Oxygen saturation monitoring using resonance Raman spectroscopy

Area of Science:

• Biomedical Engineering
• Spectroscopy
• Physiology

Background:

• Hemoglobin oxygen saturation (SO2) and tissue oxygenation are crucial for identifying shock and guiding therapy.
• Resonance Raman spectroscopy (RRS) enables measurement of oxy- and deoxyhemoglobin species.
• RRS-StO2 has been utilized for aggregate microvascular oxygenation assessment.

Purpose of the Study:

• To test if noninvasive RRS-StO2 can serve as a surrogate for systemic central venous SO2.
• To evaluate the correlation between RRS-StO2 and central venous SO2 in various tissues.
• To assess the relationship between RRS-StO2 and other systemic blood parameters.

Main Methods:

• Measurements of RRS-StO2 in oral mucosa, skin, muscle, and liver of anesthetized rats.
• Comparison with central venous SO2 using multi-wavelength oximetry.
• Stepwise hemorrhage to induce various oxygenation levels, with over 100 paired measurements.
• Evaluation of RRS-StO2 correlations with systemic blood parameters like lactate, potassium, and pH.

Main Results:

• Significant correlations found between venous SO2 and RRS-StO2 in oral mucosa (r=0.913), skin (r=0.499), and liver (r=0.611).
• Mean difference between sublingual RRS-StO2 and blood sample SO2 was 5.4 ± 1.6%.
• Sublingual RRS-StO2 correlated significantly with lactate (r=0.909), potassium (r=0.757), and pH (r=0.703).

Conclusions:

• Raman-based oxygen saturation is a promising noninvasive technique for evaluating tissue oxygenation.
• Sublingual RRS-StO2 measurements show correlation with central venous SO2 under specific conditions.
• The technique is suitable for assessing oxygenation in skin, thin tissues, and solid organs.