title: Determination of baroreflex sensitivity during the modified Oxford maneuver by trigonometric regressive spectral analysis.
abstract: BACKGROUND
  Differences in spontaneous and drug-induced baroreflex sensitivity (BRS) have been attributed to its different operating ranges. The current study attempted to compare BRS estimates during cardiovascular steady-state and pharmacologically stimulation using an innovative algorithm for dynamic determination of baroreflex gain.
  
  
  RESULTS
  Forty-five volunteers underwent the modified Oxford maneuver in supine and 60° tilted position with blood pressure and heart rate being continuously recorded. Drug-induced BRS-estimates were calculated from data obtained by bolus injections of nitroprusside and phenylephrine. Spontaneous indices were derived from data obtained during rest (stationary) and under pharmacological stimulation (non-stationary) using the algorithm of trigonometric regressive spectral analysis (TRS). Spontaneous and drug-induced BRS values were significantly correlated and display directionally similar changes under different situations. Using the Bland-Altman method, systematic differences between spontaneous and drug-induced estimates were found and revealed that the discrepancy can be as large as the gain itself. Fixed bias was not evident with ordinary least products regression. The correlation and agreement between the estimates increased significantly when BRS was calculated by TRS in non-stationary mode during the drug injection period. TRS-BRS significantly increased during phenylephrine and decreased under nitroprusside.
  
  
  CONCLUSIONS
  The TRS analysis provides a reliable, non-invasive assessment of human BRS not only under static steady state conditions, but also during pharmacological perturbation of the cardiovascular system.
authors: Autonomic and Neuroendocrinological Laboratory, Department of Neurology, University Hospital Carl Gustav Carus, Dresden University of Technology, Dresden, Germany.
authors: Julia
authors: J
authors: Gasch
authors: Manja
authors: M
authors: Reimann
authors: Heinz
authors: H
authors: Reichmann
authors: Heinz
authors: H
authors: Rüdiger
authors: Tjalf
authors: T
authors: Ziemssen
mesh_terms: D000328:Adult; D000465:Algorithms; D017704:Baroreflex / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008365:Manometry / Q000379:methods*; D012044:Regression Analysis; D015203:Reproducibility of Results; D013599:Systole / Q000502:physiology; D013997:Time Factors