title: Determination of central blood pressure by a noninvasive method (brachial blood pressure and QKD interval): a noninvasive validation.
abstract: OBJECTIVE
  We validated against invasive measurements a measure of central SBP based on the QKD interval. The present objective is a comparison to the SphygmoCor device.
  
  
  METHODS
  A first cohort was used to redefine an algorithm for estimating ascending aorta SBP (cSBP) with respect to SphygmoCor. This algorithm was then tested in a second cohort under static conditions and in a third cohort during a head-up tilt to study blood pressure variations.
  
  
  RESULTS
  The first cohort (36 patients, mean age: 46 ± 20 years, SBP: 114 ± 19 mm Hg) defined the estimation algorithm as cSBP =62.687+1.35 × meanBP-0.207 × heart rate-0.251 × height-0.1 × QKD (mean difference with SphygmoCor=0 ± 7 mmHg).In the second cohort (105 patients, mean age: 51 ± 19 years, SBP: 132 ± 22 mmHg), the average difference between the two techniques was 2 ± 6 mm Hg (R=0.93). The dynamic cohort included 31 patients (mean age: 49 ± 23 years, SBP: 110 ± 19 mmHg) with 224 pairs of measurement. We studied the changes in central blood pressures compared with the basal state of each of the two techniques during head-up tilt. With QKD, the average cSBP was 104 ± 19 mmHg, the average variation was -13.00 mmHg ± 15 (range 7-74 mmHg). With SphygmoCor, average cSBP was 10  mmHg ± 18, the average variation was -14 mmHg   ± 16 (range 2-81 mmHg). The variations in blood pressure with the two techniques were well correlated (R=0.93).
  
  
  CONCLUSIONS
  cSBP estimation based on the QKD interval is comparable in precision to the SphygmoCor. Its ability to measure cSBP variations suggests that it could be employed for ambulatory measurements over 24 h.
authors.affiliation: aCardiology and Hypertension Unit, University Hospital of Bordeaux, Bordeaux, France bAustralian School of Advanced Medicine cCardiology Unit, Macquarie University Hospital, Sydney, Australia.
authors.forename: Antoine
authors.initials: A
authors.lastname: Cremer
authors.forename: Leopold
authors.initials: L
authors.lastname: Codjo
authors.forename: Mark
authors.initials: M
authors.lastname: Butlin
authors.forename: Georgios
authors.initials: G
authors.lastname: Papaioannou
authors.forename: Sunthareth
authors.initials: S
authors.lastname: Yeim
authors.forename: Emilie
authors.initials: E
authors.lastname: Jan
authors.forename: Hosen
authors.initials: H
authors.lastname: Kiat
authors.forename: Alberto
authors.initials: A
authors.lastname: Avolio
authors.forename: Philippe
authors.initials: P
authors.lastname: Gosse
mesh_terms: D000328:Adult; D000465:Algorithms; D001011:Aorta / Q000473:pathology; D001794:Blood Pressure; D001795:Blood Pressure Determination / Q000379:methods* / Q000592:standards; D015331:Cohort Studies; D005260:Female; D006439:Hemodynamics; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D015203:Reproducibility of Results; D013997:Time Factors