The Effect of Hyperbaric Oxygen Therapy on Inflammatory Parameters Induced by a Heat Injury Model (HBO-SHA)

Hyperbaric oxygen may reduce neurophatic pain and promote wound healing. Established anti inflammatory effects of HBO may contribute to this effect. In a previous publication the investigators studied the effects of HBO on secondary hyperalgesia using a well established heat injury model. In a new - blinded study design, the investigators wish to investigate and- or confirm previous results, i.e. that HBO therapy reduce secondary hyperalgesia and improving therapy of severe pain conditions.

Hyperbaric oxygen (HBO) reduces neuropathic pain, promote healing of hypoxic, chronic wounds and sores caused by radiation therapy. Nitric oxide (NO) is a contributing factor to the prolonged anti-nociceptive effect of HBO treatment. In addition, HBO stimulates the formation of reactive oxygen and nitrogen forms, reduces beta-2 integrin function, and reduces contact of leukocytes to the endothelial surface of the capillaries, improves microcirculation and causes decreased monocyte chemokine synthesis. It is the interaction of these mechanisms involved in HBO's anti-inflammatory effect. How HBO reduces pain and inflammation in humans has not been established. In healthy subjects, investigators have shown that HBO has a reducing effect on the mechanism, which at the level the of spinal cord amplifies the number and and the extension of pain impulses. Subjects who were given HBO therapy initially developed significantly less secondary hyperalgesia than the control group several weeks later by the new heat injury suggesting a protective, preconditioning effect. As in the previous experiment (NCT02025686) preconditioning effects will be assessed by means of measurements of thermal thresholds, pin-prick thresholds, erythema indices and secondary hyperalgesic areas (i.e. area under the curve per minute). Similarly,differences in the sequence of sessions (i.e. first session HBO;second session ambient pressure condition or first session ambient pressure condition;second session HBO) will be analyzed accordingly. In an improved blinded study design investigators will now investigate the effect of HBO treatment using the same cutaneous heat injury model, as in the first study. Investigators expect to finally be able to confirm previous results thereby improving treatment of severe pain conditions.

HBO given the first day of study period and sensory test battery performed. 4 weeks later no intervention is given but the sensory test battery performed.

No intervention first day of study period and sensory test battery performed. 4 weeks later HBO intervention is given and the sensory test battery performed.

Erythema and edema: DermoLab Combo, Cortex Technology, Hadsund. Pain: Is measured at specific times while the heat injury is being made using a VAS scale from 0-10. Hyperalgesia: Weighted pins (PinPrick 8, 16, 32, 64, 128, 256, 512 mN) using Dixon's "up-and-down" method. Secondary hyperalgesia: PinPrick, 8 symmetrical lines converging towards the center of the heat injury with 45 degrees difference. All parameters are compared within the two sessions to assess preconditioning.

Secondary hyperalgesia: PinPrick, 8 symmetrical lines converging towards the center of the heat injury with 45 degrees difference.

Pain: Is measured at specific times while the heat injury is being made using a VAS scale from 0-10. Hyperalgesia: Weighted pins (PinPrick 8, 16, 32, 64, 128, 256, 512 mN) using Dixon's "up-and-down" method. Secondary hyperalgesia: PinPrick, 8 symmetrical lines converging towards the center of the heat injury with 45 degrees difference.

Inclusion Criteria: male speaks and understands danish language understood and signed informed consent before medical examination Exclusion Criteria: younger than 18 years of age hypertension not able to perform equalization of ears and sinuses persons who present with a medical history of previous pneumothorax and/- or who may be considered of increased risk of pneumothorax diabetics, epilepsia,asthma neurological deficits including cognitive as well as psychomotoric disorders claustrophobia