Method and apparatus for the non-invasive detection of medical conditions by monitoring peripheral arterial tone

An apparatus for non-invasively determining a physiological condition, comprising:

• a probe to be applied to a digit of a subject, said probe sensing the peripheral arterial tone of the digit and outputting signals indicative of the peripheral arterial tone;
• and
• a processor receiving the signals output from said probe and either providing an output indicating changes in the peripheral arterial tone from which the physiological state can be determined or determining the physiological state from changes in the peripheral arterial tone and providing an output indicating the physiological state.

A method for non-invasive detection of a change in a physiological state of a patient, comprising:

• detecting a change in peripheral arterial tone of the patient;
• and
• determining the physiological or patho-physiological state of the patient when a specific change in the peripheral arterial tone has been detected.

A method for calibrating a blood pressure measuring instrument, the instrument comprising an end cap for receiving a patient's digit, the end cap having a pressure compartment configured to exert pressure on a distal part of the digit including an extreme tip of the digit, to prevent venous blood pooling in the digit, a contiguous pressure cuff having a membrane configured to exert pressure on the digit preceding the distal part of the digit, to prevent venous blood pooling in the digit, and a sensor for detecting pulsatile volume changes of the arteries in the part of the digit contained within the instrument, said method comprising generating a compliance curve of measured arterial blood vessels by inducing and monitoring transmural pressure changes within the blood vessels by changing an applied external pressure generated within the instrument, and measuring corresponding volumes and other volume correlated features of the blood vessels and then plotting said volumes and features.

A method for calibrating a blood pressure measuring instrument, comprising the generation of a compliance curve of the measured arterial blood vessels by inducing and monitoring transmural pressure changes within the blood vessels by changing an applied external pressure generated within the instrument and by altering intra-vascular hydrostatic pressure, and measuring corresponding volumes and other volume correlated features of such arterial blood vessels and then plotting such measured values and induced hydrostatic pressure changes.