Keywords
Cardiac - central line - education - effusion - phantom - SAMS - Syria - tamponade
- ultrasound - vein - war
INTRODUCTION
The use of ultrasound in the management of trauma has become an essential skill in
emergency medicine and surgery, particularly in resource-limited areas of conflict.
The extended Focused Assessment using Sonography for Trauma (eFAST) ultrasound exam
can identify causes of shock, including pericardial tamponade, tension pneumothorax,
and intraperitoneal hemorrhage. Ultrasound can also assist with IV access, particularly
in vasoconstricted patients in shock or when central venous catheters and intraosseous
needles are in shortage. Severe resource limitations and a lack of computed tomography
have led to the expanded use of ultrasonography, particularly in field hospitals in
Syria, currently the site of the largest humanitarian crisis in the world. Opportunities
for education in ultrasound training are lacking, in great part due to prohibitive
costs of commercial brand name ultrasound phantoms, such as the Blue Phantom, that
range from $449 to more than $18,000 per device for venous cannulation and pericardiocentesis
simulation.[1] Functional, cost-effective, and high-fidelity models for training health-care providers
in low-resource settings are lacking.
SUBJECTS AND METHODS
Thirty physicians and technicians enrolled in a three-day emergency medicine and critical
care training course in Gaziantep, Turkey, sponsored by SAMS. Homemade ultrasound
simulation models were created to teach participants ultrasonographic diagnosis of
pericardial effusions that may cause pericardial tamponade, and vein identification
and cannulation under dynamic ultrasound guidance.
For the vein cannulation phantom, the majority of ingredients were purchased from
a nearby supermarket. A hotel coffee maker was used to boil water from a 0.5L bottle,
which was mixed with six packages (8.5 gm each) of sugar-free gelatin (which serves
as a good acoustic window) and two tablespoons of sugar-free psyllium powder (which
added echotexture to simulate tissue granularity). One 3-cm layer of this mixture
was poured into a 15″ × 10″ × 2″ (5.9 × 3.9 × 0.8 cm) Pyrex rectangular glass baking
dish and was refrigerated until it congealed. Seven penrose drains measuring 8 inch
× 0.25 inch (45.7 cm × 0.64 cm) were cut in half, tied at one end, completely filled
with water to minimize the presence of air (a poor acoustic window) that could obstruct
visualization, tied at the other end, and placed side by side approximately 1 cm apart
on top of the first layer of the mixture. A second layer of the gelatin–psyllium mixture
was poured over the first layer and penrose drains and again refrigerated for another
three to four hours [Figure 1].
Figure 1: Left upper: Supplies for homemade phantom. Right upper: Trainee practicing vein cannulation.
Lower: Phantom vein at top of screen at 0.5-cm mark in middle of screen
For the cardiac phantom, a lamb heart purchased from a nearby butcher was placed inside
a water-filled sterile glove, which simulated a pericardial effusion, whereas another
lamb heart was placed adjacent to it simulating a normal subxyphoid ultrasound view
of the heart. In a large bowl, both hearts were placed within the gelatin–psyllium
mixture, which congealed in the refrigerator. Again, two layers were made, similar
to the vein cannulation phantom described earlier [Figure 2].
Figure 2: Left upper: Normal heart on left with heart simulating pericardial effusion on right.
Left lower: Image of pericardial effusion on ultrasound phantom. Right lower: Image
of pericardial effusion on real patient with cardiac tamponade. Right upper: Intra-operative
picture of patient with cardiac tamponade from right lower picture
RESULTS
Syrian technicians and physicians were trained to properly identify and practice vein
cannulation by using a portable GE Vscan ultrasound. In addition, they learned how
to differentiate a normal cardiac view from a pericardial effusion mimicking cardiac
tamponade. Participants verbalized satisfaction with the ability to learn proper technique
and practice on ultrasound phantoms. Within one month of the course, one of the study
authors was informed of two cases of surgically confirmed pericardial tamponade diagnosed
and surgically treated in the largest trauma hospital operated by SAMS in Northern
Syria [Figure 2]. Both patients survived.
Total cost was approximately $40 total for multiple ultrasound phantoms, much less
than $400 per unit as sold commercially. The majority of the cost was for the Pyrex
glassware, which can be reused for phantoms or cooking, or often easily borrowed.
The remainder of the ingredients can be used again (only four of 114 tablespoons of
psyllium were used) or taken from hospital supplies (such as penrose drains).
DISCUSSION
Reliance on ultrasound in resource-limited environments, particularly those in areas
of conflict lacking computed tomography, continues to increase. This coincides with
the proliferation of indications for ultrasound use in emergency medicine over the
past 20 years, including peripheral IV cannulation under dynamic ultrasound guidance,
which has become a best practice in the United States for most non-emergent central
lines. The need for training phantoms for ultrasound-guided venous access and for
identification of pericardial effusion in trauma is greater than ever. Resource limitations
and budget constraints in academic emergency departments in conjunction with the cost-prohibitive
prices of ultrasound phantoms on the market limit the ability of many residency programs
to purchase ultrasound phantoms. The difficulty in obtaining such expensive technology
is even more pronounced for resource-limited field hospitals serving patients with
trauma.
We used 0.25-inch penrose drains, as this size is closer in diameter to larger antebrachial
veins. The 0.375- or 0.5-inch penrose drains would more accurately simulate larger
central veins such as jugular or femoral veins. The models tolerated about ten attempts
per penrose drain using 18g needles. Smaller gauge needles appeared to allow for more
cannulation attempts before the penrose drain lost its structural integrity.
Darker-colored gelatin rendered the phantom opaque, limiting the participant’s ability
to visualize the location of the penrose drains without ultrasound guidance. Penrose
drains can be utilized to simulate arteries by increasing the pressure (by inserting
more water) within them. Sugar-free gelatin and psyllium are less prone to mold formation
compared with their sugar-based counterparts.
Similar models have been described as using gelatin,[2] silicone,[3] ballistics gel,[4] wax,[5],[6] and tofu.[7] We believe that, for very low-resource environments, this is a highly functional,
low-cost phantom using readily available products and low start-up costs.
In conclusion, homemade ultrasound phantoms are a promising cost-effective means for
meeting an educational gap in ultrasound training, particularly for resource-limited
hospitals and possibly more broadly in residency education. Further studies should
quantify both subjective and objective benefits from such models.
