WEARABLE SYSTEM AND METHOD FOR MEASURING PH ON PERISTOMAL SKIN

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is based upon and claims priority to U.S. Provisional Application No. 63/322,777 filed on 3/23/2022, the entire content thereof is incorporated herein by reference in its entirety.

BACKGROUND

[0002] This disclosure is related to a system for measuring pH levels. More particularly, the present disclosure pertains to a wearable system for measuring pH on peristomal skin.

[0003] At some point during their lives, 75% of all ostomy patients will experience peristomal skin complications. Even with mild peristomal skin complications, ostomy patients begin to report a lower quality of life, making this a serious issue. As ostomy patients wear their skin barriers, there is a buildup of moisture between the barrier and the peristomal skin. Currently, it is unclear what the conditions exist in the microenvironment between the ostomy barrier and the skin.

[0004] Unbeatable problems with the large intestine can be alleviated via ileostomy. This is a surgical procedure that involves removal of the large intestine and taking the portion of the small intestine, called the ileum, out through an incision in the abdomen. The ileum is permanently sutured to the abdominal skin, which forms a stoma. In 2000, at least 800,000 Americans had a stoma and that number was predicted to increase by 3% per year. Ileostomy patients must wear an ostomy pouch to collect the contents of the small intestine and maintain hydration by monitoring

1

SUBSTITUTE SHEET ( RULE 26) the dietary intake.

[0005] Peristomal skin health is a large concern for ostomy patients as a majority of such patients experience peristomal skin complications at some point in their lives. Current technologies that measure pH, hydration, and transepidermal water loss are large devices that cannot fit underneath a patient’s ostomy barrier. pH is generally measured with glass electrodes, however, there are also microelectrodes, microfluidic systems, and pH color indicators that are used to measure pH. Hydration sensors have been miniaturized and utilize the skin’s thermal and electrical properties to measure water content through the epidermis and dermis. Transepidermal water loss measurements are taken with relative humidity sensors that are located in either an open, closed, or condenser-chamber cylinder. However, there is currently no way to monitor and quantify overall peristomal skin health beneath an ostomy barrier.

[0006] Accordingly, it is desirable to provide wearable device for monitoring pH for skin health. Desirably, such a device can be worn with little to no comfort or aesthetic impact beyond known ostomy devices.

BRIEF SUMMARY

[0007] A wearable system for measuring pH levels is provided according to various embodiments.

[0008] In a first aspect, a wearable system for measuring pH levels is provided. The system may include a sensor that includes a plurality of sensor units. The system may also include a sensor layer and a bottom layer. The system may further include an adhesive layer. The adhesive layer may be configured to adhere to a user’s peristomal skin. The sensor layer may include at least one sensor that may include a sensor inlet opening, at least one sensor chamber, and a fluid pathway. The sensor inlet opening may extend from the sensor layer to the adhesive layer and may intake input fluid from the peristomal skin. The at least one sensor chamber may include a solution that detects a pH level of the input fluid. The fluid pathway may fluidically communicate the sensor inlet opening to the at least one sensor unit.

[0009] In an embodiment, the at least one sensor may further include an outlet opening, an extraction chamber, and at least one capillary bursting valve (CBV). The outlet opening may be configured to output analyzed input fluid.

[0010] In an embodiment, the at least one sensor may include three sensor units that measure a pH level in sequence or series as the input fluid travels through each of the three sensor units. [0011] In an embodiment, the three sensor units may be arranged in a circular configuration.

[0012] In an embodiment, the three sensor units may be arranged in a linear configuration.

[0013] In an embodiment, the at least one sensor may detect pH levels over a span of three days.

[0014] In an embodiment, the inlet opening may extend from the sensor layer to the adhesive layer and may be configured to surround a stoma.

[0015] In an embodiment, the at least one sensor may include four sensors.

[0016] In an embodiment, the four sensors may be arranged in a circular configuration around the stoma. Each of the four sensors may include a sensor inlet opening located near the inlet opening.

[0017] The foregoing general description and the following detailed description are examples only and are not restrictive of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The benefits and advantages of the present embodiments will become more readily apparent to those of ordinary skill in the relevant art after reviewing the following detailed description and accompanying drawings, wherein:

[0019] FIG. 1 is a front view of a wearable sensor attached to a user, according to an embodiment.

[0020] FIG. 2 is a front view of the wearable sensor of FIG. 1.

[0021] FIG. 3 is a front view of a sensor, according to an embodiment.

[0022] FIG. 4 is an exploded perspective view of the sensor and a user’s skin of FIG. 1.

[0023] FIG. 5 is a front view of a wearable sensor, according to an embodiment.

[0024] FIG. 6 is an example of a test apparatus for the wearable sensor of FIG. 5.

DETAILED DESCRIPTION

[0025] While the present disclosure is susceptible of embodiment in various forms, there is shown in the drawings and will hereinafter be described presently preferred embodiments with the understanding that the present disclosure is to be considered an exemplification and is not intended to limit the disclosure to the specific embodiments illustrated. The words “a” or “an” are to be taken to include both the singular and the plural. Conversely, any reference to plural items shall, where appropriate, include the singular. The words “first,” “second,” “third,” and the like may be used in the present disclosure to describe various information, such information should not be limited to these words. These words are only used to distinguish one category of information from another. The directional words “top,” “bottom,” up,” “down,” front,” “back,” and the like are used for purposes of illustration and as such, are not limiting. Depending on the context, the word “if’ as used herein may be interpreted as “when” or “upon” or “in response to determining.”

[0026] The present disclosure provides a wearable system for monitoring and measuring Pchanges in peristomal skin pH underneath a patient’s ostomy skin barrier. The wearable system may include a pH sensor that can allow monitoring of pH levels of peristomal skin. A majority of ostomy patients experience peristomal skin complications or irritation at some point. The wearable system can help understand the impact of ostomy barriers on peristomal skin health, allowing for an improved quality of life.

[0027] Ileostomies are a procedure that involves suturing a portion of the small intestine to the abdomen to form a stoma. An ostomy pouch is then worn over the stoma to collect output from the ileum. The stratum comeum (the outer layer of skin) has an acid mantle with a pH of about 4- 6, while ileostomy output has a neutral pH. Leakage of this fluid can lead to disruption of the skin’s barrier function due to these pH differences. There is also a buildup of moisture, known as occlusion, between the skin and the ostomy barrier. Occlusion of the skin can lead to changes in pH, bacteria counts, and transepidermal water loss.

[0028] After recovery, ostomy patients can quickly return to their normal lifestyles and despite having to be worn all day, ostomy barriers and pouches are discrete enough as to not be noticeable under clothes or to interfere with one’s regular routine. In an effort to avoid inhibiting patients’ routines, the pH sensor can be configured as part of a wearable system. To further enable patients’ retained lifestyles, the wearable system can be easy for the patients to independently apply and remove, similar to non-monitored ostomy barriers and pouches. The intuitive nature of the wearable system can also help in preventing patients from injuring the stoma while applying and removing the device. [0029] The wearable system can be designed to fit underneath an ostomy barrier. Tn one or more embodiments, the wearable system can further be designed to take up less than 10% of the adhesive area (FIG. 5). Such as system may be able to measure pH in a range of 4.5-7.5, at a sensitivity of 0.2. The wearable system can take measurements over the span of 3-4 days until a patient changes their ostomy barrier. It may be designed to allow patients to apply and remove the device themselves, similar to non-monitored barriers.

[0030] Turning now to the figures, FIG. 1 illustrates a wearable sensor 14 positioned on a user. According to example embodiments shown schematically in FIG. 1, the wearable sensor 14 can be positioned on the user’s peristomal skin around a stoma 12. The wearable sensor 14 can include a sensor 16. The sensor 16 can be used for measuring a pH level of the peristomal skin.

[0031] FIG. 2 illustrates a wearable sensor 114. According to example embodiments shown schematically in FIG. 2, the wearable sensor 114 can include an inlet opening 116, an outer edge 118, and sensors 120, 122, 124, 126. The inlet opening 116 can be configured to receive a stoma. The sensors 120, 122, 124, 126 can be configured to monitor and measure the PH levels of the skin at different points around the stoma.

[0032] FIG. 3 illustrates an example of a sensor 220. According to the example embodiment shown schematically in FIG. 3, the sensor 220 includes sensor units 222, 224, 226, an inlet opening 228 and a primary pathway 232. Each sensor unit 222, 224, 226 can also be refered to as a well. The inlet opening 228 is configured for intake of fluid. The sensor unit 222 (and similarly 224, 226) can include a chamber 230, capillary bursting valves (CBVs) 233, 234, 244, an extraction chamber 236, an outlet opening 238, and element 240. The primary pathway 232 extend to chamber 230. Secondary pathway 244 extends from primary pathway 232 to sensor unit 224 and includes CBV 234. Tertiary pathway 246 extends from secondary pathway 244 and includes CBV 234. Tn embodiments, the CBVs 234, can open periodically and allow for fluid to move within sensor 220 to their respective extraction chambers 236 for continuous monitoring and measurements. In an embodiment, element 240 may be a hole for allowing air to flow out of the chambers and allow liquid to enter the pathways of the sensor 220. In another embodiment, element 240 can be a structural element for mainting the structural integrity of the chamber 236.

[0033] In an embodiment, the sensor 220 can be a microfluidic sensor that collects fluid on the peristomal skin through inlet opening 228 and transports it into wells 222, 224, 226. The sensor 220 can include pH colorimetric sensing that can detect pH at various time intervals. The wells 222, 224, 226 can contain a material, for example a powder, which can change color based on a pH level of the fluid collected. The powder can be, for example, a red cabbage powder. The color change can be analyzed by a user or clinician or by collecting the RGB value through, for example, a photo and design platform, such as PHOTOSHOP or with an RGB sensor. The time intervals can be dependent on the rate at which the fluid can travel through the pathways 232, 244 and 246, and into each chamber 230. This can be beneficial in that the pH can be monitor and measured continuously over a period of time, for example, over a few days, and the pH can be monitored and measured in each of the sensor units 222, 224 and 226 over a period of time.

[0034] Protective Skin Barrier

[0035] The outer layer of skin, the stratum comeum, is often referred to as the acid mantle. This layer of skin has a pH ranging from 4-6, while pH becomes more basic in the deeper layers of skin. The acid mantle allows the skin to serve its function as a barrier against invading organisms. It is normal to have bacteria such as coagulase-negative staphylococci on the skin, but pathogenic bacteria begin to grow when the acidic pH is disturbed. The stratum comeum also has a lipid bilayer structure that allows it to serve as a permeability barrier. Enzymes in this bilayer are known to create ceramides, a skin component that helps reduce transepi derm al water loss. These enzymes require an acidic environment and are not active deeper in the skin. The pH of the skin is an important part of the protective barrier of the skin. There are a number of different factors that contribute to this. For example, it allows the skin to neutralize anything alkaline base. It also inhibits the growth of foreign bacteria while promoting the growth of natural bacteria in the optimal pH range. If the pH of the skin rises too much, it prevents the production of epidermal lipids and the skin will begin to lose water and can lead to diseases and infections. In addition, enzymes across the stratum corneum operate most effectively in an acidic environment. These enzymes help reduce transepidermal water loss and are only active in the stratum corneum and not in the deeper layers of the skin. This is also why the pH begins to increase in the deeper skin layers. Therefore, information on pH levels can provide information about ostomy output leakage and acid mantle condition.

[0036] Ostomy patients wear their adhesive skin barriers or pouches for up to five days at a time. During this period, there is a buildup of moisture between the skin and the adhesive, known as occlusion. The pH of skin can gradually increase from an acidic range to a neutral pH (e.g., about a pH of 7.0). Transepidermal water loss measurements can fluctuate but can eventually become saturated after a few days. The increase in transepidermal water loss suggests that the stratum corneum becomes more permeable as it gains moisture. The microbial flora of the skin can be mainly coagulase negative staphylococci when a user first mounts a skin barrier, but gramnegative rods can be observed at low levels after days of wear.

[0037] In an embodiment, the wearable system 220 can be used in a clinical setting which can allow for a better understanding of peristomal skin complications and can result in an improved design. The wearable system 220 can provide continuous information on the chemical and physical environment between the hydrocolloid barrier and peristomal skin. Qualitative information can be collected and converted to quantitative information that can be processed on a computer.

[0038] pH Color Indicator

[0039] There are numerous types of color indicators that can work in very specific pH ranges. In general, these indicators each work in the same way. The pH indicators are either a weak acid or weak base that change color as they are protonated or deprotonated. The following equation describes this general process:

[0040] HInd + H ₂ 0 H ₃ O ⁺ + Ind~

[0041] Hind is the acid form of the indicator while Ind is the conjugate base. The acid and conjugate bases have different colors associated with them and the ratio between these two determines the resulting color. The pH indicators have optimized pH ranges to work in and the expected pH range of our device will be between 5.0 and 7.0.

[0042] In order to assess the condition of peristomal skin and better understand its transition from a healthy state to an unhealthy one, the device will preferably measure certain skin parameters. This will help in the development of new materials that mitigate peristomal skin complications. The parameters considered are: for pH a range of: -4-7.5 pH; for hydration a range of about: 0-100 percent hydration; and for TEWL a range: -100-1500 pg/cm2/hr.

[0043] In an embodiment, the wearable system may have a maximum thickness of approximately 2 mm. The maximum thickness may be based on the thickness of most ostomy rings which are used to fill in uneven peristomal skin contours to create a flatter surface and prevent ostomy output from leaking under the ostomy barrier. Greater thicknesses can undermine the ostomy barrier’s occlusive effect. However, there could be some tolerance as some ostomy rings can be up to 4.5 mm thick. Modifying the ostomy barrier to allow for sensors to be placed in or over it while ensuring it still properly functions and occludes the peristomal skin is another possibile configuration.

[0044] In an embodiment, the pH may be used a source of information about ostomy output leakage and acid mantle condition. Both hydration and transepidermal water loss are important measurements of skin condition and overall health. Devices that measure these processes could be incorporated into this device by future groups or a separate device may be made for these measurements.

[0045] In an embodiment, the range of pH expected to be measured is approximately 4.5-7.5. In an embodiment, the wearable system can include a red cabbage powder as a pH indicator. Cabbage powder has a pH range of approximately 2-14 in which it will change color. This may be ideal because cabbage powder’s range in color change extends beyond the expected range of the present sensor, ensuring that no matter what the environment between the peristomal skin and ostomy barrier is, the present device will be able to record measurements. The sensitivity of the pH measured is also important. In an embodiment, the pH indicators can have a sensitivity of about 0.2 pH.

[0046] FIG. 4 illustrates a wearable sensor 314 over a skin layer 322. According to example embodiments shown schematically in FIG. 4, the wearable sensor 314 can include a first layer 316, a second layer 318, and a third layer 320. The skin layer 322 can include a stoma 324. The first layer 316 can include a first inlet opening 326, a sensor 328, and a first sensor inlet opening 330. The sensor 328 can include the sensor 220 of FIG. 3. The first layer 316 and second layer 318 can create a microfluidic network. The first layer 316 and second layer 318 can be soft elastomers that serve as the surface on which the microfluidic channels (pathways 232, 244 and 246) and chambers

230 built, and as a capping layer. The second layer 318 can be a bottom layer that can include a second inlet opening 332 and a second sensor inlet opening 334. The third layer 320 can be an adhesive layer that can include a third inlet opening 336 and a third sensor inlet opening 338. The inlet openings 326, 332, 336 can align to surround the stoma 324. The sensor inlet openings 330, 334, 338 can align to allow fluid to travel from the skin layer 322 to the sensor 328.

[0047] In an embodiment, the first layer 316 can be about 400 pm, the second layer 318 can be about 200 pm, and the third layer 320 can be a medical-grade acrylic adhesive film with a thickness of about 50 pm. The microfluidic network allows for mounting on various parts of the skin and enables sampling in any orientation. Additionally, function is not impaired by any kind of movement or deformation of the elastomer. This is ideal for a wearable device that will be used by ostomy patients in their daily lives, where the wearable device can be expected to operate in various conditions.

[0048] Flow in the microfluidic network is driven by pressure created by sweat glands due to the natural differences of osmolarity between plasma and sweat. The direction of flow is determined by a collection of CBVs (See FIG. 3, CBV 234) which enables the sequential filling of the chambers 230(See FIG. 3). The CBVs block flow at pressures lower than their characteristic bursting pressures (BPs) and can be regulated via the Young-Laplace equation (which gives the BP in a rectangular channel):

[0050] where G is the surface tension of the liquid, 0 _a is the contact angle (quantitative measure of the wettability of the elastomer surface), 9 is the min[0 _a + P; 180°], P is the diverging angle of the channel (the angle formed between the wall of the capillary valve and the wall of the input microfluidic channel), b is the width of the channel, and h is the height of the channel. The parameters can be changed to set a desired BP for each CBV, but G and 6 _a will have to be predetermined because those parameters depend on the liquid and material.

[0051] Due to the sequential filling of the wells, discrete sampling is possible, including over a span of multiple days, concurring with the time an ostomy barrier is typically used. Essentially, the microfluidic network will be composed of unit cells that each have a collection chamber with a well, three CBVs, an extraction chamber, and a sampling outlet.

[0052] In an embodiment, flow into a first CBV, which acts as an input for the chamber, occurs only after its corresponding BP is reached or exceeded, due to accumulation of the liquid. The chamber can then be filled and once liquid in the chamber has reached full capacity, sufficient pressure is created to burst a second CBV which directs flow into the first CBV of the next sensor unit. A third CBV can be designed to open only at a pressure created by the force when the microfluidic platform is inserted into a centrifuge, after collection of samples is complete. The centrifugal force allows flow from the third CBV of each sensor unit’s chamber into their corresponding extraction chambers where the samples can then be removed. The sampling outlet releases air trapped in the collection chamber. The depth of each well can be adjusted to allow for sampling at different intervals.

[0053] In an embodiment, mixing is prevented by the flow properties of the microchannels and CBVs, so new liquid input of varying pH won’t be affected by previous samples, and vice versa. However, this may apply specifically for channel dimensions of hundreds of micrometers and flow rates up to 1.0 pL per minute because this results in laminar flow in which mixing only occurs via molecular diffusion.

[0054] The microfluidic network can have significant design versatility, enabling the modification of not just the dimensions of the microchannels and chambers but also overall dimensions of the microfluidic network platform and the number of chambers, which provides the capability to consider different configurations under the ostomy barrier.

[0055] In an embodument, acquiring pH measurements from the wearable system can include taking a picture of the wearable system. Then this picture can be uploaded to a photo and design platform, such as PHOTOSHOP software on a computer. Then the RGB values from each chamber will be measured from the computer. These values will then be matched to the respective color on the pH scale such that pH can be determined for each chamber’s sample. The speed of this process can be increased through the use of individual RGB sensors that are in communication with a near- field communication (NFC) transmitter. This will increase processing time of the information and facilitate use of the device.

[0056] In an embodiment, the wearable system can be made of polymer poly(dimethylsiloxane), or PDMS. PDMS is transparent, flexible, and biocompatible, making it ideal for biomedical applications. Sylgard can similarly used for the PDMS.

[0057] FIG. 5 illustrates a wearable sensor 414. According to the example embodiment shown schematically in FIG. 5, the wearable sensor 414 can include sensor units 422, 424, 426, 428, 430, an inlet opening 432, CBVs 434, pathways 436, 437, 439, 441 and 443, and an outlet opening 438. The sensor unit 422 can be connected to sensor unit 424 through CBV 434 and the pathway 436. The sensor units 426, 428, and 430 can similarly be connected to immediately upstream sensor units 422, 424 ie pathways 437, 439, and 441, respectively. The inlet opening 432 can intake fluid from a skin layer for analysis in sensor units 422, 424, 426, 428, 430. The outlet opening 438 can ouput the fluid analyzed by sensor units 422, 424, 426, 428, 430. In an embodiment, the wearable sensor 414 can have the sensor units 422, 424, 426, 428, 430 arranged in a circular configuration. The wearable sensor 414 can be located near a stoma rather than surrounding the stoma. In another embodiment, the wearable sensor 414 can have sensor units 422, 424, 426, 428, 430 in a linear configuraion.

[0058] FIG. 6 illustrates a test device 500. According to the example embodiment shown schematically in FIG. 6, the test device 500 can include a container, such as a beaker 502, a hose fitting 504, a tube 506, and the wearable sensor 508. The wearable sensor 508 can have an inlet opening 510. The beaker 502 can be connected to the tube 506 using the hose fitting 504 and the tube 506 can be connected to the inlet opening 510 of the sensor 508. The beaker 502 can have various pH solutions that can be fed into the wearable sensor 508 through the inlet opening 510 for testing the wearable sensor 508.

[0059] To explore the properties of the red cabbage powder on its own, a solution was mixed with other solutions of acidic and alkaline pH. It was found that that the color change was almost instanteous and that the solution is reusable (i.e., after changing color once, the cabbage powder solution can continue to change colors if mixed with a new solution).

[0060] In order to solidify the red cabbage solution, it was found that gelatin has a pH tolerance of 4-10, which makes it suitable for the present sensor. After mixing the indicator solution with gelatine and allowing it to solidify, the solidified material was cut it into thin slices and solutions were applied to the material slices , which solutions had a range of pH values.

[0061] In an embodiment, a filter paper can be soaked in concentrated red cabbage solution and dried. The filter paper can allow for intense color that was achieved in 1 -2 seconds after contact with liquid. The filter paper can contain the liquid, preventing leaking. The filter paper is configured to absorb the liquid by distributing it evenly (e.g., wicking the liquid) across the surface of the filter paper and into the filter paper, which will contain small amounts as well as larger volumes of solution applied. Moreover, the treated filter paper can produce an intense color (and color change) while being very thin and compact. Thus, use of filter paper will allow efficient and convenient application of a colorimetric pH-indicator to the wearable system.

[0062] From the foregoing it will be observed that numerous modifications and variations can be effectuated without departing from the true spirit and scope of the novel concepts of the present disclosure. It is to be understood that no limitation with respect to the specific embodiments illustrated is intended or should be inferred. The disclosure is intended to cover by the appended claims all such modifications as fall within the scope of the claims.