Page 21 - JSOM Winter 2018

to the 14G AC, although both have high failure rates, and we admittance technology (Scisense 7.0F VSL Pressure- Volume
found the 10G AC and 3mm LT provided rapid effective res- Catheter with ADVantage PV System 500; Transonic Systems
cue from both t-H/PTX and PEA > 90% of the time. 14 Inc). A midline laparotomy was then performed to place a
12mm balloon-tipped trocar through the central tendinous
In this planned secondary analysis, we sought to evaluate the portion of each hemidiaphragm for thoracic insufflation of
interplay between increasing systemic hemorrhage resulting in CO and instillation of blood removed from the femoral ar-
2
HTX and tension physiology through evaluation of both the terial line.
susceptibility to tension physiology and differences in decom-
pression failure rates in the same Yorkshire swine model. To Creation and Decompression of t-H/PTX
accomplish this, we compared the standard 14G AC against Ten percent estimated blood volume (EBV) was approximated
a 10G AC, 14G mVN, and LT in class I and II hemorrhage at 7mL/kg using established veterinary guidelines and was
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HTX, defined as 10% and 20% estimated blood volume removed from the femoral arterial line and instilled into the
(EBV) HTX, respectively. We hypothesized that increasing first hemithorax. This process was then repeated with a sec-
hemorrhage and HTX would predispose the animal to tension ond 10% EBV hemorrhage on the contralateral side after the
physiology and that needle decompression would fail more initial set of four decompression events. Tension physiology
frequently as hemorrhagic shock and HTX volume increased. was simulated with thoracic CO insufflation using a standard
2
In addition, based on our previous work, we suspected that laparoscopic insufflator in pediatric mode (PneumoSure 45L
the larger-caliber devices, the 10G AC and LT, would perform insufflator; Stryker Corp). At a flow rate of 5L/min, CO was
2
better than smaller-caliber devices, the 14G AC and the 14G instilled into the pleural space at an initial insufflation pres-
mVN, in models of increased hemorrhage and HTX. sure of 5mmHg and increased by 5mmHg every 2 minutes un-
til tension physiology was achieved. Tension physiology was
defined as a 50% decrease in cardiac output. Once tension
Materials and Methods
physiology was achieved and decompression attempted, the
Our swine t-H/PTX model has been reported in detail and flow rate was decreased to 1L/min to simulate an ongoing,
14
is briefly summarized later in this section. Four devices were intermittent air leak.
compared. The 14G AC and 10G AC devices are both 8cm
(3.25 in) long over-the-needle catheters (ARS Needle Decom- Four decompression events were completed on each side with
®
pression Kit; North American Rescue, http://www.narescue randomized device and location. Animals were allowed 5 min-
.com). The 14G mVN device used was 14G, 8.6cm long (En- utes to rescue unless they developed PEA, and then the event
hanced Pneumothorax Needle; H&H Medical Corp., https:// was terminated at 2 minutes. Successful rescue was defined as
buyhandh.com/), and includes a blunt spring-based stylet to return to 80% baseline of systolic blood pressure. The animal
extend beyond the sharp needle tip as a safety mechanism once was allowed 5 minutes’ recovery between events.
it passes through soft tissue. Manufacturer instructions for use
of this product recommend use of a syringe to flush or aspirate Comparison of Susceptibility to
the device in the event of occlusion; however, all devices were Tension Physiology and Failures
used in the same way and not manipulated after placement For the purposes of this analysis, we further stratified de-
for the experimental purposes of the study. The LT (ENDO- compression events occurring during 10% versus 20% EBV
PATH 2/3mm Mini Bladeless Trocar; Ethicon Endo-Surgery) hemorrhage, which corresponded to the first and second hemi-
®
is 2–3mm, 10cm long, and requires a scalpel for skin incision thorax, respectively, studied in each animal. PEA data were
before placement. All devices used were registered with the US excluded because all PEA events were conducted with 20%
Food and Drug Administration; however, the LT is not cur- hemorrhage and HTX.
rently marketed for thoracic decompression.
We used the time to onset and the volume of CO insufflation
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Anesthesia and Animal Preparation required for tension physiology to extrapolate the suscepti-
This study was performed in compliance with the “Guide for bility to tension physiology. We then compared the incidence
the Care and Use of Laboratory Animals” of the National In- of failure and time to meaningful recovery from t-H/PTX.
stitutes of Health, Animal Welfare Act and Regulations, and These data were analyzed in total, by device, and across HTX
the applicable Department of the Navy requirements for the groups. Device specific comparisons were in reference to 14G
use of animals in research. The Naval Medical Center Ports- AC. We then clustered the devices by small caliber and large
mouth Institutional Animal Care approved the research pro- caliber for additional comparisons.
tocol and all procedures were performed in an Association for
Assessment and Accreditation of Laboratory Animal Care, Statistical Analysis
International–accredited facility. Standard descriptive statistics were generated. The Shap-
iro-Wilk test was used to assess the assumption of normal-
Female Yorkshire swine weighing 35–52kg were sedated, ity seconds to rescue, seconds from rescue to recovery, and
endotracheally intubated, and maintained under general an- CO required to induce tension physiology. Mann-Whitney-
2
esthesia. All animal procedures were conducted while the ani- Wilcoxon tests compare continuous outcomes of interest.
mal was under general anesthesia. Mechanical ventilation was Pearson χ and Fisher exact tests were used to evaluate associ-
2
provided with volume control set at 10mL/kg and respiratory ations of categorical outcome measures. We considered P < .05
rate adjusted for normal end-tidal carbon dioxide (CO ). Once statistically significant. Data are reported as proportions for
2
set, the ventilator was not adjusted for the remainder of the categorical variables and median (interquartile range [IQR])
protocol. Central venous and arterial catheters via cut-down for continuous variables as measures of central tendency. Odds
technique were placed for pressure monitoring, as well as ratios were calculated to compare failures of small to large
blood sampling and real-time assessment of cardiac output via devices across HTX groups. Data storage and management

Larger-Caliber Devices for Tension Hemopneumothorax Decompression | 19