Device and method for monitoring body fluid and electrolyte disorders

• US 8,457,722 B2
• Filed: 09/30/2005
• Issued: 06/04/2013
• Est. Priority Date: 03/16/2001
• Status: Expired due to Fees

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Covidien LP (Medtronic Plc)
• Inventors: Schmitt, Joseph M., Debreczeny, Martin
• Primary Examiner(s): Le, Long V.
• Assistant Examiner(s): IMPINK, BRADLEY GERALD
• Application Number:
  US11/239,815
• Publication Number:
  US 20060084864A1
• Time in Patent Office: 2,804 Days
• Field of Search: 600/310, 600/316, 600/322, 600/473, 600/475, 600/547, 250/339.1, 250/341.8
• US Class Current: 600/473
• CPC Class Codes: A61B 5/0053 by applying pressure, e.g. compression, indentation, palpation, grasping, gauging
• CPC Class Codes: A61B 5/0059 using light, e.g. diagnosis by transillumination, diascopy, fluorescence A61B5/0093, A61B5/1455, A61B5/02416 and A61B5/0261 take precedence
• CPC Class Codes: A61B 5/02438 with portable devices, e.g. worn by the patient
• CPC Class Codes: A61B 5/14546 for measuring analytes not otherwise provided for, e.g. ions, cytochromes
• CPC Class Codes: G01N 2021/3181 using LEDs
• CPC Class Codes: G01N 21/3554 for determining moisture content
• CPC Class Codes: G01N 21/359 using near infrared light

Abstract

Devices and methods for measuring body fluid-related metric using spectrophotometry that may be used to facilitate diagnosis and therapeutic interventions aimed at restoring body fluid balance. In one embodiment, the present invention provides a device for measuring a body-tissue water content metric as a fraction of the fat-free tissue content of a patient using optical spectrophotometry. The device includes a probe housing configured to be placed near a tissue location which is being monitored; light emission optics connected to the housing and configured to direct radiation at the tissue location; light detection optics connected to the housing and configured to receive radiation from the tissue location; and a processing device configured to process radiation from the light emission optics and the light detection optics to compute the metric where the metric includes a ratio of the water content of a portion of patient'"'"'s tissue in relation to the lean or fat-free content of a portion of patient'"'"'s tissue.

Claims

1. A device for determining an estimate of body water content, comprising:

a processing device configured to process a signal indicative of radiation detected from lean tissue of a patient to compute the estimate of body tissue water content, wherein the estimate is correlative to a computed fractional water content of the lean tissue, wherein the computed fractional water content of the lean tissue (f_w^l) is determined such that

2. The device of claim 1, wherein the computation of fractional water content of the lean tissue substantially excludes fat content and bone content of the patient.

3. The device of claim 1, comprising a display device coupled to the processing device to display the estimate of body tissue water content.

4. The device of claim 1, wherein the estimate of body tissue water content comprises a ratio of the body tissue of the patient and the lean tissue of the patient.

5. The device of claim 1, wherein the processing device receives and compares at least a first set and a second set of optical measurements, where the first set of optical measurements corresponds to the detected radiation having an absorption primarily due to water and non-heme proteins, and where the second set of optical measurements corresponds to the detected radiation having an absorption primarily due to water, and where a comparison of the first set and the second set of optical measurements provides a measure of a lean water fraction of the lean tissue.

6. The device of claim 1, wherein the processing device receives and compares at least two sets of optical measurements, where the at least two sets of optical measurements are based on detected radiation from at least two wavelengths and which are combined to form a ratio of combinations of the detected radiation.

7. The device of claim 6, wherein the processing device forms a weighted summation of the combinations.

8. The device of claim 1, wherein the processing device receives and compares at least two sets of optical measurements from at least two different wavelengths, where absorption of light at the at least two different wavelengths is primarily due to water which is in vascular blood of the patient and in extravascular tissue of the patient, and where a ratio of the at least two measurements provides a measure proportional to a difference between fractions of water in the blood and a surrounding tissue location.

9. The device of claim 1, wherein M and N are both equal to 3, wherein wavelengths indexed by m and n comprise of the same combination of wavelengths, and wherein first, second, third and fourth wavelengths are approximately 1180, 1245, 1275 and 1330 nm respectively.

10. A method for determining a body tissue water content metric as a fraction of lean tissue content of a patient, comprising:

processing radiation received from a tissue location of the patient to compute the body tissue water content metric, wherein the body tissue water content metric (f_w^l) is determined such that

11. A method of determining a physiological parameter in a human tissue location, comprising:

processing radiation received from the human tissue location to compute the physiological parameter, wherein the physiological parameter is determined such that it is equal to

12. The method of claim 11, wherein the physiological parameter comprises a tissue water fraction of the tissue location.

13. The method of claim 11, wherein the physiological parameter comprises an oxygen saturation value of the tissue location.

14. The method of claim 11, wherein the physiological parameter comprises a fractional hemoglobin concentration of the tissue location.

15. The method of claim 11, wherein the physiological parameter comprises a fractional concentration of hemoglobin in a first set comprised of one or more species of hemoglobin with respect to a concentration of hemoglobin in a second set comprised of one or more hemoglobin species in the tissue location.

16. The method of claim 15 wherein the coefficients, p_n, are chosen to substantially cancel absorbance contributions from all tissue constituents except the hemoglobin species included in the first set, and wherein the coeffients, q_m, are chosen to substantially cancel absorbance contributions from all tissue constituents except the hemoglobin species included in the second set.