TARGET TISSUE PERFUSION MONITORING CATHETER AND ASSOCIATED MONITORING SYSTEMS

Abstract

The present invention relates to a catheter (1) for monitoring the perfusion of a target tissue. The catheter (1) comprises a body (2) adapted for insertion into a patient's tubular organ. The body (2) includes a PPG sensor (3) equipped with at least one optical emitter and one optical receiver for measuring the perfusion of the target tissue by absorbance. According to the invention, the PPG sensor (3) is integrated into the body (2) of the catheter (1) by means of a flexible and watertight casing (4). The PPG sensor (3) includes means for maintaining the position of at least one optical emitter relative to the position of the optical receiver, ensuring consistency of the absorbance measurement parameters. The invention also relates to urethral and esophageal monitoring systems.

Description

TARGET TISSUE PERFUSION MONITORING CATHETER AND ASSOCIATED MONITORING SYSTEMS The present invention relates to the field of measuring devices and systems for estimating metabolic parameters relating to the perfusion of an organ of a patient, in particular an organ comprising a mucosa and muscle tissues. Such a system can be used in many applications to monitor patients susceptible to tissue hypoperfusion. These conditions can be of various origins: hemorrhagic, infectious or inflammatory. Monitoring biological parameters related to perfusion provides the user with information on the organ's microcirculation to help them choose the right treatments for the patient. Indeed, good distal perfusion of organs in at-risk patients is an important part of their care. Poor organ perfusion can lead to significant problems, including organ failure. One of the difficulties in monitoring distal perfusion is that it can be heterogeneous. Indeed, in some cases it may be sufficient in one location and insufficient in another. In states of altered blood flow, microcirculation can be impacted. According to the scientific literature, certain mucous membranes, such as the urethral mucosa and the esophageal mucosa, appear to be particularly sensitive to hemodynamic alterations. They are therefore particularly interesting for monitoring the body's response to therapeutic actions. Therapeutic actions are most often global on the body and will have an impact on each of the organs. Knowledge of the state of local perfusion of a given mucosa is an important element in enabling the management of patients who may present alterations in this perfusion. For example, photoplethysmography technology is a way to assess tissue perfusion. Typically, a catheter equipped with a photoplethysmography or PPG sensor is used. As is accepted in scientific jargon, in the remainder of this document the use of the term "PPG sensor" refers to a photoplethysmography sensor. The applicant describes in documents WO 2013 / 127819 and WO 2015 / 044336 a perfusion monitoring catheter associated with a PPG sensor concerning the monitoring of a particular tissue, namely a duodenal mucosa. Although the PPG sensor technology is well known, these documents do not describe the implementation of such a sensor in order to embed it on an infusion monitoring catheter. Generally speaking, for a PPG sensor to provide a reliable perfusion indication over time, it is necessary that the photon path between the transmitter and the receiver be constant in a given application. In particular, the applicant has developed a solution to these problems in the context of monitoring the mucosa of tubular organs such as the urethra and the esophagus. A first aspect of the present invention relates to a catheter for monitoring perfusion of a target tissue, the catheter comprising a body adapted to be inserted into a tubular organ of a patient, the body comprises a PPG sensor equipped with at least one optical transmitter and an optical receiver so as to measure by absorbance the perfusion of the target tissue. The invention is characterized in that the PPG sensor is integrated into the body of the catheter through a flexible and waterproof covering, the PPG sensor comprising means for maintaining the position of at least one optical transmitter relative to the position of the optical receiver which ensures constancy of the absorbance measurement parameters. Advantageously, the holding means make it possible to keep the photon path between at least one transmitter and the receiver constant in a given application. This characteristic contributes to the reliability of monitoring of the target tubular organ. According to a first characteristic of the first aspect of the invention, the covering comprises, on the one hand, a coating opaque with respect to the operating wavelengths of at least one optical transmitter and the optical receiver, and on the other hand, at least one transmission window arranged in the transmission axis of at least one optical transmitter and a reception window arranged in the reception axis of the optical receiver. The opaque coating and the emission and reception windows help to maintain the photon path between at least one emitter and the receiver constant in a given application. To this end, each emission window and the reception window are respectively made of a biocompatible material that is flexible and translucent with respect to the operating wavelengths of at least one optical emitter and the optical receiver. According to a second characteristic of the first aspect of the invention, at least one optical transmitter and the optical receiver are arranged on the same face of the PPG sensor and allow an absorbance measurement by reflectivity. According to a third characteristic of the first aspect of the invention, the holding means are formed by a rigid electronic card. According to a fourth characteristic of the first aspect of the invention, the catheter comprises a power supply and data transfer cable incorporated into the body through a flexible sheath connected in a sealed manner to the covering. According to a fifth characteristic of the first aspect of the invention, the PPG sensor comprises two optical transmitters each operating according to a specific wavelength, the optical receiver being adapted to capture the wavelengths emitted by each optical transmitter. According to a sixth characteristic of the first aspect of the invention, the catheter comprises a stabilizer movable between a retracted state and a deployed state in which it ensures the maintenance of the position of the catheter inserted in the tubular organ. According to a seventh characteristic of the first aspect of the invention, the body comprises a route for extracting bodily fluid present and / or secreted in the tubular organ and / or in an anatomical structure located near the tubular organ. According to an eighth characteristic of the first aspect of the invention, the body has a diameter of between 12 French and 25 French, preferably the body has a diameter of between 14 French and 18 French. A second aspect of the invention consists of a system for monitoring the mucosa of the urethral tissue. This system is characterized in that it comprises a monitoring catheter according to the first aspect of the invention. A third aspect of the invention consists of a system for monitoring the mucosa of the esophageal tissue. This system is characterized in that it comprises a monitoring catheter according to the first aspect of the invention, the catheter comprising a pathway for supplying air into the stomach. Other features and advantages will appear in the following detailed description of two non-limiting exemplary embodiments of the invention illustrated by figures 1 to 6 placed in the appendix and in which: Figure 1 is a representation of a catheter according to an exemplary embodiment of the invention; Figure 2 is a representation of a distal end of the catheter of Figure 1; Figure 3 is a representation of an exploded view of the catheter of Figure 1; Figure 4 is a representation of an exploded view of a photoplethysmographic (PPG) sensor according to an exemplary embodiment of the invention; Figure 5 is a representation of the PPG sensor of Figure 4; and Figure 6 is a representation of an absorption spectrum of deoxyhemoglobin and oxyhemoglobin. The present invention relates to a catheter 1 for monitoring perfusion of the mucosa of a target tissue. As mentioned previously, monitoring the mucosa of a target tissue provides information relating to the microcirculation of the target tissue and makes it possible to guide the choice of treatments adapted to the patient. More particularly, the catheter 1 comprises a body 2 adapted to be inserted into a tubular organ of a patient. Preferably, the body 2 is tubular and extends in a longitudinal direction. The body 2 is made of a flexible and sterilizable biocompatible material such as PVC, polyurethane, latex, PTFE-coated latex, silicone-coated latex, hydrogel, silicone, etc. The body 2 has a distal end 20 adapted to be inserted into a target tubular organ such as the urethra, the esophagus etc. The body 2 has a proximal end 21 which is opposite the distal end 20. The proximal end 21 allows the catheter 1 to be connected to accessories such as a data processing terminal etc. As illustrated in Figures 1 to 5, the body 2 comprises a PPG sensor 3 designed to measure the perfusion state of the mucosa of the target tissue. In practice, the PPG sensor 3 measures the perfusion state of the mucosa of the target tissue through an absorbance measurement of the oxygen saturation rate of the hemoglobins of the microcirculatory system irrigating the target tissue. In this example, the target tissue consists of at least a portion of a tubular organ such as the urethra or the esophagus. For this purpose, the PPG sensor 3 comprises at least one optical transmitter 30 and one optical receiver 31 configured to operate on the same wavelength ranges. Preferably, the PPG sensor 3 comprises two optical transmitters 30, 32 which operate respectively according to a determined wavelength range. In this configuration, the optical receiver 31 is configured to detect the emission wavelength of each optical transmitter 30, 32. In this example, each optical transmitter 30, 32 has an emission wavelength in the infrared spectrum. Here, each optical transmitter 30, 32 is formed by an LED type lamp having a specific emission wavelength in the infrared spectrum. In parallel, the optical receiver 31 can be formed by a photodiode configured to operate according to the wavelength emission ranges of each optical transmitter 30, 32. As illustrated in Figure 6, the absorbance curve of deoxyhemoglobin Hb is higher than the absorbance curve of oxyhemoglobin HbO2 for a wavelength range between 600 nm and 800 nm. Conversely, the absorbance curve of deoxyhemoglobin Hb is lower than the absorbance curve of dioxygen-loaded oxyhemoglobin HbO2 for a wavelength range between 800 nm and 1000 nm. As described by WO 2015 / 044336, a PPG 3 sensor optimally measures the saturation rate of a microcirculatory system by differential measurement of the deoxyhemoglobin rate relative to the oxyhemoglobin rate, thereby obtaining a perfusion index of the target tissue. For this purpose, the PPG sensor 3 comprises a first optical emitter 30 having an emission wavelength range between 890 nm and 990 nm and preferably the first optical emitter 30 has an emission wavelength range between 930 nm and 950 nm. According to the graph of FIG. 6, the first optical emitter 30 makes it possible to measure the level of oxyhemoglobin HbO2 in the microcirculatory system of the mucosa of the target tissue. Preferably, the PPG sensor 3 comprises a second optical emitter 32 having an emission wavelength range of between 610 nm and 710 nm and preferably the second optical emitter 32 has an emission wavelength range of between 650 nm and 670 nm. According to the graph of Figure 6, the second optical emitter 32 makes it possible to measure the level of deoxyhemoglobin Hb in the microcirculatory system of the mucosa of the target tissue. In the example illustrated in Figures 4 and 5, the optical receiver 32 and at least one optical transmitter 30, 32 are arranged on an upper face 33 of the PPG sensor 3. Here, each optical transmitter 30, 32 and the optical receiver 32 are arranged on the same face 33 of the PPG sensor 3 allowing an absorbance measurement by reflectivity. The use of such a measurement technique makes it possible to carry out measurements of low tissue depth. The absorbance measurement is thus confined to the mucosa of the target tubular organ. Furthermore, a measurement by reflectivity makes it possible to arrange at least one optical transmitter 30, 32 and the optical receiver 31 on the same face 33 of the PPG sensor 3. In order for the path of the photons between at least one optical emitter 30, 32 and the optical receiver 31 to be constant, the PPG sensor 3 comprises means 34 for maintaining the position of at least one optical emitter 30, 32 relative to the position of the optical receiver 31. The maintaining means 34 help to preserve the constancy of the absorbance measurement parameters. In the example of figure 4, the holding means 34 are formed by a rigid electronic card 35 supporting in particular at least one optical transmitter 30, 32 and the optical receiver 31. In the example illustrated in Figures 1 to 5, the PPG sensor 3 is integrated into the body 2 of the catheter 1 at a determined distance from the distal end 20 of the body 2. The distance between the distal end 20 and the PPG sensor 3 can vary depending on the target tissue that is to be monitored and the tubular organ in which the catheter 1 is to be installed. For example, when the catheter 1 is designed to monitor the urethra, the distance between the distal end 20 and the PPG sensor 3 may vary between 1 cm and 8 cm depending on the patient on whom the catheter 1 is to be placed. More particularly, this distance may vary depending on the patient's age (child or adult) and their gender. The presence of the prostate in male individuals is an element to be taken into account in the measurement depending on the objective of measuring prostate perfusion or urethral perfusion. In order to avoid any short circuit problem, the PPG sensor 3 is integrated into the body 2 via a covering 4 which has sealing properties. At the same time, the covering 4 has flexibility properties which facilitate the insertion of the PPG sensor 3 mounted on the body 2 through narrow and non-linear natural pathways of a patient such as the nasogastric route in the case of monitoring of the esophagus or the urethral meatus in the case of monitoring of the urethra. Of course, the covering 4 is preferably designed in a biocompatible material as described above. The flexibility of the covering 4 combined with the holding means 34 make it possible to ensure insertion of the catheter 1 through a patient's natural route and to maintain constant absorbance measurement parameters. For information purposes, the distance between at least one optical transmitter 30, 32 and the optical receiver 31, or the emission angle of each transmitter 30, 32, the reception angle of the optical receiver 31 are absorbance measurement parameters. Advantageously, the constancy of these parameters contributes to the reliability of the monitoring. As illustrated in Figures 4 and 5, the covering 4 extends longitudinally over the body 2. The covering 4 has an external face 40 configured to be pressed against the mucosa of the target tubular organ. The covering 4 also has an internal face 41 which is integrated into the body 2 of the catheter 1. The internal face 41 and the external face 40 are connected by lateral edges 42. Here, the covering 40 has a quadrangular shape, however it could be designed in different shapes capable of being integrated into the body 2 without compromising the flexibility properties of the latter. Furthermore, in order to avoid random diffusion of each optical emitter 30, 32 which would lead, for example, to the photons making a direct path between each optical emitter 30, 32 and the optical sensor 31, the covering 4 comprises a coating opaque with respect to the operating wavelengths of each optical emitter 30, 32 and the optical receiver 31. For information purposes, the covering 4 may be produced by overmolding using a biocompatible material as described above. In this case, the biocompatible material comprises an opacifying additive which gives the covering 4 its opaque character. So that air is not trapped between the covering 4 and the PPG sensor 3, the overmolding operation may be carried out under pressure. The covering 4 further comprises at least one emission window 43 arranged in the emission axis of an optical transmitter 30, 32. Preferably, the covering 4 comprises two emission windows 43 arranged respectively in the emission axis of each optical transmitter 30, 32. In parallel, the covering 4 comprises a reception window 44 arranged in the reception axis of the optical receiver 31. Each emission window 43 and the reception window 44 are respectively made of a biocompatible material as described above. However, in addition to its flexibility properties, the biocompatible material used to design the windows 43, 44 has translucent optical properties. Preferably, the windows 43, 44 do not absorb photons from the emission wavelength ranges of each optical emitter 30, 32. During the overmolding operation of the covering 4, the location of the windows 43, 44 may be reserved by a pad. The windows 43, 44 may be formed by a second overmolding operation in which the location of the windows 43, 44 is filled with a transparent biocompatible material. In order to ensure that the covering 4 of the PPG sensor 3 has a smooth external appearance, the catheter 1 may include an overlayer 23. The overlayer 23 is made of a biocompatible material as described above and which has transparency properties. The overlayer 23 ensures that there is no abrupt relief likely to irritate or injure the patient's natural pathways into which the catheter 1 is inserted. In the example illustrated in Figure 3, the catheter 1 comprises a power cable 35 for the PPG sensor 3. The power cable 35 provides power to the PPG sensor 3. The power cable 35 also provides transfer of measurement data from the PPG sensor 3 to a data processing terminal. The power cable 35 allows measurement data to be transferred via an analog signal. Here, the power cable 35 is incorporated into the body 2 via a sheath 22. Furthermore, it is possible to use a power cable 35 comprising several conductors. For example, the power cable 35 may comprise four conductors. The sheath 22 is flexible so as not to interfere with the flexibility of the body 2. Preferably, the sheath 22 is made of a biocompatible material as described previously. The catheter 1 comprises a seal arranged at the junction between the sheath 22 and the covering 4. The seal ensures a sealed junction between the sheath 22 and the covering 4. The sealed junction makes it possible to prevent any short circuit between the power cable 35 and the PPG sensor 3. The sealed junction contributes to the reliability of the monitoring of the target tubular organ. In this example, the seal is made from a biocompatible material as described above and which also has collagen properties. For information, the seal can be made from a silicone glue. The power cable 35 is connected to the treatment terminal via a connector 36. The connector 36 can be of several types, electrical and / or electronic. For information purposes, the connector 36 can be formed by a USB type connector, a DIN type connector, etc. The connector 36 is connected to the proximal end 21 of the body 2. The connector 36 is connected to the body 2 through a tube 360. The tube 360 ​​is made of a biocompatible material as described previously (illustrated in FIGS. 1 and 3). At least a portion of the power cable 35 runs in the tube 360 ​​from the connector 36 to the body 2, in which it extends in order to connect to the PPG sensor 3. The tube 360 ​​is flexible and allows the catheter 1 to be extended towards the treatment terminal. As is known, the treatment terminal allows the measured data to be processed. Thus, the treatment terminal includes a calculation unit to calculate the saturation rate of a microcirculatory system and a perfusion index of the target tissue. The treatment terminal is further equipped with a memory to store the measured and processed data. In addition, the treatment terminal may include a display screen allowing an operator to follow the patient monitoring. In some applications, the PPG 3 sensor can also be equipped with a rechargeable battery in order to be autonomous and include means of remote transmission of the measured data. As illustrated in Figures 1 to 3, the distal end 20 is equipped with a stabilizer 5 ensuring that the catheter 1 is held in position. For this purpose, the stabilizer 5 is designed to be movable between a retracted state and a deployed state. When the stabilizer 5 is in a retracted state, it is contained within the body 2 of the catheter 1. In this configuration, an operator can insert the body 2 into a tubular organ of a patient via natural routes such as the nasogastric route or the urethral meatus etc. When the catheter 1 is placed in the desired position inside the target tubular organ or an organ adjoining the target tubular organ, the operator can actuate the stabilizer 5 in order to move it from its retracted state to a deployed state. In the deployed state, the stabilizer 5 maintains the catheter 1 inserted into the target tubular organ in a determined position. The stabilizer 5 in its deployed state makes it possible to maintain the PPG sensor 3 in a determined position, thus contributing to the constancy of the absorbance measurement parameters. Indeed, maintaining the PPG sensor 3 in a determined position makes it possible to avoid any fluctuations in the measured absorbance data which would be due to a movement of the PPG sensor 3. In this example, the stabilizer 5 may be formed by a holding balloon inflatable using a sterile fluid. The sterile fluid may comprise water and / or air. It should be noted that the stabilizer 5 can be arranged at a greater or lesser distance from the PPG sensor 3 depending on the application of the catheter 1 and the anatomical differences between a patient of male, female sex, adult age, child, morphology etc. For example, in a first application, the catheter 1 is part of a urethral mucosa monitoring system. In this application, the catheter 1 is inserted into the urethral meatus in order to monitor the urethral mucosa. In this application, the stabilizer 5 can be positioned in the bladder and deployed there in order to remain at the beginning of the urethra. In the example of a second application, the catheter 1 is part of an esophageal mucosa monitoring system. In this application, the catheter 1 is inserted into the esophagus in order to monitor the esophageal mucosa. In this application, the stabilizer 5 can be positioned in the stomach and deployed there after the cardia in order to maintain the distal end 20 of the catheter 2 at the distal end of the esophagus. In order to actuate the stabilizer 5, the body 2 comprises a first channel 24 for conducting the sterile fluid in order to actuate the deployment and / or folding of the stabilizer 5. The first channel 24 is connected to means for actuating the stabilizer 5 at the proximal end 21 of the body 2. Furthermore, the body 2 may comprise a second pathway 25 acting as a pathway for extracting bodily fluid present and / or secreted in the tubular organ into which the distal end 20 of the body 2 is inserted. This second pathway 25 may also continuously extract bodily fluid present and / or secreted in an anatomical structure located near the target tubular organ. In this sense, the second path 25 called “extraction” contributes to maintaining constant the interface between the PPG sensor 3 and the wall of the mucosa. That is to say, to maintaining contact between the PPG sensor 3 and the wall of the mucosa of the target tubular organ. This characteristic thus contributes to the reliability of the monitoring of the target tubular organ. Preferably, the second channel 25 is connected at the proximal end 21 of the body 2 to a body fluid receiver. In the example of a urethral application, the extraction route allows the bladder to be emptied to prevent urine from interfering with the absorbance measurement. Indeed, if urine were to flow through the urethra, it would necessarily pass between the PPG 3 sensor and the urethral mucosa, thus modifying the interface between the mucosa and the PPG 3 sensor, which disrupts the measured absorbance data. From a patient's point of view, the extraction route allows the bladder to be emptied to prevent bladder hypertrophy. In the example of an application to the esophagus, the extraction route makes it possible to avoid a rise of gastric juices which would be likely to induce a burn of the esophagus or even to pass into the lungs. In the same way, the extraction route also ensures in this application the constancy of the interface between the mucosa of the esophagus and the PPG 3 sensor. As in most nasogastric tubes, the extraction route can also be used to ensure a supply of nutrients in the stomach. According to an optional feature not illustrated, the body 2 may comprise a third pathway ensuring, for example, the supply of air to the tubular organ. The supply of air makes it possible to avoid a depression, of the latter or of a related anatomical structure, due to the extraction of bodily fluid. This third pathway is particularly useful in the context of an application to the esophagus of the catheter 1. Indeed, in this context the third pathway makes it possible to overcome a depression in the stomach which could lead to the formation of an ulcer at the depression site. It should be noted that this third pathway can be included in the second pathway 25 or form a third independent pathway. The physiological behavior of tubular organs such as the urethra and esophagus is scientifically known to collapse under the stress of external pressure. This phenomenon, along with contractions of the sphincters for the urethra and the cardias for the esophagus, helps prevent a backflow of urine or gastric juices. However, the applicant surprisingly found that when the body 2 has dimensions larger than average for insertion into such tubular organs, the latter collapse around the body 2 sufficiently strongly to keep the PPG sensor 3 pressed against the wall of the mucosa for the duration of the monitoring. However, keeping the PPG sensor 3 against the wall of the mucosa helps to keep the absorbance measurement parameters constant and therefore the reliability of the monitoring. In this example, the body 2 has a diameter between 12 French and 25 French, preferably the body has a diameter between 14 French and 18 French.

Claims

CLAIMS 1. Catheter (1) for monitoring perfusion of a target tissue, the catheter (1) comprising a body (2) adapted to be inserted into a tubular organ of a patient, the body (2) comprises a PPG sensor (3) equipped with at least one optical transmitter (30, 32) and an optical receiver (31) so as to measure by absorbance the perfusion of the target tissue, characterized in that the PPG sensor (3) is integrated into the body (2) of the catheter (1) through a flexible and sealed covering (4), the covering (4) being produced by overmolding using a biocompatible material, the PPG sensor (3) comprising means (34) for maintaining the position of at least one optical transmitter (30, 32) relative to the position of the optical receiver (31) which ensure constancy of the absorbance measurement parameters.

2. Monitoring catheter (1) according to claim 1, characterized in that the covering (4) comprises, on the one hand, a coating opaque with respect to the operating wavelengths of at least one optical transmitter (30, 32) and the optical receiver (31), and on the other hand, at least one emission window (43) arranged in the emission axis of at least one optical transmitter (30, 32) and a reception window (44) arranged in the reception axis of the optical receiver (31).

3. Monitoring catheter (1) according to claim 2, characterized in that each emission window (43) and the reception window (44) are respectively made of a biocompatible material which is flexible and translucent with respect to the operating wavelengths of at least one optical transmitter (30, 32) and the optical receiver (31).

4. Monitoring catheter (1) according to one of claims 1 to 3, characterized in that at least one optical transmitter (30, 32) and the optical receiver (31) are arranged on the same face (33) of the PPG sensor (3) and allow an absorbance measurement by reflectivity.

5. Monitoring catheter (1) according to one of claims 1 to 4, characterized in that the holding means (34) are formed by a rigid electronic card.

6. Monitoring catheter (1) according to one of claims 1 to 5, characterized in that it comprises a power supply cable (35) and data transfer cable incorporated into the body through a flexible sheath (22) connected in a sealed manner to the covering (4).

7. Monitoring catheter (1) according to one of claims 1 to 6, characterized in that the PPG sensor (3) comprises two optical transmitters (30, 32) each operating according to a specific wavelength, the optical receiver (31) being adapted to capture the wavelengths emitted by each optical transmitter (30, 32).

8. Monitoring catheter (1) according to one of claims 1 to 7, characterized in that it comprises a stabilizer (5) movable between a retracted state and a deployed state in which it ensures the maintenance of the position of the catheter (1) inserted into the tubular organ.

9. Monitoring catheter (1) according to one of claims 1 to 8, characterized in that the body (2) comprises an extraction path (25) for bodily fluid present and / or secreted in the tubular organ and / or in an anatomical structure located close to the tubular organ.

10. Monitoring catheter (1) according to one of claims 1 to 9, characterized in that the body (2) has a diameter between 12 French and 25 French, preferably the body (2) has a diameter between 14 French and 18 French.

11. System for monitoring the mucosa of the urethral tissue, characterized in that it comprises a monitoring catheter (1) according to one of claims 1 to 10.

12. System for monitoring the mucosa of the tissue of the esophagus, characterized in that it comprises a monitoring catheter (1) according to one of claims 1 to 10, the catheter (1) comprising an air supply path into the stomach.

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