JP2001513386A - Passive and non-invasive method for objectively quantifying the level and density of nerve block - Google Patents

Abstract

(57) Summary EMG, temperature and heart rate measurements correlating with skin sensory zone levels and densities of nerve blockade are obtained passively. That is, the patient is not stimulated or exposed to sensors that require active action for measurement. No active patient involvement or response is required. The acquired measurements provide an objective and quantitative indication of epidural blockade, for example, due to local anesthesia, thus allowing an objective and real-time assessment of the level and density of nerve blockage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001] Cross References This application application concerned claims the Provisional Patent Application No. 60/024663 benefit US copending been previously filed filed August 27, 1996.

BACKGROUND OF THE INVENTION This invention relates to monitoring the effectiveness of anesthetics in humans or animals, in particular, objectively provide passive and non-invasive method to quantify the level and density of neuroleptic I do.

[0003] Quantitative and active response assessment has been applied to the measurement of nerve blockage. However, reliability, repeatability, and inter-patient correlation can be subject to large variability. Difficulties exist to increase confusion when a patient is unable or unwilling to respond to a test such as a needle stick, pinch or low temperature stimulus to determine efficacy against disability I do. In addition, an individual's perception of pain and cold cannot be correlated to a reference standard.

[0004] While conducting relatively research on anesthetics, there are limited reports on the effectiveness of using quantitative monitoring as a measure of nerve blockage. The study recognized blockage of abdominal muscles using electromyography (EMG) during lumbar epidural analgesia. One of these studies required active involvement from the subject. Other studies have examined the effects of different local anesthesia on motor blockade and EMG.

[0005] Despite the above studies, anatomical levels or densities of nerve blockages, such as local anesthetic epidural blockage (at specific skin sensory zone levels), by non-invasive, objective and automatic means. The absence of a method to passively and routinely quantify the completeness of the blockade continues.

SUMMARY OF THE INVENTION The present invention uses non-invasive monitors / sensors and associated signal processing without the patient's active involvement or response to objectively quantify the level and density of nerve blockage. By monitoring some physiological responses to nerve blockade, the above problem is solved.

The present invention is a method for passively, non-invasively and objectively quantifying the level and density of a patient's nerve blockade, wherein the physiological response to the nerve block is measured at a site in the patient's body. Deploying a non-invasive sensor to monitor changes in a physiological response to nerve blockage and quantify the level and density of nerve blockage using the sensor without any active involvement or response by the patient And c.

[0008] Physiological responses and methods of monitoring that can be monitored include surface electromyography (EMG),
Includes muscle innervation using skin temperature using temperature sensing means and heart rate using electrocardiography (EKG).

For muscle innervation, the level and density of nerve blockade are each quantified by sensor placement and changes in signal amplitude of surface EMG, with density inversely proportional to signal amplitude. For skin temperature, the level and density of the nerve block are each quantified by the placement of the sensor and the change in skin temperature, and the density of the nerve block is directly proportional to the skin temperature. Finally, for heart rate, the level and density of nerve block is quantified by heart rate, and the density of nerve block is inversely proportional to heart rate.

The method of the invention can be incorporated into an automated system, for example, to control drug delivery to a patient or to inform a clinician about a patient's condition, from start to finish Displaying the level and density of the nerve blockade of the subject. The invention can also be used to monitor nerve block in animals.

The onset of nerve blockage can be monitored objectively by the placement of one or more sensors and by quantifying the decrease in surface EMG signal amplitude, the rise in skin temperature and the change in heart rate. it can. Furthermore, the cutoff densities determined by these objective measures compare quite well with the results of traditional subjective methods. Thus, the present invention provides anesthesiologists with active information regarding the level and density of nerve blockage non-invasively without the need for active patient involvement or response.

The method of the DETAILED DESCRIPTION OF THE INVENTION The present invention, by using non-invasive sensors located at one or more sites of the patient's body, is to monitor the primary parameters and reference parameter follows. Primary parameters muscle innervation—spontaneous surface EMG temperature—ambient—skin-mounted thermocouple Heart rate (HR) and HR variability—lead II electrocardiogram (EKG) reference parameters ambient temperature—air thermocouple Core body temperature-tympanic thermocouple.

A non-invasive sensor array (FIG. 1A) including sensors for EMG, AMG (in the work described below) and ambient temperature is located at each monitor site. EKG
And the reference sensor is applied where appropriate (FIG. 1B). A waterproof cover can be used to protect each monitor site.

Preferably, a plurality of monitoring sites as shown in FIG. 1 are used to identify the head-to-tail spatial effects of nerve blockage. In the clinical trials described below, three specific sites were identified: the level of the thoracic skin sensory zone (papilla, T4) on the anterior axillary line, and
The front of the thigh representing the level of the thoracic skin sensory zone (navel, T10) and the second lumbar skin sensory zone (L2) is identified and used.

For muscle innervation, the level of nerve blockade is quantified by the placement of the sensor array, the density of nerve blockage is quantified by the change in signal amplitude of surface EMG,
Density is inversely proportional to signal amplitude. For skin temperature, the level of nerve blockage is quantified by the placement of the sensor array, the density of nerve blockage is quantified by changes in skin temperature, and the density of nerve blockage is directly proportional to skin temperature. Finally, for heart rate, the level and density of the nerve block is quantified by the change in heart rate, and the density of the nerve block is inversely proportional to the heart rate.

This invention was demonstrated in a study involving seven humans (Table 1), all of whom underwent elective radical postpubic prostatectomy using lumbar epidural blockade.

[0017]

[Table 1] Table 1-Demographics of Subjects Subject Age Weight ASA Epidural Incision Time * (years) (Kg) Status Position (min) 155 85.7 2 L4-5 N / A 2 42 83 2 L4-5 17.0 347 78 2 L2-3 17.7 4 63 104 2 L2-3 12.5 5 55 103 2 L3-4 15.0 665 110 2 L3-4 29.3 760 88 2 L4-5 15.5 * Time from main epidural administration to start of incision Note to subject 1: GA and local complications due to history of apnea; epidural administration after incision Note to Exhibitor 1: Conversion to merger of GA and local.

Spontaneous surface electromyogram (EMG), acoustic electromyogram (AMG), temperature (T) and lead II electrocardiogram (EKG) measurements were taken at the frontal axillary line at the T4, T10 and L2 skin sensory zone levels. I went along. Reference measurements included tympanic temperature, ambient temperature, and ambient sound. As discussed below, time-continuous data was acquired at predetermined intervals before and after epidural administration. A dedicated PC-type system provided control and data storage.

Based on the predicted temporal response to epidural administration, data echoes were obtained immediately before (primary baseline) and 2, 5, 10, 15, 20, 25, 30 after main epidural administration.
, 45, 60, 75 and 90 minutes. The echo was designed to have a minimum duration of 20 seconds. The recording of the temperature data was time continuous and started immediately after the thermocouple was deployed and ended 2 minutes after the last EMG / AMG / EKG sampling epoch.

Table 2 below summarizes the data acquisition conditions for the relevant parameters.

[0021]

Table 2-Data acquisition conditions for monitored parameters Parameter Passband Sampling speed Channel number (Hz) (sec- ¹ ) AMG 0.5-100 1000 4 EKG 2-100 1000 1 EMG 10-500 2000 3 Temperature DC-0.02 0.26 As discussed below, the root mean square (rms), average temperature T and average heart rate (R-R interval) of EMG and AMG are defined as the time to epidural administration. Was evaluated against the level as a function of Changes in objectively monitored variables were compared to a quantitative assessment of the effectiveness of the block (eg, a knob test).

EMG and AMG are broadband signals containing information in the time and frequency domains. What is needed is a single derived value that represents the instantaneous physiological state of the patient. Typically, the power of the signal provides such an indication in the time domain. Power is proportional to the square of the signal amplitude. For signals with non-constant (eg, alternating) components,
To generate a significant value, it is necessary to average the signal for a finite period. EM
The evaluation of G is

[0023]

(Equation 1)

The average rectified EMG (AREMG) or rectified and integrated EMG (RIEMG) was traditionally calculated, assuming that Historically, the calculation method is obviously not power indicating. Thus, the present invention provides a root mean square (rms) estimator,

[0025]

(Equation 2)

(Note: other methods such as, for example, spectral analysis, bi-spectral analysis, etc. are also effective; the slope of the signal also provides useful information). Regardless of the method used, the choice of integration period (ie, the value of n) is an important factor. The value of n is inversely proportional to the upper frequency response characterized by the calculations. The integration period was chosen to retain as much passband information as practical. EMG
Is integrated over 50 ms (n = 100) and the AMG signal is 250 ms (
n = 250).

Many discrete rms calculations are possible within a 20 second sampling epoch. The running rms value is calculated. The rms value at t = 0 includes the first n data points in the series. Subsequent rms values incrementally erase the earliest data point and add the next most recent data point in the series. Calculated r
The minimum value in the ms column is selected to represent the muscle-only condition at any given sampling epoch.

[0028] The time series data from the study subjects is such that the EMG signal and the AMG signal are
It has been proven to contain noise artifacts that correlate with the use of suction and other electrical systems. The slope and intercept of the frequency spectrum of the data was used as an acceptance criterion to confirm that the rms values were completely noise-free.

The absolute value of the EMG signal can be influenced by conditions such as skin conductance, skin temperature, electrode placement and site preparation. The EMG data is normalized to mitigate the discrepancies, but this involves applying gain factors that result in the expansion or compression of the histogram of the raw data set. Based on a common time epoch for all study subjects, the EMG data showed that the basic histogram was ± 5 mV
Normalized to include 50% of all data values in between. Other epochs were scaled by the same gain factor calculated for the base histogram.

It was clear that AMG signal artifacts correlated with movements induced directly by the surgeon or indirectly by the patient's perceptual movements. The AMG data is compensated sample by sample for the presence of acoustically transmitted noise by subtraction of the ambient signal level.

[0031] Changes in skin temperature are adversely affected by changes in body core temperature and ambient air temperature. To meet these conditions, the raw (t _{DL, SI} ) skin sensory zone temperature values are normalized by the tympanic temperature and ambient temperature (T _{DL, SI} ), as in the equation below.

[0032]

(Equation 3)

Here, DL is the level of the skin sensory zone, and SI is the sampling interval. SI
= 0 correlates with the data epoch before the main epidural administration. The normalized temperature data correlates with the EMG / AMG / EKG sampling epoch.
Decomposed into second segments. The average of each normalized epoch was calculated as a simple arithmetic mean of the data.

The average heart rate for each study subject was determined from the Lead-IIEKG data set. The average during the 20 second data interval was calculated as the simple arithmetic average of the interval between Rs involved. The occurrence of the rising edge of the R peak was determined by an automatic algorithm.

The data revealed three notable properties of the EMG signal. First, EMG
The signal amplitude decreased at a rate that was inversely related to the number of skin sensory zone levels separating the monitoring site and the epidural catheter. That is, the signal at the more perceived skin sensory zone level decreased later than the more caudal level. Second, for some time (15
After ３０30 minutes), the total EMG signal amplitude was generally constant and at a lower level than at the start of the primary dose. Third, the constant level at the L2 skin sensory zone level is T
It was almost 30% lower than that of the 4 and T10 skin sensory zone levels. This probably indicates that an effective block was generated at this discrete level simply by test administration.

All of the average temperature trends for the tympanic and surrounding compensated data showed a gradual increase as a function of time. A longer onset was noted at the more rostral skin sensory zone level. Heart rate averaged 7.8 ± 9.2b until 10 minutes after the start of primary administration
pm, then decreased by an average of 19.0 ± 10.8 bpm over the next 15 minutes.

In summary, changes in EMG, skin surface temperature, and heart rate were associated with adequate blockade and correlated with clinical assessment of the level and density of blockage. During the start of the shutdown,
The root-mean-square EMG signal level decreased more than 15 mV, the temperature rose above 1 ° C., and the EKG decreased more than 7 times per minute (bpm). AMG showed a first order correlation to external influences. The response to blockade was not apparent in the presence of noise.

FIG. 2 shows the curve of the root mean square EMG signal amplitude for all seven subjects. The data are fifth order polynomial curves that match the normalized signal amplitudes for the seven study subjects at each of the three monitor levels. The plot also showed that the pinch test applied by the attending anesthesiologist achieves typical skin sensory zone levels of blockade. Time is based on application of primary epidural administration (t
= 0), the baseline data set is plotted at t = -1 min. The curve has been normalized to the baseline by subtracting each baseline value from each subsequent data point. The time between the main dose and the clinical incision was 17 ± 6 minutes. L2
The lower amplitude limit of the signal and the T10 signal is earlier (t = 15) than the T4 signal (t = 30 minutes).
Minutes) have been reached. This suggests that L2 and T10 levels achieve the onset before T4 levels, as expected.

FIG. 3 shows the average temperature data for skin sensory zone levels for all seven subjects. All levels show the same upward trend as a function of time. All levels approach a relative increase of approximately 3.5 ° C. over the data collection period of 90 minutes. Changes in temperature represent the effect of sympathectomy when applying local anesthesia. These changes also suggest a difference in the contribution of blood volume changes and vascular relaxation at each skin sensory zone level.

The heart rate of all seven subjects is shown in FIG. These data are expressed as T1-
Consistent with previously reported effects of local anesthesia on cardiac facilitating nerve fibers in the T4 signal segment.

As a function of time, and as related to the application of local anesthesia, passive and non-invasive monitors to objectively identify the level and density of nerve blockade were considered. Data from EMG, temperature, and EKG monitors are combined with clinical evaluations and surgical procedures provided by anesthesiologists to confirm that objective measurements of block levels and densities can be performed in a clinical setting I do.

A general purpose neuroleptic monitor must be fully functional regardless of the time of use for anesthetic application. The absolute rate of change or slope of the signal gives significant information. The most remarkable indicators are the zero minute and the one as shown in FIG.
The change of the EMG signal level between 0 minute. Level L2 is approximately 1.5 of T10
Approximately 2.5 times of T4.

The use of monitored parameters in combination, rather than individually, enhances the utility of general purpose monitors. The weighted addition of EMG and temperature satisfies the basic requirements of a level-specific determination of the cut-off density.

The method of the present invention can be integrated into an automated system for controlling drug delivery to a patient or simply informing a physician or nurse about a patient's condition, for example, during a post-operative recovery period. The present invention is also applicable to animal patients.

The onset of nerve blockage can be monitored objectively by the placement of one or more sensors and by quantifying changes in surface EMG, skin temperature rise and heart rate. Furthermore, the cut-off densities determined by these objective measures appear to be comparable to the traditional and subjective method of knob testing. The present invention provides an anesthesiologist with a passive and objective tool for real-time and non-invasive monitoring of the level and density of nerve blockage.

[Brief description of the drawings]

FIG. 1 is an example of a sensor array consisting of A and B for data collection for use in the method of the present invention, and a human body for placement of such sensor arrays and other data collection devices. Representative sites are shown.

FIG. 2 shows a set of curves of the mean square EMG signal amplitude taken from seven patients who agreed to be subjects in a study of the method of the invention.

FIG. 3 shows mean temperature data at the skin sensory zone level for all seven subjects.

FIG. 4 shows the average heart rate of all seven study subjects.

[Procedure amendment]

[Submission date] November 27, 2000 (2000.11.27)

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] All figures

[Correction method] Change

[Correction contents]

FIG.

FIG. 2

FIG. 3

FIG. 4

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Greenberg, Robert E. Kenned Drive, Glenelg, Maryland 21737, USA 13810 F-term (reference) 4C017 AA02 AA16 AA19 AC11 AC15 AC30 BC07 BC11 BC14 BD06 FF05 4C027 AA00 AA02 AA04 FF00 FF01 FF02 FF03 FF05 GG05 GG11 GG13 GG16 GG18

Claims (20)

[Claims] 1. A method for passively, non-invasively and objectively quantifying the level and density of a patient's nerve blockage, comprising: measuring a physiological response to the nerve blockage at a site in the patient's body. Deploying a non-invasive sensor, and using the sensor to monitor changes in a physiological response to the nerve block to quantify the level and density of the nerve block without any active involvement or response by the patient And a method comprising: 2. The method of claim 1, wherein said physiological response comprises muscle innervation. 3. The method of claim 2, wherein said monitoring comprises monitoring muscle innervation using surface electromyography (EMG). 4. The level and density of nerve blockage and the placement of the sensor and the surface EMG
4. The method of claim 3, wherein each of the first and second changes is quantified by a change in the signal amplitude. 5. The method of claim 4, wherein the level and density of the nerve block is inversely proportional to the signal amplitude of the surface EMG. 6. The level and density of nerve blockage and the mean square (
5. The method according to claim 4, wherein each of the quantifications is quantified by: 7. The method of claim 6, wherein the level and density of nerve blockade is inversely proportional to the rmsEMG signal power. 8. The method of claim 5, wherein said physiological response further comprises skin temperature. 9. The method of claim 8, wherein said step of monitoring further comprises monitoring skin temperature using temperature sensing means. 10. The method of claim 9, wherein the level and density of nerve blockage are quantified by the placement of the sensor and changes in skin temperature, respectively. 11. The method of claim 10, wherein the level and density of nerve blockade is directly proportional to skin temperature. 12. The method of claim 11, wherein said skin temperature is normalized by tympanic temperature and ambient temperature. 13. The method of claim 5, wherein the step of monitoring further comprises monitoring heart rate using electrocardiography (EKG). 14. The method of claim 13, wherein the level and density of the nerve block is quantified by a change in heart rate. 15. The method of claim 14, wherein the level and density of the nerve block is inversely proportional to the heart rate. 16. The heart rate is averaged over the RR interval.
The described method. 17. The method of claim 15, further comprising automatically controlling the delivery of an anesthetic to the patient using the quantified level and density of nerve blockage. 18. The method of claim 15, further comprising displaying the level and density of the nerve block. 19. The method of claim 18, further comprising providing an automatic notification of the level and density of the nerve block. 20. The method of claim 15, wherein the nerve block is a local anesthetic epidural block.