title: Noninvasive estimation of central blood pressure and the augmentation index in the seated position: a validation study of two commercially available methods.
abstract: OBJECTIVE
  The aim of this study was to examine the utility of the generalized transfer function (GTF) and the late systolic shoulder of the radial pressure waveform (SBP2) for estimating seated central systolic blood pressure (c-SBP) and seated c-augmentation index (c-AIx).
  
  
  METHODS
  In 199 participants (182 cardiovascular disease patients and 17 normal individuals; mean age: 65.7 ± 10.6 years), c-SBP and c-AIx were estimated using the SphygmoCor and Omron HEM-9000AI systems. Both estimates were compared with carotid SBP and augmentation index (AIx). All measurements were performed with the participants in the seated position.
  
  
  RESULTS
  Mean c-SBP was 121.7 ± 18.6 mmHg and 122.6 ± 19.8 mmHg according to the GTF and SBP2 methods, respectively, and carotid SBP was 124.4 ± 19.2 mmHg. There were close correlations between the three values (GTF vs. carotid SBP: r = 0.986, SBP2 vs. carotid SBP: r = 0.975, GTF vs. SBP2: r = 0.989, all P < 0.0001), all of which met the AAMI SP10 criteria and the grade A British Society of Hypertension criteria. The relationship between c-AIx estimated using the GTF method and carotid AIx was comparable to that reported previously for supine individuals (r = 0.703, P < 0.0001). The seated carotid-radial artery amplifications of the first and second harmonics were identical to those reported in previous supine studies. Both methods produced reproducible estimates of c-SBP and c-AIx (r = 0.997-0.910, all P < 0.0001).
  
  
  CONCLUSIONS
  The present study indicates that the GTF and SBP2 methods can be used to estimate c-SBP and c-AIx in seated individuals.
authors.affiliation: Department of Cardiology, Saitama Medical Center, Jichi Medical University, Saitama, Japan. hirata@omiya.jichi.ac.jp
authors.forename: Kozo
authors.initials: K
authors.lastname: Hirata
authors.forename: Iwao
authors.initials: I
authors.lastname: Kojima
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Momomura
mesh_terms: D000368:Aged; D001794:Blood Pressure; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011187:Posture