With increasing life expectancy, the geriatric population continues to grow. According to the Turkish Statistical Institute (TÜİK), the average life expectancy in Turkey between 2021 and 2023 is 77.3 years. As the number of elderly surgical patients rises, optimizing anesthesia care is critical to reducing complications and improving clinical outcomes. In elderly patients with severe aortic stenosis, traditional surgical aortic valve replacement poses a high risk of complications. Consequently, Transcatheter Aortic Valve Implantation (TAVI) has emerged as a preferred, less invasive alternative. Due to technological advancements and shorter procedure durations, TAVI is increasingly performed under sedation rather than general anesthesia. However, sedation carries risks, including hypoxemia and hypoventilation, primarily due to sedative-induced respiratory depression. Pulse oximetry, the traditional monitoring method, measures only peripheral oxygen saturation and does not provide early detection of apnea or hypoventilation. Therefore, monitoring end-tidal carbon dioxide (EtCO₂) during sedation has gained importance. The American Society of Anesthesiologists (ASA) recommends EtCO₂ monitoring during sedation. However, obtaining accurate EtCO₂ values via nasal cannulas is technically challenging. Open sampling ports and high oxygen flow rates can cause dilution or loss of exhaled CO₂, resulting in inaccurate readings. The SuperNO₂VA™ nasal mask (Vyaire Medical, USA) addresses these limitations with an integrated CO₂ sampling port and the ability to provide positive airway pressure. This facilitates more accurate EtCO₂ monitoring and better ventilatory support compared to standard nasal cannulas. Prior studies have demonstrated that the SuperNO₂VA mask significantly reduces the risk and severity of hypoxia in high-risk patients during sedated endoscopic procedures. It prevents upper airway collapse and increases ventilated lung surface area, without causing clinically significant hypercapnia or CO₂ retention. This study aims to compare the incidence of hypoxia in patients aged 65 years and older undergoing TAVI under sedation using either the SuperNO₂VA nasal mask or a conventional nasal oxygen mask. Secondary outcomes include the evaluation of intraoperative hypercapnia or hypocapnia and the assessment of postoperative respiratory complications.