Device for determining the hemoglobin level or the hematocrit level of a circulating liquid

Abstract

The present invention relates to a device for determining the hematocrit level and / or the hemoglobin level of a liquid circulating in a tubular portion (2), comprising two transmitter-receiver assemblies (10; 20), each comprising a light source (11; 21) and a light sensor (12; 22), said light source and light sensor being intended to be arranged on either side of the tubular portion (2) at the circulation area of the liquid for carrying out transmission measurements; the light source (11; 21) of each of the two transmitter-receiver assemblies (10; 20) is configured to emit a light beam at an emission wavelength chosen to correspond to the isosbestic point of hemoglobin; each transmitter-receiver assembly (10; 20) further comprises a system (13; 23) for collimating the light beam emitted from the corresponding light source (11; 21) towards the corresponding light sensor (12; 22).

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a device and a method for determining a blood parameter of a circulating fluid, in particular for determining a hemoglobin level and / or a hematocrit level of a circulating fluid. The present disclosure finds a particularly advantageous application for medical applications, for example for analyzing a hemorrhagic fluid circulating in a duct. BACKGROUND

[0002] In many medical applications, it is necessary to track blood parameters to identify a patient's hemorrhagic fluid. It is useful, for example, in some surgeries, and in particular in surgical operations, to track the evolution of the hemoglobin level and / or the hematocrit level of a hemorrhagic fluid. In particular, when a patient's hemorrhagic fluid must be subjected to a particular treatment, it is advantageous to be able to continuously track the evolution of these blood parameters.

[0003] One particular and non-limiting example in which it is efficient to be able to track the evolution of blood parameters is the treatment of a patient's hemorrhagic fluid for autotransfusion of the patient's blood. Autotransfusion or autologous transfusion (i.e. transfusion with the patient's own blood) is increasingly used in surgical operations because it avoids incompatibilities that can arise during homologous or allogeneic transfusion. In addition, autotransfusion avoids the transmission of infectious diseases.

[0004] For the correct operation of these hemorrhagic fluid treatment systems, it must be possible to track in real time the evolution of the hemoglobin concentration or the hematocrit level in the fluid being treated, since the evolution of the blood parameters of such a fluid can allow the treatment system to be driven. One of the difficulties is that the fluids whose hemoglobin and / or hematocrit level is known are generally circulating in flexible ducts, which complicates detection. In addition, it is necessary to apply a specific detection method to compensate for the loss of detection sensitivity due to the movement of the fluid. Furthermore, since hemorrhagic fluid treatment systems, in particular for autotransfusion, are generally used in emergency situations, it is very important that the entire system can be used immediately by avoiding any preliminary calibration step as much as possible, including with regard to the composition allowing the hemoglobin and / or hematocrit level of the hemorrhagic fluid to be treated to be determined.

[0005] In the article entitled "Noninvasive and Continuous Hematocrit Measurement by Optical Method without Calibration" by SHOTA EKUNI and YOSHIYUKI SANKAI published in "Electronics and communications in Japan", vol. 99, no. 9, 2016, an optical detection method and system are proposed for determining the hematocrit level of a fluid circulating in a duct and avoiding the pre-calibration of the detection system. The proposed optical system consists of two transceiver assemblies operating in backscattering, each arranged on a respective support. The two supports are arranged to be attached to each other around a tubular portion through which the fluid whose hematocrit level is to be determined circulates, without deforming the tubular portion. The two transceiver assemblies are alternately operated according to different wavelengths corresponding to the isosbestic point of hemoglobin, i.e. 810 nm and 1300 nm, to avoid interference in the measurement. According to this article, the distance between the transmitter and the receiver has a significant influence on the reliability of the determination of the hematocrit level, so it is necessary to keep it as low as possible (less than 4 mm). In practice, this leads to significant limitations in terms of manufacturing and application. SUMMARY

[0006] One object of the present invention is to propose a device for determining a blood parameter such as the hemoglobin concentration (also called hemoglobin level) and / or the hematocrit level, which can be used for a fluid circulating in a tubular portion having any diameter, in particular a flexible duct used in a medical environment.

[0007] Another object of the present invention is to propose a device for determining the hemoglobin level and / or the hematocrit level of a fluid circulating in a tubular portion, which has an improved reliability and in particular allows measurements in a wider range of levels. For example, one object is to allow hematocrit level measurements for low hematocrit levels, i.e. lower than or equal to 30%, and high hematocrit levels, i.e. higher than 30%. In particular, one object of the present invention is to propose a device for determining a hematocrit level at least in the range of 5% to 60%, and in particular between 20% and 50%.

[0008] Another object of the present application is to propose a device for determining the hemoglobin level and / or the hematocrit level of a fluid circulating in a tubular portion, which can be positioned on the tubular portion in a simple manner, without the need to specifically adapt the tubular portion, and, if necessary, without the need to stop the circulation of the fluid. Advantageously, the proposed device for determining the hemoglobin level and / or the hematocrit level can be used directly in a fluid treatment system, such as a hemorrhagic fluid treatment system for autotransfusion, by using the tubing already present in the treatment system, without the need to specifically disassemble elements of the treatment system.

[0009] Another object of the present application is to propose a device for determining the hemoglobin level and / or the hematocrit level, which can be used for a fluid circulating in a tubular portion at a high flow rate, generally greater than 1,000 ml / min, for example around 2,000 ml / min, without significantly interfering with the flow rate of the circulating fluid, in order to avoid possible harmful effects on the fluid, such as the occurrence of hemolysis for a circulating hemorrhagic fluid.

[0010] Another object of the present application is to propose a method for determining the hemoglobin level and / or the hematocrit level of a fluid circulating in a tubular portion, which is reliable and easy to implement, and which allows measurements to be made in a wide range of levels, in particular for low hematocrit levels, i.e. lower than or equal to 30%, and high hematocrit levels, i.e. higher than 30%. In particular, an object of the present application is to propose a method for determining a hematocrit level in the range of at least 5% to 60%, and in particular between 20% and 50%.

[0011] To this end, a device for determining the hematocrit level and / or the hemoglobin level of a fluid circulating in a tubular portion is proposed, comprising:

[0012] - two transceiver assemblies, each comprising a light source and a light sensor, said light source and light sensor being arranged on either side of the tubular portion at the fluid circulation zone, for transmission measurements, preferably through the arcuate wall of the tubular portion;

[0013] - the light source of each of the two transceiver assemblies being configured to emit a light beam according to an emission wavelength chosen to correspond to an isosbestic point of hemoglobin;

[0014] Each transceiver assembly further comprises a collimation system for collimating the light beam emitted from the corresponding light source in the direction of the corresponding light sensor.

[0015] The present application also proposes a device for determining the hematocrit level and / or the hemoglobin level of a fluid circulating in a tubular portion, comprising:

[0016] - two transceiver assemblies, each comprising a light source and a light sensor, said light source and light sensor being arranged on both sides of the tubular portion arranged at the fluid circulation zone for transmission measurements, preferably through the arcuate wall of the tubular portion;

[0017] the light source of each of the two transceiver assemblies, configured to emit a light beam according to an emission wavelength chosen to correspond to an isosbestic point of hemoglobin;

[0018] - a processing system programmed to determine a hematocrit level and / or a hemoglobin level of the fluid from the light signals received by the light sensors of the transceiver assemblies; and

[0019] - a monitoring system comprising means for adjusting the power emitted by the light sources, the monitoring system being programmed to adjust the emission power of the light sources as a function of the hematocrit level and / or the hemoglobin level determined for the fluid.

[0020] The preferred but non-limiting aspects of any of these devices, alone or in combination, are as follows:

[0021] - the device comprises a support assembly on which the two transceiver assemblies are mounted, the support assembly being configured to be positioned around the tubular portion;

[0022] - the respective light sources of the two transceiver assemblies are configured to emit light beams at two different emission wavelengths;

[0023] - at least one of the light sources of the transceiver assemblies is configured to emit a light beam according to an emission wavelength chosen for absorbing substantially the same light beam in water or in plasma;

[0024] - at least one (and preferably each) collimation system comprises upstream lens assembly(s) having a focal plane and positioned between the respective light source and the light sensor on the side of the light source relative to the tubular portion, the light source being positioned at a distance of about 10 mm from the focal plane of the upstream lens assembly(s) and preferably in the focal plane of the upstream lens assembly(s);

[0025] - at least one (and preferably each) collimation system comprises downstream lens assembly(s) having a focal plane and positioned between the respective light source and the light sensor on the side of the light sensor relative to the tubular portion, the light sensor being positioned at a distance of about 10 mm from the focal plane of the downstream lens assembly(s) and preferably in the focal plane of the downstream lens assembly(s);

[0026] - at least one (and preferably each) collimation system comprises a downstream lens assembly having a focal plane and positioned between the respective light source and the light sensor on the side of the light sensor relative to the tubular portion, the downstream lens assembly being positioned so that the light beam exiting the outlet wall of the tubular portion converges at a distance of about 10 mm from the focal plane of the downstream lens assembly and preferably in the focal plane of the downstream lens assembly;

[0027] - at least one (and preferably each) collimation system comprises an upstream diaphragm positioned between the respective light source and the light sensor on the side of the light source relative to the tubular portion, the upstream diaphragm being arranged so that a central portion of the light beam emitted by the light source passes in the direction of the light sensor and a peripheral portion of the light beam emitted by the light source is blocked;

[0028] - at least one (and preferably each) collimation system comprises a downstream diaphragm positioned between the respective light source and the light sensor on the side of the light sensor relative to the tubular portion, the downstream diaphragm being arranged so that a central portion of the light beam transmitted through the tubular portion passes in the direction of the light sensor and a peripheral portion of the light beam transmitted through the tubular portion is blocked;

[0029] - at least one (and preferably each) collimation system comprises an upstream optical filter positioned between the respective light source and the light sensor on the side of the light source relative to the tubular portion and / or a downstream optical filter positioned between the respective light source and the light sensor on the side of the light sensor relative to the tubular portion, the upstream and downstream optical filters of the collimation system of the transceiver assembly being arranged to filter at least the emission wavelength of the light source of the other transceiver assembly;

[0030] - the device is such that the light source of a first one of the two transceiver assemblies is configured to emit a light beam whose wavelength is comprised between 780 nm and 840 nm, preferably between 800 nm and 820 nm, and more preferentially equal to 810 nm; and the light source of a second one of the two transceiver assemblies is configured to emit a light beam whose wavelength is comprised between 1270 nm and 1330 nm, preferably between 1290 nm and 1310 nm, more preferentially equal to 1300 nm;

[0031] - the light sources of the transceiver assemblies are positioned on the same side relative to the tubular portion;

[0032] - the device further comprises a system for monitoring the transceiver assemblies, the monitoring system comprising means for synchronizing the light sources and / or means for adjusting the power emitted by the light sources;

[0033] - the transceiver assemblies are assembled on a single support having a recess intended to receive the tubular portion;

[0034] - the device further comprises a cover arranged to at least partially cover the recess, said cover comprising a compression portion intended to hold the tubular portion positioned in the recess in place;

[0035] - all the elements of the light source and transceiver assembly arranged on one side of the respective light source with respect to the tubular portion are assembled on an upstream support, and all the elements of the light sensor and transceiver assembly arranged on one side of the respective light sensor with respect to the tubular portion are assembled on a downstream support different from the upstream support, the downstream support and the upstream support having a complementary shape arranged to be coupled so as to surround the tubular portion;

[0036] - the device comprises a system for deforming the tubular portion facing the transceiver assembly, the deformation system being arranged to deform the circular cross-section of the tubular portion into an elliptical cross-section;

[0037] - all the elements of the light source and transceiver assembly arranged on one side of the respective light source with respect to the tubular portion are positioned on one side of the major axis defining the elliptical cross-section, and all the elements of the light sensor and transceiver assembly arranged on one side of the respective light sensor with respect to the tubular portion are positioned on the other side of the major axis defining the elliptical cross-section;

[0038] - the elliptical cross-section is defined by a long radius (Ra) along the major axis and a short radius (Rb) along a minor axis perpendicular to the major axis, the length of the short radius (Rb) of the elliptical cross-section in the deformed state of the tubular portion being comprised between 30% and 70%, preferably around 50%, of the radius of the circular cross-section of the tubular portion in the undeformed state.

[0039] The application also proposes a method for determining the hematocrit level and / or the hemoglobin level of a fluid circulating in a tubular portion, comprising:

[0040] - emitting light beams in the direction of the tubular portion using at least two light sources, each of the two light sources being configured to emit a light beam according to an emission wavelength chosen to correspond to an isosbestic point of hemoglobin;

[0041] - receiving light signals transmitted through the tubular portion using at least two light sensors, each light sensor being associated with one of the two light sources;

[0042] - calculating the hematocrit level and / or the hemoglobin level of the fluid by processing the light signals received by the light sensors;

[0043] - characterized in that, during the determination of the hematocrit level and / or the hemoglobin level, the emission power of at least one of the light sources is adjusted as a function of the hematocrit level and / or the corresponding hemoglobin level calculated for the fluid.

[0044] The method has preferably, but not limitingly, the following aspects, alone or in combination:

[0045] - the emission power of the light source is at most equal to 100% of the maximum emission power of the light source, and preferably comprised between 10% and 60% of the maximum emission power of the light source;

[0046] - the emission power of the light source is monitored independently for each light source;

[0047] - the emission power of at least one of the light sources is increased from a threshold value of the hematocrit level and / or of the hemoglobin level calculated for the fluid;

[0048] - the method is such that:

[0049] o when the calculated hematocrit level is lower than 30%, the value of the emission power of the light source is set to be comprised between 10% and 30% of the maximum emission power of the light source, preferably equal to 20%; and

[0050] o when the calculated hematocrit level is higher than or equal to 30%, the value of the emission power of the light source is set to be comprised between 30% and 100% of the maximum emission power of the light source, preferably equal to 55%;

[0051] - the emission power of at least one of the light sources is adjusted so that:

[0052] o for a value of the hematocrit level calculated for the fluid lower than a first threshold value, the emission power of the light source is at a first power level;

[0053] o for a value of the hematocrit level calculated for the fluid higher than or equal to the first threshold value but lower than a second threshold value higher than the first threshold value, the emission power of the light source is at a second power level; and

[0054] o for a value of the hematocrit level calculated for the fluid higher than or equal to the second threshold value, the emission power of the light source is at a third power level;

[0055] - the emission power of at least one of the light sources is adjusted so that:

[0056] o when the calculated hematocrit level is lower than 20%, the value of the emission power of the light source is set to be comprised between 5% and 15% of the maximum emission power of the light source, preferably equal to 10%;

[0057] o when the calculated hematocrit level is comprised between 20% and 30%, the value of the emission power of the light source is set to be comprised between 15% and 30% of the maximum emission power of the light source, preferably equal to 20%; and

[0058] o when the calculated hematocrit level is higher than or equal to 30%, the value of the emission power of the light source is set to be comprised between 30% and 100%, preferably equal to 55%, of the maximum emission power of said light source.

[0059] - the emission power of the light source is adjusted according to the presence or absence of a fluid in the tubular portion and / or the properties of said fluid during the determination of the hematocrit level and / or of the hemoglobin level;

[0060] - the light source is monitored so as to emit the light beam in accompaniment. BRIEF DESCRIPTION OF DRAWINGS

[0061] Other features and advantages of the application will appear from the following description, which is merely illustrative and non-limiting, and should be read in conjunction with the accompanying drawings, in which:

[0062] Figure 1 The arrangement and operation of the device for determining the hematocrit level and / or the hemoglobin level of a circulating fluid according to a first exemplary embodiment are schematically illustrated.

[0063] Figure 2 The arrangement and operation of the device for determining the hematocrit level and / or the hemoglobin level of a circulating fluid according to a second exemplary embodiment are schematically illustrated.

[0064] Figure 3 The arrangement and operation of the device for determining the hematocrit level and / or the hemoglobin level of a circulating fluid according to a third exemplary embodiment are schematically illustrated.

[0065] Figure 4 The arrangement and operation of the device for determining the hematocrit level and / or the hemoglobin level of a circulating fluid according to a fourth exemplary embodiment are schematically illustrated.

[0066] Figure 5 A transceiver assembly (10; 20) of the proposed device mounted on a support is illustrated.

[0067] Figure 6 Is a perspective view of a device for determining the hematocrit level and / or the hemoglobin level of a circulating fluid.

[0068] Figure 7 The mounting of the collimation system in a mounting shaft provided for the assembly of the transceiver assembly is illustrated.

[0069] Figure 8 The mounting of the mounting shaft for the assembly of the transceiver assembly on a support is illustrated. DETAILED DESCRIPTION

[0070] The remaining part of the description will refer to the determination of the hematocrit level of a circulating fluid, but the teaching can be applied to other types of blood parameters, such as the hemoglobin level.

[0071] Apparatus for determining the hematocrit level of a circulating fluid

[0072] Figure 1 The arrangement of the apparatus 1 for determining the hematocrit level of a fluid circulating in the tubular portion 2 is schematically represented.

[0073] The proposed apparatus 1 for determining the hematocrit level can be used for determining the hematocrit level of any type of fluid, but it is particularly suitable for determining the hematocrit level of a hemorrhagic fluid, such as human blood, circulating in a pipe (for example, a flexible duct used in a standard manner in a hospital environment).

[0074] As will be described in detail hereinafter, the proposed apparatus 1 allows determining the hematocrit level of a fluid in a non-invasive manner, that is, without intervention on the fluid itself, so that the fluid can continue to circulate freely in the pipe.

[0075] The proposed apparatus 1 comprises at least two transceiver assemblies (10; 20), each comprising a light source (11; 21) and a light sensor (12; 22). The two transceiver assemblies (10; 20) are used for determining the hematocrit level of a fluid circulating in the pipe, the light beam passing through the fluid to be analyzed being used to calculate the hematocrit level of the fluid. Having two transceiver assemblies (10; 20) allows increasing the reliability of the apparatus 1, since the measurements of the two light sensors (12; 22) can be correlated with each other. Furthermore, this allows having redundancy, which can be advantageous in case one of the two transceiver assemblies (10; 20) malfunctions.

[0076] The light source (11; 21) of each of the two transceiver assemblies (10; 20) is configured to emit a light beam according to an emission wavelength selected as corresponding to an isosbestic point of hemoglobin. It should be understood that an isosbestic point corresponds to a wavelength value at which the total absorbance of a sample remains constant during a possible change in chemical reaction or state of that sample. More specifically, an isosbestic point is a wavelength (λ iso ) at which the total absorbance of a chromophore remains constant regardless of its state. At this precise point, a plurality of chromophores has the same molar extinction coefficient (a(λ iso )).

[0077] Hemoglobin has a plurality of isosbestic points.

[0078] For example, oxyhemoglobin and deoxyhemoglobin have isosbestic points at wavelengths of 550 nm, 570 nm and around 810 nm. At these wavelengths (λ iso ), a measurement related to the total volume of hemoglobin can be obtained, since the absorption of light at this wavelength is independent of the oxidation or reduction state in which the hemoglobin is found.

[0079] In addition, a wavelength around 1300 nm corresponds to another isosbestic point of hemoglobin.

[0080] Wavelengths above 1400 nm are also generally isosbestic wavelengths for hemoglobin, in particular wavelengths comprised between 1400 nm and 2200 nm. One advantage of these particular wavelengths is that the absorption of light at these wavelengths is substantially the same in water and in plasma. Thus, the hematocrit level determined at these wavelengths will be the same, regardless of the matrix in which the red blood cells are carried, whether this matrix is essentially composed of plasma or essentially composed of water. This is particularly true for wavelengths comprised between 1,400 nm and 1,700 nm and between 1,900 nm and 2,200 nm. Such wavelengths are therefore particularly advantageous when the hemorrhagic fluid whose hematocrit level is to be determined is diluted more or less strongly with an aqueous solution, for example a saline solution.

[0081] Thus, one (1 1 ; 21 ) of the light sources of the transceiver assembly (10; 20) can for example be configured to emit a light beam whose wavelength is comprised between 780 nm and 840 nm, preferably whose wavelength is comprised between 800 nm and 820 nm, and more preferentially whose wavelength is equal to 810 nm.

[0082] One (1 1 ; 21 ) of the light sources of the transceiver assembly (10; 20) can for example be configured to emit a light beam whose wavelength is comprised between 1,270 nm and 1,330 nm, preferably whose wavelength is comprised between 1,290 nm and 1,310 nm, and more preferentially whose wavelength is equal to 1,300 nm.

[0083] One (1 1 ; 21 ) of the light sources of the transceiver assembly (10; 20) can for example be configured to emit a light beam whose wavelength is comprised between 1,450 nm and 1,550 nm, preferably whose wavelength is comprised between 1,490 nm and 1,510 nm, and more preferentially whose wavelength is equal to 1,500 nm.

[0084] One (1 1 ; 21 ) of the light sources of the transceiver assembly (10; 20) can for example be configured to emit a light beam whose wavelength is comprised between 530 nm and 620 nm, preferably whose wavelength is comprised between 550 nm and 600 nm, and more preferentially whose wavelength is equal to 550 nm, 570 nm or 590 nm.

[0085] The respective light sources (11; 21) of the two transceiver assemblies (10; 20) can be configured to emit light beams at two identical emission wavelengths, but advantageously the two light sources (11, 21) are configured to emit light beams at two different emission wavelengths. In addition to the above-mentioned advantages due to the functional redundancy of the two transceiver assemblies (10; 20), the use of two light sources operating at different wavelengths allows a better correlation of the measured values in order to calculate the hematocrit level of the fluid circulating in the tubular portion 2.

[0086] According to one particular example, one of the light sources (11; 21) of the transceiver assemblies (10; 20) is configured to emit a light beam having a wavelength comprised between 780 nm and 840 nm, preferably a wavelength comprised between 800 nm and 820 nm, and more preferably a wavelength equal to 810 nm, while the other light source (11; 21) is configured to emit a light beam having a wavelength comprised between 1270 nm and 1330 nm, preferably a wavelength comprised between 1290 nm and 1310 nm, and more preferably a wavelength equal to 1300 nm. For example, it is possible to use light-emitting diodes (LEDs) such as the one proposed by the company "THORLABS" with the reference LED810L (light source for 810 nm) and the one proposed by the company "MARKTECH Optoelectronics" with the reference MTE1300NN1-WRC (light source for 1300 nm).

[0087] As shown in Figure 1 the light sources (11; 21) and the light sensors (12; 22) of each transceiver assembly (10; 20) are arranged on both sides of the fluid circulation area, which forms the detection area of the transceiver assembly (10; 20), of the tubular portion 2. This arrangement will allow measurements to be made in transmission, that is to say the light beams from each light source (11; 21) are intended to pass through the fluid circulating in the tubular portion 2 before reaching the light sensor (12; 22) of the respective transceiver assembly (10; 20). More specifically, each light beam from the light source (11; 21) passes through a first wall of the tubular portion 2, referred to as the inlet wall 201, then through the fluid circulating in the tubular portion 2, then through a second wall of the tubular portion 2, referred to as the outlet wall 202, opposite the inlet wall 201.

[0088] According to one advantageous embodiment, the light sources (11; 21) of the transceiver assemblies (10; 20) are located on the same side with respect to the tubular portion 2. This allows in particular to facilitate the installation of the different elements forming the device 1 for determining the hematocrit level, and improves the compactness of the device 1, since similar elements and therefore having the same dimensions are placed on the same side.

[0089] Advantageously, each transceiver assembly (10; 20) further comprises a collimation system (13; 23) provided for collimating the light beams emitted from the corresponding light source (11; 21) in the direction of the associated light sensor (12; 22).

[0090] More specifically, such collimation system (13; 23) is configured for collimating the light beams from the light source (11; 21) to infinity in the direction of the tubular portion 2.

[0091] When the light beams from the light source (11; 21) pass through the tubular portion 2 in which the fluid circulates, the optical path of these light beams is adjusted by passing through the inlet wall 201 of the tubular portion 2, through the fluid circulating in the tubular portion 2, then through the outlet wall 202 of the tubular portion 2. The fact of collimating the light beams from the light source (11; 21) to infinity allows to converge in the direction of the light sensor (12; 22) of the transceiver assembly (10; 20), whatever the shape of the tubular portion, especially if the tubular portion 2 is not deformed to a circular section or if the tubular portion 2 is deformed to an elliptical section.

[0092] Each collimation system (13; 23), or at least one of the two, can for example comprise an upstream lens assembly (131; 231) having a focal plane and positioned between the light source (11; 21) and the light sensor (12; 22) on the side of the light source (11; 21) relative to the tubular portion 2. Such upstream lens assembly (131; 231) can consist of a single lens having a single focal plane, or of a plurality of lenses whose components allow to define a global focal plane.

[0093] According to one exemplary embodiment, the light source (11; 21) can be located at about 10 mm from the focal plane of the upstream lens assembly, and preferably in the focal plane of the upstream lens assembly.

[0094] In addition, each collimation system (13; 23), or at least one of the two, can comprise a downstream lens assembly having a focal plane and positioned between the light source (11; 21) and the light sensor (12; 22) on the side of the light sensor (12; 22) relative to the tubular portion 2. Such downstream lens assembly can consist of a single lens having a single focal plane, or of a plurality of lenses whose components allow to define a global focal plane.

[0095] According to one exemplary embodiment, the light source (11; 21) can be located at about 10 mm from the focal plane of the upstream lens assembly, and preferably in the focal plane of the upstream lens assembly. Figure 2In one example embodiment, the light sensor (12; 22) can be positioned, for example, at a distance of about 10 mm from the focal plane of the downstream lens group(s) (132; 232) and preferably in the focal plane of the downstream lens group(s) (132; 232). Thus, when the light beams leaving the outlet wall 202 of the tubular portion 2 are substantially collimated to infinity, the downstream lens group(s) allow converging these light beams on the corresponding light sensor (12; 22).

[0096] According to another example embodiment, the downstream lens group(s) are positioned so that the light beams leaving the outlet wall 202 of the tubular portion 2 are converging at a distance of about 10 mm from the focal plane of the downstream lens group(s) and preferably in the focal plane of the downstream lens group(s). Thus, the downstream lens group(s) allow collimating the light beams to infinity in the direction of the corresponding light sensor (12; 22).

[0097] It should be noted that the upstream lens assembly (s) and / or the downstream lens group(s) can be mounted in the device 1 so as to be able to translate along the overall optical axis, for example in an automated manner, so as to be able to change their positioning according to the dimensions and deformations of the tubular portion 2 in which the hematocrit level of the fluid to be determined circulates.

[0098] Furthermore, as Figure 3 indicated, each collimation system (13; 23), or at least one of the two, can comprise an upstream diaphragm (133; 233) positioned between the corresponding light source (11; 21) and the light sensor (12; 22) on the side of the light source (11; 21) with respect to the tubular portion 2. Such an upstream diaphragm (133; 233) is configured and arranged in the device 1 so as to pass the central portion of the light beam emitted by the light source (11; 21) in the direction of the light sensor (12; 22) and to stop the peripheral portion of the light beam emitted by the light source (11; 21).

[0099] Additionally or alternatively, as Figure 3 indicated, each collimation system (13; 23), or at least one of the two, can comprise a downstream diaphragm (134; 234) positioned between the corresponding light source (11; 21) and the light sensor (12; 22) on the side of the light sensor (12; 22) with respect to the tubular portion 2. Such a downstream diaphragm (134; 234) is configured and arranged in the device 1 so as to pass the central portion of the light beam transmitted through the tubular portion 2 in the direction of the light sensor (12; 22) and to stop the peripheral portion of the light beam transmitted through the tubular portion 2.

[0100] The use of an upstream diaphragm (133; 233) and / or a downstream diaphragm (134; 234) is particularly advantageous as it allows to eliminate light beams that interfere with the reception of the light sensor (12; 22) and thus with the measurement of the device 1. Such diaphragms allow for example to reduce the noise caused by light beams reflected, diffracted or scattered by the tubular portion 2. Indeed, the upstream diaphragm (133; 233) allows to select the light beams emitted from the light source (11; 21) and to concentrate them on the tubular portion 2 in order to minimize their scattering and reflection. The downstream diaphragm (134; 234) itself allows to further refine the signal received by the light sensor (12; 22) as it only allows the passage of the central light beams transmitted by the tubular portion 2, while cutting off parasitic light beams such as those reflected, diffracted or scattered by the tubular portion 2. Another advantage of the use of the diaphragm(s) is that it allows to increase the reception level of the light sensor (12; 22) without having to increase the power of the light source (11; 21), which allows to increase the service life of the components of the device 1. It should be noted that the use of a diaphragm, in particular an upstream diaphragm, will be all the more preferred as the emission cone of the light source (11; 21) will be narrowed, that is to say the angle (ai; a2) of the emission cone of the light source (11; 21) will be smaller, so that the light beams from the light source (11; 21) are concentrated by cutting off only parasitic peripheral light beams.

[0101] Additionally or alternatively, as illustrated in Figure 4 each collimation system (13; 23) or at least one of the two can comprise an upstream filter (135; 235) positioned between the respective light source (11; 21) and the light sensor (12; 22) on the side of the light sensor (12; 22) with respect to the tubular portion 2. Such a downstream filter (136; 236) of the collimation system (13; 23) of the transceiver assembly (10; 20) is arranged to filter at least the emission wavelength of the light source (11; 21) of the other transceiver assembly (10; 20). Preferably, the downstream filter (136; 236) of the collimation system (13; 23) of the transceiver assembly (10; 20) is arranged to block all light beams that are not in the active wavelength, that is to say the emission wavelength of the respective light source (11; 21).

[0102] The use of an upstream filter (135; 235) and / or a downstream filter (136; 236) is particularly advantageous as it allows to limit the light beams received by a particular light sensor (12; 22) to the only light beams from the respective light source (11; 21), while avoiding the interference of parasitic light beams from another light source (11; 21) or from ambient light.

[0103] As mentioned above, the emission cone of the light source (11; 21), preferably defined by the angle (al; a2), is as narrow as possible so that the intensity of the light beam centered on the tubular portion 2 is as high as possible without having to use too high an emission power for the light source (11; 21), thereby not reducing the useful life of the elements forming the device 1.

[0104] Therefore, the angle (al; a2) of the emission cone of the light source (11; 21) is preferably between 1° and 25°, preferably between 5° and 20°, more preferably between 10° and 15°. It should be noted that the angle (al; a2) of the emission cone can depend on the emission wavelength used for the light source (11; 21).

[0105] For a light source (11; 21) emitting at a wavelength close to 810 nm, the angle (al; a2) of the emission cone can be for example around 13° (± 1°).

[0106] For a light source (11; 21) emitting at a wavelength close to 1,300 nm, the angle (al; a2) of the emission cone can be for example around 15° (± 1°).

[0107] As mentioned above, the device 1 proposed for determining the hematocrit level is configured to be positioned around an existing tubular portion, such as a flexible tube or pipe used in a hemorrhagic fluid treatment system, so as to allow the hematocrit level to be determined in a non-invasive manner.

[0108] To this end, the device 1 comprises a support assembly 30 on which the elements forming the device 1, in particular the transceiver assembly (10; 20), are mounted. As mentioned above, the support assembly 30 is preferably configured to be positioned around the tubular portion.

[0109] Such a support assembly 30 can for example comprise a single support 31 having a recess 32 for accommodating the tubular portion 2, as illustrated in Figures 1 to 6 The light source (11; 21) and the light sensor (12; 22) are then arranged on the support 31 on both sides of the recess 32.

[0110] The support assembly can also comprise a cover 33 arranged to at least partially cover the recess 32 of the support 31. Such a cover 33 is provided in order to prevent the tubular portion 2 inserted in the recess 32 from retracting, thus having a locking function.

[0111] According to an advantageous embodiment, the cover 33 comprises a compression portion 331 for compressing the tubular portion 2 positioned in the recess 32. This compression portion 331 is suitable for at least holding the tubular portion 2 in place in the recess 32 of the support 31 of the device 1.

[0112] According toFigure 6 In the illustrated embodiment, the support assembly 30 comprises a housing 34 for covering the support 30, in particular for protecting the elements of the device 1. Such a housing 34 forms the outer shell of the device 1.

[0113] Such a cover 33 can be mounted in a hinged manner for example with respect to the support 31. The cover 33 is assembled in a hinged manner for example on the housing 34 and is arranged facing the recess 32 of the support 31.

[0114] Preferably, the cover 33 and / or the housing 34 have an outer surface for protecting the transceiver assembly (10; 20) from external disturbances, in particular disturbances of ambient light.

[0115] The cover 33 and / or the housing 34 also preferably have a reflection of the light rays not directed towards the light sensor (12; 22) due to the light source (11; 21), such as all scattered, diffracted, reflected light rays. Preferably, the outer surface of the cover 33 and / or the housing 34 is provided to absorb these light rays.

[0116] The cover 33 and / or the housing 34 can be formed for example from a completely opaque material.

[0117] Furthermore, the cover 33 and / or the housing 34 are preferably provided to guarantee the sealing, in particular the fluidic sealing, of the device 1, in order to protect all the sensitive elements of the device 1, in particular the electronic components.

[0118] The fact that the device 1 has a single support 31 allows precise mounting and holding in place of the elements forming the transceiver assembly (10; 20). Such an embodiment is particularly advantageous because it in particular allows the best optical conditions as close as possible to the light beam, in particular with respect to its centring with respect to the tubular portion 2.

[0119] Each element forming the transceiver assembly (10; 20) can be mounted individually on the support 31 in order to form the device 1. The uniqueness of the support 31 allows holding the elements in place with respect to each other, but such a mounting can be very difficult. In order to facilitate the mounting of the elements forming the transceiver assembly (10; 20) while guaranteeing a precise positioning, it is proposed to use mounting shafts (311; 321; 312; 322) in which the elements forming the transceiver assembly (10; 20) are pre-mounted, these mounting shafts (311; 321; 312; 322) being subsequently inserted into mounting cavities provided in the support 31, these mounting cavities having a shape complementary to the mounting shafts (311; 321; 312; 322), allowing for example a forced insertion of the mounting shafts (311; 321; 312; 322) into these mounting cavities.

[0120] Each mounting shaft (311; 321; 312; 322) has one or more cavities for receiving elements forming the transceiver assembly (10; 20), each cavity being sized to receive a specific element to be positioned.

[0121] Figure 7 Indicates the use of forming a basis Figure 1 The exemplary embodiment of the collimation system (13; 23) of the example device 1 includes mounting shafts (311; 312) and a light source (11; 21). Each mounting shaft (311; 312) has a substantially elongated, preferably cylindrical shape and includes a plurality of cavities (3111, 3112, 3113, 3114; 3121, 3122, 3123, 3124) connected to each other to form a through hole through the mounting shaft (311; 312). Preferably, two adjacent cavities (3111, 3112, 3113, 3114; 3121, 3122, 3123, 3124) are segments of different sizes and / or shapes, such that the cooperation of the adjacent cavities (3111, 3112, 3113, 3114; 3121, 3122, 3123, 3124) allows for the formation of a space for receiving elements forming the collimation system (13; 23) or the light source (11; 21). The cavities (3111, 3112, 3113, 3114; 3121, 3122, 3123, 3124) are thus formed in the mounting shaft (311; 312) to allow for precise positioning of elements forming the transceiver assembly (10; 20).

[0122] according to Figure 7 In the embodiment shown, the collimation system (13; 23) includes a lens (131; 231) that can be inserted into the end cavity (3114; 3214) and abut against the shoulder formed by the adjacent cavity (3113; 3213).

[0123] The cavity (3113; 3213) adjacent to the lens (131; 231) has a length corresponding to the desired distance between the lens (131; 231) and the corresponding light source (11; 21). Preferably, this length is chosen such that the light source (11; 21) is located within the focal plane of the lens (131; 231). The cavity (3113; 3213) thus has a remote holding function.

[0124] A portion of the light source (11 ; 21 ) is intended to be inserted from the other end cavity (3111 ; 3211 ) into an adjacent cavity (3112; 3212) which is also adjacent to the remote holding cavity (3113; 3213). The light source (11 ; 21 ) can for example comprise a protrusion which abuts against a shoulder formed between the cavity (3112; 3212) for receiving the light source (11 ; 21 ) and the end cavity (3111 ; 3211 ).

[0125] Once the lens (131 ; 231 ) is pre-assembled in the mounting shaft (311 ; 312), this mounting shaft (311 ; 312) can be inserted into a mounting cavity provided for this purpose in the support 30. Figure 8 The case is shown in which the mounting shafts (311 ; 321 ; 312; 322) are inserted into mounting cavities provided for this purpose in the support 31.

[0126] According to Figure 8 According to the example shown, once the mounting shafts (311 ; 321 ; 312; 322) have been inserted into the support 30, the light source (11 ; 21 ) and the light sensor (12; 22) are assembled in the cavities arranged in the mounting shafts (311 ; 321 ; 312; 322). However, it can be provided that the light source (11 ; 21 ) and the light sensor (12; 22) are pre-assembled in the cavities arranged in the mounting shafts (311 ; 321 ; 312; 322) before the mounting shafts (311 ; 321 ; 312; 322) are inserted into the support 31.

[0127] According to an alternative arrangement (not shown), the support assembly 30 comprises two supports intended to be assembled to each other by surrounding the tubular portion 2.

[0128] It can thus be provided that an upstream support is arranged with the light sources (11 ; 21 ) and all the elements of the transceiver assembly (10; 20) arranged on it, provided to be positioned on one side of the respective light source (11 ; 21 ) with respect to the tubular portion 2.

[0129] It is also provided a downstream support, different from the upstream support, arranged with the light sensors (12; 22) and all the elements of the transceiver assembly (10; 20) arranged on it, provided to be positioned on one side of the respective light sensor (12; 22) with respect to the tubular portion 2.

[0130] Preferably, the downstream support and the upstream support have a complementary shape provided to be coupled so as to surround the tubular portion 2.

[0131] One important feature of the proposed device 1 is that the flow of the fluid circulating in the tubular portion 2 is not or hardly modified, so as not to negatively affect this fluid. For example, for a hemorrhagic fluid such as blood, an excessive adjustment of the flow, for example due to a significant constriction of the tubular portion 2 at the detection area of the device 1, can generate hemolysis, which is to be avoided for an effective treatment of the hemorrhagic fluid. In particular, it is not desirable that the tubular portion 2 at the detection area flattens, so that the inlet wall 201 and the outlet wall 202 are substantially parallel to each other, because this would generate too much hemolysis for the treatment of the hemorrhagic fluid. Therefore, the transceiver assembly (10; 20) is preferably arranged in the device 1 for measuring the transmission through the curved walls, that is to say the arcuate walls, of the tubular portion 2.

[0132] The simplest way to avoid the risk of hemolysis is not to deform the tubular portion 2. However, the high curvature of the circular section of the tubular portion 2 can interfere with the transmission of the light beam from the light source (11; 21) to the light sensor (12; 22). Therefore, it is conceivable to slightly deform the tubular portion 2 in a monitoring manner, for example with a compression rate of around 2%, so as not to interfere or hardly interfere with the fluid flow in the tubular portion 2, while reducing the curvature of the tubular portion 2 in order to reduce their influence on the orientation of the light beam passing through the tubular portion 2, thus improving the measurement accuracy of the device 1. It should be noted here that the particular arrangement of the device 1, in particular the collimation system (13; 23) used in the transceiver assembly (10; 20), makes it possible to carry out a reliable detection, which includes when the tubular portion 2 has a certain curvature at the detection area. This is why it is not necessary to flatten the tubular portion 2 at this detection area.

[0133] Preferably, the proposed device and method are provided for determining the hematocrit level and / or the hemoglobin level of the circulating fluid without deforming the tubular portion.

[0134] However, regardless of the support assembly 30 for the device 1, a system for deforming the tubular portion 2 positioned facing the transceiver assembly (10; 20) can be provided.

[0135] Preferably, the tubular portion on which the transmission measurement is carried out retains a certain curvature, so as not to flatten.

[0136] According to one preferred embodiment, a deformation system is provided to deform the circular section of the tubular portion into an elliptical section. Thus, the deformation system can for example take advantage of the cooperation of the cover 33, more particularly of the compression portion 331 with the shape of the recess 32. The recess 32 can in fact have a substantially elliptical section, and the compression portion 331 is arranged to compress the tubular portion 2 so that it deforms and substantially matches the shape of the recess 32.

[0137] The elliptical section of the deformed tubular portion 2 is defined by a major axis 2a and a minor axis 2b perpendicular to the major axis. Preferably, the deformation is such that the light sources (11; 21) and all the elements of the transceiver assembly (10; 20) arranged on one side of the respective light source (11; 21) with respect to the tubular portion 2 are positioned on one side of the major axis 2a, and the light sensors (12; 22) and all the elements of the transceiver assembly (10; 20) arranged on one side of the respective light sensor (12; 22) with respect to the tubular portion 2 are positioned on the other side of the major axis 2a.

[0138] The elliptical section of the deformed tubular portion 2 is further defined by a long radius (Ra) along the major axis 2a and a short radius (Rb) along the minor axis 2b, the length of the short radius (Rb) of the elliptical section in the deformed state of the tubular portion being comprised between 30% and 70%, preferably around 50%, of the radius of the circular section of the tubular portion 2 in the undeformed state.

[0139] The transceiver assembly (10; 20) is arranged to be coupled to a central processing unit, not only to enable it to be driven in emission and reception, but also to enable the information coming from the transceiver assembly (10; 20) to be processed.

[0140] The device 1 can for example comprise a monitoring system connected to the central processing unit and configured to control the light sources (11; 21) of the transceiver assembly (10; 20).

[0141] The device 1 can also comprise a processing system connected to the central processing unit and configured to recover and process the signals from the light sensors (12; 22) of the transceiver assembly (10; 20), in particular in order to determine the hematocrit level of the circulating fluid.

[0142] The light sources (11; 21) and the light sensors (12; 22) of the transceiver assembly (10; 20) are therefore preferably connected to an electronic circuit 40 which on the one hand allows the monitoring system to control the light sources (11; 21) and on the other hand allows the processing system to recover the signals received by the light sensors (12; 22).

[0143] According to the example shown in Figure 5 , Figure 7 and Figure 8 , the electronic circuit 40 comprises a first electronic card 41 intended to be connected to the light sources (11; 21) and a second electronic card 42 intended to be connected to the light sensors (12; 22). Each of these first and second electronic cards 41, 42 is preferably coupled to the light sources (11; 21) and the light sensors (12; 22), respectively, after being mounted in the support 31.

[0144] According to this embodiment, the electronic circuit 40 also comprises a third electronic card 43 connecting the first electronic card 41 and the second electronic card 42. This third electronic card 43 can also form a wall of the device 1, this wall forming, with the housing 34, the external casing of the device 1.

[0145] It can be envisaged that the monitoring light sources (11; 21) are such that they emit alternately with each other, especially in order to reduce possible interference between the two transceiver assemblies (10; 20). However, the particular configuration of the proposed device 1 allows not to need such an emission alternation, since other solutions are provided to avoid such interference between the transceiver assemblies (10; 20).

[0146] Thus, the monitoring system is preferably configured so that the light sources (11; 21) emit simultaneously, that is to say, concomitantly. This allows, for example, to have continuous measurement values, which allows to detect as close as possible to real time and continuously. This also allows to increase the reliability of the detection, since it is possible to associate the detections of the two light sensors (12; 22) at the same time t, and not one at time t and the other at time t+n. The association is further simplified. Thus, the monitoring system of the device 1 can comprise means for synchronizing the light sources (11; 21), the monitoring system thus being configured to synchronize with the emission of the light sources (11; 21).

[0147] As will be seen in detail hereafter, it can be advantageous to adjust the emission power of the light sources (11; 21) in the course of determining the hematocrit level of the circulating fluid in the tubular portion 2. To this end, the monitoring system can thus comprise means for adjusting the power emitted by the light sources (11; 21), the monitoring system thus being configured to adjust the power emitted by the light sources (11; 21). This adjustment of the emission power of the light sources (11; 21) can for example depend on the value of the hematocrit level detected for the fluid circulating in the tubular portion 2.

[0148] Operation of the device for determining the hematocrit level of a circulating fluid

[0149] The light signals received by the light sensors (12; 22) of the transceiver assemblies (10; 20) are intended to be processed by the processing system in order to determine the hematocrit level of the fluid circulating in the tubular portion around which the device 1 is positioned.

[0150] Thus, the device 1 for determining the hematocrit level of a circulating fluid operates according to the following steps:

[0151] - emitting a light beam in the direction of the tubular portion using a light source, wherein the light source is configured to emit the light beam according to an emission wavelength chosen to correspond to an isosbestic point of hemoglobin;

[0152] - receiving the optical signal transmitted through the tubular portion and the fluid circulating, wherein the optical sensors are associated with the light sources, respectively;

[0153] - determining the hematocrit level measured for the fluid by processing the optical signal received by the sensors, in particular by a calculation performed by the processing system.

[0154] There are different correlation calculation methods to determine the hematocrit level from the optical signal from the light source (11; 21) which emits according to an emission wavelength chosen to correspond to an isosbestic point of hemoglobin.

[0155] For example, the formula proposed in the article by SHOTAEKUNI and YOSHIYUKI SANKAI entitled "Noninvasive and Continuous Hematocrit Measurement by Optical Method without Calibration" published in "Electronics and Communications in Japan, Vol. 99, No. 9, 2016" can be used.

[0156] According to this method, the hematocrit level is calculated as follows: the concentration of an optical absorbing substance and the intensity of the transmitted light through this substance are known to have a logarithmic relationship. This method applies the scatterometry by integrating two transceiver assemblies (10; 20) operating at wavelengths λ1 and λ2 and allows to determine the value of the variable D pw according to the following formula:

[0157]

[0158] - where ΔI is the difference in intensity of the transmitted light between the two receivers;

[0159] - where [log 10 (I / (I–ΔI) λ1 ] and [log 10 (I / (I–ΔI) λ2 ] are the differences in intensity of the scattered light at wavelengths λ1 and λ2.

[0160] The value D pw obtained is a linear function of the hematocrit level.

[0161] The application of this formula to a device for determining the hematocrit level operating in transmission allows to determine the value D pw according to for example the following formula:

[0162]

[0163] - wherein I0is a blank value recorded during the calibration of the transceiver assembly (10; 20) at the wavelengths λ1and λ2;

[0164] - wherein [Log 10 I] is the logarithm of the intensity of the transmitted light at the wavelengths λ1and λ2.

[0165] The obtained value D pw is also a linear function of the hematocrit level.

[0166] It has been observed that the determination of the hematocrit level by these calculation methods can vary and sometimes be unreliable depending on the hematocrit level of the circulating fluid. In particular, situations of possible distortion of the calculation for low hematocrit levels (typically below 20%) and / or high hematocrit levels (typically above 50%) have been detected.

[0167] However, it can be necessary to have a device 1 for determining the hematocrit level that reliably operates for a wider range of hematocrit levels, which is particularly advantageous for example when the device 1 is used in a hemorrhagic fluid treatment assembly in which the hemorrhagic fluid to be treated generally has a low hematocrit level (typically below 20% or even below 10%) before starting the treatment, while the target hematocrit level to be reached by the hemorrhagic fluid to be treated is higher, for example at least 35%, even at least 45% and sometimes at least 50%.

[0168] In order to make the determination of the hematocrit level more reliable, regardless of the value of this hematocrit level, it is proposed to be able to adjust the emission power of at least one of the light sources (11; 21) of the transceiver assembly (10; 20) during the measurement of the hematocrit level as a function of the hematocrit level calculated for the fluid.

[0169] Preferably, the monitoring system is set to adjust the emission power of all the light sources (11; 21) of the transceiver assembly (10; 20) during the measurement of the hematocrit level as a function of the hematocrit level calculated for the fluid.

[0170] Advantageously, the emission power of the light sources (11; 21) is monitored independently for each light source (11; 21). This independent monitoring is particularly advantageous when the light sources (11; 21) are different, in particular when the emission wavelengths are different.

[0171] It should first be noted that it is advantageous not to use light sources (11; 21) at 100% capacity. Indeed, the light sources (11; 21) are preferably used with an emission power lower than the maximum power of the light sources (11; 21), on the one hand to increase the lifetime of the device 1, but also to avoid possible degradation of the elements of the device 1 or for example heating of the circulating fluid to be analyzed.

[0172] Increasing the sensitivity of the device 1 regardless of the value of the hematocrit level of the circulating fluid, and without adjusting the parameters of the optical sensor (12; 22), is also advantageous to vary the emission power of the light source (11; 21) as a function of the hematocrit level. In particular, the higher the hematocrit level, the greater the risk that the light signal from the light source (11; 21) is absorbed by the circulating fluid, which can be compensated for by an increase in the emission intensity of the light source (11; 21) for a similar level of the received intensity at the optical sensor (12; 22).

[0173] The emission power of the light source (11; 21) is driven as a function of the detection level of the optical sensor (12; 22) related to the measured hematocrit level.

[0174] In particular, the emission power of the light source (11; 21) can be driven as a function of a non-linear threshold below which the value measured by the optical sensor (12; 22) does not allow the hematocrit level to be calculated with sufficient reliability.

[0175] In particular, it is advantageous to drive the emission power of the light source (11; 21) so that the received signal has a power greater than the non-linear threshold but as close as possible to this non-linear threshold, while having a sufficient level as a function of the measured hematocrit level.

[0176] Alternatively or additionally, the emission power of the light source (11; 21) can be driven as a function of a saturation threshold of the optical sensor (12; 22) beyond which the light signal received at the optical sensor (12; 22) cannot be measured.

[0177] In practice, even if it is possible to use each light source (11; 21) at 100% of its maximum emission power level, it is advantageous to use an emission power of the light source (11; 21) comprised between 10% and 60% of the maximum emission power of said light source.

[0178] The proposed device 1 is provided to allow the determination of a wide range of hematocrit levels, in particular for low hematocrit levels down to 5% or even below 5%, and for high hematocrit levels around 50% or even around 60% or more.

[0179] During the use of the device 1 for determining the hematocrit level of a circulating fluid, it is advantageous to gradually increase the emission power of at least one of the light sources (11; 21), and preferably of all the light sources (11; 21), in particular when the hematocrit level of the fluid increases. Preferably, the emission power of at least one of the light sources (11; 21) is increased from a threshold value of the hematocrit level measured for the fluid.

[0180] When the measured hematocrit level is lower than 30%, the emission power of at least one of the light sources (11; 21), and preferably of all the light sources (11; 21), can for example be set to a value comprised between 10% and 30%, and preferably substantially equal to 20%, of the maximum emission power of the respective light source.

[0181] When the measured hematocrit level is higher than or equal to 30%, the emission power of at least one of the light sources (11; 21), and preferably of all the light sources (11; 21), can for example be set to a value comprised between 30% and 100%, and preferably substantially equal to 50%, of the maximum emission power of the respective light source.

[0182] According to one particular embodiment, the emission power of at least one of the light sources (11; 21), and preferably of all the light sources (11; 21), is adjusted so that:

[0183] - for a value of the hematocrit level measured for the fluid lower than a first threshold, the emission power of said light source is at a first power level;

[0184] - for a value of the hematocrit level measured for the fluid higher than or equal to the first threshold but lower than a second threshold higher than the first threshold, the emission power of said light source is at a second power level; and

[0185] - for a value of the hematocrit level measured for the fluid higher than or equal to the second threshold, the emission power of said light source is at a third power level.

[0186] According to this embodiment, specific examples of monitoring of the light source(s) (11; 21) are as follows:

[0187] - when the measured hematocrit level is lower than 20%, the value of the emission power of the light source is set to a value comprised between 5% and 15%, and preferably equal to 10%, of the maximum emission power of said light source;

[0188] - when the measured hematocrit level is comprised between 20% and 30%, the value of the emission power of the light source is set to a value comprised between 15% and 30%, and preferably equal to 20%, of the maximum emission power of said light source; and

[0189] - when the measured hematocrit level is higher than or equal to 30%, the value of the emission power of the light source is set to a value comprised between 30% and 100%, and preferably equal to 55%, of the maximum emission power of said light source.

[0190] The emission power of the light source can also be adjusted during the measurement of the hematocrit level as a function of the presence or absence of a fluid in the tubular portion 2 and / or the properties of said fluid. In particular, if the tubular portion is absent of fluid, the light source(s) (11; 21) is preferably kept at a minimum or even zero emission level.

[0191] Reference List

[0192] - SHOTAE KUNI and YOSHIYUKI SANKAI, "Noninvasive and Continuous Hematocrit Measurement by Optical Method without Calibration", Electronics and Communications, Japan, Vol. 99, No. 9, 2016.

Claims

1. A device for determining the hematocrit level and / or the hemoglobin level of a fluid circulating in a tubular portion (2), the device comprising: - two transceiver assemblies (10; 20), each transceiver assembly (10; 20) comprising a light source (11; 21) and a light sensor (12; 22), said light source and light sensor being arranged on either side of the tubular portion (2) placed at the fluid circulation area, for performing transmission measurements through the arcuate wall of said tubular portion (2); - the light source (11; 21) of each of said two transceiver assemblies (10; 20) being configured to emit a light beam according to an emission wavelength chosen to correspond to an isosbestic point of hemoglobin; each transceiver assembly (10; 20) further comprising a collimation system (13; 23) for collimating the light beam emitted from the corresponding light source (11; 21) in the direction of the corresponding light sensor (12; 22).

2. The device according to claim 1, comprising a support assembly (30) on which said two transceiver assemblies (10; 20) are mounted, said support assembly (30) being configured to be positioned around said tubular portion (2). the corresponding light source (11; 21) of said two transceiver assemblies (10; 20) being configured to emit a light beam at two different emission wavelengths. at least one of the light sources (11; 21) of said transceiver assemblies (10; 20) being configured to emit a light beam according to an emission wavelength chosen for absorbing substantially the same light beam in water or in plasma.

3. The apparatus of any one of claims 1 and 2, wherein, at least one collimation system (13; 23) comprises one or more upstream lens assemblies (131; 231) having a focal plane and positioned between the corresponding light source (11; 21) and the light sensor (12; 22) on the side of said light source (11; 21) with respect to said tubular portion (2), said light source (11; 21) being positioned at about 10 mm from the focal plane of said one or more upstream lens assemblies (131; 231).

4. The apparatus of any one of claims 1-2, wherein, said light source (11; 21) is positioned in the focal plane of said one or more upstream lens assemblies (131; 231).

5. The apparatus of any one of claims 1-2, wherein, at least one collimation system (13; 23) comprises one or more downstream lens assemblies (132; 232) having a focal plane and positioned between the corresponding light source (11; 21) and the light sensor (12; 22) on the side of said light sensor (12; 22) with respect to said tubular portion (2), said light sensor (12; 22) being positioned at about 10 mm from the focal plane of said one or more downstream lens assemblies (132; 232).

6. The apparatus of claim 5, wherein, said light sensor (12; 22) is positioned in the focal plane of said one or more downstream lens assemblies (132; 232).

7. The apparatus of any one of claims 1-2, wherein, ​ 8. The apparatus of claim 7, wherein, ​ 9. The apparatus of any one of claims 1-2, wherein, The at least one collimation system (13; 23) comprises one or more downstream lens assemblies (132; 232) having a focal plane and positioned between the respective light source (11; 21) and the light sensor (12; 22) on a side of the light sensor (12; 22) with respect to the tubular portion (2), the one or more downstream lens assemblies (132; 232) being positioned so that the light beam exiting the outlet wall (202) of the tubular portion (2) converges at about 10 mm from the focal plane of the one or more downstream lens assemblies.

10. The apparatus of claim 9, wherein, The one or more downstream lens assemblies (132; 232) are positioned so that the light beam exiting the outlet wall (202) of the tubular portion (2) converges in the focal plane of the one or more downstream lens assemblies (132; 232).

11. The apparatus of any one of claims 1-2, wherein, The at least one collimation system (13; 23) comprises an upstream diaphragm (133; 233) positioned between the respective light source (11; 21) and the light sensor (12; 22) on a side of the light source (11; 21) with respect to the tubular portion (2), the upstream diaphragm (133; 233) being arranged to pass a central portion of the light beam emitted by the light source (11; 21) in the direction of the light sensor (12; 22) and to stop a peripheral portion of the light beam emitted by the light source (11; 21).

12. The apparatus of any one of claims 1-2, wherein, The at least one collimation system (13; 23) comprises a downstream diaphragm (134; 234) positioned between the respective light source (11; 21) and the light sensor (12; 22) on a side of the light sensor (12; 22) with respect to the tubular portion (2), the downstream diaphragm (134; 234) being arranged to pass a central portion of the light beam transmitted through the tubular portion (2) in the direction of the light sensor (12; 22) and to stop a peripheral portion of the light beam transmitted through the tubular portion (2).

13. The apparatus of any one of claims 1-2, wherein, The at least one collimation system (13; 23) comprises an upstream filter (135; 235) positioned between the respective light source (11; 21) and the light sensor (12; 22) on a side of the light source (11; 21) with respect to the tubular portion (2) and / or a downstream filter (136; 236) positioned between the respective light source (11; 21) and the light sensor (12; 22) on a side of the light sensor (12; 22) with respect to the tubular portion (2), the upstream filter (135; 235) and the downstream filter (136; 236) of the collimation system (13; 23) of the transceiver assembly (10; 20) being arranged to filter at least the emission wavelengths of the light source (11; 21) of the other transceiver assembly (10; 20).

14. The device of any one of claims 1 to 2, wherein: - the light source (11; 21) of the first transceiver assembly of the two transceiver assemblies (10; 20) is configured to emit a light beam whose wavelength is comprised between 780 nm and 840 nm; and - the light source (11; 21) of the second transceiver assembly of the two transceiver assemblies (10; 20) is configured to emit a light beam whose wavelength is comprised between 1,270 nm and 1,330 nm.

15. The apparatus of any one of claims 1-2, wherein, The light sources (11; 21) of the transceiver assemblies (10; 20) are positioned on the same side with respect to the tubular portion (2).

16. The device according to any one of claims 1 to 2, further comprising a monitoring system for monitoring the transceiver assemblies (10; 20), said monitoring system comprising means for synchronizing the light sources (11; 21) and / or means for adjusting the power emitted by the light sources (11; 21).

17. The apparatus of any one of claims 1-2, wherein, The transceiver assemblies (10; 20) are assembled on a single support (31) having a recess (32) intended to receive the tubular portion (2).

18. The device according to claim 17, further comprising a cover (33) arranged to at least partially cover the recess (32), said cover (33) comprising a compression portion intended to hold in place the tubular portion (2) positioned in the recess (32).

19. The apparatus of any one of claims 1-2, wherein, The light sources (11; 21) and all the elements of the transceiver assemblies (10; 20) arranged on the side of the respective light source (11; 21) with respect to the tubular portion (2) are assembled on an upstream support, and the light sensors (12; 22) and all the elements of the transceiver assemblies (10; 20) arranged on the side of the respective light sensor (12; 22) with respect to the tubular portion (2) are assembled on a downstream support different from the upstream support, said downstream support and said upstream support having complementary shapes arranged to be coupled to surround the tubular portion (2).

20. The device according to any one of claims 1 to 2, arranged for determining the hematocrit level and / or the hemoglobin level without deforming the tubular portion (2).

21. The device according to any one of claims 1 to 2, comprising a deformation system for deforming the tubular portion (2) facing the transceiver assemblies (10; 20), said deformation system being arranged to deform the circular cross-section of the tubular portion (2) into an elliptical cross-section.

22. The apparatus of claim 21, wherein, The light sources (11; 21) and all the elements of the transceiver assemblies (10; 20) arranged on the side of the respective light source (11; 21) with respect to the tubular portion (2) are positioned on one side of the major axis defining the elliptical cross-section, and the light sensors (12; 22) and all the elements of the transceiver assemblies (10; 20) arranged on the side of the respective light sensor (12; 22) with respect to the tubular portion (2) are positioned on the other side of the major axis defining the elliptical cross-section.

23. The apparatus of claim 22, wherein, Said elliptical section is defined by a long radius (Ra) along said major axis and a short radius (Rb) along a minor axis perpendicular to said major axis, the length of the short radius (Rb) of said elliptical section in the deformed condition of the tubular portion (2) being comprised between 30% and 70% of the radius of the circular section of the tubular portion (2) in the undeformed condition.

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