This study evaluates a novel technique for measuring the minimum pressure necessary to achieve a bloodless surgical field, known as a patient's limb occlusion pressure (LOP). Patients will have tourniquets applied to their arms and legs and LOP will be measured using the new technique and a gold standard Doppler ultrasound technique.

Optimal tourniquet safety depends on accurately determining the minimum pressure necessary to achieve a bloodless surgical field, known as a patient's limb occlusion pressure (LOP). However, LOP is not yet routinely measured in all patients due to limitations of current techniques. This study evaluates a novel technique for measuring the LOP through the tourniquet cuff that overcomes many limitations of current LOP measurement techniques.

The goal of the study is to determine if the LOP measured by the new technique is statistically or clinically different from the LOP measured by a gold standard Doppler ultrasound technique in adult and pediatric patients

Inclusion Criteria:

• Scheduled for a visit to one of four surgical clinics in Vancouver, Canada
• Agreed to participate in the study and provide informed consent

Exclusion Criteria:

• Unable to give informed consent on their own behalf or by a legal guardian
• Lack of parental agreement in the case of consent from a legally competent minor
• Standard contraindications to tourniquet use
• Vascular disease or circulation problems in the extremities
• History or indication of deep vein thrombosis