Effect of Hyperbaric Oxygen Therapy on Microcirculation

Microcirculation alterations and hyperoxia are known to alter ICU-patients' prognostic.

Studies have shown that hyperoxia alters healthy volunteers' microcirculation, whereas hyperbaric oxygen therapy is commonly used to facilitate cicatrization. There seems to be a paradox. A recent study in rabbits has given some evidences that hyperbaria may restore microcirculation integrity, but to date, there is no such evidences in human.

To study hyperoxia and hyperbaric induced changes in micro and macrocirculation, fifteen healthy volunteers will be exposed to successive variations of inspired oxygen fraction and barometric pressure according to a predefine sequence so that only one parameter will change from a condition to the next one :

• FiO2 0.21 - 1 ATA
• FiO2 1 - 1 ATA
• FiO2 1 - 2.5 ATA
• FiO2 0.21 - 2.5 ATA
• FiO2 0.21 - 1 ATA

At each time, and after a 30 minutes period of exposure, measures will be made using SDF-microscopy, Laser Doppler and NIRS to assess microcirculation.

As previously described, macrocirculation can modify microcirculation due to a mechanism called hemodynamic coherence.

Hence, the investigators planned to assess macrocirculation changes at every step of the protocol using bioimpedancemetry and transthoracic echocardiography.

Each volunteer will be his own control, using the first measurements (condition 1. FiO2 0.21 - 1 ATA) as reference.

Inclusion criteria

• To provide a medical certificate of fitness to dive (< 1 year)
• Consent given for study participation
• French health insurance affiliated

Exclusion criteria

• Temporary or definitive contra-indication to dive
• Pregnancy or < 18 years of age
• Precedent dive < 24 hours
• Under a legal protection measure
• Medical history of a disease known to alter microcirculation