Introduction
Ultrasound (US) is a useful diagnostic tool for use in hospitals.
It is noninvasive and inexpensive, and causes no radiation exposure. Besides
radiologists, many emergency physicians use US to assist in their decision
making during critical conditions [1]. With the current improvement in technology,
US machines have become more portable and are available with a better
resolution. Ziegler et al [2] reported that a portable device had approximately
90% accuracy compared with high-end devices. US machines such as PRIMEDIC
HandyScan, V-scan, and Sonosite are commonly used as portable devices in
prehospital settings.
US has been brought to prehospital settings as a result of the
recent advances in technology [3]. A prehospital setting is a unique, most
likely noisy, and often limited space. Traditionally, diagnostic tools used in
prehospital settings are based on history taking and physical examination.
Physical examination alone cannot be sufficient to diagnose certain
conditions [4]. In addition, many studies suggested that prehospital US can
change the final diagnosis and treatment [5,6]. Prehospital US has a variety of
applications, such as focused assessment with sonography in trauma (FAST) [5],
assessment of cardiac arrest [7], lung US (mainly in pneumothorax) [6,8], and
others. Countries that have studied prehospital US extensively include Germany, France,
Italy, and the United states [9]. Literature was reviewed and discussed in the
following sections.
Feasibility of US in a prehospital environment
Because a prehospital space is unique and limited, a US machine
should be smaller in size but should have better image quality. Some studies
performed US at the scene, and others in a vehicle, such as an ambulance or a
helicopter. If performed at the scene, the delivery time to hospital may be
prolonged, and if performed in a helicopter or an ambulance, the transporting environment may influence the
scan. There are studies of prehospital US in a fixed wing and helicopter, which
showed good results. However, Melanson et al [10] reported in their study that
the lack of sufficient time during helicopter transport and a proper lighting
system in the helicopter can compromise the results of FAST examination. Snaith et al [11] reported that FAST
and abdominal aortic aneurysm (AAA) performed in a static and ground ambulance
is of good quality due to the availability of sufficient time and is comparable
to that performed at the emergency department.
In Taiwan, emergency medical services mainly involve ground
ambulances, and most of the ambulance beds are located at the left side; hence,
left-hand-based practice may be helpful for performing the scan. Fixation of machines
to the frontal areas of ground ambulances may be helpful in reducing shaking.
Educating
paramedics about US
Many studies have invested in the learning curve for US, especially
in FAST. They concluded that a 1-day course,including lecture and hand-on
practice, can generate good accuracy and competency [12]. Heegaard et al [13] designed
a FAST training course, which lasted 7 hours, for emergency nurses and
paramedic flight crews; they reported 100% sensitivity and specificity in nontrauma patients,
and 60% sensitivity and 93% specificity in trauma patients after 1 year of
training. Kim et al [14] also reported that a 4-hour FAST training course for
intermediate emergency medical technicians (EMT) resulted in 61% sensitivity and
96.3% specificity.
