title: Technology comparison studies require precise reference controls to be valid.
authors.forename: M R
authors.initials: MR
authors.lastname: Pinsky
authors.forename: T
authors.initials: T
authors.lastname: O'Brien
authors.forename: D
authors.initials: D
authors.lastname: Green
authors.forename: M
authors.initials: M
authors.lastname: Jonas
mesh_terms: D013505:Digestive System Surgical Procedures / Q000379:methods*; D004947:Esophagus / Q000000981:diagnostic imaging*; D005260:Female; D005440:Fluid Therapy / Q000379:methods*; D006801:Humans; D008297:Male; D016343:Monitoring, Intraoperative / Q000295:instrumentation*; D013318:Stroke Volume / Q000502:physiology*; D018608:Ultrasonography, Doppler / Q000379:methods*