Method and apparatus for estimating the fluid content of a part of the body of a subject

An apparatus for estimating a volume of extra-cellular fluid in a part of a body of a subject, the apparatus comprising:

• a set of electrodes for attachment to the part of the body of the subject;
• and
• a processor configured to:
• control the set of electrodes to apply a first current of a first frequency to the subject,
• measure a first resistance in response to application of the first current,
• control the set of electrodes to apply a second current of a second frequency to the subject,
• measure a second resistance in response to application of the second current,
• interpolate a third resistance as a third frequency approaches 0 Hz, the third resistance being associated with the third frequency based on the first resistance and the second resistance, wherein the third frequency is lower than the first frequency and the second frequency,
• receive a measurement of a circumference of the part of the body of the subject,
• compute a through-body distance through the body of the subject between a first electrode of the set of electrodes and a second electrode of the set of electrodes based on the circumference, and
• estimate the volume of extra-cellular fluid in the part of the body of the subject based on the interpolated third resistance and the computed through-body distance.

A non-transitory machine-readable storage medium encoded with instructions for execution by a processor for estimating a volume of extra-cellular fluid in a part of a body of a subject, the non-transitory machine-readable storage medium comprising:

• instructions for controlling a set of electrodes to apply a first current of a first frequency to the subject;
• instructions for measuring a first resistance in response to application of the first current;
• instructions for controlling the set of electrodes to apply a second current of a second frequency to the subject;
• instructions for measuring a second resistance in response to application of the second current;
• instructions for estimating a third resistance associated with a third frequency based on the first resistance and the second resistance, wherein the third frequency is lower than the first frequency and the second frequency;
• instructions for receiving a measurement of a circumference of the part of the body of the subject;
• instructions for computing a through-body distance through the body of the subject between a first electrode of the set of electrodes and a second electrode of the set of electrodes based on the circumference;
• and
• instructions for estimating the volume of extra-cellular fluid in the part of the body of the subject based on the interpolated third resistance and the computed through-body distance.