Methods and systems for controlling tourniquets

A system for controlling a tourniquet comprising:

• a processor having at least one output adapted to provide control signals to inflate and deflate a tourniquet, and at least one input to receive data indicating pressure in the tourniquet from a sensor, the processor being programmed with instructions which when executed are effective to perform a method having the steps of:
• (a) performing an inflation phase in which a tourniquet applied to a body part is inflated to a working pressure which exceeds the limb occlusion pressure (LOP) of said body part by an offset amount;
• (b) measuring the time-varying pressure induced in said tourniquet by the vascular system of said body part during said inflation;
• (c) deriving from said time-varying pressure a set of values for a characteristic of the induced pressure pulse in said tourniquet at a plurality of tourniquet pressures during the inflation phase;
• (d) determining from said set of values a first threshold value intermediate between the value of the characteristic at the LOP and the value of the characteristic at the working pressure;
• (e) monitoring the value of said characteristic during a working phase of the tourniquet while maintaining said working pressure;
• and
• (f) upon determining that the value of said characteristic has reached or passed said first threshold, increasing the working pressure of the tourniquet.

A computer program product comprising stored instructions which when executed in a processor having outputs adapted to provide control signals to inflate and deflate a tourniquet, cause said processor to perform a method having the steps of:

• (a) performing an inflation phase in which a tourniquet applied to a body part is inflated to a working pressure which exceeds the limb occlusion pressure (LOP) of said body part by an offset amount;
• (b) measuring the time-varying pressure induced in said tourniquet by the vascular system of said body part during said inflation;
• (c) deriving from said time-varying pressure a set of values for a characteristic of the induced pressure pulse in said tourniquet at a plurality of tourniquet pressures during the inflation phase;
• (d) determining from said set of values a first threshold value intermediate between the value of the characteristic at the LOP and the value of the characteristic at the working pressure;
• (e) monitoring the value of said characteristic during a working phase of the tourniquet while maintaining said working pressure;
• and
• (f) upon determining that the value of said characteristic has reached or passed said first threshold, increasing the working pressure of the tourniquet.