LV14444B - Method and device for the determination of efficiency of human anesthesia and for registration the same, using contactless photoplethysmography - Google Patents

Abstract

The invention relates to anaesthesia and, in particular - to the determination of efficiency of human anaesthesia and for registration the same, using contactless photoplethysmography (PPG) equipment. The device for contactless determination in real time of the effect of regional anaesthesia comprises a light source adapted for irradiation of the skin surface being anaesthetized with white light, a three-color RGB light-sensitive sensor-matrix adapted for image converting into digital format, assigning each image pixel the determined RGB value range, a device's memory, adapted for the storage of said value range, an analysis unit adapted for calculation of photopletizmographyc signal (PPG) amplitude from the green G colour channel video signal at each cardiac cycle, and for PPG average median values calculation from it in the specified time interval, an analysis block adapted for recording the effect of anaesthesia according to PPG amplitude changes, an output device designed for displaying time chart or numerical values of PPG amplitude, a control unit, which is connected with the light source, the light-sensitive sensor-matrix and the analysis unit, and adapted to control their operation.

Description

Description of the Invention

Technical field

The invention is intended to be used in anesthesiology, in particular to determine the effect of anesthesia following peripheral nerve plexus block in regional anesthesia (RA).

Analysis of known sources of information

One of the main tasks of anesthesia is to provide the patient with pain relief. Classically, RA has a positive effect on motor, sensory, and sympathetic blocks. In practice, several methods are used to determine the effect of RA. Only clinical methods are widely used. The determination of the degree of regional anesthesia in essence involves testing sensory functions and determining physiological responses. Sensory function testing is only possible if the patient is conscious and sufficiently cooperative. There is currently no direct, ideal method for detecting the presence or degree of RA in an unconscious patient.

Sensitivity limits and RA exposure (i.e., loss of sensitivity) are traditionally determined by minimal needle stabbing or, in the case of loss of cold sensation, by contact with cold, such as a piece of ice (by neurological standards). These clinical methods for detecting "sensory" RA are undoubtedly simple but subjective and based on physician / patient contact. Unfortunately, this contact tends to be difficult for a number of objective reasons. First of all, note the patient's variable level of consciousness, which depends on a number of factors: stress, the presence and severity of the injury, abnormal conditions, age-specific mentalities, comorbidities, medication background, degree of premedication and sedation, etc. As a result, it is very often physically impossible to obtain an adequate response from a patient to his or her sensory senses, and the response thus obtained may not only be inaccurate and ambiguous, but deceptively positive. This, in turn, can lead to a situation where the prepared and positioned patient is not actually anesthetized, but the possibility of switching to another type of anesthesia is not feasible. The situation is dangerous not only from an ethical point of view, but also from a medical point of view, as unexpected severe pain associated with surgical manipulation can lead, for example, to dangerous coronary pain or hypertensive crisis, especially against the backdrop of other adverse conditions.

The technology available to measure the degree of pain does not yet exist, but many factors help to judge the level of pain indirectly. Occurrence of motor block secondary indicates anesthesia, but without adequate correlation with sensory block. In other words, the motor unit may not be present, but anesthesia occurs and vice versa. Second, contact with the patient is needed to enable them to make conscious active movements. Symptomatic block, such as physiological and hormonal changes in the body in response to stress, surgery, anesthesia, is more difficult to detect but independent of the patient. Some of the changes are detectable in laboratories (plasma levels of adrenal hormone cortisol, IL6, CRP in the second phase of inflammation), but are limited by the time and cost limit, which makes it impractical to detect changes in the laboratory specifically for routine anesthesia. The other part of the change is related to direct measurements that reflect neurophysiological changes in the brain related to stress and pain. The third is associated with physiological changes in response to RA administration. After RA administration, sensory, motor, and sympathetic blocks are expected in the area of compromised innervation with adequate anesthesia. If it is not possible to measure the sensor unit directly, then the sympathetic effect can be evaluated and the implied sensor effect can be judged indirectly. The sympathetic effect is associated with a marked peripheral vasodilation, an increase in peripheral blood flow and consequently an increase in peripheral skin temperature. Temperature change monitoring is very effective, but limited to a small area of the skin, meaning that the temperature can only be detected at the point of attachment of the thermosensor. One of the state-of-the-art methods to estimate a larger body area is the tennographic camera, which allows for indirect visualization of RA in the dynamic process.

The global quantification of RA is the focus of attention, as in clinical practice only clinical methods are used widely in anesthesiology, which mainly focus on the detection of RA sensory block. These clinical methods are non-quantitative and based on physician-patient contact. Because the patient's mental state is variable and depends on a number of factors, such as age, degree of sedation, general somatic condition, other quantitative methods are required.

There are several non-invasive RA detection methods and devices that have been invented and patented in recent years.

There is known a device and method for monitoring successful spinal anesthesia (International Patent Application WO 2010075997), which involves placing at least one electronic temperature sensor on the skin surface within at least one dermatoma. The device gives an optical and / or acoustic signal when the temperature measurement results change by 2-3 ° C, indicating a positive anesthetic effect.

There is a known method for evaluating the evolution of an adequate block of ductal anesthesia (RA) (patent RU2357660) which utilizes a patient's pulse index, which is measured every minute starting from the 5th minute, simultaneously on the operated and healthy limbs. The average coefficient per blocked and healthy limb is evaluated and when one coefficient exceeds the other three times the anesthesia is considered successful.

There are publications describing methods that evaluate the difference in temperature between anesthetized and non-anesthetized areas in patients undergoing surgery on the upper limb using a thermography camera (Tejs Jansen et al; 2010).

An ultrasound imaging device in combination with pulse oximetry for RA and peripheral block validation is very popular (WO 2010076808).

Other methods of detecting anesthesia are based on different principles, such as electrodermal activity. Changes in skin conductance were controlled after the onset of sympathetic block, indicating successful RA (T.Ledovski et al; Anesthesia, 2007, 62, p.989993).

Other devices, such as PAINVISION PS-210 (osachi Itd; 2003), for quantitative perceptual monitoring using common anesthetic standard observation parameters (electrocardiography, TA, etc.) and adjustable electrical stimuli have also been developed.

There are also mechanical devices (so-called palpometers) that require contact with the patient (Nature Medicine, Volume I, N 11, Nov. 1995, p. 11391140). There is another known method using special needles with weights offered to control the sensory sensation in diabetic patients. This method can be compared to measuring the level of anesthesia by the peripheral block (A W Chan; J Neurol Neurosurg Psychiatry. 1992; 55 (1); 56-59).

Compared to RA preventive methods, general anesthesia (VA) stress detection methods, which in theory cannot be used, can also be considered. Surgical stress can practically only be observed in failed RAs that have not been diagnosed in time. The method is based on changes in the descending portion of the patient's photoplethysmography pulse wave in response to increased heart rate and increased arterial pressure in response to stress (patent application CN101785660 A).

Photoplethysmography (PPG) is a non-invasive optical method for measuring blood volume ripple. The method is based on the ability of optical radiation to penetrate the tissue to a depth of several millimeters. Radiation is absorbed into soft tissues and blood. As a result of cardiac and respiratory and vasomotor activity, blood volume changes periodically, and the intensity of radiation in the subcutaneous tissue is modulated at the expense of these processes. Changes in blood volume can be detected using a contact PPG method based on one or more radiation sources and a photodiode that detects transmitted or reflected radiation to the skin (tissues). The PPG method is used to measure blood pulse and oxygen content in commercial medical monitoring systems. The disadvantage of the PPG contact method is that the blood volume ripple can only be measured in a small area of skin (tissue) that is in direct contact with the sensor. By removing the radiation source and the sensor from the skin surface, the method becomes a non-contact PPG. You can use a lens-mounted camcorder sensor to record radiation. The skin surface image is focused on the sensor and the PPG signal is recorded at each skin point. This results in a two-dimensional distribution of the PPG signal reflected from the skin surface. This is a photoplethysmography imaging (PPGI) method. With the PPGI method it is possible to perform PPG amplitudes, phases, etc. hemodynamic mapping. The method can be used to monitor the blood flow (perfusion) of skin tissue, which is important for medical examinations.

The sympathetic effect of RA results in an increase in peripheral blood flow, which results in an increase in the PPG signal amplitude of the skin surface until it reaches a certain threshold. The onset of increase in PPG amplitude can be considered as the successful onset of RA.

An experimental PPGI device for skin perfusion monitoring was developed in Aachen (Germany) in 2003 [T.Wung. PPGI: New Development in Noninvasive and Contactless Diagnosis of Dermal Perfusion Using Near InfraRed Light. J. GCPD e.V, 7 (1): 17-24, 2003]. This unit consists of an IR LED source and a camcorder. After penetration into the skin, the radiation emitted by the LED was detected at a depth of several millimeters by a camcorder with an infrared filter placed in front of it. The camcorder was connected to a computer and operated using a dedicated controller that provided real-time operation of the camcorder as well as displaying video on the monitor screen. At the same time, it was possible to change the size and coordinates of the area of interest of the image, i.e. the position of the virtual PPG sensor on the skin surface as well as the frame rate. At the end of the measurements, the computer program performed various calculations of image processing, such as motion compensation, median filtering, and image segmentation.

In Louisville, USA, a new method for obtaining arterial pulse from thermal video signal was developed in 2006 [S.Y. Chekmenev, A.A. Farag and E.A. Essock. Multiresolution Approach for Non-Contact Measurements of Arterial Pulse using Thermal Imaging. Proc. 2006 Conf. based on the fact that the distribution of skin surface temperature can be determined using a thermal imaging, because as a result of blood pressure ripple, the skin's thermal image periodically pulsates in areas where the arteries are located. Choosing sufficiently accurate locations on arteries with a sufficiently strong pulse can provide a high quality ripple signal. Automatic selection of such areas of interest can be a serious problem and is therefore done manually. The human face and neck were monitored in the study. First, the area where the thermal signal is of sufficient amplitude was selected. This may be the back or neck area. The special algorithm then divides the area of interest into images of different resolutions and performs deeper analysis.

Researchers from Irvine (USA), in collaboration with researchers from Trondheim (Norway), recorded a PPG signal in 2008 using daylight and a conventional standard definition (SD) camcorder [W. Verkruysse, L.O. Svaasand, J.S. Nelson. Remote plethysmographic imaging using ambient light. Opt. Erpress, 16 (26): 21434-21445, 2008], It was found that in the visible light, the green light component alone contains a significant portion of the PPG signal associated with the peak of blood hemoglobin absorption in this spectral range. Filming took place for a few minutes at a frame rate of 15 or 30 frames per minute and a resolution of 320x240 or 640x480 pixels. Each frame was divided into 50x40 pixel areas. PPG amplitude mapping of whole face skin in green RGB spectrum was performed. Measurements were taken on facial skin with pathological “Wine stain” syndrome before and after a course of laser therapy. Fourier analysis of the PPG signal revealed a phase shift between healthy and abnormal cutaneous PPG signal.

OBJECT, NATURE, DESCRIPTION OF THE DRAWINGS AND DETAILED DESCRIPTION OF THE INVENTION

The object of the present invention is to provide a novel non-invasive and non-contact method that can quantify successful and unsuccessful RA and exclude subjectivity in RA detection.

The proposed technique uses visible-spectrum radiation, which is recorded by a light-sensitive RGB sensor to reflect the anesthetized skin surface, to determine the contactless effect of the regional anesthetic. From the green G video signal, the amplitude of the photoplethysmographic signal in each heart rate cycle is calculated and the amplitude of the photoplethysmographic signal at each time interval is calculated and compared with the standard deviation of the initial amplitude.

The present invention provides novel, non-invasive, and non-contact capabilities for utilizing peripheral circulatory changes in the upper limb of the Plexus brachialis regional block detected by a contactless PPG signal obtained from reflected light during video recording to determine successful and failed RA.

The following figures illustrate the invention:

Fig. 1 a diagram of a non-contact regional anesthesia monitoring method is shown;

Fig. 2 a graph of the recorded PPG signal and the moment of its increment detection indicating the onset of regional anesthetic effects are shown;

Fig. 3 a block diagram of a non-contact regional anesthesia monitoring device is shown containing:

- a white light source 1, such as an operating lamp or LED spotlight, which irradiates the surface of the skin to be anesthetized;

- a lens-equipped digital light-sensitive RGB sensor, or camcorder 3, which converts the image into a digital format, assigning a certain number of RGB values to each pixel and storing it in the device memory 4;

- an analyzer 5, which calculates the amplitude of the PPG from each green G video signal in each heartbeat cycle and calculates an average median value of the PPG at one minute intervals;

- an analysis unit 6, which registers the effect of anesthesia following a change in PPG amplitude;

an output device 7, such as a graphical display or a numeric indicator, which plots the time series or numerical values of the PPG amplitude;

- a control unit 8 which controls elements 1, 3 and 5.

The device operates as follows: the control unit 8 sends a signal to the white light source 1, which irradiates the surface of the anesthetized skin; upon receiving command from unit 8, the photosensitive digital RGB sensor 3 captures an image of the surface of the irradiated skin to be irradiated and digitizes it, assigning each pixel a specific series of RGB values; said string of values is stored in the device memory 4; upon receiving command from unit 8, the analyzer 5 calculates, from the green G video signal, the PPG amplitude for each heartbeat cycle and the mean median PPG value over the PPG amplitude at one minute intervals; analysis unit 6 records the effect of anesthesia from the PPG amplitude change calculated in block 5; The time schedule or numerical value of the PPG amplitude is displayed on the output device 7.

The patient was placed in a supine position with the arm shoulder joint 90 ° abduction and the elbow joint 90 ° flexion, the arm inserted into the positioner at an angle of 30 ° to the horizontal axis and fixed. The camcorder is mounted on a tripod at a distance of one meter from the patient's wrist so that recording is not obstructed by personnel during manipulation. The light source is mounted at a distance of three meters to minimize the effect of temperature measurement and is in focus.

All patients underwent 'standard' anesthetic perioperative monitoring (ECG, NIBP, SpO2, CO2) according to the LR Association of Anesthesiologists and Reanimatologists recommendations for minimum safety requirements.

All patients underwent preoperative regional anesthesia of the Plexus brachialis at the armpit level, US supported and / or using the PNS method. Four peripheral nerves (N. Medainus, N. Musculocutaneus, N. Ulnaris,

N. Radialis) and topically administered: S. Lidocaini 2% - 10, Omi + S. Marcaini 0.5% - 10.0 ml.

The measurements were made in one room (according to IS02000 standard in a certified operating room with controlled air temperature 23.2 ± 0.8 ° C). The measurement reference point was two minutes before the start of the manipulation (after temperature stabilization) and the measurement duration was up to 30 minutes.

During measurements, skin PPGI damage was calculated as the median (mean) value of PPG amplitude from the selected skin area in each heart rate cycle. The median (mean) value of the PPG amplitude and the standard deviation value at a minute interval were calculated every minute. The time at which the PPG amplitude at two standard deviations (SN ₂ ) exceeded the baseline PPG amplitude at two standard deviations (SNj) was considered as statistically significant anesthesia (see Fig. 2). As soon as a statistically significant onset of anesthesia occurs, measurement may be interrupted and surgical manipulations may commence.

According to the invention, anesthesia is considered adequate (successful) if there is no need to use additional analgesic medication or to switch completely to another type of anesthesia, as well as traditional clinical criteria: motor block, sensory block, patient's cold feeling in contact with ice, feelings of discomfort or pain following surgical manipulation. Anesthesia is considered inadequate (failed or partially successful) when the provision of adequate analgesia necessitates the addition of additional analgesics or a complete switch to another type of anesthesia due to the disproportionate increase of the patient's subjective discomfort.

With the proposed method and appropriate equipment, the onset of regional anesthesia is easy to detect and not complicated from the user's point of view. Detection is objective and independent of the patient's mental and physical condition. There are no restrictions related to the subjective opinion of the patient or doctor. There are no limitations associated with the time limit or the high cost of the hardware used, given its widespread availability and easy availability (in virtually any operating room). There are no restrictions associated with lengthy and costly staff training on PC and camcorder use.

Claims (5)

A device for detecting a non-contact regional anesthetic effect comprising; a white light source (1) suitable for irradiating the surface of the anesthetized skin with white light; a light sensitive RGB sensor (3) suitable for converting images into a digital format by assigning each pixel a specific series of RGB values; a device memory (4) suitable for storing said series of values; an analyzing device (5) adapted to calculate the amplitude of the photoplethysmographic signal (PPG) of the green G video signal in each heartbeat cycle and to calculate an average median value of the PPG therefrom at a defined time interval; an assay unit (6) adapted to record the effect of anesthesia following a change in PPG amplitude; an output device (7) for displaying a time plot or numerical value of the PPG amplitude; a control unit (8) connected to a light source (1), a digital RGB sensor (3) and an analysis device (5) suitable for controlling their operation. Device according to Claim 1, characterized in that the output device (7) is a monitor. 3. A method for determining the non-contact effect of regional anesthesia using visible-spectrum radiation, which is recorded by a light-sensitive RGB sensor (3) reflected from the surface of the anesthetized, whereby the amplitude of the photoplethysmographic signal is calculated for each cardiac cycle the amplitude of the photoplethysmographic signal over a time interval is calculated and compared with the standard deviation of the initial amplitude. A method according to claim 3, characterized in that the timing or numerical value of the PPG amplitude is displayed on the output device (7). A method according to claim 3, characterized in that the output device (7) displays a statistical plausibility of the PPG signal increase and a defined anesthetic exposure threshold.