title: Air and its Sonographic Appearance: Understanding the Artifacts.
abstract: BACKGROUND
  Although air has traditionally been considered a barrier to sonographic imaging, when encountered in unusual settings it can serve as an important indicator of various pathologic states as well. Clinician recognition and thorough understanding of the characteristic pattern of artifacts generated by air are critical for making a number of important diagnoses.
  
  
  METHODS
  We present five emergency department cases in which air was visualized in a pathologic location. Pneumothorax, pneumoperitoneum, necrotizing fasciitis, or Fournier's gangrene, and subcutaneous emphysema and pneumomediastinum, can be rapidly and easily identified on ultrasound by the presence of air artifacts. The relevant sonographic findings are described and discussed in this article. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Due to its inherent impedance mismatch with other human tissues, air has a characteristic appearance on ultrasound that includes irregular hyperechoic structures, "dirty shadowing," A-lines, and decreased visualization of deeper structures. Knowledge of the sonographic appearance of air artifacts can assist the physician in making a diagnosis, selecting appropriate additional imaging, and enlisting specialist consultation.
authors.affiliation: Department of Emergency Medicine, Division of Emergency Ultrasound, Mount Sinai St. Luke's Hospital, Mount Sinai West Hospital, New York, New York.
authors.forename: Simran
authors.initials: S
authors.lastname: Buttar
authors.affiliation: Department of Emergency Medicine, Division of Emergency Ultrasound, Mount Sinai St. Luke's Hospital, Mount Sinai West Hospital, New York, New York.
authors.forename: Denrick
authors.initials: D
authors.lastname: Cooper
authors.affiliation: Department of Emergency Medicine, Division of Emergency Ultrasound, Mount Sinai St. Luke's Hospital, Mount Sinai West Hospital, New York, New York.
authors.forename: Patrick
authors.initials: P
authors.lastname: Olivieri
authors.affiliation: Department of Emergency Medicine, Division of Emergency Ultrasound, Mount Sinai St. Luke's Hospital, Mount Sinai West Hospital, New York, New York.
authors.forename: Michael
authors.initials: M
authors.lastname: Barca
authors.affiliation: Department of Emergency Medicine, Division of Emergency Ultrasound, Mount Sinai St. Luke's Hospital, Mount Sinai West Hospital, New York, New York.
authors.forename: Aaran B
authors.initials: AB
authors.lastname: Drake
authors.affiliation: Department of Emergency Medicine, Division of Emergency Ultrasound, Mount Sinai St. Luke's Hospital, Mount Sinai West Hospital, New York, New York.
authors.forename: Melvin
authors.initials: M
authors.lastname: Ku
authors.affiliation: Department of Emergency Medicine, Division of Emergency Ultrasound, Mount Sinai St. Luke's Hospital, Mount Sinai West Hospital, New York, New York.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Rose
authors.affiliation: Department of Emergency Medicine, Division of Emergency Ultrasound, Mount Sinai St. Luke's Hospital, Mount Sinai West Hospital, New York, New York.
authors.forename: Sebastian D
authors.initials: SD
authors.lastname: Siadecki
authors.affiliation: Department of Emergency Medicine, Division of Emergency Ultrasound, Mount Sinai St. Luke's Hospital, Mount Sinai West Hospital, New York, New York.
authors.forename: Turandot
authors.initials: T
authors.lastname: Saul
mesh_terms: D000328:Adult; D000368:Aged; D000388:Air / Q000032:analysis*; D019115:Fasciitis, Necrotizing / Q000175:diagnosis / Q000503:physiopathology; D005260:Female; D018934:Fournier Gangrene / Q000175:diagnosis / Q000503:physiopathology; D006801:Humans; D008297:Male; D008478:Mediastinal Emphysema / Q000175:diagnosis / Q000503:physiopathology; D008875:Middle Aged; D011027:Pneumoperitoneum / Q000175:diagnosis / Q000503:physiopathology; D011030:Pneumothorax / Q000175:diagnosis / Q000503:physiopathology; D019095:Point-of-Care Systems / Q000639:trends; D013352:Subcutaneous Emphysema / Q000175:diagnosis / Q000503:physiopathology; D014463:Ultrasonography / Q000379:methods*
keywords: air artifact; bedside ultrasound; point of care ultrasound; sonographic artifact; ultrasound