The Emergency Physician (EP) has performed bedside ultrasound (US) for more than three decades. US is ubiquitous today in Emergency Medicine (EM). Each year, new EPs learn the skill, fresh evidence is brought to light supporting the practice, and novel indications are explored.1 Technological advances have delivered smaller machines with improved image quality that are less expensive than ever before. US training is an important component of an EM residency program and a required core competency procedure of the Accreditation Council for Graduate Medical Education Residency Review Committee.2 It is tested on board examinations and is endorsed by EM societies.1,3 There are numerous opportunities for supplementary training in emergency US ranging from local courses to established fellowship training programs.
Safety considerations have also contributed to the acceptance of bedside US. Sonography is noninvasive, is safe in pregnancy, does not involve ionizing radiation, does not require nephrotoxic contrast agents, does not cause subcutaneous extravasation, and does not cause allergic reactions like other modes of imaging.4 With increasing concern in the medical community over the long-term effects of ionizing radiation, US is recognized as an attractive alternative.5 The U.S. Department of Health and Human Services Agency for Healthcare Research and Quality has highlighted US guidance for central line insertion as one of their top 10 recommended practices.6
The intent of this chapter is to provide an introduction to bedside US. The physician-sonographer should have a general understanding of the physics underlying the properties of an US wave. “Knobology” is a colloquial term used to describe the study of the buttons, dials, switches, and knobs on the console of an US machine. It is important that all users have a good sense of their machine’s operational functions. Typical US machines and transducers used in the ED will be described.
BRIEF HISTORY OF EMERGENCY ULTRASOUND
Bats and toothed whales have used sound for echolocation for millions of years. Dolphins produce a series of clicks that pass through the lipid-rich melon on their heads, an acoustical lens of sorts that focuses the sound waves into a beam. Returning echoes are processed to determine the location of objects for navigation and hunting.7 Sonar (acronym for sound navigation and ranging) is a maritime technique that uses sound waves for identifying oceanic objects. It was initially introduced in response to the sinking of the Titanic in 1912.8 It was further developed and employed in World Wars I and II for submarine detection.8
In the early 1950s, a Radiologist named Douglas Howry and a team of other physicians introduced the first diagnostic US machine using a water-bath immersion tank. In the 1960s, direct contact (i.e., transducer to patient) scanners were developed, and the contemporary saga of US as a viable diagnostic modality commenced.9 The technology was only found ...