System for estimating patient recovery time using neuromuscular transmission measurements

Abstract

The present invention provides a method and system for monitoring neuromuscular blockade of a patient during a surgical procedure. The system and method utilize a stimulator (115) to provide stimulation (904), such as a train of four (TOF), to the patient's nerves. After such stimulation, the system and method monitor the muscle twitch response (906), and based on the monitored muscle twitch, the system and method create (912) a neuromuscular blockade trend curve (706, 804). The neuromuscular blockade trend curve (706, 804) provides an estimated recovery time (808) for the patient, and provides the estimated recovery time (916) to a clinician. If necessary, the estimated recovery time allows the clinician to modify the patient's treatment to accelerate recovery.

Description

Technical Field

[0001] The present disclosure relates to medical devices, and more particularly to medical devices and methods of operating medical devices for monitoring neuromuscular transmission during surgical procedures. Background Art

[0002] Neuromuscular transmission (NMT) is the transmission of impulses between nerves and muscles at the neuromuscular junction. NMT may be blocked during surgery on a patient, for example, by neuromuscular blockers / drugs, which may cause transient muscle paralysis and prevent the patient from spontaneously moving and breathing.

[0003] Muscle relaxation is used during general anesthesia to enable endotracheal intubation and provide optimal working conditions for the surgeon. At the end of a surgical procedure, the level of NMT is used to determine when the patient can be extubated. Thus, the level of neuromuscular blockade can be monitored to ensure that the appropriate block is provided for a given procedure and to determine when the patient can be safely extubated. Summary of the invention

[0004] In one embodiment, a method for estimating a recovery time for a patient to recover from neuromuscular blockade includes applying a first TOF stimulus to a nerve of the patient at a first measurement time. Measuring a first muscle twitch, a second muscle twitch, a third muscle twitch, and a fourth muscle twitch in response to the first TOF stimulus. Applying a second TOF stimulus to the nerve of the patient at a second measurement time, and measuring the muscle twitch in response to the second TOF stimulus. Based on the muscle twitches in response to the first TOF stimulus and the second TOF stimulus, the method calculates an estimated recovery time, and provides the estimated recovery time to a clinician.

[0005] In one embodiment, the estimated recovery time is calculated by creating a predictive neuromuscular blockade trend curve. The predictive neuromuscular blockade trend curve is extrapolated from the measured TOF ratio to estimate the recovery time when the TOF ratio will exceed a predetermined level. The predictive neuromuscular blockade trend curve can be calculated using different algorithms involving measured parameters from the patient or based on historical patient trends. In either case, the predictive neuromuscular blockade trend curve presents an estimated recovery time at which the cannula can be removed from the patient and the patient can breathe spontaneously.

[0006] In another embodiment, a medical device for multi-parameter monitoring of a patient includes a stimulator for applying four trains of stimulation to the patient's nerves. An electromyogram (EMG) sensor or other type of sensor detects a first muscle twitch, a second muscle twitch, a third muscle twitch, and a fourth muscle twitch in response to the TOF stimulation. A controller is operable to create a predicted neuromuscular blockade trend curve based on the detected muscle twitch and other parameters, such as historical patient trends. The medical device includes a display that visually displays the predicted neuromuscular blockade trend curve and the measured TOF ratio and the predicted TOF ratio. The controller monitors the measured TOF ratio relative to the predicted TOF ratio and adjusts the predicted neuromuscular blockade trend curve as needed.

[0007] It should be understood that the above brief description is provided to introduce in a simplified form selected concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is solely defined by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The present invention will be better understood by reading the following description of non-limiting embodiments with reference to the accompanying drawings, in which:

[0009] Figure 1 An exemplary neuromuscular transmission monitoring system is shown;

[0010] Figure 2 is a graph showing muscle twitch response to a train-of-four (TOF) stimulus over time;

[0011] Figure 3 is a graph showing a muscle twitch response twitch with T4 moving above T2;

[0012] Figure 4 is a graph showing a muscle twitch response twitch with T4 moving above T1;

[0013] Figure 5 is a graph showing TO2 ratio and TOF ratio over time;

[0014] Figure 6 is similar to Figure 5 A graph where the TOF trend moves above the TO2 trend;

[0015] 7A to 7H is a series of graphs showing the display of measured TOF ratios relative to predicted neuromuscular blockade trend curves over time;

[0016] Figure 8 is a display showing estimated recovery time and predicted neuromuscular blockade trend curve; and

[0017] Fig. 9 is a flow chart illustrating one method of operating the systems and methods of the present disclosure. DETAILED DESCRIPTION

[0018] The following description relates to various embodiments of a neuromuscular transmission (NMT) monitoring system, which is configured to monitor the amount of neuromuscular blockade after a muscle relaxant is applied to a patient during a surgical operation. Neuromuscular transmission (NMT) is the transmission of impulses between nerves and muscles in a neuromuscular junction. NMT can be blocked by neuromuscular blockers / drugs, which may cause transient muscle paralysis and prevent the patient from spontaneously moving and breathing. In addition, muscle relaxation can be used during general anesthesia to achieve endotracheal intubation and provide optimal working conditions for surgeons. At the end of a surgical operation, neuromuscular blockade is reversed so that neuromuscular activity can be restored to normal, and the patient can breathe without assistance before removing the endotracheal tube (i.e., extubation). Therefore, appropriate assessment of the degree of NMT blockade can be used to ensure the appropriate timing of intubation and guide the intraoperative administration of neuromuscular blockers, maintain the desired degree of intraoperative neuromuscular blockade, and ultimately prevent the occurrence of residual muscle paralysis.

[0019] The NMT monitor can be used to monitor the response of muscles to electrical stimulation of motor nerves (e.g., ulnar nerves). For example, electrical stimulation can be provided at the ulnar nerve near the wrist, and the response of the muscles near the thumb (adductor pollicis) can be monitored. In a clinical setting, a neurostimulator is attached to the patient's motor nerves, and an electrical stimulation current is applied to the patient before inducing anesthesia. The NMT monitor records reference values ​​for muscle responses, and once a muscle relaxant is applied, it is used to normalize the muscle response. Then, the induced muscle response can be monitored by measuring the electrical response of the muscle (electromyogram (EMG)). In EMG, multiple electrodes can be used to record the compound muscle potential stimulated by the stimulation generator.

[0020] According to embodiments disclosed herein, neuromuscular transmission monitoring may be performed by measuring electrical potentials at the muscle via an electromyography (EMG) sensor in response to electrical stimulation of a motor nerve.

[0021] Figure 1 An example of a neuromuscular transmission monitoring system is provided in . An NMT monitoring system may include a nerve stimulator and one or more electrical sensors (referred to as EMG sensors) that detect the electrical activity of the muscle in response to nerve stimulation. Figure 1The NMT monitoring system also includes a computing system including instructions for executing one or more control routines for determining a muscle response baseline and monitoring a patient's neuromuscular blockade during surgery and during post-surgery recovery.

[0022] Figure 1 An exemplary neuromuscular transmission (NMT) monitoring system 100 is shown, which is configured to monitor neuromuscular activity via EMG technology. The NMT monitoring system 100 includes a neuromuscular transmission monitor 110, which is communicatively coupled to a host patient monitor 140 via a communication link 141. The neuromuscular transmission monitor 110 includes a plurality of neurostimulators 115a and 115b for providing stimulation outputs (e.g., electrical stimulation) of different types and frequencies to the patient, and at least one input connected to one or more transducers for monitoring muscle responses induced in response to the electrical stimulation provided by the neurostimulators. The transducer includes an EMG sensor 160, which is composed of a plurality of electrical sensors for measuring the action potential of muscle contraction in response to nerve stimulation. The signal detected by the transducer can then be converted into an electrical signal by an A / D converter 122 of the neuromuscular transmission monitor 110.

[0023] In the depicted example, the neurostimulators 115a and 115b are connected to stimulation electrodes 120a and 120b, respectively, which can apply electrical stimulation to the ulnar nerve of the patient at predetermined time intervals. The amount of electrical stimulation provided to the neurostimulator is controlled by a current stimulation generator that receives a command signal from a microcontroller 123. The microcontroller 123 is connected to a user interface of a control unit 129, which includes a display unit 190 and a button / knob 180. The type and frequency of the stimulation output can be manually adjusted by the user (manual mode) or automatically selected by the system (automatic mode). In one example, the type and frequency of the stimulation output can be adjusted by the user by pressing a button or knob 180 on the patient host monitor 140. In one example, the neurostimulators 115a and 115b can be two wires of positive and negative charge that can be attached to the stimulation electrodes 120a and 120b on the skin of the patient's forearm by an alligator clip.

[0024] A power supply (not shown) may provide power to an isolated power supply 126, which in turn provides power to a current source stimulation generator 125. A microcontroller 123 may be connected to the current source stimulation generator 125 to regulate the amount of current provided to the neurostimulators 115a-115b. The current stimulation generator 125 may generate different types of neurostimulation, including train of four (TOF), single twitch (ST), double short tonic (DBS), post-tetanic count (PTC), current range (e.g., 1-70 mA with a step size of 1 mA), pulse width / frequency (e.g., 100, 200, 300 μs or 1 Hz, 2 Hz, etc.). In addition, the type of neurostimulation may be selected via a manual or automatic stimulation mode. For example, if a manual stimulation mode is selected, the user may input the desired neuromuscular stimulation type, current range, and pulse width and / or frequency by pressing a button 180 of the host patient monitor 140. Alternatively, if a touch screen is used as a display unit (eg, display unit 190 of host patient monitor 140), user input may be provided via touch input to the touch screen on the display unit.

[0025] If the automatic neural stimulation mode is selected, the microcontroller 123 of the neuromuscular transmission monitor 110 may select a first neural stimulation type as its default setting, such as TOF stimulation, and based on the muscle response signals received from the EMG sensor, the microcontroller reports the muscle response signals to the user by displaying graphs and numbers (e.g., via the display unit 190 of the host patient monitor 140). The display unit 190 may display the muscle response data / information to the user, and may also include an alarm signal / message for alerting a user of a potential sensor error.

[0026] In addition, the neuromuscular transmission monitor 110 can be connected to a host patient monitor 140 via a communication link 141. The host patient monitor 140 may include a memory 127, a CPU 128, and a control unit 129. The memory 127 may have similar functions as the memory 121. The control unit 129 may include control buttons / knobs 180 and a display unit 190. The control buttons and knobs of the control unit 129 may be configured to allow user input. The display unit 190 may be configured to receive touch input from the user.

[0027] The preferred neuromuscular stimulation output of the present disclosure is a train of four (TOF). In one example, TOF can typically use four short (between 100 μs and 300 μs) current pulses (usually less than 70 mA) at 2 Hz as electrical stimulation, repeated every 10 to 20 seconds. The resulting twitch (i.e., muscle response) can be measured and quantified for electromyographic response via an EMG sensor. Comparing the first twitch (called T1 twitch) and the last twitch (called T4 twitch), and the ratio of the last twitch to the first twitch (called the TOF ratio) can provide an estimate of the level of neuromuscular blockade experienced by the patient (e.g., relaxation depth). The TOF ratio can be in the range of, for example, 0% to 100%. The electrical TOF stimulation series can be spaced ten or more seconds apart (usually 20s is used to provide a safety margin) to provide a rest time for fully restoring steady-state conditions, because faster stimulation results in a smaller induced response. TOF stimulation is the most commonly used technique for monitoring neuromuscular blockade in patients with mild blockade and patients recovering from neuromuscular blockade.

[0028] In addition to the TOF ratio, another ratio that can be calculated during TOF stimulation is called TO2. TO2 is the ratio of the second twitch (T2) to the first twitch (T1) in a train of four stimulation pulses.

[0029] The EMG sensor 160 may include a plurality of electrical sensing connections 116, 117, and 118 connected to sensing electrodes 120c, 120d, and 120e, respectively. Most commonly, three sensing electrodes are positioned to give the most consistent EMG signal. In the depicted example, sensing electrode 120e is placed above a muscle tendon or finger, sensing electrode 120d is placed above the middle portion of the muscle near the neuromuscular junction, and sensing electrode 120c may be variable. In one example, electrodes 120d and 120e may be recording electrodes, and electrode 120c may be a ground electrode. The ground electrode provides a common reference for the EMG recording electrode. For example, recording electrode 120d may be placed above the adductor pollicis in the thenar eminence, and recording electrode 120e may be placed above the distal interphalangeal joint of the thumb, and ground electrode 120c may be placed at the centerline above the flexor retinaculum at the palm side of the wrist. The EMG sensor 160 measures the magnitude of electrical activity sensed by the electrodes 120c-120e in response to nerve stimulation and, when received at the neuromuscular transmission monitor, is recorded as an EMG muscle response signal.

[0030] The stimulation electrodes 120a-120b and the sensing electrodes 120c-120e may have a mechanism for improving electrical contact with the skin (such as ultrasound gel) and a mechanism for improving fixation with the skin (such as a biocompatible adhesive placed under the electrode). In addition, the electrodes can be suitable electrodes, such as silver / silver chloride electrodes. In addition, the electrodes can be disposable electrodes that can be discarded after a single use. In another example, the stimulator (e.g., stimulators 115a and 115b) and the sensing connectors (e.g., electrical sensing connectors 116-118 and mechanical sensing connector 114) together with their corresponding electrodes can be incorporated into a disposable sensing unit. In one example, the disposable sensing unit can be included as part of a universal stretchable glove that can be discarded after a single use.

[0031] In addition, information about the EMG muscle response signal received from the EMG sensor 160 can be sent to the neuromuscular transmission monitor 110 via the main connector 113 and the cable 112. In one example, the muscle response signal from the EMG sensor 160 sensor is fed into a signal scaling and filtering circuit (not shown). After scaling the signal and filtering noise, the signal can be converted from an analog signal to a digital signal in an analog-to-digital (A / D) converter 122 and sent to a microcontroller 123 for processing. In addition, the muscle response signal can also be amplified via an amplifier (not shown) before being transmitted to the A / D converter 122. The microcontroller 123 or processing unit is connected to the memory 121, and once the signal is processed, the signal data can be displayed on the display unit 190 of the host patient monitor. In one example, the processed signal can be transmitted to the host patient monitor 140 and displayed on the display unit 190 in real time. In addition, the processed signal can be updated and stored in the memory 121. The memory 121 may be a conventional microcomputer including: a central processing unit (CPU), a read-only memory (ROM), a random access memory (RAM), and a conventional data bus. In addition, the memory may include an automatic calibration module to determine the optimal supramaximal current to be provided to the patient based on the muscle response value received by the EMG sensor, and based on the raw signal received from the sensor, the module may determine a value that can be used as a reference value for monitoring neuromuscular blockade of the patient. In addition, the automatic calibration module may be executed only when the patient is not in a paralyzed state. In other words, when the patient is in a non-relaxed state (e.g., before administering a muscle relaxant), the automatic calibration module may utilize a reference value based on the signal received from the sensor.

[0032] The control unit 129 may also include a user interface (not shown) that may be used to control the operation of the NMT monitoring system 100, including controlling the input of patient data, changing monitoring parameters (e.g., stimulation type, current range, frequency / pulse width, etc.), etc. The user interface may also include a graphical user interface configured for display on a display device such as the display unit 190. The graphical user interface may include information to be output to the user (such as muscle response signals, patient data, etc.), and may also include menus or other elements through which the user may input input to the control unit 129.

[0033] As discussed above, during neuromuscular stimulation of the patient to determine the depth of relaxation, a train of four (TOF) stimulation is applied to the patient, and a muscle response signal is received from the EMG sensor for each of the four pulses of stimulation. The TOF stimulation is applied to the patient at regular intervals (such as every 10-20 seconds), and the EMG sensor 160 measures and quantifies the resulting twitch (i.e., muscle response) for the electromyographic response.

[0034] Figure 2 The EMG response to each of the four pulses of TOF stimulation within the measurement period shown on the horizontal axis of the graph is shown. In graph 200, the first twitch, referred to as the T1 twitch, is graphically shown by trace 202. The second twitch, referred to as the T2 twitch, is shown by trace 204, and the third twitch, T3, is shown by trace 206. The last and final twitch, referred to as the T4 twitch, is shown by trace 208. Figure 2 As can be seen from the combined curve graph 200, the T1 trace 202 begins to be detected at the earliest time point when the T1 twitch is in response to the first stimulus of the TOF stimulation sequence. The T2 twitch, T3 twitch, and T4 twitch begin to be detected at a time slightly delayed from the detection of the T1 twitch, as is well known for patients recovering from neuromuscular blocking agents.

[0035] In well-known recovery monitoring methods, extubation of the patient should only occur when the patient's recovery reaches a recovery threshold, at which neuromuscular blockade has been sufficiently reduced to ensure appropriate spontaneous breathing of the patient. In the present disclosure and many monitoring systems, the recovery threshold is based on the ratio of T4 twitch to T1 twitch (T4 / T1), which is generally referred to as the TOF ratio or TOF%. As previously mentioned, the TOF ratio can range between 0% and 100%. Generally, it is considered safe to extubate the patient when the TOF ratio reaches 90%. Therefore, the relationship between T1 twitch and T4 twitch is very important in determining when a patient can be safely extubated. As relative to Figure 2 As can be appreciated, when the T4 trace 208 begins to closely correspond to the T1 trace 202 , a 90% TOF ratio occurs.

[0036] During currently available relaxation depth monitoring utilizing TOF stimulation, the clinician must continue to monitor the patient and wait for the TOF ratio to reach 90% or higher before removing the cannula. Although this type of monitoring has been shown to be effective, it requires the clinician to continuously monitor the patient and wait for the TOF ratio to reach the desired value. This requires the clinician to wait sometimes for a considerable amount of time (20 minutes or more) while monitoring the TOF ratio. There is no effective way to estimate the time of recovery when the TOF ratio will reach and / or exceed the threshold.

[0037] See now Figure 3 , graph 210 illustrates the similarity in shape between T2 trace 204 and T4 trace 208 by superimposing T4 trace 208 onto T2 trace 204. Thus, the inventors have recognized that the shape of each of traces 202, 204, 206, and 208 are similar in shape and are only delayed along time axis 220. Since the T1 trace occurs more quickly than the T4 trace when monitoring a patient, the inventors have recognized that the shapes of the T1 trace and the T2 trace can be used to predict the shape of the T4 trace and can be used as an estimate to determine when the TOF ratio will reach the 90% threshold. Figure 4 Further evidence is provided that the T4 trace 208 closely matches the T1 trace 202 , which is confirmed by superimposing the T4 trace 208 onto the T1 trace 202 .

[0038] See now Figure 5 , graph 500 shows two separate ratios calculated from a representative patient. The first ratio, referred to as the T2 ratio, represents the ratio of the T2 trace to the T1 trace (T2 / T1) and is shown by trend 502. Figure 5 The second trend 504 shown is the TOF ratio, which is the T4 twitch relative to the T1 twitch (T4 / T1). Figure 5 In the graph 500 of FIG. 5A , the vertical axis 506 is the ratio and the horizontal axis 508 is the time axis. As previously discussed, extubation of a patient typically occurs when the TOF ratio represented by the trend 504 exceeds a threshold 510, which is Figure 5 In the embodiment shown, the TOF ratio exceeds the threshold 510 at approximately 10:19. Figure 6 4 is a diagram illustrating the shape correspondence between the TOF ratio trend 504 and the TO2 ratio trend 502 . Figure 6 The graphical representation shown illustrates that the TO2 trend can be used as an early representative estimate of the TOF trend, which will allow prediction of when the TOF trend 504 will exceed the threshold 510 .

[0039] According to this disclosure, Figure 1The illustrated microcontroller 123 is configured to provide an estimated recovery time for the patient, which indicates when the TOF ratio will exceed a decannulation threshold, typically 90%, in the future. The estimated recovery time calculated by the microcontroller 123 can be displayed to the clinician via a display so that the clinician can make a treatment decision, such as allowing the patient to recover as is or the clinician can decide whether an antidote is needed to speed up the recovery process.

[0040] 7A to 7H 1 is a graph showing several graphical displays based on clinical data taken over time. Each graphical display shows an estimated recovery time calculated using the system and method of the present disclosure. Fig. 7A , a series of measured TOF ratios 702 are plotted along a time axis 704. Fig. 7A As can be seen in FIG. 7 , as the relaxation depth decreases, a series of individually measured TOF ratios 702 begin to rise. According to the present disclosure, following the measured TOF ratios, a predicted neuromuscular blockade trend curve 706 is calculated and displayed along the time axis. Fig. 7A In the embodiment shown, the estimated TOF will be over 90% at 10:21:16. This prediction was generated by the system at 10:00:00. Therefore, if the measurement of changes in the TOF ratio is simply monitored, the clinician will have an estimated extubation time of approximately twenty-one minutes before the clinician otherwise knows this information.

[0041] 7B to 7H A further measurement 702 of the TOF ratio for a later time period is shown as plotted on the predicted neuromuscular blockade trend curve 706. As time passes, it can be seen in the graph of FIG. 7 that the measured TOF ratio 702 closely matches the predicted neuromuscular blockade trend curve 706 until Figure 7H , where the last measured TOF ratio 708 exceeds the 90% recovery ratio threshold. In the illustrated embodiment, when the TOF ratio exceeds 90%, the estimated recovery time of 10:21:16 predicted at 10:00:00 closely matches the actual time of 10:20:08. Thus, in the clinical data plotted and illustrated in FIG7 , the method of the present disclosure is able to predict the estimated recovery time with high accuracy and provide the estimated recovery time to the clinician more than twenty minutes in advance before the TOF ratio reaches the 90% extubation threshold.

[0042] Figure 8Shown is a display 800 that can be presented to a clinician using the method and system of the present disclosure.Display 800 includes similar information as described above with reference to FIG. 7. Specifically, the measured TOF ratio 802 obtained from the patient is displayed to the clinician relative to the vertical axis and horizontal time axis that the TOF ratio is expressed as a percentage.In addition to the measured TOF ratio, display 800 also includes a predicted neuromuscular blockade trend curve 804 that is separated from the measured TOF trend by visually using different backgrounds and trend visualizations.The predicted neuromuscular blockade trend curve 804 is used to create an estimated recovery time shown to the clinician relative to the current time 806.In addition, display 800 includes a predicted recovery time 808, which provides the clinician with the time amount needed to carry out until extubation can occur.In this way, the actual time 806 and the time amount that needs to pass before extubation can occur are presented to the clinician.This information allows the clinician to make a decision about whether to give an antidote, the type of antidote, or whether to allow the patient to recover normally.

[0043] Figure 8 The display in also includes a digital graphical representation 810 of the current TOF ratio and a T1 percentage 812. The T1 percentage 812 is the ratio of the T1 muscle twitch relative to a reference value. The T1 percentage also provides an indication of how close the patient is to recovering to allow extubation.

[0044] As discussed above, the methods and systems of the present disclosure create Figure 8 A predicted neuromuscular blockade trend curve 804 is shown which allows prediction of the time when the TOF ratio will exceed a threshold percentage and allow the patient to be safely extubated. The calculation of the predicted neuromuscular blockade trend curve can be accomplished using a variety of different algorithms that utilize not only measurements taken from the patient during TOF stimulation, but also based on data obtained from historical patient groups. Based on data analysis and studies of recovery times, common trends and recovery graph shapes have been identified for patients in the patient group that are similar to the monitored patient. The shape of the TOF trend curve determined on a large patient group can be used to generate a predicted neuromuscular blockade trend curve for the monitored patient, and thereby implemented using measurements from actual patients.

[0045] In one contemplated example, before the T4 response and TOF ratio are available, two serial (TO2) ratios may be calculated for the patient. These TO2 ratios may then be used to calculate the slope of the TO2 trend. As the patient continues to recover, the slope calculated from the TO2 ratios may be applied to the TOF ratios measured from the patient and a predicted neuromuscular blockade trend curve may be generated. Based on the predicted neuromuscular blockade trend curve, an estimated recovery time is determined and reported in a manner similar to Figure 8The estimated time to recovery is shown to the clinician in the display of the display 800. While this is one type of estimation method for predicting the estimated time to recovery, a variety of different methods and algorithms are contemplated to be within the scope of the present disclosure.

[0046] Fig. 9 A method of operating a patient monitoring system according to the present disclosure is shown. Fig. 9 As shown, the method begins by injecting a neuromuscular blocking agent (NMBA) into a patient in step 902. After the NMBA has been injected and begins to take effect, it is necessary to continuously monitor the patient during the surgical procedure.

[0047] At the end of the surgical procedure, when the NMBA has decreased and been neutralized, the method begins applying TOF stimulation to the patient in step 904. As previously described, TOF stimulation is a type of common monitoring method used to determine the depth of relaxation and determine when the patient can be safely extubated. In step 906, the method utilizes Figure 1 The EMG sensor 160 shown measures the patient's response to the TOF stimulus. The application of the TOF stimulus in step 904 and the measurement of the response in step 906 are common processes and generate Figure 2 After measuring the response in step 906, the microcontroller of the neuromuscular transmission monitor 110 calculates standard values, such as the TOF ratio, the TO2 ratio, and any other ratio that may be required to monitor the depth of relaxation.

[0048] Before generating a recovery time estimate according to the method of the present disclosure, the system determines in step 910 whether the TOF ratio exceeds a predefined level. The predefined level is used to determine when the patient initially begins to recover from the NMBA injected in step 902. The predetermined level is a value that indicates that the patient has begun to recover and the following estimate calculation can be started. If the patient has not begun to recover, the system returns to step 904 and applies the next TOF stimulation. This process continues until the TOF ratio exceeds the predefined level in step 910, and then the method proceeds to step 912.

[0049] In step 912, the method calculates a predicted neuromuscular trend curve based on the calculations performed in step 908 and possibly based on historical patient trend data. As discussed in previous sections of this application, a variety of different types of algorithms and data analysis techniques may be utilized to calculate the predicted neuromuscular blockade trend curve calculated in step 912. One possible algorithm and technique utilizes the TO2 ratio calculated at a plurality of different time points during which TOF stimulation is applied to the patient. The TO2 ratio may be used to generate a slope, and this slope may be used to infer a predicted neuromuscular blockade trend curve for the TOF ratio. FIG7 and FIG7 of the present disclosure Figure 8 Such a curve is shown in .

[0050] Once the predicted NMB trend curve is calculated in step 912, the method proceeds to step 914 where the measured TOF ratio and NMB trend curve are displayed, as shown in FIG. Figure 8 as shown in . Figure 8 The display shown may also include an estimated recovery time calculated and displayed in step 916. In this way, the systems and methods of the present disclosure provide the clinician with not only the actual measured TOF rate, but also a predicted neuromuscular blockade trend curve in step 914 and an estimated recovery time in step 916. Based on all of this information, the clinician can then make treatment decisions, such as administering an antidote, what type of antidote to administer, or whether to allow the patient to recover under normal circumstances.

[0051] In step 918, the method and system may compare the most recently measured TOF ratio to the estimated TOF ratio based on the predicted neuromuscular blockade trend curve. If the actual measured TOF ratio corresponds closely enough to the estimated TOF ratio during that time, the system proceeds to step 920 where the next TOF stimulation is applied to the patient. This process continues as long as the patient remains intubated. Once the patient is extubated, the process may be terminated. Fig. 9 The method and system shown.

[0052] If the system determines in step 918 that the measured TOF ratio does not correspond closely enough to the estimated TOF ratio during the time, the system returns to step 912 where a new predicted NMB trend curve is calculated. In this way, the system and method adjust the predicted neuromuscular blockade trend curve based on the measurements from the patient. In this way, the systems and methods of the present disclosure are able to most accurately estimate the recovery time and present the most accurate estimate information to the clinician.

[0053] As used herein, the elements or steps listed in the singular and beginning with the word "one" or "a kind of" should be understood as not excluding a plurality of the elements or steps, unless such exclusion is explicitly stated. In addition, the reference to "an embodiment" of the present invention is not intended to be interpreted as excluding the existence of additional embodiments that also include the cited features. In addition, unless explicitly stated to the contrary, the embodiment of "including", "comprising" or "having" an element or multiple elements with a specific characteristic may include additional such elements without the characteristic. The terms "including" and "in..." are used as the concise language equivalents of the corresponding terms "including" and "wherein". In addition, the terms "first", "second" and "third" etc. are only used as marks, and are not intended to impose numerical requirements or specific positional order on their objects.

[0054] This written description uses examples to disclose the invention, including the best mode, and also to enable a person of ordinary skill in the relevant art to practice the invention, including making and using any devices or systems and performing any included methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to a person of ordinary skill in the art. Such other examples are intended to fall within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insignificant differences from the literal language of the claims.

Claims

1. A system for estimating recovery time for a patient recovering from neuromuscular blockade, comprising: A stimulator, the stimulator being configured to: applying a first series of stimuli to a nerve of the patient at a first measurement time; applying a second series of stimuli to the nerve of the patient at a second measurement time; An electromyography sensor, the electromyography sensor being configured to: measuring a muscle twitch in response to each of the first series of stimuli; measuring a muscle twitch in response to each of the second series of stimuli; A controller, the controller being configured to: predicting changes in later responses to the series of stimuli based on changes in earlier responses to the series of stimuli; estimating a recovery time based on the predicted change in the later response; and A display, the display being configured to: Provide an estimated recovery time.

2. The system of claim 1, wherein the first series of stimulations and the second series of stimulations are trains of four stimulations.

3. The system of claim 2, wherein a first muscle twitch, a second muscle twitch, a third muscle twitch, and a fourth muscle twitch are measured for each of the first four trains of stimulation and the second four trains of stimulation.

4. The system of claim 3, wherein the controller is further configured to: calculating a first four train ratio based on the first muscle twitch and the fourth muscle twitch at the first measurement time; calculating a second four train ratio based on the first muscle twitch and the fourth muscle twitch at the second measurement time; determining predicted slopes of the four clustered ratios over time; applying the predicted slope to the calculated first four train ratios and the calculated second four train ratios to create a predicted neuromuscular blockade trend curve; as well as An estimated recovery time is predicted based on the predicted neuromuscular blockade trend curve.

5. The system of claim 4, wherein the predicted neuromuscular blockade trend curve relates four train ratios to time.

6. The system of claim 5, wherein the predicted recovery time occurs when the four train ratios of the predicted neuromuscular blockade trend curve exceed a recovery threshold.

7. The system of claim 4, wherein the display is further configured to display the predicted neuromuscular blockade trend curve.

8. The system of claim 7, wherein the displayed predicted neuromuscular blockade trend curve includes both the measured four train ratios and the predicted four train ratios.

9. The system of claim 1, wherein the display is further configured to output a notification instructing a user to initiate an extubation procedure at the estimated recovery time.

10. The system of claim 4, wherein the controller is further configured to: determining the four train ratios at regular intervals after the second measurement time until the predicted recovery time is determined at regular intervals; comparing the determined four train ratios with the four train ratios of the predicted neuromuscular blockade trend curve for the measured time; and wherein The display is further configured to: When the determined four burst ratios are different from the predicted four burst ratios for the measurement time, a user is alerted.

11. A medical device for monitoring relaxation depth of a patient, comprising: a stimulator operable to apply four trains of stimulation to a nerve of the patient at a first measurement time and a second measurement time; an electromyographic sensor operable to detect a first muscle twitch, a second muscle twitch, a third muscle twitch, and a fourth muscle twitch in response to the four trains of stimulation at the first measurement time and the second measurement time; A controller is operable to create a predicted neuromuscular blockade trend curve based on the muscle twitches detected at the first measurement time and the second measurement time, wherein the predicted neuromuscular blockade trend curve indicates a predicted extubation time.

12. The medical device of claim 11, further comprising a display for visually displaying the predicted neuromuscular blockade trend curve.

13. The medical device of claim 12, wherein the predicted neuromuscular blockade trend curve comprises four measured train ratios and four predicted train ratios.

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