Improved sensors and sensing for monitoring neuromuscular blockade

• US 20100081963A1
• Filed: 09/14/2007
• Published: 04/01/2010
• Est. Priority Date: 09/16/2006
• Status: Active Grant

• Current Assignee: Terence Gilhuly
• Original Assignee: Terence Gilhuly
• Inventors: Gilhuly, Terence
• Granted Patent: US 8,506,502 B2
• Time in Patent Office: Days
• US Class Current: 600/554
• CPC Class Codes: A61B 5/0002 Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network A61B5/07 takes precedence; transmission systems for measured values G08C; transmission H04B; transmission of digital information H04L; wireless communication networks H04W
• CPC Class Codes: A61B 5/01 Measuring temperature of body parts ; Diagnostic temperature sensing, e.g. for malignant or inflamed tissue clinical contact thermometers G01K13/20
• CPC Class Codes: A61B 5/02055 Simultaneously evaluating both cardiovascular condition and temperature
• CPC Class Codes: A61B 5/05 Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves impedance plethysmography A61B5/0295; measuring movement of the entire body or parts thereof A61B5/11; detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof A61B5/24
• CPC Class Codes: A61B 5/1106 to assess neuromuscular blockade, e.g. to estimate depth of anaesthesia
• CPC Class Codes: A61B 5/4821 Determining level or depth of anaesthesia A61B5/1106 takes precedence
• CPC Class Codes: A61B 5/72 Signal processing specially adapted for physiological signals or for diagnostic purposes character recognition, recognising digital ink, document-oriented image-based pattern recognition G06V30/00; recognition or understanding of postal images G06V30/424
• CPC Class Codes: A61B 5/746 Alarms related to a physiological condition, e.g. details of setting alarm thresholds or avoiding false alarms alarms per se G08B
• CPC Class Codes: A61M 2005/14208 with a programmable infusion control system, characterised by the infusion program
• CPC Class Codes: G05B 17/02 electric
• CPC Class Codes: G16H 40/63 for local operation
• CPC Class Codes: G16H 50/50 for simulation or modelling of medical disorders
• CPC Class Codes: G16Z 99/00 Subject matter not provided for in other main groups of this subclass
• CPC Class Codes: Y02A 90/10 Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation

Abstract

Improved sensors and sensing methods for detection of Neuromuscular Blockade (NMB), for example to improve monitoring generally, as well as facilitate automated NMB drug administration. The methods, systems, devices, etc., herein can increase the quantity and quality of data available. The methods, etc., include translation between commonly available sensing types, use of partially saturated sensor measurements, use of a model of neurotransmitter storage and release and sophisticated use of more than one sensor simultaneously. These methods are aided by new sensors and methods of decreasing electrical noise. An implementation of the methods, systems, devices, etc., herein is automated drug delivery for NMB, whether through an advisor system or through with full computer control.

Claims

1. A method of quantifying a neuromuscular response evoked from a first mode of stimulation as a measurement in a second mode of stimulation, comprising:

(a) applying a first mode of neuromuscular stimulation to a patient;

(b) measuring a neuromuscular response from the patient;

(c) converting the measurement of neuromuscular response from the first mode to an equivalent measurement with respect to a second mode of neuromuscular stimulation in an objective fashion using a mathematical correlation established between the first and second modes.

2. The method of claim 1 where the first mode of neuromuscular stimulation includes one of single twitch (ST), double burst (DBS), tetanus, post-tetanic count (PTC), post-tetanic burst (PTB) and train-of-four (TOF) responses of less than four twitches;

the second mode of neuromuscular stimulation includes TOF; and

the mathematical correlation comprises a linear correlation of experimental data.

3. The method of claim 2 where the first mode is a TOF of less than four measurable twitches, the second mode is a TOF corresponding measurement;

and the correlation is a fit based on relationships between T1/T0 and unsaturated TOF under similar drug conditions, and T1/T0 when the twitches are absent under similar drug conditions.

4. The method of claim 3 where the TOF of less than four twitches is converted to an equivalent TOF measurement of −

31% if there are no twitches, −

19% if there is one twitch, −

7% if there are two twitches and −

0.07% if there are three twitches.

5. The method of claim 4 where the values assigned by the conversion vary by up to 25% from the values stated in claim 4.

6. The method of claim 1 where the first mode is a TOF of at least three measurable twitches, the second mode is a TOF corresponding measurement and the correlation is a fit based on mathematical relationships established between the third twitch and first twitch in full TOF measurements.

7. The method of claim 6 where the relationship is described by the equation:

TOF=0.97 To3−

3.4% where To3 is the ratio of the size of the third twitch to the first twitch.

8. The method of claim 7 where the constant terms of the equation vary by up to 25% from stated values in claim 7.

9. The method of claim 1 where the first mode is a TOF of at least two measurable twitches, the second mode is a TOF corresponding measurement and the correlation is a fit based on mathematical relationships established between the second twitch and first twitch in full TOF measurements.

10. The method of claim 9 where the relationship is described by the equation:

TOF=1.07 To2−

23% where To2 is the ratio of the size of the second twitch to the first twitch.

11. The method of claim 10 where the constant terms of the equation vary by up to 25%.

12. The method of claim 1 where the first mode is PTC;

the second mode is a less sensitive mode including TOF;

the method further comprising a model of NMB response as a function of a patient mathematical construct and a drug state mathematical construct; and

where converting the measurement of neuromuscular response from the first mode to an equivalent measurement with respect to a second mode of neuromuscular stimulation comprises;

(a) predicting an amount of time until the less sensitive stimulation measurement is measurable;

(b) calculating a future drug state mathematical construct at the time the less sensitive stimulation measurement is measurable;

(c) determining a present drug state mathematical construct by bringing the future drug state mathematical construct backwards in time by the amount of time until the less sensitive stimulation measurement is measurable; and

(d) determining a corresponding less sensitive measurement response at the present time from the product of the patient mathematical construct and the calculated present drug state mathematical construct.

13. The method of claim 1 where the first mode is PTC;

the second mode is a less sensitive mode including TOF;

further comprising a model of NMB response as a function of a patient mathematical construct and a drug state mathematical construct; and

converting the measurement of neuromuscular response from the first mode to an equivalent measurement with respect to a second mode of neuromuscular stimulation comprises;

(a) predicting an amount of time until the less sensitive stimulation measurement is measurable;

(b) calculating a future drug state mathematical construct at the time that the less sensitive stimulation measurement is measurable;

(c) approximating a future corresponding response based on the response model and the future drug state mathematical construct;

(d) estimating a current drug state mathematical construct by scaling the future drug state mathematical construct by the ratio of the estimated future corresponding response and the response that would be had at the time that the less sensitive measurement is measurable;

(e) determining a current corresponding less sensitive measurement as the product of the patient mathematical construct and the estimate of current drug state mathematical construct.

14. A system for decreasing sensor sensitivity to electrical noise including electrical interference produced by electro-surgical instruments, the system comprising at least one layer of conductive material shaped to surround the sensor in situ and conductively connected to an electrical ground.

15. The system of claim 14 where the at least one layer of conductive material is physically and conductively connected to a grounding strap, and the grounding strap is conductively connected to an electrical ground.

16. The system of claim 14 further comprising an adherent configured to temporarily adhere the system to the patient.

17. The system of claim 16 where the temporary adherent is a cuff formed by or inserted into the conductive material.

18. The system of claim 14 where the conductive material includes a flexible paper or plastic with conductive traces on it.

19. A system for monitoring neuromuscular blockade where more than one muscle is stimulated comprising:

(a) two or more neuromuscular response sensors for measuring neuromuscular response of the more than one muscles, such that the sensors comprise means of conveying stimulation and sensing energy;

(b) at least one stimulator configured to provide stimulation to the more than one muscles through the two or more stimulation conveying means; and

(c) at least one quantifying device configured to quantify responses produced by the stimulation and conveyed to the quantifying device by the sensing conveying means.

20. The system of claim 19 further comprising a multitude of models of drug response, with at least one model for each muscle being stimulated.

21. The system of claim 20 further comprising a calculation mechanism to convert response measurements made at one muscle to corresponding measurements at other muscles to estimate muscle strengths at the other muscles using conversion between the two drug models.

22. The system of the claim 19 where at least one of the two or more neuromuscular sensors is operably connected to a system for decreasing sensor sensitivity to electrical noise, said system for decreasing sensor sensitivity to electrical noise comprising at least one layer of conductive material shaped to surround the sensor in situ and conductively connected to an electrical ground.

23. A method of monitoring neuromuscular blockade where more than one muscle is stimulated using two or more neuromuscular response sensors, said sensors comprising means of conveying stimulation and sensing energy;

at least one stimulator configured to provide stimulation to the more than one muscles; and

at least one quantifying device configured to quantify responses generated by the stimulation, comprising;

a) placing two or more neuromuscular response sensors at the more than one muscles to be stimulated, with connection to the at least one stimulator and at least one quantifying device;

b) applying neuromuscular stimulus at the more than one muscles to be stimulated with the at least one stimulator;

c) measuring two or more neuromuscular responses from the more than one muscles; and

d) quantifying the two or more neuromuscular responses with the at least one quantifying device.

24. The method of claim 23 where the two or more neuromuscular response sensors are applied to muscles of different sensitivity to NMB drugs and stimulation and sensing is repeated continuously at one or more of the muscles or switched between one or more of the muscles at intervals in time.

25. The method of claim 23 where the two or more neuromuscular response sensors are applied to muscles of similar sensitivity to NMB drugs and stimulation is alternated between the muscles.

26. The method of claim 23 where the two or more neuromuscular response sensors are applied to muscles of similar sensitivity to NMB drugs and muscle stimulation occurs at rates higher than used in standard clinical practice.

27. The method of claim 23 where the two or more neuromuscular response sensors are applied to different muscles and at least one sensor is applied to a muscle representative of the laryngeal muscles or a muscle representative of the diaphragm.

28. A system for monitoring and modeling neuromuscular blockade comprising:

(a) one or more neuromuscular response sensors comprising a stimulation means and a sensing means,

(b) one or more stimulators configured to provide stimulation at the one or more sensors,

(c) one or more transducers configured to process the output from the one or more sensing means,

(d) a computing mechanism to quantify neuromuscular response through steps including;

(i) applying a first mode of neuromuscular stimulation to a patient;

(ii) measuring a neuromuscular response from the patient;

(iii) converting the measurement of neuromuscular response from the first mode to an equivalent measurement with respect to a second mode of neuromuscular stimulation in an objective fashion using a mathematical correlation established between the first and second modes.

(e) and said computing mechanism further comprising mathematical modeling of the patient'"'"'s response to NMB drug.

29. The system of claim 28 further comprising methods of warning the user on future response levels.

30. The system of claim 28 further comprising methods of advising the user on future drug needs.

31. The system of claim 28 further comprising methods of providing closed loop drug administration.

32. A method of monitoring physiological signals where at least one physiological sensor is positioned in conjunction with a patient and a system for decreasing sensor sensitivity to electrical noise including electrical interference produced by electro-surgical instruments, the system comprising at least one layer of conductive material shaped to surround the sensor in situ and conductively connected to an electrical ground.