Page 67 - 2022 Spring JSOM

(Avalon Elite; Getinge Group) inserted into the right jugular On day 2 of the study, the animals underwent bilateral pulmo-
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vein. Oxygen was used as the sweep gas at all times. After nary contusions using a modified captive bolt stunner (Model
ECLS initiation, MV was reduced using a modified ARDS- ML; Karl Schermer, Packers Engineering), followed by bilat-
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Net protocol to stepwise reduce V by 2mL/kg and RR by 2 eral chest tube placement, as previously described. 6,10–12 The
T
breaths/minute sequentially, until minute ventilation was ap- travel described above was repeated in the injured state, in-
proximately 50% of baseline settings. cluding all phases of transport to and from the chamber. At the
conclusion of data collection after return to the origin ICU on
The animals were next prepared for ground transport. The day 2, the animals were humanely euthanized in accordance
SAVe II was set up according to the manufacturer’s instruc- with our Institutional Animal Care and Use Committees–
tions and was tested for proper operation prior to use. The approved protocol.
SAVe II settings (Fio , PEEP, V , RR) were matched to the ICU
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2
ventilator settings, and the animals were then switched from Data Collection
the V500 to the SAVe II. The PIP limit on the SAVe II, ad- Transport times on both days were recorded, defined as time
justable in increments of 5 cm H O only, was adjusted down- from departure from the origin ICU to the beginning of data re-
2
ward until the PIP alarm was reached, and then returned to cording at the destination hypobaric chamber, and from the end
the next highest setting (i.e., if the PIP limit alarmed when of data recording in the chamber back to the ICU of origin. The
set to 25 cm H O, it was then set at 30 cm H O). Animals time reported does not reflect the time of use of the transport
2
2
that were on 21% Fio on the ICU ventilator were ventilated oxygen cylinders because not every animal required supplemen-
2
with 21% Fio on the SAVe II. Animals that required supple- tal oxygen during transport, and upon entry into the hypobaric
2
mental oxygen received 10L/min oxygen, bled into the SAVe chamber or origin ICU, the first step conducted was transfer
II circuit during transport from a size D or E cylinder (based from transport oxygen to the larger cylinder banks. Data on
on cylinder availability), via the designated oxygen reservoir hemodynamics (i.e., heart rate and mean arterial blood pres-
designed for use with the SAVe II circuits. The animals were sure), MV settings, ECLS therapy, and arterial blood gas anal-
then transported, via a standard NATO litter (Model RES- ysis were collected by manual transcription before and after all
7309-00; Life Support International) attached to a wheeled transports. Blood gas analysis was conducted via the i-STAT1
litter carrier (Item 9636; Brenner Metal Products) fitted with point-of-care blood gas analyzer (Abbott Point of Care). When
a medical equipment rail kit (Smeed Technologies), through supplemental oxygen delivery was required through the SAVe
the facility and to an adjacent building, thus simulating intra- II, an oxygen delivery calculation was utilized to estimate deliv-
and interhospital casualty transport (Figure 1). Our transports ered Fio , as previously described by our group. 7
2
included approximately 50 m of hallway, a four-floor elevator
ride, transition from a loading dock to ground level, and ap- Using SAS version 9.4, a paired t-test or a Wilcoxon signed-rank
proximately 200 m of open-road ground transport between test, depending on the distribution, was performed to evaluate
buildings before entering a building, travel in hallways for the differences between each variable pre- and post-transport.
another 100 m, and loading and unloading into a hypobaric Bland-Altman analysis was conducted using the variables par-
chamber, analogous to loading into and unloading from an tial pressure of oxygen:fraction of inspired oxygen (Pao :Fio ;
2
2
aircraft. PFR)—an accepted index of lung function—as well a noninva-
sive PFR surrogate, the pulse oximetry saturation percentage:-
FIGURE 1 Simulation of intra- and interhospital casualty fraction of inspired oxygen (Spo :Fio ) ratio (SFR). Statistical
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transport. 2 2
significance was accepted at p < .05; data are represented as
mean ± SEM (standard error of the mean).
Results
A total of 33 ground transports were completed in this study.
Of the 11 animals that entered the study, all completed day 1
(uninjured control conditions) (Figure 2). Through all phases
of our ground transport, no device failures were observed, and
adjunctive use of a simplified ventilator did not contribute to
(A) Litter with critical care equipment on practice test run before live
study. Note the SAVe II at the head of the litter and the ECLS system any clinical decline in the animals. Six animals died after chest
at the foot of the litter. (B) User interface of the device. Image from the trauma before transport on day 2: two died from suspected
Quick Start guide enclosed with the device. myocardial infarction following injury, and four died from
post–pulmonary-contusion cardiac contusion and unrespon-
The animals remained on the SAVe II operating on battery siveness to vasopressors and fluids, signifying the severity of
power throughout transport. Data from hypobaric exposure our injury model. Each surviving animal underwent transport
are outside the scope of this manuscript and are reported else- four times: twice on day 1 in the uninjured state and twice on
where. Next, we repeated all steps of the transport in the day 2 after polytrauma (Figure 2).
6,7
reverse order, culminating with arrival back at the origin ICU
and return to ventilation via the V500, which concluded the Mean total transport time was 38.8 ± 2.1 minutes. Mean
events of day 1. Animals were maintained in the ICU overnight transport time on day 1 was 37.5 ± 2.6 minutes (mean time
under continuous monitoring, remaining anesthetized and me- out of the origin ICU, 44.9 ± 2.6 minutes; mean time returning
chanically ventilated via the V500 (Figure 2). Overnight, the to the origin ICU, 30.2 ± 2.9 minutes). Mean transport time in
animals remained with ECLS circulating without sweep gas to the critical state on day 2 was 41.4 ± 3.9 minutes (mean time
prevent thrombus formation and limit decannulation/recannu- out of the origin ICU, 47.5 ± 5.0 minutes; mean time returning
lation problems and supply use on day 2. to the origin ICU, 34.1 ± 4.6 minutes).

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