title: Baroreflex sensitivity estimation by the sequence method with delayed signals.
abstract: OBJECTIVE
  To evaluate a modified sequence method with delayed time series for baroreflex sensitivity (BRS) estimation during supine position and orthostatism in healthy human beings.
  
  
  METHODS
  Nineteen clinically healthy volunteers (12 men, age 28.4 ± 6.2 years old) were included. Blood pressure recordings were obtained during supine position and orthostatism (15 min each) with a Finometer. Systolic blood pressure (SBP) and inter beat intervals (IBI) measured from all heartbeats were used to estimate BRS in both positive and negative sequences, with SBP delayed between 0 and 5 heartbeats. BRS estimations were compared by ANOVA, p < 0.05 was considered significant. Optimal recording time based on fixed BRS error estimation was calculated for each time series.
  
  
  RESULTS
  BRS estimation was similar between positive and negative sequences in all conditions (BRS = 12.0 ± 2.0 ms/mmHg in supine position, delay 0). BRS with no delay was similar to BRS with delays between 1 and 5 heartbeats. Compared to supine position, BRS was smaller in orthostatism in all delays (BRS = 8.0 ± 2.0 ms/mmHg with delay 0). The shortest optimal recording time with delayed time series was similar in supine position and orthostatism (4.3 ± 1.7 vs. 3.74 ± 0.07 min, respectively). Estimation error was linearly correlated to IBI, regardless of the delay.
  
  
  CONCLUSIONS
  BRS estimation with sequence method improves with delayed time series, during supine position and orthostatism. Reduced BRS estimation error and recording time from this method could benefit studies with large populations or patients with low tolerance to orthostatism.
authors.affiliation: Posgrado de Física Médica, Instituto de Física, Universidad Nacional Autónoma de México, Mexico, D.F., Mexico.
authors.forename: Paola
authors.initials: P
authors.lastname: Martínez-García
authors.forename: Claudia
authors.initials: C
authors.lastname: Lerma
authors.forename: Oscar
authors.initials: O
authors.lastname: Infante
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D000465:Algorithms; D017704:Baroreflex / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology*; D001795:Blood Pressure Determination / Q000295:instrumentation / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D011187:Posture / Q000502:physiology*; D012016:Reference Values; D013997:Time Factors; D055815:Young Adult