Quantification of the dermal vascular response to hyperbaric oxygen with laser-Doppler flowmetry

The vasoconstrictive response to hyperbaric oxygen (HBO2) therapy was non-invasively quantified in eight healthy volunteers at 1.95 and 2.5 atm abs (197.5 and 253.2 kPa; multiplace chamber, air environment) by laser-Doppler flowmetry (LDF). The sensors for continuous measurement of microvascular perfusion (flux) and skin temperature were localized on the thenar eminence. Transcutaneous oxygen (tcPO2) and carbon dioxide (tcPCO2) tensions, blood pressure, heart rate, respiration rate, peripheral oxygen saturation, and temperature of the hyperbaric chamber were recorded at five conditions: 1) baseline--air breathing at 1.0 atm abs, 2) after 15 min of HBO2 at 2.5 atm abs, 3) after 15 min of HBO2 at 1.95 atm abs, 4) 1 min after decompression with oxygen breathing at 1.0 atm abs, and 5) after 15 min of breathing air at 1.0 atm abs. Flux decreased continuously at conditions 2 (76.5%), 3 (50.6%), and 4 (37% of baseline, P < 0.05; Tukey test). Skin temperature fell below baseline at conditions 2, 3, 4 (P < 0.01, Tukey test), and 5 (P < 0.05, Tukey test, P < 0.001, analysis of variance). Range of correlation between inspired gas PO2 (PIO2) and alteration of flux 0.91 to 0.72, median -0.41. Correlation between PIO2 and tcPO2, r = 0.98. Chamber temperature and tcPCO2 remained stable. HBO2 reduced dermal microcirculation and temperature disproportionate to PIO2. LDF is suitable for use under hyperbaric conditions.