A New Oxygen Mask for Carotid Endarterectomy Under Local Anaesthesia

• The primary aim of this study the aim is to determine the effectiveness of the vortex oxygen mask in increasing blood oxygen levels during CEA in the awake patient during carotid clamping. [ Time Frame: 0 hours ] [ Designated as safety issue: No ]
  

• To determine whether or not increased cerebral oxygen levels are associated with reduced cerebral injury, as measured by biomarkers: neuron-specific enolase and S100B. [ Time Frame: 2.5 hours. ] [ Designated as safety issue: No ]
  
• A further secondary outcome is to determine whether the mask is acceptable to patients, as recorded by a questionnaire. [ Time Frame: Within 24 hours post-operatively ] [ Designated as safety issue: No ]
  

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.