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.