Light guide

Abstract

A light guide to be used for inserting a medical tube (3) into a body for nasogastric tube feeding, the light guide including: a main body part (40) having a long length, the main body part being configured to guide light entering a proximal end part from a light source device, to emit resultant light from a distal end part, wherein the main body part includes a linear part (401) having a predetermined length from the distal end part, and a curved part (402) continuous with the linear part, the curved part having a predetermined curvature radius, the linear part has a length in a range of from 40 mm to 100 mm, and the curved part has a curvature radius in a range from 105 mm to 225 mm.

Description

Light guide

[0001] The present invention relates to a light guide.

[0002] For patients who have difficulty taking food orally, a procedure called nasogastric tube feeding is used to provide food and drink directly to the stomach. Specifically, a medical tube is inserted through the patient's nostrils and its tip is advanced through the esophagus to the stomach. Food and drink are then injected through the proximal end of the medical tube, which is located outside the body.

[0003] There is a known technique for confirming that the distal end of the medical tube has passed through the esophagus and reached the stomach.

[0004] For example, Patent Document 1 discloses a detection wire having a pair of insulated wires and a sensor portion formed at the tip of the pair of insulated wires. The detection wire is inserted into a medical tube, and when the sensor portion comes into contact with gastric juice, the resistance value between the pair of insulated wires changes. By detecting this change in resistance value between the pair of insulated wires, it can be determined that the sensor portion has come into contact with gastric juice, and therefore that the medical tube has correctly reached the stomach.

[0005] JP 2016-77450 A

[0006] However, the medical tube described in Patent Document 1 does not take into consideration ease of insertion into the patient's body.

[0007] SUMMARY OF THE INVENTION It is an object of the present invention to provide a light guide for use in easily inserting medical tubing into a patient's body.

[0008] The present invention to achieve the above object is a light guide used when inserting a medical tube for nasogastric tube feeding into a body, the light guide comprising a long main body that guides light from a light source device incident on a base end and emits the light from a tip end, the main body having a straight portion having a predetermined length from the tip end and a curved portion continuous with the straight portion and having a predetermined radius of curvature, the straight portion having a length of 40 mm or more and 100 mm or less, and the curved portion having a radius of curvature of 105 mm or more and 225 mm or less. Other features of the present invention will become apparent from the description and drawings that follow.

[0009] According to the present invention, it is possible to provide a light guide that can be used to easily insert a medical tube into a patient's body.

[0010] FIG. 1 is a schematic diagram illustrating the overall configuration of a medical tube position confirmation system according to an embodiment; FIG. 2 is a diagram illustrating the configuration of a light guide according to an embodiment; FIG. 3 is a diagram illustrating a medical tube and a light guide according to an embodiment inserted into a body; FIG. 4 is a diagram illustrating a medical tube and a light guide according to an embodiment inserted into a body; FIG. 5 is a diagram illustrating a light guide inserted into a human body model; FIG. 6 is a table showing various conditions and evaluation results of examples.

[0011] 1 is a diagram illustrating the overall configuration of a medical tube position confirmation system 1 according to this embodiment. The medical tube position confirmation system 1 includes a light source device 2, a medical tube 3, and a light guide 4.

[0012] [Light Source Device] The light source device 2 supplies light to the light guide 4. The light source device 2 has a housing 2a and a light-emitting unit 2b. The housing 2a has a light source 21 inside. The light source 21 generates light containing wavelengths that are transmitted through a living body. The light-emitting unit 2b has a group of lenses (not shown) for focusing the light generated by the light source 21 and emits the focused light to the outside. By connecting the base end 4b of the light guide 4 to the light-emitting unit 2b, the light source device 2 can supply light from the light source 21 to the light guide 4. The light from the light source 21 is used to confirm the position of the tip end 3a of the medical tubing 3 (details will be described later).

[0013] [Medical Tube] The medical tube 3 is a long, flexible tube. The medical tube 3 has a distal end 3a and a proximal end 3b. The medical tube 3 is used in nasogastric tube feeding procedures. Specifically, the surgeon inserts the medical tube 3 through the patient's nasal cavity and passes the distal end 3a of the medical tube 3 through the esophagus to the stomach. Food and drink are then injected through the proximal end 3b of the medical tube 3, which is located outside the patient's body. This allows food and drink to be directly supplied to the patient's stomach.

[0014] [Light Guide] The light guide 4 of this embodiment will be described with reference to FIG. 2 . The light guide 4 is a long member that guides light from the light source device 2. The light guide 4 has a tip end 4a and a base end 4b. The light guide 4 is, for example, an optical fiber, and has a core and a cladding. The core transmits light from the light source device 2. The core is made of a material such as quartz, glass, plastic, etc. The cladding fills the outside of the core. The cladding is made of a material such as quartz, glass, plastic, etc., and has a smaller refractive index than the core. Light that enters the light guide 4 propagates through the core while repeatedly undergoing total reflection at the interface between the core and the cladding.

[0015] The light guide 4 has elasticity. When the light guide 4 is subjected to an external force and its shape is deformed from its natural state, a restoring force that returns the light guide 4 to its natural state is generated inside the light guide 4. Here, the natural state refers to a state in which the light guide 4 is not subjected to an external force. The shape of the light guide 4 will be described in detail below, and the shape of the light guide 4 described using Figure 2 is the shape in its natural state.

[0016] Furthermore, the light guide 4 can be inserted into the medical tubing 3. When the light guide 4 is inserted into the medical tubing 3, the shape of the medical tubing 3 changes shape to follow the shape of the light guide 4. In other words, the natural shape of the light guide 4 alone and the natural shape of the light guide 4 inserted into the medical tubing 3 are roughly the same.

[0017] In this embodiment, the diameter of the light guide 4 is 0.7 mm or more and 2.5 mm or less. If the diameter of the light guide 4 is within this range, the light guide 4 can maintain its natural shape when inserted into the medical tubing 3. Furthermore, the light guide 4 can easily deform to conform to the shape of the inside of the body, making insertion easier.

[0018] If the diameter of the light guide 4 is smaller than 0.7 mm, the restoring force against external forces is too small, and the light guide 4 cannot maintain its natural shape when inserted into the medical tubing 3. In other words, the shape of the light guide 4 will deform to follow the shape of the medical tubing 3. Therefore, the natural shape of the light guide 4 alone will no longer match the natural shape of the light guide 4 when inserted into the medical tubing 3.

[0019] If the diameter of the light guide 4 is greater than 2.5 mm, the restoring force against external forces is too large, making it difficult for the light guide 4 to deform to conform to the shape inside the body. This makes it difficult to insert the light guide 4 into the body.

[0020] The light guide 4 has a main body 40. The main body 40 is a long member. The diameter of the main body 40 corresponds to the diameter of the light guide 4. The main body 40 guides light from the light source device 2 that is incident on the base end 4b of the light guide 4, and emits it from the tip end 4a of the light guide 4. The main body 40 has a straight portion 401, a curved portion 402, and an extension portion 403.

[0021] The straight portion 401 is a portion corresponding to a predetermined length L from the tip 4a of the light guide 4. The axis of the straight portion 401 is a straight line.

[0022] The length L of the straight portion 401 is between 40 mm and 100 mm. If the length L of the straight portion 401 is within this range, when the medical tube 3 is inserted into the patient's body, the distal end 3 a of the medical tube 3 is more likely to move toward the esophagus at the bifurcation between the esophagus and the trachea, thereby preventing the medical tube 3 from being inserted into the trachea.

[0023] If the length L of the straight portion 401 is less than 40 mm, when the medical tube 3 is inserted into the patient's body, the tip 3a of the medical tube 3 will be more likely to move toward the trachea at the bifurcation between the esophagus and the trachea, and there is a risk that the medical tube 3 will be inserted into the trachea.

[0024] On the other hand, if the length L of the straight portion 401 is longer than 100 mm, when the medical tube 3 is inserted into the patient's body, the tip 3 a of the medical tube 3 will hit the patient's nasopharynx, and the curvature of the curved portion 402 that continues from the straight portion 401 will make it impossible to insert the medical tube 3 from the oropharynx to the hypopharynx, making insertion into the esophagus difficult.

[0025] The curved portion 402 is a portion that continues from the straight portion 401 and has a predetermined radius of curvature R. The axis of the curved portion 402 is an arc. In FIG. 2, a portion of a circle of curvature C that passes through the axis of the curved portion 402 is shown by a dashed line. Note that the tangent to the axis of the curved portion 402 at the end portion on the tip portion 4a side coincides with the straight line L1. In other words, the curved portion 402 and the straight portion 401 are smoothly connected to each other.

[0026] The radius of curvature R of curved portion 402 is 105 mm or greater and 225 mm or less. If the radius of curvature R of curved portion 402 is within this range, it is possible to prevent distal end 3 a of medical tubing 3 from hitting the patient's nasopharynx when medical tubing 3 is inserted into the patient's body.

[0027] If the radius of curvature R of the curved portion 402 is less than 105 mm, when the medical tube 3 is inserted into the patient's body, the tip 3a of the medical tube 3 will be more likely to move toward the trachea at the bifurcation point between the esophagus and the trachea, and there is a risk that the medical tube 3 will be inserted into the trachea.

[0028] If the radius of curvature R of the curved portion 402 is greater than 225 mm, when inserting the medical tubing 3 into the patient's body, the tip 3a of the medical tubing 3 may hit the patient's nasopharynx, making further insertion difficult.

[0029] More preferably, the radius of curvature of the curved portion 402 is 105 mm or more and 175 mm or less. As will be described in detail later, when the light guide 4 is inserted into the medical tubing 3, the distal end 4 a of the light guide 4 is located at approximately the same position as the distal end 3 a of the medical tubing 3. Here, the surgeon visually confirms the position of the distal end 3 a of the medical tubing 3 by visually observing the light emitted from the distal end 4 a of the light guide 4 and transmitted through the patient's abdomen. At this time, the closer the distal end 3 a of the medical tubing 3 inserted into the patient's stomach reaches a position within the patient's stomach that is closer to the abdominal surface, the easier it is for the surgeon to visually observe the light emitted from the distal end 4 a of the light guide 4. When the radius of curvature R of the curved portion 402 is within the above range, the distal end 3 a of the medical tubing 3 reaches a position closer to the abdominal surface. Therefore, the surgeon can more easily visually observe the light emitted from the distal end 4 a of the light guide 4.

[0030] 2 also shows dashed lines L1 and L2, which are tangents to the axis at both ends of curved portion 402. Line L1 is a tangent to the axis of curved portion 402 at a joint between curved portion 402 and straight portion 401. Line L2 is a tangent to the axis of curved portion 402 at a joint between curved portion 402 and extended portion 403. Here, the line passing through the axis of straight portion 401 coincides with line L1.

[0031] The angle θ (see FIG. 2 ) formed by the tangents (lines L1 and L2) to the axis at both ends of curved portion 402 is 29 degrees or greater. If angle θ is within this range, it is possible to prevent tip portion 3 a of medical tubing 3 from striking the patient's nasopharynx when inserting medical tubing 3 into the patient's body. If angle θ is smaller than this range, tip portion 3 a of medical tubing 3 may strike the patient's nasopharynx when inserting medical tubing 3 into the patient's body, and the curvature of curved portion 402, which continues from straight portion 401, may prevent insertion from the oropharynx to the hypopharynx, potentially making insertion into the esophagus difficult.

[0032] The extension portion 403 is a portion that is continuous with the curved portion 402 and extends to the base end portion 4b of the light guide 4. At the joint between the curved portion 402 and the extension portion 403, the tangent to the axis of the curved portion 402 (straight line L2) coincides with the tangent to the axis of the extension portion 403. In other words, the curved portion 402 and the extension portion 403 are smoothly connected to each other.

[0033] The main body 40 of the present embodiment has been described as being provided with the straight portion 401, the curved portion 402, and the extension portion 403 in a single member. However, the straight portion 401, the curved portion 402, and the extension portion 403 may each be formed from separate members, and may be connected to each other to form a single main body 40.

[0034] ==Medical Tubing and Light Guide Inside the Body== The state of the medical tubing 3 and light guide 4 inside the body will be described with reference to Figures 3 to 5. As described above, when the medical tubing 3 is inserted into a patient's body, the light guide 4 is inserted. In addition, in this embodiment, the tip 4a of the light guide 4 is located at approximately the same position as the tip 3a of the medical tubing 3. Note that as long as the surgeon can visually recognize the light emitted from the tip 4a of the light guide 4, the embodiment is not limited to one in which the tip 4a of the light guide 4 is located at approximately the same position as the tip 3a of the medical tubing 3.

[0035] First, the medical tubing 3 is inserted into the patient's nasal cavity or oral cavity from the tip 3a. Figures 3 to 5 show an example of the medical tubing 3 being inserted through the nasal cavity. Figure 3 shows the medical tubing 3 inserted into the nasal cavity from the tip 3a by the length L of the straight portion 401. In Figure 3, the circle of curvature C of the curved portion 402 of the light guide 4 is indicated by a dashed line. In the state of the medical tubing 3 shown in Figure 3, the circle of curvature C of the curved portion 402 of the light guide 4 is located on the oral cavity side of the light guide 4. Furthermore, in the state shown in Figure 3, the straight portion 401 and the curved portion 402 of the light guide 4 are in a substantially natural state.

[0036] 4 shows the state in which the medical tubing 3 has been inserted further into the patient's body from the state shown in FIG. 3, with the straight portion 401 of the light guide 4 reaching the patient's pharynx. At this time, the straight portion 401 and the curved portion 402 of the light guide 4 remain in a nearly natural state, and the circle of curvature C has moved toward the pharynx compared to FIG. 3.

[0037] 3 to 4, curved portion 402 of light guide 4 is inserted into the nasal cavity. During this process, medical tubing 3 experiences almost no resistance from the inner walls of the nasal cavity and pharynx, and straight portion 401 and curved portion 402 of light guide 4 remain in a nearly natural state. As curved portion 402 is further inserted into the nasal cavity, curved portion 402 moves with the position of circle of curvature C remaining almost unchanged from the position shown in FIG. 4. Accordingly, tip 3a of medical tubing 3 moves downward relative to the patient. As a result, tip 3a of medical tubing 3 moves downward through the patient's pharynx without hitting the upper part of the pharynx.

[0038] In the state shown in Figure 4, the distal end 3a of the medical tubing 3 has not yet reached the esophagus. Also, in the state shown in Figure 4, the distal end 3a of the medical tubing 3 faces the esophagus, not the trachea. This is because the main body 40 of the light guide 4 has a straight portion 401.

[0039] When medical tubing 3 is further inserted into the patient's body from the state shown in Figure 4, distal end 3a of medical tubing 3 is inserted into the esophagus (Figure 5). When medical tubing 3 is further inserted into the patient's body, distal end 3a of medical tubing 3 reaches the patient's stomach.

[0040] When the switch of the light source device 2 is turned on at any timing during the process of inserting the medical tubing 3 into the body, light is emitted from the tip 4a of the light guide 4. The surgeon can confirm the position of the tip 3a of the medical tubing 3 by visually observing the light that is emitted from the tip 4a of the light guide 4 and passes through the patient. Alternatively, the position of the tip 3a of the medical tubing 3 may be confirmed by detecting the light that is emitted from the tip 4a of the light guide 4 and passes through the patient using an imaging device or the like.

[0041] As described above, the light guide 4 of this embodiment is a light guide 4 used when inserting a medical tube 3 for nasogastric tube feeding into the body, and includes a long main body 40 that guides light from the light source device 2 that is incident on the base end 4 b and emits it from the tip end 4 a. The main body 40 has a straight portion 401 that has a predetermined length L from the tip end 4 a, and a curved portion 402 that is continuous with the straight portion 401 and has a predetermined radius of curvature R. The length L of the straight portion 401 is 40 mm or more and 100 mm or less, and the radius of curvature R of the curved portion 402 is 105 mm or more and 225 mm or less.

[0042] According to the above configuration, because the main body 40 of the light guide 4 has the curved portion 402, when the medical tubing 3 with the light guide 4 inserted therein is inserted into the patient's body, the distal end 3 a of the medical tubing 3 can be prevented from hitting the nasopharynx. Furthermore, because the main body 40 of the light guide 4 has the straight portion 401, when the medical tubing 3 with the light guide 4 inserted therein is inserted into the patient's body, the distal end 3 a of the medical tubing 3 that has passed through the pharynx moves toward the esophagus without moving toward the trachea. This makes it easier to insert the medical tubing 3 toward the esophagus. In other words, the light guide 4 according to this embodiment can be used to easily insert the medical tubing 3 into the patient's body.

[0043] Furthermore, in the light guide 4, the curved portion 402 preferably has a radius of curvature R of 105 mm or more and 175 mm or less. With this configuration, the distal end 3a of the medical tubing 3 is positioned in the patient's stomach close to the surface of the patient's abdomen. Therefore, at the distal end 3a of the medical tubing 3, the light emitted from the distal end 4a of the light guide 4 is easily visible from outside the body, allowing the surgeon to accurately confirm the position of the distal end 3a.

[0044] Furthermore, the medical tube position confirmation system 1 of this embodiment includes a light source device 2, a medical tube 3 used for nasogastric tube feeding, and a light guide 4 that guides light from the light source device 2 and is insertable into the medical tube 3. The light guide 4 has a long main body 40 that guides light from the light source device 2 that enters through a base end 4b and emits it from a tip end 4a. The main body 40 has a straight portion 401 that has a predetermined length L from the tip end 4a, and a curved portion 402 that is continuous with the straight portion 401 and has a predetermined radius of curvature R. The length L of the straight portion 401 is 40 mm or more and 100 mm or less, and the radius of curvature R of the curved portion 402 is 105 mm or more and 225 mm or less.

[0045] With the above configuration, because the main body 40 of the light guide 4 has the curved portion 402, when the medical tube 3 with the light guide 4 inserted therein is inserted into the patient's body, the distal end 3 a of the medical tube 3 can be prevented from hitting the nasopharynx. Furthermore, because the main body 40 of the light guide 4 has the straight portion 401, when the medical tube 3 with the light guide 4 inserted therein is inserted into the patient's body, the distal end 3 a of the medical tube 3 that has passed through the pharynx moves toward the esophagus without moving toward the trachea. This makes it easier to insert the medical tube 3 toward the esophagus. In other words, the medical tube position confirmation system 1, having the light guide 4 configured as described above, allows the medical tube 3 to be easily inserted into the patient's body.

[0046] Furthermore, in the above-described medical tube position confirmation system 1, it is preferable that the radius of curvature R of curved portion 402 is 105 mm or more and 175 mm or less. With this configuration, within the patient's stomach, distal end 3a of medical tube 3 is positioned close to the patient's abdominal surface, and the tip of 4a faces toward the body surface. Therefore, at distal end 3a of medical tube 3, the light emitted from distal end 4a of light guide 4 is easily visible from outside the body, allowing the surgeon to accurately confirm the position of distal end 3a.

[0047] The ease of insertion of the light guide into the body was evaluated using a human dummy. As described in the embodiment, when the light guide is inserted into the medical tubing, the shape of the medical tubing changes to match the shape of the light guide. Therefore, when the light guide is inserted into the medical tubing, the position and shape of the medical tubing inside the body are roughly the same as the shape and position of the light guide. Therefore, even if the medical tubing is omitted as in this example, the same results as when the light guide is inserted into the medical tubing can be obtained.

[0048] [Evaluation Method] A method for evaluating the ease of insertion of a light guide into the body will be described with reference to Figures 6 and 7. In this example, the ease of insertion of a light guide into the body was evaluated by checking the position of the tip of the light guide with respect to a human anatomical model. Specifically, attention was paid to two positions: position P2 (details will be described later) of the tip of the light guide during the process of inserting the light guide through the nasal cavity of the human anatomical model, and position P4 (details will be described later) of the tip of the light guide at the completion of insertion. Here, the completion of insertion refers to the time when the tip of the light guide abuts against the stomach wall after inserting the light guide through the nasal cavity of the human anatomical model.

[0049] Position P2 is the position where the tip of the light guide, located near the pharynx, abuts against the inner wall of the esophagus during the process of inserting the light guide through the nasal cavity of the human model and bringing the tip of the light guide into the stomach.

[0050] In this example, the position of the bifurcation between the esophagus and the trachea was set to position P1. The distance between positions P1 and P2 was measured. If the distance between positions P1 and P2 was 12 mm or more, it was determined that the tip of the light guide could be easily inserted into the esophagus.

[0051] Position P4 is the position on the stomach wall where the tip of the light guide comes into contact when the insertion of the light guide into the phantom is complete.

[0052] In this example, the position on the stomach wall of the phantom model that was closest to the abdominal surface of the phantom model was designated as position P3. The distance between positions P3 and P4 was then measured. It was determined that if the distance between positions P3 and P4 was within 30 mm, the light emitted from the tip of the light guide would be easily visible.

[0053] [Common Conditions] In this example, the human body model used was a tube feeding simulator (MW8) manufactured by Kyoto Scientific Co., Ltd. The light guide was an optical fiber, which was processed to have the curvature of the curved portion and the length of the straight portion for each condition.

[0054] 8 is a table showing the conditions of each example and the evaluation results for each example. For each example, the conditions of the diameter of the light guide, the radius of curvature of the curved portion, and the length of the straight portion were given.

[0055] [Evaluation Results] In Examples 1 to 11, the distance between positions P1 and P2 was 12 mm or more. As described above, when the distance between positions P1 and P2 was 12 mm or more, the distal end of the light guide could be easily inserted into the esophagus.

[0056] This result indicates that if the length of the straight portion is between 40 mm and 100 mm and the radius of curvature of the curved portion is between 105 mm and 225 mm, when the light guide is inserted into the patient's body, the tip of the light guide that has passed through the pharynx is likely to move toward the esophagus without moving toward the trachea. In other words, this result indicates that if the length of the straight portion and the radius of curvature of the curved portion are each within these ranges, the light guide can be easily inserted into the patient's esophagus.

[0057] As mentioned above, even when the light guide is inserted into the medical tube, the same results as when the medical tube is omitted as in this example are obtained. Therefore, the results of Examples 1 to 11 show that the medical tube can be easily inserted into the patient's esophagus as long as the length of the straight portion and the radius of curvature of the curved portion are within the above ranges.

[0058] The distance between positions P3 and P4 was 30 mm or less in Examples 4, 5, 6, 9, 10, and 11. As described above, when the distance between positions P3 and P4 is 30 mm or less, the tip of the light guide is close to the abdominal surface of the patient, and the light emitted from the tip of the light guide is easily visible.

[0059] This result indicates that if the radius of curvature of the curved portion is 105 mm or more and 175 mm or less, the tip of the light guide reaches a position in the patient's stomach close to the abdominal surface of the patient, which means that the light emitted from the tip of the light guide becomes easily visible.

[0060] Therefore, the results of Examples 4, 5, 6, 9, 10, and 11 show that if the radius of curvature of the curved portion is within the above-mentioned range, even if the light guide is inserted into the medical tubing and then inserted into the patient's stomach, the light emitted from the tip of the medical tubing via the light guide can be easily seen.

[0061] 1: Medical tube position confirmation system 2: Light source device 2a: Housing 2b: Light emitting section 21: Light source 3: Medical tube 3a: Tip section 3b: Base section 4: Light guide 4a: Tip section 4b: Base section 40: Main body section 401: Straight section 402: Curved section 403: Extension section

Claims

1. A light guide used when inserting a medical tube for nasogastric tube feeding into the body, comprising a long main body that guides light from a light source incident on the base end and emits it from the tip, said main body having a straight section that has a predetermined length from the tip, and a curved section that is continuous with said straight section and has a predetermined radius of curvature, said straight section having a length of 40 mm or more and 100 mm or less, and said curved section having a radius of curvature of 105 mm or more and 225 mm or less.

2. The light guide according to claim 1, wherein the curved portion has a radius of curvature of 105 mm or more and 175 mm or less.

3. A medical tube position confirmation system comprising: a light source device; a medical tube used for nasogastric tube feeding; and a light guide that guides light from the light source device and is insertable into the medical tube, wherein the light guide has a long main body that guides light from the light source device that enters from a base end and emits it from a tip end, wherein the main body has a straight portion that has a predetermined length from the tip end, and a curved portion that is continuous with the straight portion and has a predetermined radius of curvature, wherein the straight portion has a length of 40 mm or more and 100 mm or less, and the curved portion has a radius of curvature of 105 mm or more and 225 mm or less.

4. A medical tube position confirmation system according to claim 3, wherein the curved portion has a radius of curvature of 105 mm or more and 175 mm or less.