title: Fluorescence dilution technique for measurement of cardiac output and circulating blood volume in healthy human subjects.
abstract: BACKGROUND
  The authors previously validated in an animal model a new indicator dilution technique for measuring cardiac output and circulating blood volume by recording transcutaneously the fluorescence of circulating indocyanine green with an optical probe placed on the skin surface. The current study compared fluorescence dilution recordings recorded from several locations on the human face in terms of signal intensity and stability and estimated the subjects' cardiac output and circulating blood volume from the recordings.
  
  
  METHODS
  Fluorescence dilution traces were recorded transcutaneously in six healthy human volunteers after rapid intravenous injection of 1 mg indocyanine green. Three placements of the optical probe were tested: the nose ala, the ear lobe, and the temple area. In three subjects, the recordings were calibrated in terms of circulating indocyanine green concentration to estimate cardiac output and circulating blood volume.
  
  
  RESULTS
  Fluorescence dilution traces had the same duration for the three locations, but the recordings obtained from the nose ala and the ear lobe were twice as intense as those from the temple. The fluorescence intensity at each site was linearly related to the local laser Doppler perfusion index. The coefficient of variation for the area under the first pass curve (inversely proportional to cardiac output) was approximately 6% for triplicate measurements at the same location. Cardiac output and circulating blood volume derived from the fluorescence recordings were in the normal range.
  
  
  CONCLUSIONS
  The study demonstrates that intense and reproducible fluorescence dilution signals can be measured transcutaneously in healthy humans and could potentially be used to measure cardiac output and circulating blood volume minimally invasively.
authors.affiliation: Department of Biomedical Engineering, University of Southern California, Los Angeles, California 90089-1111, USA.
authors.forename: Jean-Michel I
authors.initials: JM
authors.lastname: Maarek
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Holschneider
authors.forename: Eduardo H
authors.initials: EH
authors.lastname: Rubinstein
mesh_terms: D000328:Adult; D001810:Blood Volume / Q000502:physiology*; D001811:Blood Volume Determination / Q000379:methods; D002302:Cardiac Output / Q000502:physiology*; D004396:Coloring Agents / Q000008:administration & dosage; D004431:Ear, External / Q000098:blood supply; D005260:Female; D005456:Fluorescent Dyes / Q000008:administration & dosage; D005546:Forehead / Q000098:blood supply; D006801:Humans; D007201:Indicator Dilution Techniques; D007208:Indocyanine Green / Q000008:administration & dosage; D017078:Laser-Doppler Flowmetry / Q000379:methods; D008297:Male; D009666:Nose / Q000098:blood supply; D012016:Reference Values; D015203:Reproducibility of Results; D013055:Spectrophotometry, Infrared / Q000379:methods; D013997:Time Factors
chemical_list: D004396:Coloring Agents; D005456:Fluorescent Dyes; D007208:Indocyanine Green