Sublingual microvascular perfusion is altered during normobaric and hyperbaric hyperoxia.

Area of Science:

• Physiology
• Biomedical Engineering
• Vascular Biology

Background:

• Hyperoxia and hyperbaric oxygen therapy can restore oxygen levels in ischemic tissues.
• These therapies are believed to promote angiogenesis and regulate tissue perfusion.
• Understanding microcirculatory responses to hyperoxia is crucial for therapeutic applications.

Purpose of the Study:

• To develop a model for quantifying hyperoxia-driven microvascular changes.
• To test the reversibility of microcirculatory responses to normobaric (NB) and hyperbaric (HB) hyperoxia.
• To investigate the effects of varying oxygen concentrations under NB and HB conditions on sublingual mucosa microcirculation.

Main Methods:

• Male rabbits were subjected to sequential breathing of O2/air mixtures (21%, 55%, 100%, then 21%) under NB (1.0 bar) and HB (2.5 bar) conditions.
• Microcirculation parameters including vessel density, perfused vessel proportion, vessel diameters, and microvascular flow index were measured.
• Macrohemodynamic and blood gas parameters were also monitored.

Main Results:

• NB hyperoxia decreased microvascular density and vessel diameters, increasing blood pressure, with no change in flow indices.
• HB normoxia/hyperoxia decreased microvascular density and transiently increased systolic blood pressure, without altering vessel diameter or flow indices compared to NB hyperoxia.
• All measured microcirculation parameters returned to baseline upon returning to NB normoxia.

Conclusions:

• Normobaric and hyperbaric hyperoxia induce reversible physiological changes in sublingual mucosa blood perfusion.
• Cardiovascular function remained stable throughout the experiments.
• The lack of microvascular vasoconstriction during HB conditions suggests a mechanism that maintains peak tissue perfusion.