High-flow nasal oxygen (HFNO) vs standard oxygen therapy in patients undergoing transfemoral transcatheter aortic valve implantation (TAVI)

The Treating anaesthetist will administer the following intervention: a) High Flow Nasal Oxygen (up to 50 l/min warmed and humidified using the Optiflow delivery system) OR Standard Oxygen Therapy (2 l/min increasing to 8 l/min as required, delivered via nasal specs) commenced immediately on establishment of intravenous access (approximately at the commencement of IV sedation in the form of remifentanil) b) duration 60-90 minutes c) Oxygen therapy ceased at the time of transfer on to the bed prior to moving the patient to the recovery room d) Oxygen will be administered at 50L/min via HFNO at FiO2 0.3 or 2L nasal prongs (approximately FiO2 0.3) to achieve a minimum of SpO2 94-98% for patients without respiratory comorbidities OR 88-92% or patient specific target range for those at risk of hypercapnoeic respiratory failure e) Saturation monitoring will be a routine for all patients along with end tidal carbon dioxide Procedure: Once the allocated oxygen therapy has begun, patients will be sedated and the TAVI procedure will commence as per standard hospital protocol: 1. Oxygen started depending on randomisation allocation 2. Conscious sedation is started (by remifentanil intravenous infusion) 3. Regional block sited on side of TAVI procedure. 4. Transthoracic echocardiogram performed. 5. An arterial blood gas (ABG) sample is taken for analysis and repeated every 20 min or as determined according to clinical need. 6. TAVI valve implantation takes place. 7. Sedation stopped once confirmed that no bleeding from femoral artery. If surgical intervention required (e.g. due to damage to femoral artery), this can normally take place under sedation and regional block, but occasionally general anaesthetic may be required. Follow-up: Following the TAVI procedure patients will be transferred to the recovery area and, once the standard recovery criteria are met, then transferred to the ward. Clinical data will be recorded whilst patients are on the recovery area and ward. Patients will also be asked to verbally complete a short patient comfort questionnaire (three questions with multiple choice answers)whilst in the recovery area. Patients will be followed up until the standard discharge criteria are met and the patient can be discharged home. Serious adverse events (SAEs): Non-serious Adverse Events will not be recorded unless they form part of the clinical event dataset. All Serious Adverse Events (SAEs) occurring between randomisation and the end of follow-up will be reported to Papworth Clinical Trials Unit Collaboration (PTUC) within 24 hours of knowledge of the event. Data handling: The trial will be conducted according to Good Clinical Practice and PTUCs own standard operating procedures to ensure the monitoring and safety of trial participants and data validity. A secure, restricted-user, trial-specific database will be developed at PTUC. A member of the research team will enter the data into the database, which will only be accessible by the trial personnel.