Relation between blood flow and tissue blood oxygenation in human fingertip skin

Background: Tissue blood flow (BF) is thought to be involved in the regulation of tissue blood oxygenation (StO₂). The purpose of the present study was to show the relation between BF and StO₂ by measuring them simultaneously under different conditions. Methods: Twenty-one healthy subjects (age 21-30years) participated in this study. We measured BF and StO₂ in a small area of skin (fingertip, palm, forearm) simultaneously using a laser Doppler flowmeter and a tissue oxygenation monitor. Three measurements were made at rest while performing mental arithmetic and during constriction of the ipsilateral upper arm. Results: At rest, BF and StO₂ were higher in the fingertip than in the palm or forearm (p<0.01). Performing mental arithmetic produced significant decreases in BF, oxygenated hemoglobin, and StO₂ in the fingertip (p<0.05). Constriction of the ipsilateral upper arm produced significant decreases in BF and StO₂ (p<0.05) and an increase in oxygenated hemoglobin (p<0.05). Both procedures produced significant increases in deoxygenated hemoglobin (p<0.05), which was in antiphase to the decrease in StO₂. Conclusions: BF decrease produced a significantly decreased StO₂ in fingertip skin. The results show that simultaneous measurement of BF and StO₂ is beneficial for showing the close relation between them.