RU2682474C1 - Finger photoplethysographic system device for continuous non-invasive measurement of arterial pressure - Google Patents

Abstract

FIELD: medicine.SUBSTANCE: invention relates to medical equipment. Device of digital photoplethysmographic system for continuous non-invasive measurement of arterial pressure contains finger base (1), on which two photoplethysmographic cuffs and finger retainers (3, 4) are installed. Each photoplethysmographic cuff comprises air chamber (2.1) with optoelectronic pair (2.2). Finger base is configured to overlap at least one interarticular spacing and at least one adjacent joint, and its size corresponds to size of two fingers. Finger base is made with possibility of its location under finger. Photoplethysmographic cuff is located inside the finger retainer. On the finger base there is an additional finger retainer intended for fixation of the remaining part of the finger. Finger base is made in the form of a plate on which a chute for finger (1.1) is formed. Finger retainer is equipped with adjustable buckle and is configured to stretch and contract.EFFECT: higher reliability and accuracy of measuring blood pressure by limiting motor activity finger phalanxes in sections of interphalangeal articulation of joints and articulated joints of fingers with palm, and thereby reducing the likelihood of occurrence of corresponding artefacts caused by motor activity, as well as by measuring pressure on two fingers by periodically switching measurement between two fingers, in which second finger rest, which provides virtually unlimited duration of monitoring.8 cl, 2 dwg

Description

The present invention relates to sensors designed for continuous non-invasive measurement of blood pressure and can be applied if necessary, continuous monitoring of the patient's blood pressure using the fingers of his hands.

Continuous non-invasive measurement of blood pressure is based on the principle of "unloaded artery", proposed in 1969 by the Czech researcher Penyaz [1]. This principle is based on a continuous assessment of the volume of finger vessels using a photoplethysmographic signal and a follow-up electro-pneumatic system that creates pressure that counteracts a change in the diameter of the arterial vessels passing under the cuff in the finger. In this case, the photoplethysmographic signal is constant at a given level, and the pressure in the cuff repeats the blood pressure in the arteries of the finger.

Known devices [1-5], the main functions performed by which include a continuous non-invasive measurement of blood pressure (BP) in the blood vessels of the fingers based on the Penyaz principle. During the operation of devices [1-5], external pressure is created on one of the phalanges of the finger, and at the same time a photoplethysmogram is recorded on this part of the body. External pressure is generated by the finger cuff, and the photoplethysmogram is recorded using optoelectrics built into the cuff body. However, the drawback of the cuffs is that their design does not provide for a restriction on the possibility of finger movement, and therefore, situations of the appearance of various artifacts are not excluded during measurements. In particular, artifacts can occur with the motor activity of the phalanges of the fingers, as well as due to the possibility of movement of the fingers in areas of the articular joint with the palm of the hand. The design of the cuffs did not use mechanical restrictions that created an obstacle to this kind of motor activity. With these movements, a shift in the tissues of the finger is created in the region of the location of the cuff and optoelements, which entails a change in the optical characteristics of the measured area, not related to changes in blood pressure, and thus is a source of artifacts. It is noteworthy that movements can occur inadvertently and randomly, involuntarily. Due to artifacts, the recorded photoplethysmogram and blood pressure signals are distorted, and this can lead to a malfunction of the tracking mode of the device, and lead to an uncontrolled decrease in the accuracy of blood pressure measurement. Thus, a consequence of the cuff design deficiency is the manifestation of possible artifacts caused by movements occurring due to the lack of fixation of the finger phalanges in a fixed position relative to each other. At the same time, there is the possibility of transmitting movements to neighboring body tissues in the area of the phalanx, where the finger cuff and optoelements are located.

A finger cuff that is closer in technical essence is proposed in the monitor of vital signs [6]. With the monitor [6], measurements are carried out simultaneously on two fingers, and a number of physiological parameters, including blood pressure, are determined. For this, two cuffs are used, located on the fingers of one or different hands. The two-finger cuff system provides advantages in signal processing and data interpretation by reducing the number of false alerts from the monitor. However, the design of the cuffs does not exclude the occurrence of finger phalanges and finger movements relative to the palm during measurements. At the same time, there remains the possibility of the appearance of artifacts associated with movements that reduce the reliability and accuracy of blood pressure measurement.

The closest in technical essence to the claimed invention and adopted as a prototype is a device [7]. This device is a two-finger photoplethysmographic system used as part of equipment designed for continuous non-invasive measurement of blood pressure. It is a detachable design with a replaceable part. The device combines an irreplaceable basic part (in other terms, - the case, or base), a single design of two cuffs detachable from the case with built-in optical elements and a clasp. The single cuff design is designed to be placed on two adjacent fingers, respectively. The cuffs together with the optical elements built into them represent the photoplethysmographic system of the device [7]. For operation, the removable part of the combined cuffs is connected to the device body and, being a replaceable part thereof, is easily replaced if necessary. The fastener of the device [7] is used to connect in a mutually fixed position the phalanges of adjacent fingers and cuffs with optoelements located on these phalanges. Designed to be used for two fingers, the cuff system of the device [7] has an advantage over analogues. Namely, due to the fixation of the position of the phalanges of neighboring fingers relative to each other, an obstacle is created in this case, limiting their motor activity. This reduces the likelihood of the appearance of the corresponding artifacts and increase the accuracy of blood pressure measurement. However, the design of the device does not exclude the possibility of bending and extensor movements of the finger phalanges in the areas of the interphalangeal joint of the joints and in the areas of the articular joint of the fingers with the palm during measurements. Therefore, there remains the possibility of artifacts associated with movements in these areas, which reduces the reliability and accuracy of blood pressure measurement in comparison with the situation when movements do not occur.

The technical result of the claimed invention is to increase the reliability and accuracy of blood pressure measurement, achieved by limiting the motor activity of the finger phalanges in the areas of the interphalangeal joint of the joints and in the areas of the articular joint of the fingers with the palm of the hand, and thereby reducing the likelihood of the appearance of the corresponding artifacts caused by motor activity.

The technical result is achieved due to the fact that the device is a finger photoplethysmographic system for continuous non-invasive measurement of blood pressure, containing a finger base, on which two photoplethysmographic cuffs and finger clamps are installed, each photoplethysmographic cuff includes an air chamber with an optoelectronic pair, while the finger base is made with the possibility of overlapping at least one inter-articular distance and at least one adjacent joint, and its size is accordingly etstvuet size of two fingers.

Implementation options are possible in which:

- the finger base is made with the possibility of its location under the finger;

- the finger base is made with the possibility of its location above the finger;

- photoplethysmographic cuff is located inside the finger retainer;

- on the finger base an additional finger lock is fixed, designed to fix the rest of the finger;

- the finger base is made in the form of a plate;

- the finger base is made in the form of a plate on which a groove is formed under the finger;

- the finger lock is equipped with an adjustable fastener;

- the finger lock is made rigid;

- the finger lock is made in the form of an annular grip;

- the finger lock is flexible;

- the finger lock is made with the possibility of stretching and compression;

- the finger lock is made in the form of a tape;

- The finger base is equipped with a level sensor.

The essence of the claimed invention is illustrated by the drawings and the following description.

In FIG. 1 presents an embodiment of the inventive device.

In FIG. 2 presents an example of the application of the inventive device on a patient.

1 - finger base;

1.1 - groove under the finger;

2.1 - air chamber;

2.2 - optoelectronic pair;

3 - finger lock;

4 - additional finger lock;

5 - level sensor.

The device of the finger photoplethysmographic system for continuous non-invasive measurement of blood pressure (Fig. 1, 2) contains a finger base 1 on which two photoplethysmographic cuffs and finger clips 3 are mounted.

Each photoplethysmographic cuff includes an air chamber 2.1 with an optoelectronic pair 2.2, which is connected to an electro-pneumatic unit (not shown) through an air tube (not shown in the drawing) and electric wires (not shown in the drawing).

Finger base 1 is configured to overlap at least one inter-articular distance and at least one adjacent joint, i.e. the size of the finger base 1 is selected depending on the size (length, width, volume) of at least one inter-articular distance and the size of at least one adjacent joint.

The more inter-articular distances and adjacent joints will be closed, the more reliable is the fixation of the finger. In this case, the finger base 1 can be made with the possibility of its location under the finger or above the finger. The size of the finger base 1 in this case corresponds to the size of two fingers.

The photoplethysmographic cuff may be located within or adjacent to the finger retainer 3.

At least one additional finger lock 4 can be fixed on the finger base 1, which is used to fix the remaining part of the finger / fingers.

Long-term exposure to excessive pressure on the finger can lead to a change in the state of the vessels of the finger, which increases the error in measuring blood pressure. One way to eliminate this effect is to measure the pressure on two fingers. For this, two photoplethysmographic cuffs with finger clips are installed on the finger base 1. In the two-finger cuff, the measurement is periodically switched between two fingers, while the second rests. This achieves an almost unlimited monitoring duration.

The finger base 1 can be made flat or three-dimensional, for example, in the form of a plate on which a groove 1.1 can be formed under the finger (Fig. 1, 2), which provides centering of the finger and its best retention. The cuff can be fixed on the finger base 1, for example, with glue, the finger retainer 3 and the additional finger retainer 4 can be fixed on the finger base 1 with glue and / or special slots in the base 1 through which part of the retainer 3 will be threaded. Finger base 1 can be made of plastic, wood, metal and other hard material.

Finger latch 3 and additional finger latch 4 can be made rigid, for example, in the form of an annular grip, or flexible, with the possibility of stretching and compression, for example, in the form of a belt, tape, etc., and can be equipped with an adjustable fastener, for example, Velcro and etc.

A level 5 sensor can be installed inside or on the surface of the finger base 1, which corrects blood pressure readings according to the position of the cuff relative to the level of the heart and is, for example, a pressure sensor to which a flexible tube (not shown) is attached, filled with liquid, for example, water. The end of the tube (free), opposite from the pressure sensor, is located at the level of the heart, thereby determining the difference between the levels of the heart muscle and the place of measuring pressure on the finger. Pressure measurement example.

To measure the pressure, the inventive device of a suitable size is put on the finger of the hand, for example, the middle one, the cuff is located as close to the wrist as possible. Neighboring phalanges are fixed (attracted) to the finger base 1 using the finger clips 3 and 4, while limiting the mobility of the finger in the joints. Through an air tube (not shown in the drawing) and electrical wires (not shown in the drawing), the cuff is connected to an electro-pneumatic unit (not shown in the drawing). The free end of the tube of the finger level sensor 5 is placed at the level of the heart. The electro-pneumatic unit is turned on (not shown in the drawing). According to the “start” command, the electro-pneumatic block (not shown in the drawing), according to the specified algorithm, changes the pressure in the cuff and, controlling the photoplethysmographic signal, implements the “unloaded artery” algorithm [1, 2]. Namely, it monitors the constancy of the blood vessels of the finger by the feedback signal in the photodetector circuit located on this finger. At the same time, the pressure in the cuff is continuously recorded, which repeats the blood pressure in the finger vessels.

After completion of work, the electro-pneumatic unit (not shown in the drawing) automatically turns off, the pressure in the cuff is vented.

In the case of a two-finger cuff, the control algorithm provides for the alternation of measuring pressure on different fingers.

List of sources used

Patentova Listina, CISLO 133 205. - 1969.one.

Patentova Listina, CISLO 133 205. - 1969.

2. Penaz. Automatic noninvasive blood pressure monitor. US 4869261. Prior. 03/27/1987. Publ. 09/26/1989.

3. Inflatable finger cuff. US 4726382 and EP 0260807 application EP 19870307192 from 09/14/1987, publ. 03/23/1988.

4. Inflatable finger cuff for use in non-invasive monitoring of instantaneous blood pressure. Europ. pat. application No. 0537383; Application number: 91202676.2; Date of filing: 10/15/91; Applicant: Nederlandse organisatie TNO. 04/21/93 Bulletin 93/16.

5. Inflatable finger cuff. US 4726382. Prior. 02/23/1988.

6. Dual-finger vital signs monitor. US 5152296. Publ. 10/10/1992.

7. Disposable and detachable sensor for continuous non-invasive arterial blood pressure monitoring. US 8798703. Publ. September 5, 2014.

Claims (8)

1. The device is a digital photoplethysmographic system for continuous non-invasive measurement of blood pressure, containing a finger base, on which two photoplethysmographic cuffs and finger clips are installed, each photoplethysmographic cuff includes an air chamber with an optoelectronic pair, and the finger base is configured to overlap at least one interarticular distance and at least one adjacent joint, and its size corresponds to the size of two fingers. 2. The device according to p. 1, characterized in that the finger base is made with the possibility of its location under the finger. 3. The device according to claim 1, characterized in that the photoplethysmographic cuff is located inside the finger retainer. 4. The device according to p. 1, characterized in that on the finger base is attached an additional finger lock, designed to fix the remaining part of the finger. 5. The device according to claim 1, characterized in that the finger base is made in the form of a plate. 6. The device according to p. 5, characterized in that the finger base is made in the form of a plate on which a groove is formed under the finger. 7. The device according to claim 1, characterized in that the finger lock is equipped with an adjustable fastener. 8. The device according to p. 1, characterized in that the finger lock is made with the possibility of stretching and compression.

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