Patients with pulmonary disease due to occlusion of mechanical obstruction of pulmonary circulation, above all when worsen by right heart failure, are often hospitalized with respiratory complaints, with hypoxemia being the most common presenting sign. These patients often require increasing amounts of supplemental oxygen to maintain oxygenation, including high-flow nasal cannula (HFNC), noninvasive ventilation (NIV), or mechanical ventilation (MV), necessitating Intensive Care Unit stay. Patients with severe pulmonary compromission in these setting often have concomitant pulmonary hypertension. These patients may present with signs of right ventricular failure as their initial presentation or develop right ventricular failure during their Intensive Care Unit stay. The signs of right ventricular failure are often nonspecific, such as severe hypoxemia and hypotension, and can be confused with other potential etiologies, leading to delays in diagnosis and management. Pulmonary embolism mortality is linked to increased pulmonary artery pressure, right ventricular dysfunction, and hypoxemia. Oxygen, a potent pulmonary vasodilator, can reduce PA pressure and reverse hypoxic pulmonary vasoconstriction, even without systemic hypoxemia. Thus, it is important the choice of the best way of O2 administration in this scenario.