Buccal visible light spectroscopy and laser Doppler flowmetry: reliability analysis

Background

There are insatiable demands for new technologies to advance basic biological investigation at the microcirculatory level. Oxygen to see (O₂C)^® is a newly developed system that combines laser Doppler flow (LDF) and visible light spectroscopy (VLS) technology. The aim of our study was to assess the reliability of O₂C^® measurements applied to the buccal mucosa and to the thenar eminence in healthy volunteers.

Methods

Microcirculatory hemoglobin oxygen saturation (μHbO₂, %) and blood flow (flow, AU) were measured using an O₂C^® (Lea Medizintechnik GmbH, Giessen, Germany) probe applied to the buccal mucosa and to the thenar eminence. Measurements were obtained simultaneously at two depths, superficial (2 mm) and deep (6 mm), every 2 seconds for 5 minutes and were recorded for later analysis. The procedure was repeated on another occasion at least 1 week apart.

Results

We studied 20 healthy subjects; 10 males and 10 females (mean age = 38 ± 18 years, range 21–74 years). Both μHbO₂ and flow measurements were consistently higher when measured from the deep tissue layers (6 mm) than those measured from the superficial layers, regardless of the site of measurement. Buccal mucosal μHbO₂ ranged from 78% to 96% and varied only minimally (CV: 4–7.5%), whereas there was a marked variability in flow measurements (CV: 29–63.9%). The reproducibility of buccal mucosal μHbO₂ and flow measurements were moderate to good (that is, intra-individual reliability, ICC: range 0.7–0.87, P < 0.05). However, only measurements from the superficial mucosal layers showed a moderate to good degree of inter-individual agreement (that is, inter-individual reliability, ICC: range 0.68–85, P < 0.001). LDF and VLS values measured on the thenar eminence were highly variable, were not reproducible, and the inter-individual agreement was poor.

Conclusion

O₂C^® provides reliable measurement of buccal μHbO₂ and microvascular flow. Skin measurements on the thenar eminence are highly variable and unreliable.