Background Transcatheter aortic valve replacement is a risky procedure, performed in patients that can also be considered at risk of developing complications. The use of HFNO could be justified in this context and could improve the results and safety of these procedures. The use of HFNO during sedation for TAVR could increase oxygen content and minimise hypercapnia, which occurs frequently. This may have 2 potential benefits: one in terms of facilitating the patient's tolerance to anaesthetic sedation; and the other to optimise oxygen delivery to organs such as the brain, kidneys, and myocardium.

Primary aim The number of oxygen desaturation episodes. An oxygen desaturation episode is defined as any episode of Sp02 <93% for more than 10 seconds.

Method A single-center prospective randomised controlled clinical trial with 132 individuals comparing the use of High Flow Nasal oxygen (intervention group) with the conventional standard of care oxygenation with nasal cannula standard oxygenation (control group) of patients undergoing sedation for transfemoral TAVR. The randomisation process will be carried out with a 1:1 assignment, using the RedCap Clínic tool for this purpose. Both groups will be treated at the same centre and by the same interventional cardiology and anaesthesia team. Sedation regime will be based on Target controlled infusion (TCI) with propofol and remifentanil. Local anaesthesia will be infiltrated by interventional cardiologist prior obtaining femoral vascular access. 50 L/min with 0.6% FiO2 will be administered through a high-flow nasal cannula in the intervention group. In the control group, oxygen therapy will also be administered in all cases, using the usual procedure: oxygen therapy through a conventional nasal cannula and at a flow of 5 L/min.

Inclusion Criteria:

• All patients >18 years of age undergoing transfemoral TAVR procedure under local anaesthesia and sedation consenting to participate in the study

Exclusion Criteria:

• <18 years and/or refusal to give informed consent for participation General anaesthesia required to perform complex cases of TAVR