The purpose of this study is to determine the effectiveness of oxygenation and patient-acceptability of a novel oxygen face mask in patients undergoing carotid endarterectomies (CEAs).

Carotid endarterectomy (CEA) is a procedure to remove plaques from a carotid artery (one of the two main arteries supplying blood to the brain). The procedure is effective at reducing the risk of subsequent stroke. To access the artery, an incision is made in the artery wall which means that the artery must be clamped in order to prevent blood loss. Consequently, the blood supply (and therefore oxygen supply) to the brain is reduced. To ensure that the patient has sufficient oxygen to avoid brain damage, this procedure is often carried out under local anaesthetic as this means the anaesthetist can talk to them during the operation; by this means they can determine the patient's conscious level and whether or not they need supplementary oxygen.

There are various ways to administer the supplementary oxygen. Most oxygen masks completely cover the mouth and nose which inevitably limits patient-doctor communication. Oxygen is therefore usually administered via nasal tubes. However, the actual level of oxygen taken in by the patient is very hard to measure, and at best is only 40%.

A novel mask with an open design. By creating a 'vortex' of oxygen it can deliver higher concentrations of oxygen to the patient without significantly interfering with doctor-patient communication and, at the same time, improving patient comfort.

We wish to test the efficacy of this mask during CEA and plan to do this by measuring the oxygen content of blood directly using blood samples; we also monitor markers of brain damage which may occur from lack of oxygen. Finally, we will survey the patients as to acceptability of the mask.

Inclusion Criteria:

• Male or female
• Booked for carotid endarterectomy under local anaesthetic
• Competent to consent to inclusion

Exclusion Criteria:

• Patient refusal and inability to provide consent
• Patients who are unable to understand instruction or communicate effectively
• Aged below 16 years
• Decreased conscious level during the period of study

Vascular Surgical Outpatients, booked for CEA under local anaesthetic