title: Non-invasive estimation of systolic blood pressure and diastolic blood pressure using photoplethysmograph components.
abstract: OBJECTIVE
  Photoplethysmography (PPG) is a noninvasive optical technology that detects changes in blood volume in the vascular system. This study aimed to investigate the possibilities of monitoring the cardiovascular system status by using PPG.
  
  
  METHODS
  Forced hemodynamic changes were induced using cardiac stimulants; dopamine and epinephrine, and PPG components were recorded by a noninvasive method at the peripheral blood vessels. The results were compared among 6 dogs. Endotracheal intubation was performed after an intramuscular injection of 25 mg/kg ketamine sulfate, and anesthesia was maintained with 2% enflurane. After stabilizing the animals for 15 min, 16 mg/mL diluted dopamine was injected into a vein for 2 min at 20 microg/kg min(-1) by using an infusion pump. Thereafter, the infusion pump was stopped, and 1 mg epinephrine was injected intravenously. Fluid administration was controlled to minimize preload change in blood pressure.
  
  
  RESULTS
  After stimulant administration, systolic blood pressure (SBP) and diastolic blood pressures (DBP) increased. The direct current (DC) component, which reflects changes in blood volume, decreased while the alternating current (AC) component, which reflects changes in vascular compliance and resistance, increased. The correlation coefficient between SBP and the foot of the DC component was 0.939 (p < 0.01), while it was 0.942 (p < 0.01) for DBP and the peak of the DC component. The AC component could predict the increase in vascular resistance from a stable pulse blood volume, even with increased pulse pressure.
  
  
  CONCLUSIONS
  These results support the possibility that PPG components may be used for easy and noninvasive measurement of hemodynamic changes in the cardiovascular system.
authors.affiliation: Department of Biomedical Engineering, Yonsei University, 234 Meaji, Heungeup, Wonju 220-710, Korea.
authors.forename: Incheol
authors.initials: I
authors.lastname: Jeong
authors.forename: Sukhwan
authors.initials: S
authors.lastname: Jun
authors.forename: Daeja
authors.initials: D
authors.lastname: Um
authors.forename: Joonghwan
authors.initials: J
authors.lastname: Oh
authors.forename: Hyungro
authors.initials: H
authors.lastname: Yoon
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000502:physiology*; D015924:Blood Pressure Monitors; D004285:Dogs / Q000502:physiology*; D006801:Humans; D023421:Models, Animal; D017156:Photoplethysmography / Q000379:methods*