Assessment of cardiovascular safety in medium pressure hyperbaric oxygenation therapy

Abstract

The “hyperbaric oxygenation therapy” (HBOT) is currently used as an adjunct therapy in many pathologies. Its therapeutic action is based on that hyperoxia at high pressure (2.4 atm) induces vasoconstriction and reduction of inflammation among others effects. Recently, a more accessible Medium Pressure Hyperbaric Oxygenation therapy” (mHBOT) at 1.4 atm is also used as therapy that resulted equally effective at a lower cost. However, up to date no studies have been carried out to support the cardiovascular safety of both treatments. For this reason, we studied the cardiovascular safety of mHBOT in rats subjected to a protocol equivalent to that applied in humans. Male Sprague Dawley rats were submitted to 30 sessions of 60 min in a hypebaric chamber at 1.44 atm. and 100% O2 . Isolated hearts were perfused through aorta at 37ºC, paced at 3 Hz, and exposed to 30 min ischemia (I) followed by 45 min reperfusion (R). Simultaneous mechanical and heat measurements and the heart damaged area (trifeniltetrazolium) were evaluated. Also aorta rings were superfused and the noradrenaline response was analyzed. Hearts from mHBOT-treated rats showed an increase in resting pressure (RP) during ischemia (p<0.05) but no changes were observed in R. An improvement (p<0.05) in post ischemic contractile recovery was observed in hearts from mHBOT-treated rats (65.4±12.9%) respect to control ones (33.5±6.1%) at 45 min R. mHBOT did not alter total heat rate (Ht), but an increase (p<0.05) in contractile economy during R (120.9±20%) respect to control (53.2±8.9%) at 45 min was observed. Also mHBOT reduced the heart damage area induced by I/R. Furthermore, arteries from mHBOT-treated rats showed similar response to noradrenaline than controls. Conclusion: the mHBOT cardioprotects hearts from I/R injury acting as a preconditioning agent. The use of this therapy is safety for the cardiovascular system.