Background: Hypoxemia is a severe perioperative complication that can substantially increase intensive care unit and hospital stay and mortality. The aim of this study was to determine the effects of non-invasive positive-pressure ventilation (NIPPV) in patients with hypoxemia after surgery for Stanford type A aortic dissection, and to compare the effects of helmet and mask NIPPV. Material/Methods: We recruited 40 patients who developed hypoxemia within 24 h after extubation after surgery for Stanford type A aortic dissection in the Beijing Anzhen Hospital. The patients were randomly divided into the helmet and mask NIPPV groups. The primary endpoints were blood oxygenation levels at 1 and 6 h after initiation and at the end of the treatment. The secondary endpoint was patient outcome, including mortality; incidence of pulmonary atelectasis, pneumonia, re-intubation, and sepsis; and length of ICU and hospital stays. Results: NIPPV improved oxygenation in both groups. Compared with pretreatment levels, the oxygenation index (PaO2/FiO(2)), PaO2, PaCO2, and respiratory rate (RR) improved in the initial (0-1 h), maintenance (1-6 h), and end stages of the treatment (P<0.05). Compared with mask ventilation, helmet ventilation better improved pH, PaO2, SpO(2), PaO2/FiO(2), and decreased PaCO2 in the 3 stages (P<0.05). The incidence of major complications, including flatulence, intolerance, and facial pressure sores, was significantly lower with helmet ventilation. Conclusions: NIPPV effectively improved oxygenation and reduced PaCO2 in patients who developed hypoxemia soon after extubation following surgery for Stanford type A aortic dissection. Compared with mask NIPPV, helmet NIPPV more rapidly increased PaO2 and reduced PaCO2, increased patient tolerance and comfort, and reduced complications.