Device and method for determining hemoglobin or hematocrit levels in a flowing liquid

Abstract

The present invention relates to a device and a method for determining the hematocrit and / or hemoglobin level of a liquid flowing in a tubular portion (2), the method comprising: emitting a light beam in the direction of the tubular portion (2) with at least two light sources (11; 21), each of the two light sources (11; 21) being configured to emit a light beam at an emission wavelength selected to correspond to the isosbestic point of hemoglobin; receiving light signals transmitted through the tubular portion (2) with at least two light sensors (12; 22), each light sensor (12; 22) being associated with one of the two light sources (11; 21); calculating the hematocrit or hemoglobin level in the liquid by processing the light signals received by the light sensors (12; 22); characterized in that, when determining the hematocrit level and / or hemoglobin level, the emission power of at least one light source (11; 21) is adjusted according to the calculated hematocrit and / or corresponding hemoglobin level of the liquid.

Description

Technical Field

[0001] The present disclosure relates to apparatus and methods for determining blood parameters of a circulating fluid, in particular for determining the hemoglobin level and / or the hematocrit level of a circulating fluid. The present disclosure finds a particularly advantageous application in medical applications, such as for analyzing hemorrhagic fluids circulating in tubing. Background Art

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

[0003] A specific and non-limiting example where being able to track the evolution of blood parameters is useful is the treatment of hemorrhagic fluids for autologous transfusion of a patient's blood. Autologous or autotransfusion (i.e., transfusion with the patient's own blood) is increasingly used during surgical procedures because it avoids incompatibilities that can arise during homologous or allogeneic transfusions. In addition, autologous transfusions avoid the spread of infectious diseases.

[0004] For the correct operation of these hemorrhagic fluid treatment systems, it is necessary to be able to track in real time the evolution of the hemoglobin concentration or the hematocrit level in the treated fluid, since the evolution of the blood parameters of this fluid allows the treatment system to be driven. One of the difficulties lies in the fact that the fluid, whose hemoglobin and / or hematocrit level is known, usually circulates in flexible tubing, which complicates the detection. In addition, it is necessary to apply specific detection methods to compensate for the loss of detection sensitivity caused by the movement of the fluid. In addition, since hemorrhagic fluid treatment systems (especially for autologous blood transfusions) are usually used in emergency situations, it is very important to make the entire system ready for immediate use by avoiding as much as possible any preliminary calibration steps (including those regarding allowing the detection of the hemoglobin and / or hematocrit level of the hemorrhagic fluid to be treated).

[0005] In an article titled "Noninvasive and Continuous Hematocrit Measurement by Optical Method without Calibration," published in Japan's Electronics and Communications (Vol. 99, No. 9, 2016), SHOTA EKUNI and YOSHIYUKI SANKAI proposed an optical detection method and system for measuring the hematocrit level of a fluid circulating in a pipe, eliminating the need for prior calibration of the detection system. The proposed optical system consists of two transceiver assemblies operating in backscatter, each mounted on a respective support. The two supports are positioned so as to surround a tubular portion through which the fluid whose hematocrit level is to be measured circulates, while being attached to each other without deforming the tubular portion. The two transceiver assemblies operate alternately at different wavelengths (i.e., 810 nm and 1300 nm) corresponding to the isosbestic point of hemoglobin 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 and therefore 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 of the Invention

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

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

[0008] 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 device can be positioned on the tubular portion in a simple manner without requiring special adjustments to the tubular portion and, if necessary, without stopping 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 (e.g., a hemorrhagic fluid treatment system for autologous blood transfusion) by using pre-existing tubing in the treatment system, without requiring special disassembly of components of the treatment system.

[0009] Another object of the present invention is to provide a device for determining the hemoglobin level and / or the hematocrit level, which device can be used for a fluid circulating in a tubular portion at a high flow rate (generally greater than 1000 ml / min, for example around 2000 ml / min) without significantly disturbing the flow rate of the circulating fluid in order to avoid possible harmful effects on the fluid, for example avoiding hemolysis in the case of circulating hemorrhagic fluids.

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

[0011] For this purpose, 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 transceiver assembly comprising a light source and a light sensor, the light source and the light sensor being arranged on either side of the tubular portion at the fluid circulation area for performing transmission measurements, preferably through the curved wall of the tubular portion;

[0013] The light source of each of the two transceiver assemblies is configured to emit a light beam according to an emission wavelength selected 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 respective light source in the direction of the respective light sensor.

[0015] Also proposed is 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 transceiver assembly comprising a light source and a light sensor, the light source and the light sensor being arranged on either side of the tubular portion at the fluid circulation area for performing transmission measurements, preferably through the curved wall of the tubular portion;

[0017] The light source of each of the two transceiver assemblies is configured to emit a light beam according to an emission wavelength selected 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 based on the optical signal received by the optical sensor of the transceiver assembly; and

[0019] A monitoring system comprising means for adjusting the power emitted by a light source, the monitoring system being programmed to adjust the emitted power of the light source based on a measured hematocrit level and / or hemoglobin level of a fluid.

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

[0021] - the apparatus 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 assembly is configured to emit a light beam according to an emission wavelength selected to be substantially the same as the light beam absorbed in water or plasma;

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

[0025] 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 light sensor being positioned approximately 10 mm from the focal plane of the downstream lens assembly and preferably positioned in the focal plane of the downstream lens assembly;

[0026] at least one (and preferably each) collimating system comprises a downstream lens assembly having a focal plane and being positioned between the respective light source and the light sensor, the downstream lens assembly being positioned on the side of the light sensor with respect to the tubular portion such that the light beam exiting the exit wall of the tubular portion converges at a distance of approximately 10 mm from, and preferably in, the focal plane of the downstream lens assembly;

[0027] at least one (and preferably each) collimation system comprises an upstream aperture positioned between the respective light source and the light sensor, on the side of the light source with respect to the tubular portion, the upstream aperture being arranged to allow a central part of the light beam emitted by the light source to pass in the direction of the light sensor and to block a peripheral part of the light beam emitted by the light source;

[0028] at least one (and preferably each) collimation system comprises a downstream aperture positioned between the respective light source and the light sensor, on the side of the light sensor with respect to the tubular portion, the downstream aperture being arranged to allow a central portion of the light beam transmitted through the tubular portion to pass in the direction of the light sensor and to block a peripheral portion of the light beam transmitted through the tubular portion;

[0029] at least one (and preferably each) collimation system comprises an upstream filter and / or a downstream filter, the upstream filter being positioned between the respective light source and the light sensor, on the light source side relative to the tubular portion, and the downstream filter being positioned between the respective light source and the light sensor, on the light sensor side relative to the tubular portion, the upstream filter and the downstream filter of the collimation system of a 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 the first of the two transceiver assemblies is configured to emit a light beam having a wavelength comprised between 780 nm and 840 nm, preferably between 800 nm and 820 nm, and more preferably equal to 810 nm; and the light source of the second of the two transceiver assemblies is configured to emit a light beam having a wavelength comprised between 1270 nm and 1330 nm, preferably between 1290 nm and 1310 nm, and more preferably equal to 1300 nm;

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

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

[0033] - the transceiver assembly is assembled on a single support having a groove intended to receive the tubular portion;

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

[0035] - all elements of the light source and transceiver assembly that are arranged on the side of the respective light source relative to the tubular portion are assembled on an upstream support, and all elements of the light sensor and transceiver assembly that are arranged on the side of the respective light sensor relative to the tubular portion are assembled on a downstream support separate from the upstream support, the downstream support and the upstream support having complementary shapes configured to be coupled 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 elements of the light source and transceiver assembly that are arranged on the side of the respective light source relative to the tubular portion are positioned on one side of the major axis defining the elliptical cross-section, and all elements of the light sensor and transceiver assembly that are arranged on the side of the respective light sensor relative 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 major radius (Ra) along the major axis and a minor radius (Rb) along the minor axis perpendicular to the major axis, the length of the minor radius (Rb) of the elliptical cross-section being, in the deformed state of the tubular portion, 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] Further proposed is a method for determining the hematocrit level and / or the hemoglobin level of a fluid circulating in a tubular portion, comprising:

[0040] - emitting a light beam in the direction of the tubular portion with at least two light sources, each of the two light sources being configured to emit a light beam according to an emission wavelength selected to correspond to the 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 hemoglobin level of the fluid by processing the light signals received by the light sensor;

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

[0044] Preferred but non-limiting aspects of the method, alone or in combination, are as follows:

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

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

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

[0048] -The method enables:

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

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

[0051] - adjusting the emission power of at least one light source so that:

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

[0053] o for values ​​of the calculated hematocrit level of the fluid that are greater than or equal to a first threshold but less than a second threshold that is greater than the first threshold, the emission power of the light source is at a second power level; and

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

[0055] - adjusting the emission power of at least one light source so that:

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

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

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

[0059] - during the determination of the hematocrit level and / or the hemoglobin level, adjusting the emission power of the light source as a function of the presence or absence of a fluid in the tubular portion and / or as a function of the properties of said fluid;

[0060] - A monitoring light source is provided to concomitantly emit a light beam. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Other features and advantages of the present invention will appear from the following description, which is intended to be illustrative and not restrictive, and should be read in conjunction with the accompanying drawings, in which:

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

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

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

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

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

[0067] - Figure 6 is a perspective view of a proposed apparatus for determining the hematocrit level and / or hemoglobin level of a circulating fluid.

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

[0069] - Figure 8 The installation of a mounting shaft is shown, which is provided for assembly of the transceiver assembly on the support. DETAILED DESCRIPTION

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

[0071] Device for determining the hematocrit level of circulating fluids

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

[0073] The proposed device 1 for determining the hematocrit level can be used to determine the hematocrit level of any type of fluid, but it is particularly suitable for determining the hematocrit level of hemorrhagic fluids, such as human blood, circulating in tubing, such as flexible tubing used in a standard manner in a hospital environment.

[0074] As will be described in detail below, the proposed device 1 allows the hematocrit level of a fluid to be determined in a non-invasive manner, that is to say without requiring intervention in the fluid, which can therefore continue to circulate freely in the tubing.

[0075] The proposed device 1 comprises at least two transceiver assemblies (10; 20), each transceiver assembly (10; 20) comprising a light source (11; 21) and a light sensor (12; 22). The two transceiver assemblies (10; 20) are used to determine the hematocrit level of a fluid circulating in a tube, the light beam passing through the fluid to be analyzed being used to calculate the hematocrit level of the fluid. The fact of having two transceiver assemblies (10; 20) allows the reliability of the device 1 to be increased, since the measured values ​​of the two light sensors (12; 22) can be correlated with each other. Furthermore, this allows for redundancy, which can be advantageous in the event of a failure of one of the two transceiver assemblies (10; 20).

[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 to correspond to the isosbestic point of hemoglobin. It will be understood that the isosbestic point corresponds to a wavelength value at which the total absorbance of the sample remains constant during a chemical reaction or a possible change of state of the sample. More specifically, the isosbestic point is a wavelength (λ iso ), at which the total absorbance of the chromophore remains constant, regardless of its state. At this precise point, multiple chromophores have the same molar extinction coefficient (α(λ iso )).

[0077] Hemoglobin has multiple isosbestic points.

[0078] For example, oxyhemoglobin and deoxyhemoglobin have isosbestic points at wavelengths around 550 nm, 570 nm, and 810 nm. iso ) can obtain measurements related to the total volume of hemoglobin because the absorption of light at this wavelength is independent of the oxidized or reduced state of hemoglobin.

[0079] Furthermore, a wavelength near 1300 nm corresponds to another isosbestic point of hemoglobin.

[0080] Wavelengths above 1400 nm are also generally isosbestic wavelengths for hemoglobin, particularly wavelengths between 1400 nm and 2200 nm. One advantage of these specific wavelengths is that the absorption of light at these wavelengths is essentially the same in water and in plasma. Therefore, the hematocrit level measured at these wavelengths will be the same regardless of the matrix carrying the red blood cells, whether that matrix is ​​primarily composed of plasma or primarily composed of water. This is particularly true for wavelengths between 1,400 nm and 1,700 nm and between 1,900 nm and 2,200 nm. Therefore, these wavelengths are particularly advantageous when the hemorrhagic fluid whose hematocrit level is to be measured is more or less strongly diluted with an aqueous solution (e.g., saline solution).

[0081] Thus, one of the light sources (11; 21) of the transceiver assembly (10; 20) may for example be configured to emit a light beam having a wavelength comprised between 780 nm and 840 nm, preferably between 800 nm and 820 nm, and more preferably equal to 810 nm.

[0082] One of the light sources (11; 21) of the transceiver assembly (10; 20) can, for example, be configured to emit a light beam having a wavelength comprised between 1,270 nm and 1,330 nm, preferably between 1,290 nm and 1,310 nm, and more preferably equal to 1,300 nm.

[0083] One of the light sources (11; 21) of the transceiver assembly (10; 20) can, for example, be configured to emit a light beam having a wavelength comprised between 1,450 nm and 1,550 nm, preferably between 1,490 nm and 1,510 nm, and more preferably equal to 1,500 nm.

[0084] One of the light sources (11; 21) of the transceiver assembly (10; 20) can, for example, be configured to emit a light beam having a wavelength comprised between 530 nm and 620 nm, preferably a wavelength comprised between 550 nm and 600 nm, and more preferably a wavelength 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 aforementioned advantages due to the functional redundancy of the two transceiver assemblies (10; 20), the use of two light sources operating at different wavelengths allows for better correlation of the measured values ​​and thus calculation of the hematocrit level of the fluid circulating in the tubular portion 2.

[0086] According to a specific example, one of the light sources (11; 21) of the transceiver assembly (10; 20) is configured to emit a light beam having a wavelength comprised between 780 nm and 840 nm, preferably between 800 nm and 820 nm, and more preferably 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 between 1290 nm and 1310 nm, and more preferably equal to 1300 nm. For example, light emitting diodes (LEDs) can be used, such as the LED810L proposed by the company "THORLABS" (for 810 nm light sources) and the MTE1300NN1-WRC proposed by the company "MARKTECH Optoelectronics" (for 1300 nm light sources).

[0087] like Figure 1 As shown, the light source (11; 21) and the light sensor (12; 22) of each transceiver assembly (10; 20) are arranged on both sides of the tubular portion 2 at the fluid circulation area, which forms the detection area of ​​the transceiver assembly (10; 20). This arrangement allows measurement in transmission, that is, the light beam from each light source (11; 21) is intended to pass through the fluid circulating in the tubular portion 2 before reaching the light sensor (12; 22) of the corresponding 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 (called the inlet wall 201), then passes through the fluid circulating in the tubular portion 2, and then passes through a second wall of the tubular portion 2 (called the outlet wall 202) opposite the inlet wall 201.

[0088] According to an advantageous embodiment, the light sources (11; 21) of the transceiver assembly (10; 20) are situated on the same side relative to the tubular portion 2. This notably facilitates the mounting 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 elements of the same size, are placed on the same side.

[0089] Advantageously, each transceiver assembly (10; 20) further comprises a collimation system (13; 23) arranged to collimate the light beam emitted from the respective light source (11; 21) in the direction of the associated light sensor (12; 22).

[0090] More specifically, such a collimation system (13; 23) is configured to collimate the light beam coming from the light source (11; 21) infinitely 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 paths of these light beams are adjusted by passing through the inlet wall 201 of the tubular portion 2, through the fluid circulating in the tubular portion 2, and then through the inlet wall 202 of the tubular portion 2. The fact of collimating the light beams from the light source (11; 21) to infinity allows them to be focused in the direction of the light sensor (12; 22) of the transceiver assembly (10; 20) regardless of the shape of the tubular portion, in particular if the tubular portion 2 is not deformed to have a circular cross section or if the tubular portion 2 is deformed to have an elliptical cross section.

[0092] Each collimation system (13; 23) or at least one of the two may, 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 respective light source (11; 21) with respect to the tubular portion 2. Such an upstream lens assembly (131; 231) may consist of a single lens having a single focal plane, or of a plurality of lenses whose assembly allows defining an overall focal plane.

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

[0094] Furthermore, each collimating system (13; 23) or at least one of the two may comprise a downstream lens assembly having a focal plane and 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 lens assembly may consist of a single lens having a single focal plane or of a plurality of lenses whose assembly allows defining an overall focal plane.

[0095] according to Figure 2In an exemplary embodiment shown, the light sensors (12; 22) can be positioned, for example, approximately 10 mm from the focal plane of the downstream lens assembly (132; 232), and preferably in the focal plane of the downstream lens assembly (132; 232). Thus, the downstream lens assembly allows the light beams exiting the outlet wall 202 of the tubular portion 2 to be converged onto the corresponding light sensors (12; 22), while being substantially collimated to infinity.

[0096] According to another exemplary embodiment, the downstream lens assembly is positioned so that the light beam exiting the outlet wall 202 of the tubular portion 2 converges approximately 10 mm from the focal plane of the downstream lens assembly and preferably lies in the focal plane of the downstream lens assembly. Thus, the downstream lens assembly allows the light beam to be collimated to infinity in the direction of the corresponding light sensor (12; 22).

[0097] It should be noted that the upstream lens assembly and / or the downstream lens assembly 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 fluid whose hematocrit level is to be determined circulates.

[0098] In addition, if Figure 3 As shown, each collimation system (13; 23) or at least one of the two may include an upstream aperture (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) relative to the tubular portion 2. Such an upstream aperture (133; 233) is configured and arranged in the device 1 to allow a central portion of the light beam emitted by the light source (11; 21) to pass in the direction of the light sensor (12; 22) and to block a peripheral portion of the light beam emitted by the light source (11; 21).

[0099] Additionally or alternatively, such as Figure 3 As shown, each collimation system (13; 23) or at least one of the two may include a downstream aperture (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) relative to the tubular portion 2. Such a downstream aperture (134; 234) is configured and arranged in the device 1 to allow a central portion of the light beam transmitted through the tubular portion 2 to pass in the direction of the light sensor (12; 22) and to block a peripheral portion of the light beam transmitted through the tubular portion 2.

[0100] The use of an upstream aperture (133; 233) and / or a downstream aperture (134; 234) is particularly advantageous because it allows the elimination of light beams that interfere with the reception of the optical sensor (12; 22) and therefore interfere with the measurement of the device 1. Such apertures allow, for example, the reduction of noise caused by light beams reflected, diffracted, or scattered by the tubular portion 2. In fact, the upstream aperture (133; 233) allows the light beam emitted by the light source (11; 21) to be selected and concentrated on the tubular portion 2, thereby minimizing its scattering and reflection. The downstream aperture (134; 234) itself allows further refinement of the signal received by the optical sensor (12; 22), since it allows only the central light beam transmitted by the tubular portion 2 to pass, while cutting off parasitic light beams, such as those reflected, diffracted, or scattered by the tubular portion 2. Another advantage of using an aperture is that it allows the reception level of the optical sensor (12; 22) to be improved without having to increase the power of the light source (11; 21), which allows the service life of the components of the device 1 to be increased. It should be noted that, compared to narrowing the emission cone of the light source (11; 21), that is, the angle (α1; α2) of the emission cone of the light source (11; 21) will become smaller, it is more preferable to use an aperture (especially an upstream aperture), which allows the main part of the light beam from the light source (11; 21) to be concentrated by cutting only the parasitic peripheral light beams.

[0101] Additionally or alternatively, such as Figure 4 As shown, each collimation system (13; 23) or at least one of the two may include an upstream filter (135; 235) positioned between the corresponding 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. The downstream filter (136; 236) of the collimation system (13; 23) of such a 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 at a valid wavelength, that is, the emission wavelength of the corresponding light source (11; 21).

[0102] The use of an upstream filter (135; 235) and / or a downstream filter (136; 236) is particularly advantageous because it allows limiting the light beam received by a particular light sensor (12; 22) to a unique light beam coming from the corresponding light source (11; 21), while avoiding interference from parasitic light beams coming 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 (α1; α2), is as narrow as possible so that the intensity of the light beam concentrated on the tubular portion 2 is as high as possible, without having to use an excessively high emission power of the light source (11; 21), thereby not reducing the service life of the elements forming the device 1.

[0104] Therefore, the angle (α1; α2) of the emission cone of the light source (11; 21) is preferably comprised between 1° and 25°, preferably between 5° and 20°, more preferably between 10° and 15°. It should be noted that the angle (α1; α2) of the emission cone may depend on the emission wavelength used by the light source (11; 21).

[0105] For a light source (11; 21) emitting a wavelength around 810 nm, the angle (α1; α2) of the emission cone may be, for example, around 13° (±1°).

[0106] For a light source (11; 21) emitting at a wavelength around 1,300 nm, the angle (α1; α2) of the emission cone may be, for example, around 15° (±1°).

[0107] As mentioned above, the proposed device 1 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 handling 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 may, for example, include Figures 1 to 6 A single support 31 is shown, which has a groove 32 for receiving the tubular portion 2. A light source (11; 21) and a light sensor (12; 22) are then arranged on the support 31 on either side of the groove 32.

[0110] The support assembly may further comprise a cover 33 arranged to at least partially cover the groove 32 of the support 31. Such a cover 33 is provided to prevent the tubular portion 2 inserted into the groove 32 from being retracted, 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 groove 32. This compression portion 331 is suitable for keeping at least the tubular portion 2 in position in the groove 32 of the support 31 of the device 1.

[0112] according to Figure 6 In the embodiment shown, the support assembly 30 comprises a casing 34 for covering the support 30 and in particular for protecting the elements of the device 1. Such casing 34 forms the outer housing of the device 1.

[0113] Such a cover 33 can be mounted, for example, in an articulated manner relative to the support 31. The cover 33 is assembled, for example, in an articulated manner 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 interference, in particular interference from ambient light.

[0115] The cover 33 and / or the housing 34 also preferably have an outer surface that prevents reflection of light rays from the light source (11; 21) that are not directed toward the light sensor (12; 22) (e.g., all scattered, diffracted, reflected light rays). Preferably, the outer surface of the cover 33 and / or the housing 34 is configured to absorb such light rays.

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

[0117] Furthermore, the cover 33 and / or the housing 34 are preferably configured to ensure the tightness, in particular the fluid tightness, of the device 1 , thereby protecting all 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 allows obtaining as close as possible to the optimal optical conditions of the light beam, in particular as regards its centering relative to the tubular portion 2.

[0119] Each element forming the transceiver assembly (10; 20) can be individually mounted on a support 31 to form the device 1. The uniqueness of the support 31 allows the elements to be held in position relative to each other, but mounting in this manner can be difficult. In order to facilitate the mounting of the elements forming the transceiver assembly (10; 20) while ensuring precise positioning, it is proposed to use mounting shafts (311; 321; 312; 322), wherein the elements forming the transceiver assembly (10; 20) are pre-mounted and then the mounting shafts (311; 321; 312; 322) are inserted into mounting cavities provided in the support 31, these mounting cavities having a shape complementary to the mounting shafts (311; 321; 312; 322), thereby allowing, for example, the mounting shafts (311; 321; 312; 322) to be forcibly inserted into these mounting cavities.

[0120] One or more cavities for receiving components forming the transceiver assembly (10; 20) are arranged in each mounting shaft (311; 321; 312; 322), each cavity being sized to receive the specific component to be positioned.

[0121] Figure 7 Indicates the use of Figure 1 An exemplary embodiment of an element of a collimation system (13; 23) of an exemplary device 1 and a mounting shaft (311; 312) of a light source (11; 21). Each mounting shaft (311; 312) has a substantially elongated, preferably cylindrical shape and comprises a plurality of cavities (3111, 3112, 3113, 3114; 3121, 3122, 3123, 3124) connected to one another so as to form a through hole passing through the mounting shaft (311; 312). Preferably, two adjacent cavities (3111, 3112, 3113, 3114; 3121, 3122, 3123, 3124) have sections of different sizes and / or shapes, so that the cooperation of the adjacent cavities (3111, 3112, 3113, 3114; 3121, 3122, 3123, 3124) allows the formation of a space for receiving the 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 axis (311; 312), thereby allowing the precise positioning of the elements forming the transceiver assembly (10; 20).

[0122] according to Figure 7 In the embodiment shown, the collimation system (13; 23) comprises a lens (131; 231) which can be inserted into an end cavity (3114; 3214) and abuts against a shoulder formed by an 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, the length is selected so that the light source (11; 21) is located within the focal plane of the lens (131; 231). The cavity (3113; 3213) thus has a distance-keeping function.

[0124] The light source (11; 21) itself is intended to be inserted from the other end cavity (3111; 3211) into an adjacent cavity (3112; 3212), which is also adjacent to the distance-maintaining cavity (3113; 3213). The light source (11; 21) may, for example, include a protrusion that 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) has been pre-mounted in the mounting shaft (311; 312), the mounting shaft (311; 312) can be inserted into a mounting cavity provided for this purpose in the support 30. Figure 8 The insertion of a mounting shaft (311; 321; 312; 322) into a mounting cavity provided for this purpose in the support 31 is shown.

[0126] according to Figure 8 In the example shown, once the mounting shafts (311; 321; 312; 322) have been inserted into the support 30, the light sources (11; 21) and the light sensors (12; 22) are installed in the cavities arranged in the mounting shafts (311; 321; 312; 322). However, it is possible to arrange to pre-install the light sources (11; 21) and the light sensors (12; 22) in the cavities arranged in the mounting shafts (311; 321; 312; 322) before inserting the mounting shafts (311; 321; 312; 322) into the support 31.

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

[0128] Thus, an upstream support can be provided on which are arranged the light sources (11; 21) and all elements of the transceiver assembly (10; 20) arranged on the side of the respective light source (11; 21) relative to the tubular portion 2.

[0129] A downstream support separate from the upstream support is also provided on which are arranged the optical sensors (12; 22) and all elements of the transceiver assembly (10; 20) arranged on the side of the respective optical sensors (12; 22) relative to the tubular portion 2.

[0130] Preferably, the downstream support and the upstream support have complementary shapes arranged to couple so as to surround the tubular portion 2 .

[0131] An important feature of the proposed device 1 is that the flow of the fluid circulating in the tubular portion 2 is not altered or hardly altered, thereby not negatively affecting the fluid. For example, in the case of hemorrhagic fluids (such as blood), excessive changes in the flow, for example due to a significant constriction of the tubular portion 2 at the detection area of ​​the device 1, could lead to hemolysis, which is to be avoided for effective treatment of hemorrhagic fluids. In particular, it is undesirable for the tubular portion 2 at the detection area to be flattened so that the inlet wall 201 and the outlet wall 202 are substantially parallel to each other, as this would lead to excessive hemolysis for the treatment of hemorrhagic fluids. Therefore, the transceiver assembly (10; 20) is preferably arranged in the device 1 for measuring the transmission through the curved wall (that is, the arcuate wall) of the tubular portion 2.

[0132] The simplest way to avoid the risk of hemolysis is to not deform the tubular portion 2. However, the high curvature of the circular cross-section of the tubular portion 2 would 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 controlled manner (for example, with a compression rate of around 2%), so as not to interfere or barely interfere with the flow of the fluid in the tubular portion 2, while reducing the curvature of the tubular portion 2 to reduce the influence of the curvature of the tubular portion on the orientation of the light beam passing through the tubular portion 2, thereby improving the measurement accuracy of the device 1. It should be noted here that the specific arrangement of the device 1, in particular the use of the collimation system (13; 23) in the transceiver assembly (10; 20), allows reliable detection, including when the tubular portion 2 at the detection area has a certain curvature. This is why it is not necessary to flatten the tubular portion 2 at the 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 deformation of the tubular portion.

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

[0135] Preferably, the tubular portion where the transmission measurement is performed maintains a certain curvature and therefore does not flatten out.

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

[0137] The elliptical cross-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 all elements of the light source (11; 21) and the transceiver assembly (10; 20) disposed on one side of the tubular portion 2 corresponding to the light source (11; 21) are positioned on one side of the major axis 2a, and all elements of the light sensor (12; 22) and the transceiver assembly (10; 20) disposed on one side of the tubular portion 2 corresponding to the light sensor (12; 22) are positioned on the other side of the major axis 2a.

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

[0139] The transceiver assembly (10; 20) is arranged to be connected to a central processing unit, not only to enable the transmission and reception thereof to be driven, but also to enable the processing of information from the transceiver assembly (10; 20).

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

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

[0142] Therefore, the light source (11; 21) and the light sensor (12; 22) of the transceiver assembly (10; 20) are preferably connected to an electronic circuit 40 which, on the one hand, allows a monitoring system to control the light source (11; 21) and, on the other hand, allows a processing system to recover the signal received by the light sensor (12; 22).

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

[0144] According to this embodiment, the electronic circuit 40 further comprises a third electronic card 43 connecting the first and second electronic cards (41; 42). This third electronic card 43 can further form a wall of the device 1 which together with the housing 34 forms the outer casing of the device 1.

[0145] It is possible to envisage monitoring light sources (11; 21) such that their emission alternates with one another, in particular in order to reduce possible interference between the two transceiver assemblies (10; 20). However, the specific configuration of the proposed device 1 allows for eliminating the need for such emission alternation, since other solutions are provided to avoid such interference between the transceiver assemblies (10; 20).

[0146] Therefore, the monitoring system is preferably configured so that the light sources (11; 21) emit simultaneously (that is, concomitantly). This allows, for example, to have continuous measurement values, allowing for detection that is as close to real time and continuous as possible. This also allows for increased detection reliability, since it is possible to correlate the detections of two light sensors (12; 22) at the same time t, rather than one at time t and the other at time t+n. This further simplifies correlation. Therefore, the monitoring system of the device 1 can include means for synchronizing the light sources (11; 21), the monitoring system being thus configured to synchronize the emission of the light sources (11; 21).

[0147] As will be seen in detail below, it may be advantageous to adjust the power emitted by the light source (11; 21) during the determination of the hematocrit level of the fluid circulating in the tubular portion 2. For this purpose, the monitoring system may therefore comprise means for adjusting the power emitted by the light source (11; 21), the monitoring system being thus configured to adjust the power emitted by the light source (11; 21). This adjustment of the power emitted by the light source (11; 21) may, for example, be based on the value of the detected hematocrit level of the fluid circulating in the tubular portion 2.

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

[0149] The optical signal received by the optical sensor (12; 22) of the transceiver assembly (10; 20) is intended to be processed by a processing system to determine the hematocrit level of the fluid circulating in the tubular portion around which the device 1 is located.

[0150] Thus, the apparatus 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 with a light source, wherein the light source is configured to emit the light beam according to an emission wavelength selected to correspond to the isosbestic point of hemoglobin;

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

[0153] - Determining a hematocrit level measured for the fluid by processing the optical signals received by the sensor, in particular by calculations performed by a processing system.

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

[0155] For example, a formula proposed in an article titled “Noninvasive and Continuous Hematocrit Measurement by Optical Method without Calibration” published by SHOTA EKUNI and YOSHIYUKI SANKAI in Japan’s Electronics and Communications (Vol. 99, No. 9, 2016) can be used.

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

[0157]

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

[0159] - Among them, [log 10 (I / (I–ΔI) λ1 ] and [log 10 (I / (I–ΔI) λ2 ] is the difference in the intensity of scattered light at wavelengths λ1 and λ2.

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

[0161] Applying this formula to a device operating in transillumination for determining the hematocrit level allows the value D to be determined, for example, according to the following formula pw :

[0162]

[0163] -wherein I0 is the blank value recorded during calibration of the transceiver assembly (10; 20) at wavelengths λ1 and λ2;

[0164] - Among them, [Log 10 I] is the logarithm of the intensity of the transmitted light of wavelengths λ1 and λ2.

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

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

[0167] However, it may be necessary to have an apparatus 1 for determining the hematocrit level that operates reliably for a wide range of hematocrit levels, which is particularly advantageous when the apparatus 1 is used, for example, in a hemorrhagic fluid treatment assembly, in which case the hemorrhagic fluid to be treated typically has a low hematocrit level before treatment begins (typically below 20% or even below 10%), while the target hematocrit level that the hemorrhagic fluid after treatment is to reach is high, 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 transmission power of at least one light source (11; 21) of a transceiver assembly (10; 20) according to the calculated hematocrit level of the fluid during the measurement of the hematocrit level.

[0169] Preferably, the monitoring system is arranged to adjust the transmission power of all light sources (11; 21) of the transceiver assembly (10; 20) according to the calculated hematocrit level of the fluid during measurement of the hematocrit level.

[0170] Advantageously, the emission power of each light source (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] First of all, it should be noted that it is not always possible to use the light source (11; 21) at 100% of its capacity. In fact, it is preferable to use the light source (11; 21) at an emission power lower than its maximum power, on the one hand to increase the life of the device 1, while also avoiding possible degradation of the components of the device 1 or, for example, heating of the circulating fluid to be analyzed.

[0172] In order to increase the sensitivity of the device 1 regardless of the value of the hematocrit level of the circulating fluid and without having to adjust the parameters of the light sensor (12; 22), it is further advantageous to vary the emission power of the light source (11; 21) according to the hematocrit level. In particular, the higher the hematocrit level, the greater the risk that the light signal from the light source (11; 21) will be absorbed by the circulating fluid, which can be compensated by increasing the emission intensity of the light source (11; 21) so that the received intensity level at the light sensor (12; 22) is similar.

[0173] Thus, the emission power of the light source (11; 21) is driven according to the detection level of the light sensor (12; 22) associated with the measured hematocrit level.

[0174] In particular, the emission power of the light source (11; 21) may be driven according to a non-linear threshold below which the value measured by the light 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 nonlinear threshold but as close as possible to the nonlinear threshold, which is a sufficient level depending on the measured hematocrit level.

[0176] Alternatively or additionally, the emission power of the light source (11; 21) may be driven according to a saturation threshold of the light sensor (12; 22), the light signal received at the light sensor (12; 22) being unmeasurable when it exceeds the saturation threshold.

[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 sources (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 determination of a wide range of hematocrit levels, in particular for hematocrit levels as low as 5% or even below 5%, as well as for high hematocrit levels around 50% or even around 60% or higher.

[0179] During 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 light source (11; 21), and preferably all light sources (11; 21), in particular as the hematocrit level of the fluid increases. Preferably, the emission power of the at least one light source (11; 21) is increased from a threshold value of the measured hematocrit level of the fluid.

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

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

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

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

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

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

[0186] According to this embodiment, a specific example of monitoring of the light source (11; 21) is as follows:

[0187] - when the measured hematocrit level is lower than 20%, the emission power of the light source is set to a value comprised between 5% and 15%, 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 emission power of the light source is set to a value comprised between 15% and 30%, 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 emission power of the light source is set to a value comprised between 30% and 100% of the maximum emission power of said light source, preferably equal to 55%.

[0190] The emission power of the light source can also be adjusted during the measurement of the hematocrit level depending on the presence or absence of fluid and / or the properties of said fluid in the tubular portion 2. In particular, if no fluid is present in the tubular portion, the light source (11; 21) is preferably kept at a minimum or even zero emission level.

[0191] References

[0192] -Shota Ekuni and Yoshiyuki Sankai, “Noninvasive and Continuous Hematocrit Measurement by Optical Method without Calibration,” Electronics and Communications, Vol. 99, No. 9, 2016.

Claims

1. A method for determining the hematocrit level and / or the hemoglobin level of a fluid circulating in a tubular portion (2), the method comprising: - Using at least two light sources (11; 21) emitting a light beam in the direction of the tubular portion (2), each of the two light sources (11; 21) being configured to emit a light beam according to an emission wavelength selected to correspond to the isosbestic point of hemoglobin; - receiving light signals transmitted through the tubular portion (2) using at least two light sensors (12; 22), one light sensor being associated with one light source, the light source and the light sensor being arranged on both sides of the tubular portion (2) at the fluid circulation area for transmission measurement; - calculating the hematocrit level and / or the hemoglobin level of the fluid by processing the light signal received by the light sensor (12; 22); It is characterized in that during the determination of the hematocrit level and / or the hemoglobin level, the emission power of at least one light source (11; 21) is adjusted according to the respectively calculated hematocrit level and / or hemoglobin level of the fluid.

2. The method according to claim 1, wherein The emission power for the light source (11; 21) is at most equal to 100% of the maximum emission power of the light source (11; 21).

3. The method according to claim 2, wherein: The emission power for the light source (11; 21) is between 10% and 60% of the maximum emission power of the light source (11; 21).

4. The method according to claim 1, wherein The emission power of the light sources (11; 21) is monitored independently for each of the light sources (11; 21).

5. The method according to claim 1, wherein The emission power of the at least one light source (11; 21) is increased from a threshold value of a calculated hematocrit level and / or hemoglobin level of the fluid.

6. The method according to claim 5, wherein: - when the calculated hematocrit level is lower than 30%, setting the emission power of the light source (11; 21) to a value comprised between 10% and 30% of the maximum emission power of the light source (11; 21); and - when the calculated hematocrit level is higher than or equal to 30%, setting the emission power of said light source (11; 21) to a value comprised between 30% and 100% of the maximum emission power of said light source (11; 21).

7. The method according to claim 1, wherein The emission power of at least one light source (11; 21) is adjusted so that: - for a calculated value of the hematocrit level of the fluid below a first threshold, the emission power of the light source (11; 21) is at a first power level; - for a calculated value of the hematocrit level of the fluid that is higher than or equal to the first threshold but lower than a second threshold that is higher than the first threshold, the emission power of the light source (11; 21) is at a second power level; and - for a calculated value of the hematocrit level of the fluid higher than or equal to said second threshold value, the emission power of said light source (11; 21) is at a third power level.

8. The method according to claim 7, wherein: The emission power of at least one light source (11; 21) is adjusted so that: - when the calculated hematocrit level is lower than 20%, setting the emission power of said light source (11; 21) to a value comprised between 5% and 15% of the maximum emission power of said light source (11; 21); - when the calculated hematocrit level is comprised between 20% and 30%, setting the emission power of said light source (11; 21) to a value comprised between 15% and 30% of the maximum emission power of said light source (11; 21); and - when the calculated hematocrit level is higher than or equal to 30%, setting the emission power of said light source (11; 21) to a value comprised between 30% and 100% of the maximum emission power of said light source (11; 21).

9. The method according to claim 1, wherein: During the determination of the hematocrit level and / or the hemoglobin level, the emission power of the light source (11; 21) is adjusted depending on the presence or absence of fluid in the tubular portion (2) and / or depending on the properties of the fluid.

10. The method according to any one of claims 1 to 9, wherein The light source (11; 21) is monitored to concomitantly emit a light beam.

11. 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 components (10; 20), each transceiver assembly (10; 20) comprising a light source (11; 21) and a light sensor (12; 22) which are arranged on both sides of the tubular portion (2) at the fluid circulation area for transmission measurement; 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 to correspond to the isosbestic point of hemoglobin; a processing system programmed to determine the hematocrit level and / or hemoglobin level of the fluid based on the optical signal received by the optical sensor (12; 22) of the transceiver assembly (10; 20); and A monitoring system comprising means for adjusting the power emitted by the light source (11; 21), the monitoring system being programmed to adjust the power emitted by the light source (11; 21) in dependence on the determined hematocrit level and / or hemoglobin level of the fluid.

12. The apparatus of claim 11, comprising a support assembly (30) on which the two transceiver assemblies (10; 20) are mounted, the support assembly (30) being configured to be positioned around the tubular portion (2).

13. The apparatus according to claim 11, wherein The respective light sources (11; 21) of the two transceiver assemblies (10; 20) are configured to emit light beams at two different emission wavelengths.

14. The apparatus according to claim 11, wherein At least one collimating system (13; 23) comprises an upstream lens assembly (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 the light source (11; 21) relative to the tubular portion (2), the light source (11; 21) being positioned 10 mm from the focal plane of the upstream lens assembly (131; 231).

15. The apparatus according to claim 11, wherein At least one collimation system (13; 23) comprises an upstream lens assembly (131; 231) having a focal plane and positioned between the respective light source (11; 21) and the light sensor (12; 22), the light source (11; 21) being positioned in the focal plane of the upstream lens assembly (131; 231) on the side of the light source (11; 21) relative to the tubular portion (2).

16. The apparatus according to claim 11, wherein At least one collimating system (13; 23) comprises a downstream lens assembly (132; 232) having a focal plane and positioned between the respective 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), the light sensor (12; 22) being positioned 10 mm from the focal plane of the downstream lens assembly (132; 232).

17. The apparatus according to claim 11, wherein At least one collimating system (13; 23) comprises a downstream lens assembly (132; 232) having a focal plane and positioned between the respective 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), the light sensor (12; 22) being positioned in the focal plane of the downstream lens assembly (132; 232).

18. The apparatus according to claim 11, wherein At least one collimating system (13; 23) comprises a downstream lens assembly (132; 232) having a focal plane and positioned between the respective light source (11; 21) and the light sensor (12; 22), the downstream lens assembly (132; 232) being positioned on the side of the light sensor (12; 22) relative to the tubular portion (2) so that a light beam exiting the outlet wall (202) of the tubular portion (2) converges at a distance of 10 mm from the focal plane of the downstream lens assembly.

19. The apparatus according to claim 11, wherein At least one collimating system (13; 23) comprises a downstream lens assembly (132; 232) having a focal plane and positioned between the respective light source (11; 21) and the light sensor (12; 22), the downstream lens assembly (132; 232) being positioned on the side of the light sensor (12; 22) relative to the tubular portion (2) such that a light beam exiting the outlet wall (202) of the tubular portion (2) converges in the focal plane of the downstream lens assembly (132; 232).

20. The apparatus according to claim 11, wherein At least one collimation system (13; 23) comprises an upstream aperture (133; 233) positioned between the corresponding light source (11; 21) and the light sensor (12; 22), and on the side of the light source (11; 21) relative to the tubular portion (2), the upstream aperture (133; 233) being arranged to allow a central part of a light beam emitted by the light source (11; 21) to pass in the direction of the light sensor (12; 22) and to block a peripheral part of the light beam emitted by the light source (11; 21).

21. The apparatus according to claim 11, wherein At least one collimation system (13; 23) comprises a downstream aperture (134; 234) positioned between the respective 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), the downstream aperture (134; 234) being arranged to allow a central portion of the light beam transmitted through the tubular portion (2) to pass in the direction of the light sensor (12; 22) and to block a peripheral portion of the light beam transmitted through the tubular portion (2).

22. The apparatus according to claim 11, wherein At least one collimation system (13; 23) comprises an upstream filter (135; 235) and / or a downstream filter (136; 236), the upstream filter being positioned between the corresponding 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), and the downstream filter being positioned between the corresponding 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), 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 wavelength of the light source (11; 21) of the other transceiver assembly (10; 20).

23. The apparatus of claim 11, wherein: - the light source (11; 21) of the first of the two transceiver assemblies (10; 20) is configured to emit a light beam having a wavelength comprised between 780 nm and 840 nm; and The light source (11; 21) of the second of the two transceiver assemblies (10; 20) is configured to emit a light beam having a wavelength comprised between 1,270 nm and 1,330 nm.

24. The apparatus of claim 11, wherein The light sources (11; 21) of the transceiver assembly (10; 20) are positioned on the same side relative to the tubular portion (2).

25. The device according to claim 11, further comprising a system for monitoring the transceiver assembly (10; 20), the 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).

26. The apparatus of claim 11, wherein The transceiver assembly (10; 20) is assembled on a single support (31) having a groove (32) intended to receive the tubular portion (2).

27. Device according to claim 26, further comprising a cover (33) arranged to at least partially cover said groove (32), said cover (33) comprising a compression portion intended to hold in place said tubular portion (2) positioned in said groove (32).

28. The apparatus of claim 11, wherein All elements of the light source (11; 21) and the transceiver assembly (10; 20) that are arranged on a side of the corresponding light source (11; 21) relative to the tubular portion (2) are assembled on an upstream support, and all elements of the light sensor (12; 22) and the transceiver assembly (10; 20) that are arranged on a side of the corresponding light sensor (12; 22) relative to the tubular portion (2) are assembled on a downstream support separate from the upstream support, the downstream support and the upstream support having complementary shapes that are arranged to be coupled to surround the tubular portion (2).

29. The device according to any one of claims 11 to 28, arranged to determine the hematocrit level and / or the hemoglobin level without deformation of the tubular portion (2).

30. Device according to any one of claims 11 to 28, comprising a system for deforming the tubular portion (2) facing the transceiver assembly (10; 20), the deformation system being arranged to deform the circular cross section of the tubular portion (2) into an elliptical cross section.

31. The apparatus of claim 30, wherein: All elements of the light source (11; 21) and the transceiver assembly (10; 20) that are arranged on one side of the corresponding light source (11; 21) relative to the tubular portion (2) are positioned on one side of the major axis defining the elliptical cross-section, and all elements of the light sensor (12; 22) and the transceiver assembly (10; 20) that are arranged on one side of the corresponding light sensor (12; 22) relative to the tubular portion (2) are positioned on the other side of the major axis defining the elliptical cross-section.

32. The apparatus of claim 31, wherein The elliptical cross section is defined by a major radius (Ra) along the major axis and a minor radius (Rb) along the minor axis perpendicular to the major axis, wherein in the deformed state of the tubular portion (2), the length of the minor radius (Rb) of the elliptical cross section is comprised between 30% and 70% of the radius of the circular cross section of the tubular portion (2) in the undeformed state.

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