Page 38 - Ultrasonography in Prehospital and Emergency Medicine - Rein Ketelaars
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Chapter 2
PHUS in general
The use of PHUS provides diagnostic and therapeutic benefit, and it does not delay patient management.3,8,13–15 It has been found to be feasible to enhance clinical assessment in a variety of out-of-hospital settings.15 Price was among the first to show that ultrasonography (US) is also feasible during helicopter transport and that focused assessment with sonography for trauma (FAST) can be rapidly performed in-flight and has no influence on aircraft avionics.16
Physicians and paramedics without being educated as a radiologist can be trained effectively to perform PoCUS. Lyon et al. demonstrated that prehospital critical care providers could learn to detect the sonographic sliding lung sign with a high level of sensitivity (97%) and specificity (94%) and retain their skill over time.17 Forty physicians participated in a 4-hour hands-on training and demonstrated significant improvements in the ability to perform US examinations.18 Although the initial learning curve for FAST is steep, it starts to flatten after 30-100 scans.19 Probably even more training and experience is required for advanced applica- tions such as transcranial doppler for ischemic stroke or specific triage protocols.
With the right education and mentorship, paramedics can obtain ultrasound images of suffi- cient quality to positively identify significant pathologies in critically ill patients.20 A recent Canadian study found that PHUS performed by both physicians and non-physicians sup- ported interventions in both trauma and medical patients.21
The reported diagnostic accuracy of PHUS varies widely. Some reported a sensitivity of 85–90% and a specificity of 96–100% for chest, abdominal, and cardiac US. Positive predic- tive value (PPV) and negative predictive value (NPV) were 100% and 95.5%.3,13 Diagnostic accuracy during transportation also varies. For PHUS during transfer by ground ambulance and PHUS on-scene, Brun reported a sensitivity of 94.7% and 95.2%, respectively.22 In-flight ultrasound examinations of the lung, abdomen, and pericardium yielded a sensitivity of only 50–64.7% when compared to pathology that required an intervention, rather than to all pos- itive findings.23 Others found a sensitivity of 78.6% for in-flight extended FAST (eFAST) compared to CT-scan.24 Because of the high specificity, the activation of a trauma surgery team is justified for positive PHUS findings.23
Despite the range in diagnostic accuracy, PHUS is still highly reliable compared to clinical assessment.3,5 In 169 non-trauma patients, PHUS improved the diagnostic accuracy based on traditional clinical examination to 67% compared to the final in-hospital diagnosis. Diagnos- tic accuracy was improved in 90% of patients in whom the initial diagnosis was uncertain (n = 115).25 Blaivas found that PHUS improved the certainty of the diagnosis in 68% of 25
  


























































































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