System and method for reducing iatrogenic damage to nerves

• US 5,916,179 A
• Filed: 04/18/1997
• Issued: 06/29/1999
• Est. Priority Date: 04/18/1997
• Status: Expired due to Fees

• Current Assignee: Nigel Sharrock
• Original Assignee: Nigel Sharrock
• Inventors: Sharrock, Nigel
• Primary Examiner(s): Lateef, Marvin M.
• Assistant Examiner(s): MANTIS MERCADER, ELENI M
• Application Number:
  US08/844,097
• Time in Patent Office: 802 Days
• Field of Search: 600/398, 600/407, 600/554, 600/587, 600/553, 128/897, 128/898
• US Class Current: 600/587
• CPC Class Codes: A61B 5/03 Detecting, measuring or recording fluid pressure within the body other than blood pressure, e.g. cerebral pressure; Measuring pressure in body tissues or organs A61B5/205 takes precedence
• CPC Class Codes: A61B 5/4041 Evaluating nerves condition

Abstract

A method for predicting peripheral nerve damage comprising the steps of placing a pressure transducer on the skin of a patient proximate to a peripheral nerve; measuring the pressure with the pressure transducer over time; and estimating a damage to the nerve based on the pressure and duration of application and a nerve damage model.

Claims

1. A method for predicting nerve damage due to external mechanical effects, comprising the steps of:

(a) placing a transducer external to a patient at a location where a mechanical effect is sensed by the transducer correlates with a local pressure to which a nerve is subjected;

(b) measuring the mechanical effect over time by means of the transducer; and

(c) predicting a damage to the nerve based on the measured mechanical effect over time, and a model of susceptibility of the nerve to damage.

2. The method according to claim 1, wherein said prediction is based on a model of nerve damage based on time-weighted pressure.

3. The method according to claim 1, wherein said prediction comprises an estimate based on an estimate of ischemic damage to the nerve.

4. The method according to claim 1, wherein said prediction comprises an estimate of non-ischemic damage to the nerve.

5. The method according to claim 1, further comprising the step of producing an alarm if the estimate of damage exceeds a threshold.

6. The method according to claim 5, wherein said threshhold is adaptive to a clinical condition of the patient.

7. The method according to claim 1, further comprising the step of relieving pressure on the nerve.

8. The method according to claim 7, wherein the pressure on the nerve is relieved automatically.

9. The method according to claim 8, further comprising the step of controlling an actuator to relieve a pressure on the nerve.

10. The method according to claim 1, further comprising the step of estimating a damage to the nerve.

11. The method according to claim 10, further comprising the step of producing alarms if either the prediction or estimate exceed respective thresholds.

12. The method according to claim 1, wherein said transducer is applied proximate to the skin proximate to the ulnar nerve.

13. The method according to claim 1, wherein the transducer comprises a fluid-filled bladder in proximity to the skin.

14. The method according to claim 1, wherein the transducer comprises a planar electromechanical transducer affixed to the skin.

15. The method according to claim 14, wherein the transducer comprises a plurality of regions, each region producing an output.

16. The method according to claim 15, further comprising the step of basing said prediction on an output representing the largest applied force.

17. The method according to claim 1, wherein the transducer is applied in proximity to the eye.

18. The method according to claim 17, wherein the transducer comprises a fluid filled bladder placed adjacent to the eyelid.

19. The method according to claim 1, further comprising the step of wirelessly transmitting a signal corresponding to the mechanical effect.

20. The method according to claim 1, further comprising the step of adapting the model of susceptibility of the nerve to damage based on a clinical state of the patient.

21. A method for predicting nerve damage due to external mechanical effects, comprising the steps of:

(a) placing a transducer external to a patient at a location where an external mechanical effect is sensed by the transducer correlates with a local pressure to which a nerve is subjected;

(b) measuring the external mechanical effect over time by means of the transducer; and

(c) predicting a damage to the nerve based on the magnitude and duration of the measured external mechanical effect.

22. A method for predicting neuropraxic effects, comprising the steps of:

(a) directing an optical sensor, differentially sensitive to hemoglobin in an oxygenated and deoxygenated state, toward vital tissues having a pressure which corresponds to a pressure to which a nerve is subjected;

(b) estimating a blood perfusion to the nerve over time based on the optical sensor; and

(c) predicting a damage to the nerve based on the estimate of blood perfusion over time and a modeled sensitivity of the nerve to ischemic injury.

23. The method according to claim 22, further comprising the steps of estimating a pressure applied to the nerve over time and predicting a damage to the nerve based on the estimate of pressure applied to the nerve over time and a modeled sensitivity of the nerve to mechanical injury.

24. The method according to claim 22, wherein said optical sensor senses capillary blood in skin.

25. The method according to claim 22, wherein said optical sensor senses retinal blood flow.

26. The method according to claim 22, wherein the nerve is in the retina.

28. The sensor according to claim 23, further comprising a pressure transducer for measuring a pressure of the fluid and an analyzer for determining risk of damage to the retina based on applied forces over time.

27. A sensor for predicting retinal damage due to externally applied forces, comprising a fluid filled bulb adapted for placement over the eyelid, covering the orbit and a tube for transmitting a pressure of the fluid to a pressure transducer.

29. A method for predicting ischemic nerve damage due to external mechanical effects, comprising the steps of:

(a) providing a transducer at a location of a patient to sense a mechanical effect which correlates with a local pressure to which a nerve is subjected;

(b) measuring the mechanical effect over time by means of the transducer; and

(c) predicting a damage to the nerve based on a susceptibility of the nerve to ischemic damage, a measured blood pressure of the patient and the measured mechanical effect over a period of time.

30. The method according to claim 29, further comprising the step of selectively producing an output if one or more conditions selected from the following group is met:

(i) the measured mechanical effect correlates with an applied pressure which is in excess of diastolic pressure for a predetermined period;

(ii) the measured mechanical effect correlates with an average applied pressure over an interval of time is in excess of a predetermined threshold;

(iii) the measured mechanical effect correlates with an average applied pressure over an interval of time is in excess of a threshold dependent on the diastolic pressure; and

(iv) the measured mechanical effect correlates with an applied pressure which, over the course of an interval of time is in excess of a predetermined threshold for a predetermined cumulative duration.

31. The method according to claim 29, further comprising the step of selectively producing an output if the measured mechanical effect correlates with an applied pressure which is in excess of diastolic pressure for a predetermined period.

32. The method according to claim 29, further comprising the step of selectively producing an output if the measured mechanical effect correlates with an average applied pressure over an interval of time is in excess of a predetermined threshold.

33. The method according to claim 29, further comprising the step of selectively producing an output if the measured mechanical effect correlates with an average applied pressure over an interval of time is in excess of a threshold dependent on the diastolic pressure.

34. The method according to claim 29, further comprising the step of selectively producing an output if the measured mechanical effect correlates with an applied pressure which, over the course of an interval of time is in excess of a predetermined threshold for a predetermined cumulative duration.

35. A method for predicting nerve damage due to external mechanical effects, comprising the steps of:

(a) placing a transducer external to a patient to measure a surrogate factor, relating to a local pressure is applied to a nerve as a result of a mechanical effect;

(b) measuring the surrogate factor;

(c) predicting a damage to the nerve based on the measured surrogate factor over time, and a model of susceptibility of the nerve to damage.

36. The method according to claim 35, wherein the surrogate factor is nerve conduction and the transducer measures a nerve conduction phenomena through the region of applied local pressure.