title: Pulse transit time by R-wave-gated infrared photoplethysmography: review of the literature and personal experience.
abstract: OBJECTIVE
  Pulse transit time (PTT) is the time it takes a pulse wave to travel between two arterial sites. A rela tively short PTT is observed with high blood pressure (BP), aging, arteriosclerosis and diabetes mellitus. Most methods used for measuring the PTT are cumbersome and expensive. In contrast, the interval between the peak of the R-wave on the electrocardiogram and the onset of the corresponding pulse in the finger pad measured by photoplethysmography can be easily measured. We review herein the literature and impart the experience at our institution on clinical applications of R-wave-gated photo-plethysmography (RWPP) as measurement of PTT.
  
  
  METHODS
  The MEDLINE data base on clinical applications of RWPP was reviewed. In addition, studies performed in the author's institution are presented.
  
  
  RESULTS
  When used as a surrogate for beat-to-beat BP monitoring, RWPP did not meet the level of accuracy required for medical practice (two studies). RWPP produced accurate and reproducible signals when utilized as a surrogate for intra-thoracic pressure changes in obstructive sleep apnea, as well as BP arousals which accompany central sleep apnea (five studies). In estimation of arterial stiffness, RWPP was unsatisfactory (one study). In assessment of cardiovascular reactivity, abnormal values of RWPP were noted in autonomic failure (one study), while disease-specific reactivity patterns were identified utilizing a method involving RWPP (two studies).
  
  
  CONCLUSIONS
  In clinical practice, sleep-apnea may be accurately monitored by RWPP. RWPP seems to reflect autonomic influences and may be particularly well-suited for the study of vascular reactivity. Thus, further descriptions of disease-specific cardiovascular reactivity patterns may be possible with techniques based on RWPP. Other clinical uses of RWPP are investigational.
authors.affiliation: Departmentments of Internal Medicine A, Bnai-Zion Medical Center and Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel. naschitz@tx.technion.ac.il
authors.forename: Jochanan E
authors.initials: JE
authors.lastname: Naschitz
authors.forename: Stanislas
authors.initials: S
authors.lastname: Bezobchuk
authors.forename: Renata
authors.initials: R
authors.lastname: Mussafia-Priselac
authors.forename: Scott
authors.initials: S
authors.lastname: Sundick
authors.forename: Daniel
authors.initials: D
authors.lastname: Dreyfuss
authors.forename: Igal
authors.initials: I
authors.lastname: Khorshidi
authors.forename: Argyro
authors.initials: A
authors.lastname: Karidis
authors.forename: Hagit
authors.initials: H
authors.lastname: Manor
authors.forename: Mihael
authors.initials: M
authors.lastname: Nagar
authors.forename: Elisabeth Rubin
authors.initials: ER
authors.lastname: Peck
authors.forename: Shannon
authors.initials: S
authors.lastname: Peck
authors.forename: Shimon
authors.initials: S
authors.lastname: Storch
authors.forename: Itzhak
authors.initials: I
authors.lastname: Rosner
authors.forename: Luis
authors.initials: L
authors.lastname: Gaitini
mesh_terms: D001794:Blood Pressure; D004562:Electrocardiography; D006339:Heart Rate; D006801:Humans; D017156:Photoplethysmography / Q000379:methods; D011674:Pulse; D012891:Sleep Apnea Syndromes / Q000175:diagnosis; D014655:Vascular Resistance