title: Reduced arteriovenous shunting capacity after local heating and redistribution of baseline skin blood flow in type 2 diabetes assessed with velocity-resolved quantitative laser Doppler flowmetry.
abstract: OBJECTIVE
  To compare the microcirculatory velocity distribution in type 2 diabetic patients and nondiabetic control subjects at baseline and after local heating.
  
  
  METHODS
  The skin blood flow response to local heating (44 degrees C for 20 min) was assessed in 28 diabetic patients and 29 control subjects using a new velocity-resolved quantitative laser Doppler flowmetry technique (qLDF). The qLDF estimates erythrocyte (RBC) perfusion (velocity x concentration), in a physiologically relevant unit (grams RBC per 100 g tissue x millimeters per second) in a fixed output volume, separated into three velocity regions: v <1 mm/s, v 1-10 mm/s, and v >10 mm/s.
  
  
  RESULTS
  The increased blood flow occurs in vessels with a velocity >1 mm/s. A significantly lower response in qLDF total perfusion was found in diabetic patients than in control subjects after heat provocation because of less high-velocity blood flow (v >10 mm/s). The RBC concentration in diabetic patients increased sevenfold for v between 1 and 10 mm/s, and 15-fold for v >10 mm/s, whereas no significant increase was found for v <1 mm/s. The mean velocity increased from 0.94 to 7.3 mm/s in diabetic patients and from 0.83 to 9.7 mm/s in control subjects.
  
  
  CONCLUSIONS
  The perfusion increase occurs in larger shunting vessels and not as an increase in capillary flow. Baseline diabetic patient data indicated a redistribution of flow to higher velocity regions, associated with longer duration of diabetes. A lower perfusion was associated with a higher BMI and a lower toe-to-brachial systolic blood pressure ratio.
authors.affiliation: Division of Biomedical Instrumentation, Department of Biomedical Engineering, Linköping University, Linköping, Sweden. ingfr@imt.liu.se
authors.forename: Ingemar
authors.initials: I
authors.lastname: Fredriksson
authors.forename: Marcus
authors.initials: M
authors.lastname: Larsson
authors.forename: Fredrik H
authors.initials: FH
authors.lastname: Nyström
authors.forename: Toste
authors.initials: T
authors.lastname: Länne
authors.forename: Carl J
authors.initials: CJ
authors.lastname: Ostgren
authors.forename: Tomas
authors.initials: T
authors.lastname: Strömberg
mesh_terms: D000368:Aged; D001783:Blood Flow Velocity; D002196:Capillaries / Q000503:physiopathology; D003924:Diabetes Mellitus, Type 2 / Q000503:physiopathology*; D005260:Female; D006358:Hot Temperature; D006801:Humans; D017078:Laser-Doppler Flowmetry; D008297:Male; D008833:Microcirculation; D008875:Middle Aged; D011446:Prospective Studies; D012039:Regional Blood Flow; D012867:Skin / Q000098:blood supply* / Q000503:physiopathology
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