title: Relationship between plethysmographic waveform changes and hemodynamic variables in anesthetized, mechanically ventilated patients undergoing continuous cardiac output monitoring.
abstract: OBJECTIVE
  To assess the relation between photoplethysmographically-derived parameters and invasively-determined hemodynamic variables.
  
  
  METHODS
  After induction of anesthesia and placement of a Swan-Ganz CCOmbo catheter, a Nonin OEM III probe was placed on each patient's earlobe. Photoplethysmographic signals were recorded in conjunction with cardiac output. Photoplethysmographic metrics (amplitude of absorbance waveform, maximal slope of absorbance waveform, area under the curve, and width) were calculated offline and compared with invasively determined hemodynamic variables. Subject-specific associations between each dependent and independent variable pair were summarized on a per-subject basis by the nonparametric Spearman rank correlation coefficient. The bias-corrected accelerated bootstrap resampling procedure of Efron and Tibshirani was used to obtain a 95% confidence interval for the median subject-specific correlation coefficient, and Wilcoxon sign-rank tests were conducted to test the null hypothesis that the median of the subject-specific correlation coefficients were equal to 0.
  
  
  METHODS
  University hospital.
  
  
  METHODS
  Eighteen patients undergoing coronary artery bypass graft surgery.
  
  
  METHODS
  Placement of a Swan-Ganz CCOmbo catheter and a Nonin OEM III pulse oximetry probe.
  
  
  RESULTS
  There was a positive, statistically significant correlation between stroke volume and width (median correlation coefficient, 0.29; confidence interval, 0.01-0.46; p = 0.034). The concordance between changes in stroke volume and changes in width was 53%. No other correlations achieved statistical significance.
  
  
  CONCLUSIONS
  This study was unable to reproduce the results of prior studies. Only stroke volume and photoplethysmographic width were correlated in this study; however, the correlation and concordance (based on analysis of a 4-quadrant plot) were too weak to be clinically useful. Future studies in patients undergoing low-to-moderate risk surgery may result in improved correlations and clinical utility.
authors.affiliation: Department of Anesthesiology, University of Virginia Health System, Charlottesville, VA 22908, USA. rht7w@virginia.edu
authors.forename: Robert H
authors.initials: RH
authors.lastname: Thiele
authors.forename: Douglas A
authors.initials: DA
authors.lastname: Colquhoun
authors.forename: James
authors.initials: J
authors.lastname: Patrie
authors.forename: Sarah H
authors.initials: SH
authors.lastname: Nie
authors.forename: Julie L
authors.initials: JL
authors.lastname: Huffmyer
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000758:Anesthesia; D019540:Area Under Curve; D001794:Blood Pressure / Q000502:physiology; D002302:Cardiac Output / Q000502:physiology*; D001026:Coronary Artery Bypass; D047549:Coronary Artery Bypass, Off-Pump; D003627:Data Interpretation, Statistical; D005260:Female; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods* / Q000592:standards / Q000706:statistics & numerical data; D010092:Oximetry; D010991:Plethysmography / Q000706:statistics & numerical data*; D015203:Reproducibility of Results; D012121:Respiration, Artificial; D012984:Software; D013318:Stroke Volume / Q000502:physiology; D014655:Vascular Resistance / Q000502:physiology