The pneumatic tourniquet: a biomechanical and electrophysiological study.

The pneumatic tourniquet is used routinely in extremity surgery, not only to prevent unnecessary blood loss, but also to increase the safety of the operative procedure. The mechanical part of this study shows that the system can fail in either of two major ways, each causing serious problems. The tourniquet may be inadequate if the pressure delivered to the cuff is not accurately displayed on the gauge or if the pre-set pressure is not maintained for the duration of the operative procedure. In our hospital, three of seven tourniquets (43%) in daily use showed significant errors in this regard. The electrophysiological part of this study indicates that nerve conduction does not necessarily return to preoperative levels immediately postoperatively, and that the conduction block is generally at the level of the cuff. Our observations confirm those of others and implicate both direct pressure as well as ischemia as the cause of the problem.