Microcirculation assessment using an individualized model for diffuse reflectance spectroscopy and conventional laser Doppler flowmetry.
Microvascular assessment would benefit from co-registration of blood flow and hemoglobin oxygenation dynamics during stimulus response tests. We used a fiber-optic probe for simultaneous recording of white light diffuse reflectance (DRS; 475-850 nm) and laser Doppler flowmetry (LDF; 780 nm) spectra at two source-detector distances (0.4 and 1.2 mm). An inverse Monte Carlo algorithm, based on a multiparameter three-layer adaptive skin model, was used for analyzing DRS data. LDF spectra were conventionally processed for perfusion. The system was evaluated on volar forearm recordings of 33 healthy subjects during a 5-min systolic occlusion protocol. The calibration scheme and the optimal adaptive skin model fitted DRS spectra at both distances within 10%. During occlusion, perfusion decreased within 5 s while oxygenation decreased slowly (mean time constant 61 s; dissociation of oxygen from hemoglobin). After occlusion release, perfusion and oxygenation increased within 3 s (inflow of oxygenized blood). The increased perfusion was due to increased blood tissue fraction and speed. The supranormal hemoglobin oxygenation indicates a blood flow in excess of metabolic demands. In conclusion, by integrating DRS and LDF in a fiber-optic probe, a powerful tool for assessment of blood flow and oxygenation in the same microvascular bed has been presented.
Linköping University, University Hospital, Department of Biomedical Engineering, Linköping 581 85, Sweden.
Tomas
T
Strömberg
Linköping University, University Hospital, Department of Biomedical Engineering, Linköping 581 85, Sweden.
Hanna
H
Karlsson
Linköping University, University Hospital, Department of Biomedical Engineering, Linköping 581 85, SwedenbPerimed AB, Datavägen 9A, Järfälla 175 43, Sweden.
Ingemar
I
Fredriksson
Linköping University, University Hospital, Department of Medical and Health Sciences, Linköping 581 85, Sweden.
Fredrik H
FH
Nyström
Linköping University, University Hospital, Department of Biomedical Engineering, Linköping 581 85, Sweden.
Marcus
M
Larsson
D000328:Adult; D000465:Algorithms; D003198:Computer Simulation; D005260:Female; D005542:Forearm / Q000502:physiology; D006801:Humans; D017078:Laser-Doppler Flowmetry / Q000379:methods*; D008297:Male; D008833:Microcirculation / Q000502:physiology*; D009010:Monte Carlo Method; D010100:Oxygen / Q000097:blood; D012815:Signal Processing, Computer-Assisted; D012867:Skin / Q000098:blood supply*; D013057:Spectrum Analysis / Q000379:methods*; D014920:Wine
D010100:Oxygen