The most studied exam type in EMS is the focused assessment of
sonography in trauma (FAST), which is used to identify hemoperi-toneum (i.e., blood in the abdomen). In one prospective study using
prehospital ultrasound, a series of 202 trauma patients were examined
and the sensitivity, specificity and accuracy of prehospital FAST were
93%, 99% and 99% respectively, in comparison to physical exam at the
scene 93%, 52% and 57%.
Blood or fluid in the abdomen was detected in 14% of patients and
use of prehospital ultrasound led to a change in management for 30%
of cases and a change in hospital destination in 22% of cases.
is a significant finding and demonstrates real-world application and
validity for ultrasound usage.
In another prospective study examining 230 medical patients
receiving either CPR or in various shock states (sustained hypotension), prehospital ultrasound led to a change in management as
well as to improved diagnostic capability. In 35% of arrest patients
presenting with asystole on the monitor, as well as 58% of those
with PEA, coordinated cardiac motion was in fact detected, and the
implementation of prehospital ultrasound was associated with statistically increased survival.
Data obtained while scanning these critically ill patients led to
a change in management in a staggering 78% of cases, leading the
authors to conclude that ALS-compliant point-of-care ultrasound “is
feasible, and alters diagnosis and management in a significant number of patients.”
Given the trend of increased use of ultrasound during resuscitation
in critical care and emergency medicine, and the introduction of more
portable, durable devices, there’s a natural inclination to explore the
potential applications of prehospital ultrasound.
A 2014 survey of EMS medical directors conducted by the National
Association of EMS Physicians (NAEMSP) found that although only
4.1% of current systems implemented prehospital ultrasound, an additional 21.7% are considering implementation. The authors highlighted
that providers can use ultrasound to obtain “immediate anatomical,
diagnostic and functional information for their patients.”
Reasonably, most medical directors surveyed desired further research
showing the utility of prehospital ultrasound in reducing patient morbidity and mortality. They also cited equipment and training costs as
challenges to implementation. (See Table 2.)
Despite the hurdles inherent in the prehospital environment, such
as attempting to scan in the back of a moving ambulance, noncompliant patients, variable ambient lighting, and an inconsistent power
source, research from the United Kingdom indicates ultrasound could
be performed to a standard consistent with those performed in the
Nevertheless, further research needs to be done on the specific presenting complaints, call types, and the potential exam types where
ultrasound might improve diagnostic accuracy and, ultimately, improve
patient outcomes while not adding to scene or transport time.
THE TRAINING IMPERATIVE
The successful incorporation of ultrasound in a prehospital setting
requires a paradigm shift in our approach to critically ill and injured
patients. This must include a robust training program that mandates
education and careful implementation amongst the providers who
would employ the modality.
High-quality training, including in-situ simulation, helps to firmly
embed the principles of a particular technology within a provider’s
If specific prehospital ultrasound algorithms could also be inserted
into a service’s protocols it would also serve as an additional reminder for
providers to perform the examination as time and circumstance allow.
Given that most of the literature for prehospital ultrasound is derived
from European systems implementing the Franco-German crew resource
management model—commonly staffed by a critical care physician—a
recent systematic review focused on prehospital ultrasound curricula
designed specifically for paramedics, attempting to probe optimal content, duration, setting, design and evaluation.
The authors noted many out-of-hospital algorithms that are being
successfully implemented by providers, including FAST, obtaining
pleural windows to screen for pneumothorax and pulmonary edema,
as well as detecting early stroke and the assessment of hemodynamic
status. The authors concluded that “FAST and pleural ultrasound is feasible and time effective with successful application;” whereas, “curricula
designed to detect cardiac standstill have been too short.”
As reported in the literature, the duration of the abdominal ultrasound curricula has varied widely, from four hours over one day to 13
hours over two months of training, with most curricula using a 1-day
course. The duration of pleural ultrasound curricula is typically shorter
than FAST, and studies have suggested that image acquisition is a separate skill from image interpretation.
Paramedics can also be taught to interpret thoracic ultrasound in as
little as 10 minutes with significantly higher diagnostic accuracy than
one might imagine.
Comprehensive studies combining imaging acquisition and interpretation taught pleural ultrasound curricula from 25 minutes to 10
hours. Interestingly, one study showed 26% of patients receiving a needle thoracostomy for a suspected pneumothorax in the field had a positive sliding lung sign upon arrival, suggesting the patient didn’t have
Table 2: Barriers to implementing ultrasound as
perceived by EMS medical directors (n = 198)
Equipment cost 177 (89.4%)
Training costs 146 (73.7%)
Challenges in training 106 ( 53.5%)
Transport times 95 ( 48.0%)
Concerns about delaying time to
definitive care 90 ( 45.5%)
Ultrasound beyond the scope of
practice of providers 76 ( 38.4%)
Lack of evidence 76 ( 38.4%)
Regulatory factors 29 ( 14.6%)
Approval by EMS administration 25 ( 12.6%)
Buy-in by other EMS medical directors 21 ( 10.6%)