Page 74 - JSOM Fall 2020

and ventilation, it is reasonable to confirm a PTX by chest FIGURE 2 Thoracic U/S images obtained while using M mode.
radiograph or ultrasound prior to tube thoracostomy.” 9 (A) Characteristic seashore sign (PTX absent). (B) Barcode or
stratosphere sign (PTX present).
Two modes have historically been used to detect PTX with
U/S. B mode, or “brightness mode,” is the standard two- (A)
dimensional mode most commonly applied to look for lung
sliding at the pleural interface (Figure 1). M mode, or “mo-
tion mode,” which examines the sonographic movement
across a linear area over time, is sometimes used to augment
the B-mode examination. Examination of a normal, uninjured
lung will create characteristic findings commonly referred to
as the “seashore sign,” whereas a PTX will create a charac-
teristic “stratosphere” or “barcode” sign (Figure 2). Studies
evaluating the value of M mode on the sensitivity/diagnostic
accuracy of PTX detection have been mixed. 10,11
FIGURE 1 Thoracic U/S image obtained when using B mode,
depicting pleural interface at which dynamic lung sliding is typically
seen in the absence of PTX.

(B)

Though U/S is a potentially valuable adjunct in the hand of
military medical technicians, scant literature exists on the em-
ployment of U/S by military medics or the optimal training
required to allow them to effectively use U/S at the point-of- defined as active duty enlisted Army soldiers with military oc-
care. 12,13 We postulate that rapid detection of a PTX by mil- cupational specialty (MOS) 68W assigned to a brigade combat
itary medical personnel equipped with portable or handheld team, were recruited via email to voluntarily participate. Those
U/S could overcome the demonstrated physical examination with previous formal U/S training, as defined as expert-led di-
limitations and lead to more accurate detection/differentiation dactic/hands-on training longer than 1 hour, were excluded
of thoracic injuries, timely integration of life-saving interven- from participation. We used a random number sequence gen-
tions, and/or proper evacuation to a higher echelon of care. erator (Random Sequence Generator, Randomness and In-
The aims of this study were to (1) assess the ability of US Army tegrity Services Ltd., Dublin, Leinster, Ireland) to randomize
combat medics to use portable U/S to detect sonographic find- subjects into one of two groups. Participants randomized to
ings of PTX in human cadaver models after a brief training the didactic-only cohort received a 20-minute PowerPoint pre-
intervention, (2) determine the value of hands-on U/S training sentation that detailed the PTX portion of the FAST exam. The
compared to didactic alone, and (3) compare the employment instruction, provided by an U/S fellowship-trained emergency
of brightness mode (B mode or two-dimensional) vs motion medicine physician assistant (PA), covered both image acqui-
mode (M mode) in the detection of PTX sonographic findings. sition and image interpretation. A second “blended” cohort
underwent the same training followed by 1 hour of additional
Materials and Methods instructor-guided hands-on training with two different U/S ma-
chines (Sonosite iVIZ and Sonosite M-Turbo , SonoSite, Inc,
®
®
The US Army Regional Health Command-Central Institu- Bothell, WA), each with a high-frequency linear transducer.
tional Review Board approved this study and investigators Blended cohort participants practiced image acquisition and
have adhered to the policies for protection of human subjects interpretation using other group members as U/S models and
as prescribed in 45 CFR 46. This randomized, prospective, were given opportunities to ask questions and receive feedback
observational cohort study was conducted at a single US mil- on their techniques prior to examining cadaver models.
itary installation in October 2018 in conjunction with a US
Army Brigade combat team cadaver lab training event. U/S- Three unembalmed, nonfrozen, fresh (<72 hours from time
naive conventional force US Army combat medic participants, of death) human cadaver models were provided by Southwest

72 | JSOM Volume 20, Edition 3 / Fall 2020