Background: The aim of this study was to examine the action of inhaled nitric oxide in the patients with pulmonary hypertension administered with a face mask before anesthesia induction. Methods: Ten adult patients scheduled for heart surgery with sternotomy were included in this prospective, interventional, single centre study. The inclusion criteria were patients scheduled for heart surgery with sternotomy with cardiopulmonary bypass (CPB), aged >18 years which presents a pulmonary hypertension (PH) (class 2 or 3 according to the Dana Point classification) with systolic pulmonary arterial pressure (PAPS) >40 mmHg diagnosed by preoperative right cardiac catheterization or by transthoracic echocardiography. The exclusion criteria were: heart transplant, PH of type 1, 4, 5, according to the Dana Point classification, methemoglobin reductase deficit, incapacity to understand the protocol and sign the consent. Results: The administration of iNO decrease pulmonary hypertension ( P < 0,001 compared to room air; P = 0,01 compared to pure oxygen administration). The iNO administration did not improve arterial blood oxygenation. The hyperoxia, decrease the cardiac index even with right ventricular post charge decrease. The increased blood oxygenation content cause systemic vascular vasoconstriction and decrease the peripheral oxygen extraction showed with VO 2 linear increase ( P < 0,001). Conclusions: The administration of inhaled nitric oxide with a face mask before anaesthesia induction is safe and effective method to reduce pulmonary hypertension. The oxygen and hyperoxia influences the systemic vascular resistance and peripheral oxygen consumption.