Hand surgery requires a reduced blood flow to the hand during the operation, which is achieved using a tourniquet (tightly inflated circumferential cuff) around the upper arm. However this tourniquet is painful. This study investigates whether breathing oxygen can reduce the pain associated with the tourniquet to both improve patient experience and potentially to allow longer operations to be completed under a local anaesthetic (rather than a general anaesthetic, where the patient is put to sleep, which is more costly, time consuming and risky for the patient).

• This study is a randomised controlled trial of healthy volunteers (for example medical students, nurses and doctors).
• Each volunteer is randomised to receive either oxygen or normal air through a mask whilst wearing an inflated upper arm tourniquet and rating their pain on a scale. The equipment set-up is identical for each volunteer, with the tourniquet inflated to a pressure of 250mmHg in every person.
• Within each arm of the study, volunteers are again randomised to wear the tourniquet on either their dominant or non-dominant arm.
• The study is double-blind (the volunteer and the investigator running the test are unaware of whether oxygen or air is being received) to avoid bias.
• The volunteer can ask for the tourniquet to be removed at any time and will wear the tourniquet for a maximum of 30 minutes.
• The pain ratings and also heart rate and blood pressure are then analysed to identify whether the volunteers receiving oxygen experienced less pain or were able to tolerate the tourniquet for longer than those receiving air.

Inclusion Criteria:

• Healthy
• More than 18 years of age

Exclusion Criteria:

• Diabetes
• Vascular disease
• Previous operations to arms
• Raynaud's disease
• Analgesia taken in last 24 hours
• Chronic pain
• Hypertension
• Allergy to any substance used in the study
• Unable to give valid consent to participate
• Obesity