title: A novel hands-free carotid ultrasound detects low-flow cardiac output in a swine model of pulseless electrical activity arrest.
abstract: OBJECTIVE
  To determine if a hands-free, noninvasive Doppler ultrasound device can reliably detect low-flow cardiac output by measuring carotid artery blood flow velocities. We compared the ability of observers to detect carotid artery flow velocity differences between pseudo-pulseless electrical activity (PEA) and true-PEA cardiac arrest.
  
  
  METHODS
  Five swine were instrumented with aortic (Ao) and right atrial pressure-transducing catheters. The Doppler ultrasound device was adhered to the neck over the carotid artery. Continuous electrocardiogram, pressure readings, and Doppler signal were recorded. Each swine underwent multiple episodes of fibrillation and resuscitation. Episodes of true-PEA and pseudo-PEA were retrospectively identified from all resuscitation attempts by examination of electrocardiogram and Ao waveforms. The sensitivity and specificity of the device to detect pseudo-PEA was obtained using observers blinded to Ao waveform recordings.
  
  
  RESULTS
  There was good interobserver reliability related to identification of pseudo- and true-PEA (κ = 0.873). The observers blinded to Ao waveform recordings agreed on 8 of the 9 episodes of pseudo-PEA, whereas 4 false positives of 26 true-PEA events were reported (sensitivity, 0.89; specificity, 0.85). The Doppler device was able to detect carotid flow velocity over a wide range of Ao blood pressures.
  
  
  CONCLUSIONS
  This hands-free, noninvasive Doppler ultrasound device can reliably differentiate pseudo-PEA from true-PEA during resuscitation from cardiac arrest, detecting pressure gradient changes of less than 5 mm Hg through to normotension. This device distinguishes conditions of no cardiac output from low cardiac output and may have applications for use during resuscitation from various etiologies of arrest and shock.
authors: Department of Emergency Medicine, University of Colorado Denver School of Medicine, Denver, CO 80045, USA. todd.larabee@ucdenver.edu
authors: Todd M
authors: TM
authors: Larabee
authors: Charles M
authors: CM
authors: Little
authors: Balasundar I
authors: BI
authors: Raju
authors: Eric
authors: E
authors: Cohen-Solal
authors: Ramon
authors: R
authors: Erkamp
authors: Scott
authors: S
authors: Wuthrich
authors: John
authors: J
authors: Petruzzello
authors: Michael
authors: M
authors: Nakagawa
authors: Shervin
authors: S
authors: Ayati
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D002303:Cardiac Output, Low / Q000000981:diagnostic imaging* / Q000503:physiopathology; D002339:Carotid Arteries / Q000000981:diagnostic imaging* / Q000503:physiopathology; D004195:Disease Models, Animal; D004562:Electrocardiography; D006323:Heart Arrest / Q000175:diagnosis / Q000000981:diagnostic imaging* / Q000503:physiopathology; D015588:Observer Variation; D011674:Pulse; D013552:Swine / Q000502:physiology; D018608:Ultrasonography, Doppler / Q000295:instrumentation