B-type natriuretic peptide in healthy subjects after exposure to hyperbaric oxygen at 2.5 ATA.
INTRODUCTION: B-type natriuretic peptide (BNP) is a cardiac hormone used as a marker of cardiac dysfunction with diuretic and vasodilating properties secreted by the ventricles in response to wall stress. Hyperbaric oxygen (HBO) exposure is known to induce hemodynamic effects in humans which can be complicated by acute pulmonary edema. The aim of this study was to investigate if HBO has any effects on the secretion of BNP in healthy human subjects. METHODS: Eight healthy volunteers underwent the following HBO protocol in a hyperbaric chamber: compression to 2.5 atmospheres absolute (ATA); 45 min breathing 100% oxygen; 5 min breathing air; another 45 min in 100% oxygen; then decompression to atmospheric pressure. A venous blood sample was drawn before entering the chamber (To), immediately at the end of the treatment (T1), and at 5 h from To (T2). BNP concentration was determined using a rapid point-of-care immunoassay. Non-parametric statistics were used to analyze data. RESULTS: No difference in BNP levels was found between T0 and T1 or T2. DISCUSSION: The findings of this preliminary study show that in healthy subjects a single HBO exposure does not significantly modify BNP plasma levels. We hypothesize that this can be the net result between the stimulating effect of the HBO-induced vasoconstriction and the direct inhibitory effect on BNP secretion of myocyte hyperoxia. We conclude that HBO does not modify BNP secretion in healthy volunteers and that the direct effect of extreme hyperoxia on BNP secretion deserves further investigation.