DEVICE FOR SECURING A PHYSIOLOGICAL SENSOR TO THE BODY OF A USER
TECHNICAL FIELD
This invention relates to the field of non-invasive monitoring devices, and more particularly concerns a device and method for holding such a device on the body of a user.
BACKGROUND
The periodically measurement of a physiological parameter such as blood glucose levels is a painful and cumbersome task. Diabetic patients not only have to control their sugar consumption, but also have to manage their insulin intake to prevent hypoglycemic events. Wearable devices for monitoring physiological characteristics such as glucose would represent a significant improvement of the quality of life of patients by allowing a permanent monitoring of their condition and providing real-time alerts and status information. However, currently available medical devices that can monitor blood-sugar levels and alert the user of an oncoming hypoglycemic event are not very discrete and suitable regions on the body for their use are very limited.
Currently, glucose monitors such as a Continuous Glucose Monitoring System (CGMS) may help to fill in the gaps between finger-stick blood tests, but such systems usually use invasive technology (e.g. a needle through the skin) and are not optimized for user comfort.
Physiological probes being currently developed for long-term wear include noninvasive optical probes and the like, which allow a constant monitoring of glucose levels or other physiological characteristics through an optical assembly in contact with the skin of the user. In order to ensure the accuracy and consistency of measurement taken with such devices, it is however important to make certain that they are securely held in place and easy to repositioned in a similar spot each time they are temporarily removed.
International application no. WO2008/134847 (BEDARD et al) for example shows such a sensor provided with a protuberance projecting towards the skin of the user in use in order to improve the performance of the device and minimizes motion artifacts. The device can be affixed to the skin or held thereon through an elastic band.
U.S. patent no. 6,402,690 (RHEE et at) discloses a monitoring system for monitoring the vital signs of a patient by performing measurements such as skin temperature, blood flow, blood constituent concentration, and pulse rate at the finger of a patient. Physically, the monitoring system has an inner ring close to the surface of the skin, as well as an outer ring mechanically decoupled from the inner ring thereby shielding it from external loads.
U.S. patent no. 6,603,995 (CARTER) discloses a portable ECG monitoring apparatus comprising a sensor device detachable from a monitoring device. Although this device is wearable, it can not be entirely installed and removed by the user alone. Only authorized personnel can freely remove the apparatus from the patient. Moreover, this apparatus is not intended for long-time wear on the patient.
U.S. patent no. 6,631 ,282 (RULE et al) shows a device for isolating regions of living tissue, where a site selector is positioned on the skin of a patient, for example on his arm, and affixed thereon through a fastening strap, for example made of Velcro (trademark). This device is however adapted for interaction with a larger device and is not adapted for ease of use in long term monitoring of a physiological factor through the daily life of the patient. U.S. patent no. 7,020,508 (STIVORIC et al) teaches a wearable device for collecting and storing data relating to an individual's physiological state. The device contains a flexible section which engages the wearer's body and a housing removably attached to the flexible section. The housing supports one or more sensor and a processor in electrical communication with the sensor(s).
There is therefore a need for a method of attaching a physiological sensor to the skin of a patient which alleviates at least some of the drawbacks mentioned above.
SUMMARY
In accordance with a first aspect of the invention, there is provided a securing device for securing a physiological sensor assembly to a skin region of the body of a user, the sensor assembly having a skin-contacting side comprising a sensor portion and an adhesive portion, the device comprising a housing having a skin-side bottom surface and an opposite top surface. The housing defines a sensor receptacle area opening on said top surface to receive the sensor assembly, the housing having an opening extending from the receptacle area to the bottom surface of the housing and is shaped to allow the skin-contacting side of the sensor assembly therethrough; securing means for removably securing the sensor assembly to the housing; and a strap having opposite extremities attachable to the housing and a length adjusted for securing the housing to the body of the user.
Another aspect of the present invention provides a physiological sensor kit for sensing at least one physiological parameter through a skin region of the body of a user, the kit comprising: a physiological sensor having a skin-contacting side comprising a sensor head; at least one adhesive layer affixable to the skin-contacting side of the sensor around the sensor head; a securing device, having: a housing having a skin-side bottom surface and an opposite top surface. The housing defines a sensor receptacle area opening on the top surface to receive the sensor, the housing having an opening extending from the receptacle area to the bottom surface of the housing and shaped to allow the skin-contacting side of the sensor therethrough; a strap having opposite extremities attached to the housing and a length adjusted for securing the housing to the body of the user; and a securing mechanism for removably securing the sensor to the housing.
Another aspect of the present invention provides a physiological sensor kit for continuously monitoring at least one physiological parameter through a skin region of the body of a user. The kit includes a physiological sensor having a skin-contacting side comprising a sensor head, and at least two housings. Each housing includes: a skin-side bottom surface and an opposite top surface; a sensor receptacle area for receiving the sensor therein, the sensor receptacle area opening on the bottom surface of the housing to allow the skin-contacting side of the sensor therethrough; a rechargeable power supply provided within the housing, and a power connector associated with this power supply and accessible through the receptacle area. The kit further includes a securing mechanism for removably securing the sensor to any one of the housings, and at least one strap. Each strap has opposite extremities attachable to any one of the housings and a length adjusted for securing the housings to the body of the user.
BRIEF DESCRIPTION OF THE DRAWINGS
A preferred embodiment that implements the various features of this invention will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate the features of this invention and not to limit the scope of this invention.
FIGs. 1A and 1 B are respectively bottom and top perspective views of a sensor assembly for use with securing devices according to embodiments of the present invention; FIG. 1C is a perspective view of an adhesive layer for such an assembly according to one embodiment;
FIGs. 2A and 2B are perspectives view of a securing device in accordance with one embodiment of the present invention, respectively shown without and with a sensor assembly affixed thereto;
FIG. 3 is a partial cross-sectional view of an engagement between the housing and the strap of a securing device according to one embodiment of the present invention;
FIG. 4A is a top plan view of the strap in accordance with an alternative embodiment of the present invention; FIG. 4B is a cross sectional view of an arm wearing the securing device of FIG. 4A;
FIG. 5 is a bottom perspective view of the securing device in accordance with a preferred embodiment of the present invention, including a skin-engaging layer;
FIG. 6 is a perspective view of a kit for the continuous monitoring of a physiological parameter in accordance with one embodiment of the present invention;
FIG. 7 is a plan back view of the securing device installed on an arm of a person in accordance with a preferred embodiment of the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The present invention generally provides securing devices for securing a physiological sensor assembly to a skin region of the user, and kits, incorporating at least one such securing device and the physiological sensor assembly. The physiological sensor assemblies to be secured by devices according to embodiment of the invention may be any device intended to monitor values and/or variations of a physiological parameter of the user such as, but not limited to, glucose levels, heart rate, respiration rate, blood metabolites, oxygen levels, etc. Preferably, the physiological sensor is based on non-invasive technology, such as optical technology or the like, but other variants could be envisioned without departing from the scope of the invention. Preferably, the physiological sensor provides a long time or a constant monitoring of the physiological parameter of interest.
Devices according to embodiments of the invention may be used to secure the physiological sensor assembly to any appropriate body part of the user. Preferably, the sensor assembly is secured to one of the arms of the user, for example the upper arm, and is preferably in direct contact with a skin region of the user. Other body locations could however be considered without departing from the scope of the invention, such as the abdomen or a leg.
Sensor assembly
Referring to FIGs. 1A, 1 B and 1C, there is shown an example of a sensor assembly 29 which may be affixed to a user by a securing device according to an embodiment of the invention. The sensor assembly 29 has a skin-contacting side 34, that is, one side thereof meant to be in contact with the skin region of the user at the selected location on the body of the user. The skin-contacting side 34 includes a sensor portion, which may be a sensor head 32. In one embodiment, the skin-contacting side also has an adhesive portion 36. The adhesive portion 36 preferably prevents small movements of the sensor assembly 29 when secured in place, ensuring a greater consistency in the measurements of the sensor.
The expression "physiological sensor assembly" is understood to refer to the sensor itself, which may include one of more components, as well as any accessory collaborating with the sensor. Preferably, the sensor assembly 29 includes an adhesive layer 38 affixed on the skin-contacting side 34 thereof and surrounding the sensor head 32. In this embodiment, the adhesive layer 38 embodies the adhesive portion 36. In other embodiments, more than one adhesive components of any appropriate shape or an adhesive substance could be considered.
An adhesive layer is understood to mean a layer having at least one adhesive surface. The adhesive layer is preferably a consumable product intended to be discarded after one use. Referring to FIG. 1C there is shown one embodiment of an adhesive layer 38 of the present invention. The adhesive layer 38 has a first adhesive surface 40 for adhering to the skin of the user and an opposite surface 42 to be affixed to the skin-contacting side 34 of the sensor 30. The adhesive layer 38 preferably has a hole 46 therein, bordered by an inner edge 98, for the measurement head 32 to project therethrough when the adhesive layer 38 is affixed to the sensor. In the illustrated embodiment of FIG. 1C, the hole 46 has a contour defining a non- circular symmetry designed to ensure that the adhesive layer 38 stays properly aligned on the skin-contacting side of the sensor during the installation procedure. Preferably, the sensor head 32 is provided with a peripheral rib 94 (see FIG. 1A) extending around a portion thereof, and the adhesive layer 38 is installed under the sensor by engaging the inner edge 98 of the hole 46 between the skin-contacting surface 34 of the sensor 30 and this peripheral rib 94. The shape of the hole 46 and position of the peripheral rib 94 preferably ensure that upon engagement of the adhesive layer 38 between the peripheral rib 94 and the skin-contacting side 34 of the sensor 30, the adhesive layer 38 is correctly positioned around the measurement head 32 of the sensor and matches the geometry of the skin-contacting side 34.
In an alternative embodiment, the second surface is also adhesive, and therefore adheres to the skin-contacting side 34 of the sensor. Such a "double-sided" adhesive layer 38 could also have a hole therethrough in order to install the adhesive layer around the measurement head 32. The adhesive layer 38 could be a peel-off layer, a consumable layer having a thin rigid backing, a medical-grade sensitive adhesive, a foam or plastic layer with Silicon medical adhesive layer on the skin side, a foam or plastic layer with Acrylic adhesive layer, a foam or plastic layer with hydrocolloid adhesive layer, etc.
In use, the adhesive layer 38 is first affixed to the sensor 30, and the resulting sensor assembly 29 is then secured in the securing device as explained below.
In some embodiments, the adhesive layer 38 may be designed to remain on the skin during removal of the sensor 30 from the body of the user. This may be accomplished by ensuring that the adhesive force between the skin and the adhesive surface of the adhesive layer is greater than the force holding the adhesive layer to the sensor. In this manner, the user can remove the sensor assembly and securing device while the adhesive layer still remains on the skin. The user can then gently remove the adhesive layer with minimal skin trauma.
Securing device
Referring to FIG. 2A, there is shown a securing device 10 according to a preferred embodiment of the invention, which includes a housing 12. The housing 12 has a skin-side bottom surface 18 which is intended to be positioned along the skin of the user when the physiological sensor assembly 29 is secured thereto, and an opposite top surface 20 which defines a receptacle area 22 to receive the physiological sensor assembly 29 as described above. The housing 12 further includes an opening 24 extending from the receptacle area 22 to the bottom surface 18. The opening 24 has a compatible shape with the skin-contacting side 34 of the sensor assembly 29, allowing the skin-contacting side 34 to contact the skin of the user through the opening 24 when the sensor assembly 29 is secured. In one embodiment, the housing is made of a rigid material.
Referring to FIG. 5, in a preferred embodiment of the present invention, the securing device 10 further includes a skin-engaging layer 60. The skin engaging-layer 60 is affixed on the skin-side bottom surface 18 of the housing 12 and is made of a resilient material providing a tractional engagement with the skin of the user in order to stabilize the securing device on the skin of the user. The resilient material could be silicone, plastic, rubber, fabric, etc. The skin-engaging layer 60 is preferably glued or otherwise permanently affixed to the bottom surface of the housing. Preferably, the skin-engaging layer 60 has a bottom side 62 which defines a curvature substantially matching the curvature of the body of the user at the location where the device is to be worn, providing a better comfort for the user. It will be apparent to those skilled in the art that depending upon where on a patient the securing device 10 is intended to be used, the skin-engaging layer 60 could be formed with different shapes or different curvatures without departing from the scope of the invention. Advantageously, in an exemplary embodiment where the securing device is intended to be worn on an arm of the user, different choices of skin-engaging layers may be provided, each having a different curvature, providing a convenient "arm size adapter" which allows the securing device to be easily adapted to different arm circumferences. A user may be provided with a securing device already fitted with an appropriate skin-engaging layer based on provided measurements, or with a set of different skin-engaging layers to try on before making an appropriate selection.
In one embodiment, the housing 12 includes a rechargeable power supply compartment 64 containing a battery and a power connector 66 as shown on FIG. 2A. The power connector 66 is accessible through the receptacle area 22 allowing the sensor assembly 29 to be connected to it as the sensor assembly engages the receptacle area 22.
Referring to FIGs. 1A, 2A and 2B, the securing device 10 further includes securing means 14 for removably securing the sensor assembly to the housing 12. The securing means may be embodied by any suitable mechanism for securing the sensor assembly to the housing 12 in such a manner that the sensor assembly is held securely in place in the receptacle area 22 while being removable therefrom. In one embodiment, the securing means 14 of the housing 12 include a first mechanical structure 100 in or on the housing 12, such as for example, a projection, a groove, a tab, a shoulder, etc, compatible with a second mechanical structure 102 presents on the physiological sensor assembly 29, the first and second structures 100 and 102 defining two pieces of a click-on engagement. A click-on engagement is understood to refer to the first structure 100 and the second structure 102 connecting together mechanically, often with an audible "click", and being held in this relationship through biaising forces and a complementarity of their shapes. Generally, a slight temporary shifting or deformation of part of one or both structures 100 and 102 upon application of a light pressure thereon allows them to engage in this manner. In the illustrated embodiment, the first and second structures 100 and 102 are flaps projecting from the housing 12 and sensor assembly 29, respectively, and having opposite hook shape cross-sections interlocking together. Sets of such first and second mechanical structures are preferably provided on both sides of the device. Preferably, the sensor assembly includes locking tabs 56 and 58, mechanically coupled to the second mechanical assemblies, so that the sensor 30 is engaged within the receptacle area 22 by pressing the locking tabs. Upon releasing the pressed tabs, the sensor 30 is securely installed within the receptacle area 22. The sensor 30 may later be disengaged from the receptacle area 22 by again pressing the locking tabs 56 and 58. In one embodiment, the contact sides of the locking tabs 56 and 58 may be textured to improve the gripping thereof.
Of course, one skilled in the art will readily understand that different engagement mechanisms could be used without departing from the scope of the present invention.
As shown on FIGs. 2A and 2B, the securing device 10 further includes a strap 16 having opposite extremities 26 and 28 attachable to the housing 12 and a length adjusted for securing the housing 12 and the sensor assembly 29 to the body of the user. Preferably, the strap is made of an elastic material or includes a portion made of an elastic material. Further preferably, the length of the strap 16 is pre-adjusted prior to the first wear by the user depending upon the desired fit of the device on the part of the body of the user on which the securing device 10 is intended to be worn. Properly pre-adjusting the length of the strap ensures that a constant pressure is applied on the user's skin during the operation.
Different manners of pre-adjusting the length of the strap may be provided. Referring to FIG. 3, there is shown one embodiment where at least one of the extremities of the strap defines a connector portion 70 for engaging the housing 12. The connector portion 70 has a protruding end 72 which is received within a connector cavity 74 in the housing 12. The connector cavity 74 defines a shoulder 76 which engages the protruding end 72 to secure the strap 16 to the housing 12. In a preferred embodiment, the connector portion 70 includes a plurality of consecutive longitudinally distributed protrusions 78. The connector portion 70 can be broken or cut between the consecutive distributed protrusions 78 to permanently select one as the protruding end 72 of the connector portion, thereby pre-adjusting the length of the strap. The protruding end 72 of the connector is preferably laterally sled within the cavity 74 to ensure that the strap is secured to the housing 12. The strap may be attached, laminated or otherwise affixed to the connector portion 70 in any appropriate manner. In one embodiment the strap is laminated to the connector and extends to the protruding end 72 so that the end of the strap is also held within the cavity 74. As one skilled in the art will readily understand, the connector portion 70 described above needs to be provided at only one of the extremities of the strap to provide the desired length adjustability, although both extremities of the strap may be provided with such a connector portion without departing from the scope of the present invention.
Referring to FIGs. 4A and 4B, there is shown a strap according to another embodiment of the invention providing a different length-adjusting mechanism. In this embodiment, one or both extremities of the strap are made of a non-extensible material 92 and are provided with a flexible hook-and-eye section 80. The flexible hook-and-eye section 80 contains one or many hooks 82 and a longitudinal row of eyes 84 associated with each of the hooks 82. In this embodiment, the housing 12 comprises a slit 86 to receive the end 88 of the hook-and-eye section 80 as shown on FIG. 4B. The end 88 is then folded on itself to allow an engagement of each of at least one hook 82 with a selected one of the eyes of the corresponding row to adjust the length of the strap depending upon where on a patient the securing device 10 is intended to be used as shown on FIG. 4B.
Preferably, the initial and daily installation processes of the sensor assembly and securing device are performed as follows.
The following steps are preferably performed before using the sensor for the first time. The user first measures or has someone else measure the curvature of the body part where the sensor is to be worn, for example his mid-upper arm circumference. Once this measure is determined, an appropriate skin-engaging layer is selected. For example, if the user has a mid-upper arm circumference of 30 cm, according to a provided table, the user would select a medium size skin-engaging layer. Then the user or an attendant adjusts the strap length with the provided length adjusting mechanism according to the mid-upper arm circumference. Again, a provided table may allow the user to select the correct armband length corresponding to his arm circumference. Next, the selected skin-engaging layer is installed on the bottom face of the housing 18 and the adjusted strap is installed on the housing sides. The steps above usually need to be performed only once, to adjust and personalize the securing device to the user's size, or whenever the user's mid-upper arm circumference has significantly changed.
The daily or regular installation process is preferably performed as follows. The user begins the procedure by inserting the strap and housing over his arm or other selected body part, and vertically centers the device on the upper arm. Next, the user installs a new consumable adhesive layer to the skin-side bottom surface of the sensor, therefore creating the full sensor assembly. Once the consumable adhesive layer is set into place on the sensor, the user removes the peel-off layer, if provided, from the adhesive side of the layer. Next, the sensor assembly is inserted in the sensor receptacle area of the housing. Once both components are assembled, the adhesive side of the adhesive layer comes into contact with the skin of the user. The sensor is then ready to start its operation, as seen on FIG. 7, for example by pressing the "power on" button 112 on the top of the sensor.
As will be readily understood by one skilled in the art, the adhesive layer being installable on the skin contacting side of the sensor prior to engaging the sensor within the housing, a perfect positioning of the sensor can be obtained before the adhesive layer contacts the skin of the user, avoiding repetitive repositioning of the adhesive layer on the skin which causes skin trauma.
The embodiments of the present invention described above generally provide securing devices for securing a physiological sensor assembly to a skin region of the body of the user permitting a long period of monitoring. Securing devices of at least some embodiments of the present invention allow the user to use only one hand to install the sensor in the securing device assuring an easy and quick installation. This is particularly advantageous when the device is worn on one arm, and the user can therefore use only the opposite hand for the operation. This securing device could be installed by the user (child as well as elderly) without any extra help. In addition, the securing device may be fixed on the body of the user preventing any undesired lateral movement of the device. In addition, the device is designed to be very comfortable which is desirable for a long monitoring period.
Kits
In accordance with one aspect of the present invention, a securing device as described above or according to different embodiments of the invention may be provided as part of a kit with the corresponding physiological sensor, as well as one or more adhesive layers affixable to the skin-contacting side of the sensor around the sensor head.
Preferably, the kit includes several adhesive layers, each intended for one time use. The user may obtain additional adhesive layers when the one initially provided with the kit have been used.
In accordance with another aspect of the invention, with reference to FIG. 6, there is provided a physiological sensor kit 110 for continuously monitoring a physiological parameter through a skin region of the body of the user. The term "continuously monitor" is understood to mean monitoring the physiological parameter for a long period of time, i.e. several days, weeks, or months, with only brief breaks in the monitoring function.
The kit includes a physiological sensor 30 as described above, at least two housings 12, at least one strap 16 and a securing mechanism as described above. The receptacle area 22 of the housing 12 may open on the top surface 20 of the housing allowing the sensor to be received within the receptacle area, or could be of a different construction altogether. In addition, each of the housings 12 of the present kit include a rechargeable power supply 64 and a power connector 66 accessible through the receptacle area 22. The sensor 30 is then automatically connected to the power supply 64 through the power connector 66 when affixed to the housing 12. The housings 12 of this kit provide rechargeable batteries independently from the physiological sensor 30. By providing at least two securing devices 10 for one sensor, a user can wear the sensor 30 using one securing device 10 while the batteries of the second securing device are being recharged, for example on a docking station (not shown). In one embodiment, the docking station may have a same or similar shape to the sensor 30, in order to be attached to the housing in the same manner, for example using the click-on mechanism described above. Alternatively, the docking station may include a protruding head portion having a shape similar to that of the sensor 30. The housing 12 serves as a socket for the sensor 30 and the docking station serves as a charging unit for the battery. In embodiments where the strap is removably attached to the housing, only one strap needs to be provided within the kit. However, the kit could contain two straps or more which would avoid the removal of the strap from the housing upon replacing the housing for recharging it.
Advantageously, a user of such a kit needs not to wait for batteries that would be provided on the sensor or the securing device to be recharged to continue monitoring the physiological parameter. As soon as the batteries of the securing device worn by the user need to be recharged, the user removes the securing device to replace it with a recharged one. In addition, the user can install the recharged securing device on the other arm prior to remove the one that needs to be recharged. The sensor needs just to be secured within the recharged securing device for ensuring a continuous monitoring of the physiological parameter. Therefore, the time between the installation process of the replacing securing device is reduced to its minimum. Alterning the securing device from arm to arm when it is replaced, allows the skin of the other arm to be free until the following installation.
Although preferred embodiments of the invention have been described in detail, certain variations and modifications will be apparent to those skilled in the art, including embodiments that do not provide all of the features and benefits described herein. Accordingly, the scope of the invention is not to be limited by the illustrations or the foregoing descriptions thereof, but rather solely by reference to the appended claims.