title: Oxygen saturation monitoring using resonance Raman spectroscopy.
abstract: The knowledge of hemoglobin oxygen saturation (SO2) and tissue oxygenation is critical to identify the presence of shock and therapeutic options. The resonance vibrational enhancement of hemoglobin allows measurement of oxy- and deoxy species of hemoglobin and resonance Raman spectroscopy (RRS-StO2) has been successfully used to measure aggregate microvascular oxygenation. We tested the hypothesis that noninvasive oxygen saturation measured by RRS-StO2 could serve as surrogate of systemic central venous SO2.
  
  
  
  In anesthetized rats, measurements of RRS-StO2 made in oral mucosa, skin, muscle, and liver were compared with measurements of central venous SO2 using traditional multi-wavelength oximetry. Various oxygenation levels were obtained using a stepwise hemorrhage while over 100 paired blood samples and Raman-based measurements were performed. The relationships between RRS-StO2 and clinically important systemic blood parameters were also evaluated. RRS-StO2 measurements were made in 3-mm diameter tissue areas using a microvascular oximeter and a handheld probe.
  
  
  
  Significant correlations were found between venous SO2 and RRS-StO2 measurements made in the oral mucosa (r = 0.913, P < 0.001), skin (r = 0.499, P < 0.01), and liver (r = 0.611, P < 0.05). The mean difference between sublingual RRS-StO2 and blood sample SO2 values was 5.4 ± 1.6%. Sublingual RRS-StO2 also correlated with lactate (r = 0.909, P < 0.01), potassium (r = 0.757, P < 0.01), and pH (r = 0.703, P < 0.05).
  
  
  
  Raman-based oxygen saturation is a promising technique for the noninvasive evaluation of oxygenation in skin, thin tissues, and solid organs. Under certain conditions, sublingual RRS-StO2 measurements correlate with central venous SO2.
authors.affiliation: Department of Anesthesiology, Virginia Commonwealth University and the Virginia Commonwealth University Reanimation Engineering Science Center, Richmond, Virginia; Department of Emergency Medicine, Virginia Commonwealth University and the Virginia Commonwealth University Reanimation Engineering Science Center, Richmond, Virginia; Damage Control Resuscitation, U.S. Army Institute of Surgical Research, Fort Sam Houston, Texas. Electronic address: ivo.p.torresfilho.civ@mail.mil.
authors.forename: Ivo
authors.initials: I
authors.lastname: Torres Filho
authors.affiliation: Department of Anesthesiology, Virginia Commonwealth University and the Virginia Commonwealth University Reanimation Engineering Science Center, Richmond, Virginia.
authors.forename: Nguyen M
authors.initials: NM
authors.lastname: Nguyen
authors.affiliation: Department of Anesthesiology, Virginia Commonwealth University and the Virginia Commonwealth University Reanimation Engineering Science Center, Richmond, Virginia.
authors.forename: Rizwan
authors.initials: R
authors.lastname: Jivani
authors.affiliation: Department of Chemistry, Virginia Commonwealth University and the Virginia Commonwealth University Reanimation Engineering Science Center, Richmond, Virginia.
authors.forename: James
authors.initials: J
authors.lastname: Terner
authors.affiliation: Pendar Medical, Cambridge, Massachusetts.
authors.forename: Padraic
authors.initials: P
authors.lastname: Romfh
authors.affiliation: Pendar Medical, Cambridge, Massachusetts.
authors.forename: Daryoosh
authors.initials: D
authors.lastname: Vakhshoori
authors.affiliation: Department of Emergency Medicine and the Michigan Center for Integrative Research in Critical Care, University of Michigan, Ann Arbor, Michigan.
authors.forename: Kevin R
authors.initials: KR
authors.lastname: Ward
mesh_terms: D000818:Animals; D001785:Blood Gas Monitoring, Transcutaneous / Q000379:methods*; D010100:Oxygen / Q000032:analysis*; D017207:Rats, Sprague-Dawley; D013059:Spectrum Analysis, Raman
chemical_list: D010100:Oxygen
keywords: Hemorrhage; Oxygen saturation; Raman spectroscopy; Shock; Tissue oxygenation