also thank
that only a prospective, randomized, study involving real sce- the staff of the Army-Baylor Emergency Medicine Physician
narios would be able to answer the question of which device is Assistant residency at San Antonio Military Medical Center
superior when used early in a prehospital setting.
(SAMMC) for their additional guidance and assistance with
this project, especially MAJ Monica Casmaer, DSc, PA-C;
A significant limitation of this study came from integrating MAJ Timothy Bonjour, DSc, PA-C; MAJ Sean Therein, DSc,
our protocol into the BCT3 training. We were limited to short PA-C; and Sue Love, DSc, PA-C. Finally, we thank Dr John
periods of ventilation because of training requirements of the A. Ward, PhD, research physiologist, Department of Clinical
course, which included moving Medics to different stations Investigations, SAMMC, for his time and recommendations
and evaluating multiple aspects of casualty management. It is for the Results section of this study.
possible that there would be different rates seen over time with
both devices when used for longer durations, and this should Funding
be considered in future studies.
No funding was obtained for completion of this study.

62 | JSOM Volume 17, Edition 3/Fall 2017