Introduction: We have recently shown that the clinical use of hyperbaric oxygen therapy (HBOT) reduces fasting blood glucose and increases insulin sensitivity after 3 and 30 treatments in patients with type 2 diabetes¹. Whether this occurs in a non-patient population with and without type 2 diabetes is unclear, along with the mechanism of effect.
Methods: Insulin sensitivity was assessed by hyperinsulinemic euglycemic clamp (80mU/m2/min) in overweight and obese men without (n=11) or with type 2 diabetes (n=8) at baseline and during the third HBOT session. Fasting blood samples were also collected at baseline and 60 and 120 minutes of the first HBOT session, and at 120 minutes immediately following the fourth exposure to HBOT. Subcutaneous abdominal adipose tissue samples were collected at baseline and imediately after the fourth HBOT session. 
Results: Insulin sensitivity was significantly increased by 29±10% in overweight men and by 57±23% in overweight men with type 2 diabetes (P<0.01). This increase was maintained for 30-minutes after exit from the hyperbaric chamber whilst breathing normobaric air. Reductions in serum inflammatory markers MCP-1 and TNF-α were observed after 4 days of HBOT in both groups (P<0.05), whilst IL-6 was increased in non-diabetics only (P=0.05). The increase in IL-6 correlated with the increase in insulin sensitivity (r2=.36, p=.02).
Conclusion: Insulin sensitivity was increased by HBOT in individuals with and without type 2 diabetes and this effect was maintained for at least 30-minutes after exit from the hyperbaric chamber. Changes in inflammatory cytokines may partly explain this effect.