Condition category
Date applied
Date assigned
Last edited
Prospectively registered
Overall trial status
Recruitment status
No longer recruiting

Plain English Summary

Background and study aims
This is a study of two different methods of providing oxygen to patients having a transcatheter aortic valve implantation (TAVI) under conscious sedation. TAVI is a type of treatment for patients who have a narrowing of the aortic valve in the heart (aortic stenosis). Traditionally treatment of aortic stenosis has required open-heart surgery but with this procedure doctors can place a new valve in the heart through one of the large blood vessels in the leg (transfemoral TAVI). Usually patients having a TAVI recover from their treatment faster and can go home sooner. Also, unlike patients having open-heart surgery, patients having a TAVI will be under conscious sedation, meaning they will have been given medication to make them relaxed and sleepy but will be awake. Studies have shown that this leads to reduced procedure times, fewer complications and faster recovery. Sometimes during a TAVI the patient’s blood oxygen levels can become too low (known as hypoxaemia). Therefore all patients having a TAVI under conscious sedation need to be given oxygen. This study is investigating two different methods of providing oxygen to patients having a TAVI under conscious sedation. These are:
Standard oxygen therapy: patients are given 2 l/min of oxygen via nasal cannula (tube) increasing to 8 l/min if required (which is our normal practice).
High Flow Nasal Oxygen (HFNO): patients are given a high flow nasal oxygen delivery device. Oxygen from this device is heated and humidified, starting with a low flow of 30% oxygen at 30 l/min and slowly increased up to 50l/min if needed.
The two devices are compared to see if either is better at preventing hypoxaemia or leads to improved patient comfort.

Who can participate?
Patients aged over 18 who are scheduled to have a transfemoral TAVI

What does the study involve?
Before the procedure starts participants are randomly allocated to be given one of the two oxygen delivery devices. Their TAVI proceeds as normal. An anaesthetist monitors all patients closely and makes adjustments to oxygen and sedation levels as required. Information is collected during the procedure and recovery period and patients answer a short questionnaire during their recovery. Patients’ involvement in the study ends when they are discharged from hospital.

What are the possible benefits and risks of participating?
Patients may or may not benefit from participating. Patients in the HFNO group may benefit if their blood oxygen levels are improved. Future patients may benefit if HFNO is shown to improve the care, safety and comfort of patients undergoing TAVI under conscious sedation. There is always a risk of discomfort with the use of any oxygen device. With HFNO this can include feeling hot, stomach bloating or having a dry nose and mouth.

Where is the study run from?
Royal Papworth Hospital NHS Foundation Trust (UK)

When is the study starting and how long is it expected to run for?
January 2018 to November 2020

Who is funding the study?
Fisher and Paykel Healthcare Limited

Who is the main contact?
Claire Matthews

Trial website

Contact information



Primary contact

Ms Claire Matthews


Contact details

Royal Papworth Hospital NHS Foundation Trust
Papworth Road
Cambridge Biomedical Campus
United Kingdom



Additional contact

Prof Andrew Klein


Contact details

Royal Papworth Hospital NHS Foundation Trust
Papworth Road
Cambridge Biomedical Campus
United Kingdom
+44 (0)1480364406



Additional contact

Dr Stefanie Scheuermann


Contact details

Royal Papworth Hospital NHS Foundation Trust
Papworth Road
Cambridge Biomedical Campus
United Kingdom
+44 (0)1223 639666

Additional identifiers

EudraCT number

Nil known number

Nil known

Protocol/serial number


Study information

Scientific title

A randomised controlled trial of high-flow nasal oxygen (HFNO) vs standard oxygen therapy in patients undergoing transfemoral transcatheter aortic valve implantation (TAVI) under conscious sedation


Study hypothesis

The primary aim is to determine if high flow nasal oxygen (HFNO) in patients undergoing transcatheter aortic valve implantation (TAVI) under conscious sedation compared to standard oxygen delivery (2 litres via nasal specs) improves patients’ gas exchange as measured by blood tests of oxygen availability.

Secondary aims are to determine whether the use of HFNO:
1. Reduces the number of times either the patient or the anaesthetist has to interfere with the sedation level, airway or oxygen delivery device (e.g. verbal commands/chin lift by the anaesthetist or hand movement towards the oxygen delivery device by the patient)
2. Improves cerebral oxygenation by reducing the number of and severity of cerebral desaturation episodes
3. Is associated with reduced stay in recovery (hours)
4. Is associated with reduced admissions to the intensive care unit
5. Is associated with a reduced requirement for conversion to general anaesthesia (GA), escalation of respiratory support, tracheal intubation or pulmonary complication

Ethics approval

Approved 28/03/2019, East of England - Cambridge East Research Ethics Committee (The Old Chapel, Royal Standard Place, Nottingham, NG1 6FS; Tel: +44 (0)207 104 8101; Email:, ref: 19/EE/0104

Study design

Randomised; Interventional; Design type: Prevention, Device, Active Monitoring

Primary study design


Secondary study design

Randomised controlled trial

Trial setting


Trial type


Patient information sheet

Not available in web format, please use the contact details to request a patient information sheet


Transcatheter aortic valve implantation


Screening and consent:
Patients scheduled to undergo a TAVI procedure will be identified by a member of the study team. Patients meeting the entry criteria will be provided with a patient information sheet and given at least 24 hours to consider participation. Prior to their TAVI procedure, a member of the research team will meet them to answer any questions and ask for consent to take part in the study.

Patients will be transferred to the cardiac catheterisation laboratory for their TAVI procedure, baseline measurements will be taken and then the randomisation performed. Patients will be randomised in a 1:1 ratio to receive either:
1. High Flow Nasal Oxygen (up to 50 l/min warmed and humidified using the Optiflow delivery system)
2. Standard Oxygen Therapy (2 l/min increasing to 8 l/min as required, delivered via nasal specs)

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.

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.

Intervention type



Not Applicable

Drug names

Primary outcome measure

The partial pressure of oxygen dissolved in the blood (PaO2) taken from an arterial blood gas sample during the procedure

Secondary outcome measures

1. The number of desaturations (defined as SpO2 <93% for >10 seconds or SpO2 drop more than 5% from baseline for >10 seconds) at any time during the procedure measured by pulse oximetry
2. Time spent on the Recovery ward post-procedure measured in hours
3. Number of patients requiring conversion to general anaesthesia during the procedure
4. Duration of oxygen provision during and post-procedure measured in hours
5. Patient-reported comfort measured using the Patient Comfort Questionnaire post-procedure
6. Time spent in hospital measured in days at discharge

Overall trial start date


Overall trial end date


Reason abandoned (if study stopped)


Participant inclusion criteria

1. Able to provide informed consent
2. Adult patients (> 18 years)
3. Patients undergoing an elective transfemoral TAVI procedure

Participant type


Age group




Target number of participants

Planned Sample Size: 70; UK Sample Size: 70

Total final enrolment


Participant exclusion criteria

1. Contraindication to HFNO such as a nasal septum defect
2. Participation in another randomised controlled trial

Recruitment start date


Recruitment end date



Countries of recruitment

United Kingdom

Trial participating centre

Royal Papworth Hospital NHS Foundation Trust
Papworth Road Cambridge Biomedical Campus
United Kingdom

Sponsor information


Royal Papworth Hospital NHS Foundation Trust

Sponsor details

Royal Papworth Hospital NHS Foundation Trust
Papworth Road
Cambridge Biomedical Campus
United Kingdom
+44 (0)1480 830541

Sponsor type

Hospital/treatment centre



Funder type


Funder name

Fisher and Paykel Healthcare Limited

Alternative name(s)

Funding Body Type

Funding Body Subtype


Results and Publications

Publication and dissemination plan

1. Peer-reviewed scientific journals
2. Internal report
3. Conference presentation
4. The researchers will invite participants at the end of the trial to come to a presentation about the results and impact of the trial and provide them with a written report of the trial, and ask them for feedback and thank them for their participation

IPD sharing statement
The datasets generated during and/or analysed during the current study are/will be available upon request from Dr A Klein ( once the study has been published on contacting Dr Klein.

Intention to publish date


Participant level data

Available on request

Basic results (scientific)

Publication list

Publication citations

Additional files

Editorial Notes

08/12/2020: IPD sharing statement added. 02/12/2020: The following changes were made to the trial record: 1. The recruitment end date was changed from 31/12/2020 to 07/10/2020. 2. The overall trial end date was changed from 31/12/2020 to 06/11/2020. 3. The intention to publish date was changed from 31/12/2021 to 31/07/2021. 4. Total final enrolment added. 5. Sponsor/contact/trial participating centre address updated. 11/05/2020: The recruitment end date has been changed from 30/04/2020 to 31/12/2020. 16/04/2020: Due to current public health guidance, recruitment for this study has been paused. 30/04/2019: Uploaded protocol Version 3.4, 15 January 2019 (not peer reviewed). 15/04/2019: Trial's existence confirmed by the NIHR.