title: The relationship between vascular expansion of the aorta and pulmonary artery and the genesis of the impedance cardiogram using the technique of sonomicrometry.
abstract: OBJECTIVE
  This prospective animal study aims to evaluate the contribution of the pulmonary artery (PA) and aorta on the morphology of the impedance cardiogram using sonomicrometry.
  
  
  METHODS
  Impedance electrodes were placed around the thorax, aorta and in the oesophagus of five dogs. Sonomicrometry crystals were mounted on the PA and aorta for tracking vascular distension while a Doppler flow probe measured aortic blood flow.
  
  
  RESULTS
  No significant differences (p > 0.05) were recorded between the onset of aortic expansion, aortic blood flow and the start of the impedance dZ/dt signal. Significant differences (p > 0.001) were recorded between the onset of PA expansion and the dZ/dt signal. PA expansion began 41.6 +/- 6.0 ms, 60.7 +/- 7.2 ms and 42.2 +/- 4.9 ms respectively, before surface, aortic and oesophageal impedance recordings.
  
  
  CONCLUSIONS
  The genesis of the impedance cardiogram is attributed to volumetric expansion of the aorta.
authors.affiliation: Department of Anesthesiology, University of Virginia Health Sciences, P O Box 800710, Charlottesville, VA 22903, USA. jkh2n@virginia.edu
authors.forename: J K
authors.initials: JK
authors.lastname: Hayes
authors.forename: J L
authors.initials: JL
authors.lastname: Peters
authors.forename: B D
authors.initials: BD
authors.lastname: Hare
authors.forename: L E
authors.initials: LE
authors.lastname: Baker
mesh_terms: D000818:Animals; D001011:Aorta / Q000502:physiology*; D001783:Blood Flow Velocity / Q000502:physiology*; D002307:Cardiography, Impedance / Q000379:methods*; D004285:Dogs; D011651:Pulmonary Artery / Q000502:physiology*; D013223:Statistics as Topic; D018608:Ultrasonography, Doppler / Q000379:methods*; D018924:Vascular Capacitance / Q000502:physiology; D014655:Vascular Resistance / Q000502:physiology