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some providers requiring higher-resolution V adjustments implemented. It is plausible that the need for and utilization
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to provide the best care for their patients. The lower limit of of ECLS with and without MV is slated to increase as we pre-
RR adjustment was 8 breaths/minute, which in our experi- pare for multidomain and large-scale combat operations with
ence may not be adequate for patients who are profoundly the great likelihood of high numbers of casualties with severe
hypocapnic or who are receiving ventilation through extra- injury. The Special Operations Forces community is likely to
corporeal means. However, the argument may be made that benefit from considering such an approach because evacua-
at present, any patient requiring extracorporeal lung support tion of surviving casualties from engagement zones will ensure
may already be in a facility equipped with more robust ventila- higher survival rates when comprehensive life-sustaining capa-
tors, capable of more ventilation options, thus potentially ren- bilities such as ECLS are available.
dering this particular criticism moot. For the intended market
of prehospital use, this limitation may not be an issue. Limitations
This study is limited by being a convenience sample taken
The inspiratory flow of the device is variable, which is beneficial from a larger study, with no designated control experiments;
in comparison with fixed-flow devices, but it is limited to a max- all animals received both SAVe II support and ECLS. We also
imum of 27L/min and is not changeable by the user. The device recognize our inherent bias: we did not choose the device we
is designed for patients weighing >45 kg, for whom flow rates tested; rather, it filled the need of our not taking our ICU venti-
this low may be inadequate. The literature suggests that flow lator between buildings repeatedly. We chose to collect data on
rates are an independent factor in patient–ventilator synchrony, the use of this device as a glance at a potential-use case during
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and flow rates of up to 80L/min may be required. Because the evacuation with primary lung support provided by ECLS,
SAVe II is incapable of such flow, patient–ventilator synchrony which is not what the SAVe II was designed or marketed for.
may be an issue with patients who require higher flow rates,
subsequently leading to increased sedation requirements. The device is indicated for short-term ventilatory support for
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patients weighing at least 45 kg, and the listed device speci-
On every transport in this study, when the stands of the fications suggest the ability to achieve up to 30 beats per min-
wheeled litter carrier were lifted, the abrupt motion caused ute at 800mL V , with combinations capped at a maximum
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the High Peak Pressure alarm to sound. The motion of the minute ventilation of 8L per minute, suggesting that the de-
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litter during transport also regularly caused either High Peak vice is potentially capable of providing standalone ventilatory
Pressure, High PEEP, or Spontaneous Breath Detected alarms support for casualties with minimal to moderate respiratory
to sound, sometimes in combinations of two or three simulta- insufficiency. However, it is unlikely to provide adequate sup-
neously. Although alarms alerting caregivers to problems de- port for a patient with severe ARDS who requires fine-tuned
livering breaths are a requirement of all ventilator types, the monitoring and adjustment of settings with a wider range of
sensitivity of these alarms may warrant further investigation. parameter options. Given the limitations of the allowable de-
The alarms were sufficiently audible from a distance of up to vice settings, the SAVe II seems to be a better adjunct to ECLS
5 meters, although the visual alarm indicator was difficult to than a standalone ventilator.
identify if one was not looking directly at the control panel
of the device. Our team also found the ventilator circuits de-
signed for the SAVe II to be not very durable, with several Conclusion
ripping apart during removal after the experiments. In this combat-relevant, large-animal model of respiratory fail-
ure resulting from polytrauma treated with ECLS, the SAVe II
The SAVe II model we tested does not provide physiologic data performed without failure or degradation in animal clinical con-
on the patient (e.g., exhaled V , PIP, plateau airway pressure). ditions when used as an adjunctive supportive device to ECLS
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This can be troublesome to clinicians wanting to ensure that during 33 total intra- and interfacility transports. The light
plateau pressures remain below the safe threshold of 30 cm weight and cube shape make the SAVe II easily transported and
H O. PIP can be realized only within a range of 5 cm H O, and likely more available for use by field medics, while the built-in
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only as a range between two limits. The manufacturer states simplicity of the device makes its employment more likely by
that the display of actual measured PIP is an update that they field medics for patients with mild respiratory insufficiency.
have fielded, but it was not available on the device we tested Further standalone testing of the SAVe II or similar transport
(personal communication with Automedx, January 2017). ventilators is warranted and already planned in our lab.

Our experience with the SAVe II was unique in that both healthy Meeting Presentations
and injured animals were receiving at least partial lung support Portions of this work were presented at the 2017 and 2018
through ECLS. In standard clinical practice, ECLS for healthy Advances in the Care of Critically Ill Neonates, Children, and
lungs is not provided, thus rendering this data set unique and Adults conferences, Snowbird, UT (March 21–25 and April
not singularly representative of standalone performance of the 3–7, respectively), and the 2017 and 2018 Military Health
device. Standard practice for ECLS patients dictates rest set- System Research Symposium, Kissimmee, FL (August 27–30
tings on the ventilator, with 76% of centers targeting ventila- and August 20–23, respectively).
tion below 6mL/kg. The lowest V available on the SAVe II
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provides a breath size of 4.44mL/kg when used with patients Acknowledgments
of the lowest recommended weight; larger patients will be ca- The authors wish to thank Teryn Roberts, PhD, for her efforts
pable of receiving lower per-kilogram tidal volumes, but at the in the analysis of this data.
expense of limited inspiratory flow, as discussed above.
Author Contributions
As suggested by Macku et al., ECLS is currently underuti- AIB and LCC conceived of the study design. BMB, GH, DSW,
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lized in the military setting and should be further explored and JHC, KS, VK, LCC, and AIB collected and analyzed data,

68 | JSOM Volume 22, Edition 1 / Sping 2022