title: Use of generalized transfer function-derived central blood pressure for the calculation of baroreflex gain.
abstract: BACKGROUND
  Peripheral blood pressure measurement underestimates pressure changes during baroreflex testing, resulting in an overestimation of baroreflex gain. This error might be reduced by measuring central blood pressure; the invasive measurement, however, may represent ethical and practical problems. The solution may be the derivation of central blood pressure from the peripheral pulse using a generalized transfer function.
  
  
  METHODS
  In the current study, we tested the agreement between catheter-measured and generalized transfer function derived central blood pressure measurements and corresponding baroreflex gains. ECG and blood pressure waveforms were monitored continuously during a phenylephrine-induced pressure rise in 22 subjects undergoing cardiac catheterization. Pressure was measured with a catheter positioned in the aorta and with applanation tonometry in the radial artery. Radial pressure waveforms were subject to a generalized transfer function built in the SphygmoCor device to derive central pressure waveforms. Radial tonometric signal was calibrated with catheter-measured (invasive) and sphygmomanometric (noninvasive) pressures. Baroreflex gains were calculated from the linear regressions between heart period and systolic pressure changes.
  
  
  RESULTS
  When radial tonometric signal was calibrated invasively, there was no group difference between baroreflex gains calculated from SphygmoCor-derived and catheter-measured pressures (8.2 +/- 1.2 vs. 7.2 +/- 1.2 ms/mmHg, P = NS). When radial tonometric signal was calibrated noninvasively, however, baroreflex gains calculated from SphygmoCor-derived pressures overestimated those calculated from catheter-measured pressures.
  
  
  CONCLUSIONS
  Using a generalized transfer function is an accurate method to derive central pressure changes for baroreflex gain calculation. The technique, however, requires invasive pressure measurements for calibration, leaving the problem of a fully noninvasive central pressure measurement unresolved.
authors.affiliation: Institute of Human Physiology and Clinical Experimental Research, Semmelweis University, Budapest, Hungary. p_studi@yahoo.com
authors.forename: Péter
authors.initials: P
authors.lastname: Studinger
authors.forename: Imre
authors.initials: I
authors.lastname: Ungi
authors.forename: Zsuzsanna
authors.initials: Z
authors.lastname: Lénárd
authors.forename: Beatrix
authors.initials: B
authors.lastname: Mersich
authors.forename: László
authors.initials: L
authors.lastname: Rudas
authors.forename: Márk
authors.initials: M
authors.lastname: Kollai
mesh_terms: D000368:Aged; D017704:Baroreflex / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology*; D001795:Blood Pressure Determination; D006328:Cardiac Catheterization; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular