Page 89 - Ultrasonography in Prehospital and Emergency Medicine - Rein Ketelaars
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                 Which ultrasound transducer type is best for diagnosing pneumothorax in pre-hospital care? 87
sensitivity and specificity of 83% and 100%, respectively. The phased-array transducer showed a sensitivity and specificity of 67% and 100%. Sensitivity of both auscultation and chest radi- ography was only 50%. In our study, the gold standard was a thoracoscopically induced and confirmed pneumothorax. Because we assessed 495 ultrasound clips showing pneumothorax, the diagnostic performance we found is more reliable.
We hypothesized that the linear-array transducer would have the best diagnostic perfor- mance. This study, however, showed no difference in diagnostic accuracy between the trans- ducers.
The Nijmegen HEMS introduced prehospital ultrasonography to the Netherlands in 2006 and used a phased-array transducer ever since. Only years later, a linear-array transducer was added. A curved-array transducer has never been used. This history might explain the trans- ducer preferences of the observers and the high and equal diagnostic performance between transducers.
Although diagnostic performance is equal, we recommend the linear-array transducer for (prehospital) lung ultrasonography. The diagnosis is made faster and with a better image quality. These are important advantages in the dynamic prehospital environment, HEMS physicians encounter challenges such as time pressure, limited working space, residual cloth- ing, defibrillator pads, and Velcro® straps. Most importantly, the interpretation of US im- ages may be hampered by sunlight or precipitation. When the HEMS physicians have the best possible image quality, they can better deal with these factors and do the best possible for our patients.
Furthermore, when the linear-array transducer is installed as the default transducer, it may have additional advantages. It is the preferred transducer for vascular access and assessment of the airway and endotracheal tube position.15 These matters often take precedence over de- tailed assessment of breathing, although it may be of vital importance to be informed about a significant pneumothorax before airway management is commenced.
In addition, the linear-array transducer is superior for ultrasound-guided regional anesthe- sia (UGRA) in severely injured or trapped extremities and for optic nerve sheath diameter (ONSD) measurements in traumatic brain injury (TBI) patients.17 For abdominal ultrasound and echocardiography, however, the phased-array or curved-array transducer is still invalu- able.
The observers were able to successfully assess the video clips of normal ventilation and pneu- mothorax without having access to the US machine or the patient. This situation is compara-
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