Keep Biomedical Sensors Firmly in Place and Reduce Errors with Medical Securement Tapes
Contributed By Digi-Key's North American Editors
As the Internet of Things (IoT) expands into medical devices there has been an increase in the number and variety of biometric sensors that must be attached to human skin. The collected data is used to monitor and diagnose medical conditions, as well as study and improve the performance of professional athletes and commercial at-home personal exercise programs.
While specially manufactured medical securement tape is commonly used to secure the sensors, these tapes are not “one-size-fits-all”. Instead, various factors must be considered such as comfort, air and moisture permeability, and resistance to fluids, all adding to the complexity of tape selection. In addition, for some applications, the tape must be quickly and easily removed and reattached to the skin to reposition the sensors, which can be important in emergency situations. What is needed is a variety of medical tapes that are easily differentiated so that they can be applied to the appropriate situation.
This article introduces a family of medical tapes from 3M designed for different human skin attachment situations. The article explains the uses of four 3M medical tapes and how they address specific medical securement applications. It also looks at the advantages of standardizing on one family of medical tape, which include simplifying purchasing, consistency of documentation, and ease of use.
Medical securement tape applications
Just as the availability and wide selection of environmental sensors has spurred growth in commercial IoT as well as Industrial IoT (IIoT), the availability and variety of biometric sensors are encouraging new medical sensing devices, including medical IoT devices. Consumer biometric sensing products such as smart watches with heartbeat monitors can easily be strapped to a wrist, while consumer heart monitors can be strapped around a person’s chest to provide even better-claimed accuracy. This improved accuracy is due not only to using a more precise sensor but also to the secure placement of the heart monitor over the heart. The accuracy of biometric sensor data is directly related to both sensor type and proper placement on the skin.
However, for medical-grade biometric sensing applications, many sensors must be attached to locations not amenable to a simple strap. In addition, they may also need to be more tightly and securely coupled to the skin surface for a reliable biometric reading. This requires the use of medical securement tape to keep the sensor in place. As seen in Figure 1, most medical securement tape is composed of a printable and writable backing that is the tape itself, an adhesive to affix the tape to skin, and a removable liner that is pulled away to expose the adhesive.
Figure 1: Medical securement tape is usually composed of a backing (top) and an adhesive (middle). A liner (bottom) protects the adhesive and is pulled away when ready for use. (Image source: 3M Medical Materials)
The selection of backing and adhesive in the construction of a medical tape determines its use characteristics. Medical securement tape situations are not all the same, and the proper selection and use of the tape requires considering a number of ergonomic factors. These combined factors dictate the construction of the tape’s backing and the choice of adhesive used.
Medical securement tape ergonomics
One important consideration is fluid resistance. For long-term use, a medical securement tape can become wet due to frequent washing of the area or during a shower, resulting in a lack of adhesion, leading to unreliable sensor readings. If fluid resistance is a requirement, that often involves a tape backing made of polyethylene with an acrylic-based medical adhesive. This construction is not only resistant to fluids but also prevents water vapor—such as in a hot shower or an area with high humidity—from permeating the tape.
A complementary requirement to fluid resistance is the typical moisture vapor transmission rate (MVTR) of the tape. MVTR is typically specified in grams per square meter (gm/m²) of moisture allowed through the material over a 24 hour period. While in some situations no fluids or water vapor at all may be allowed past the tape (MVTR = ~0), in others it may be necessary to allow moisture such as perspiration to pass through the tape. In the latter, a nonwoven fabric tape backing allows the skin to breathe and perspiration to evaporate.
There are some use cases where a tape must be easily repositionable so that the sensor can be quickly relocated or allow for limited multiple uses on the same patient. While a variety of adhesives are available for one-time-use tapes, silicone-based medical adhesives allow the sensor to be easily removed and securely attached again.
The comfort of the tape is always important, especially for extended-wear tapes. Nonwoven fiber tape with at least a moderate MVTR is usually the most comfortable, although polyethylene tape can be somewhat comfortable depending on the construction and placement. Tape comfort is also related to the thickness of the backing and the length of time a tape is used. Extended-wear tape needs to be comfortable for up to a week without causing patient discomfort, and thinner backing material can provide more flexibility and comfort.
3M medical securement tapes
To address these different applications, 3M Medical Materials manufactures a variety of different medical securement tapes. These securement tapes take into account the various ergonomic factors discussed above. In addition, because these tapes can be standardized and are available from one supplier, 3M simplifies inventory management and provides consistent documentation between products, which can simplify purchasing and reduce errors.
For extended wear applications, 3M manufactures their 3M-4077 extended wear nonwoven tape (Figure 2). The 3M 4077 4" X 10YD (Figure 1) is a popular size at 4 inches (in.) x 10 yards (yds) with a white nonwoven polyurethane backing that is 0.16 millimeter (mm) thick. It uses an extended wear acrylic adhesive, which makes it highly comfortable for extended use. Its MVTR is specified at ~185 gm/m² and is somewhat fluid resistant, allowing skin to breathe for up to 14 days of recommended use.
Figure 2: The 3M 4077 medical securement tape is recommended for extended wear of up to 14 days. It ships in a convenient roll that is less than 8 in. diameter. (Image source: 3M Medical Materials)
The 3M 4077 medical securement tape is not repositionable and is recommended for one-time use only, making this tape applicable for extended wear biometric sensors that are discarded after one application.
Like all the tapes discussed here, the 3M 4077 ships in a roll for ease of use. The roll is less than 8 in. in diameter and is easily stored in a medical bay or emergency room.
For medical securement tape applications where the skin must be allowed to breathe, the tape must have a high MVTR. For these applications, 3M offers the 3M 1530 4" X 10YD. This tape measures 4 in. x 10 yds with a 0.14 mm white nonwoven rayon backing material and comes with a surgical-grade acrylate medical adhesive. This construction results in a very high MVTR rate of 4200 gm/m². It is not repositionable and has no resistance to fluids, making it unsuitable for most consumer biometric applications. With its high MVTR and good comfort level, the tape is specified for surgical applications and extended inpatient monitoring. It is easy to tear by hand—an advantage in emergency medical situations where events are progressing rapidly.
For applications where a high degree of comfort and flexibility is required, 3M provides the 3M 9836 4" X 10YD polyurethane film surgical tape with an acrylic medical adhesive. The tape is in the standard-sized 4 in x 10 yds. The backing is polyurethane film and at only 0.03 mm thick is the thinnest tape here, providing flexibility and comfort. It is water resistant and reasonably breathable at ~450 gm/m², providing a good compromise between breathability and water resistance. This tape’s thin comfortable backing, flexibility, reasonable breathability, and water resistance can make it applicable for attaching sensors to a child where the sensor and securement tape must withstand some twisting—especially important with a patient that may not be able to provide effective verbal feedback as to the comfort of the sensor attachment.
For some sensor monitoring applications, the sensor must be repositionable for multiple uses, and must also secure a medical instrument to the skin of the patient. In these applications, double-coated tape like the 3M 2477P 4" X 10YD is very useful (Figure 3). The tape measures 4 in. x 10 yds with a very thin 0.04 mm thermoplastic elastomer (TPE) backing, with adhesive on both sides (layer C). The TPE is translucent, allowing a convenient view of the sensor and skin to assist in proper placement. On one side is a silicone acrylate medical adhesive (layer B) that is designed to be gently removed and repositioned on the skin to secure a biometric sensor. On the reverse side of the TPE backing is an acrylic-based adhesive (layer D). This second adhesive can attach securely to a miniature medical biometric sensor device.
Figure 3: The layers of the double-sided 3M 2477P 4 x 10 YD medical securement tape includes a silicon acrylate adhesive on one side (layer B) and an acrylic-based adhesive (layer D) on the other. (Image source: 3M medical Materials)
This unique medical securement tape can serve two purposes. First, it can serve as securement for both the sensor and the medical biometric recording device. This provides a compact biometric recording system without long wires. The biometric sensor device can be a very lightweight embedded computer powered by a CR2032 battery. It could record the sensor reading in flash memory or send the sensor readings via Bluetooth or Wi-Fi to a computer or mobile device. This is also useful for prototyping commercial biometric sensor devices based on postage stamp-sized single-board computers (SBCs).
Second, this tape can be used as a standalone medical tape. The silicone adhesive side can be used for repositionable or reusable biometric sensors. This allows biometric sensors for athletes to be used and reused on a daily basis. The tape has moderate resistance to fluids and has an MVTR of 400 gm/m²—good for short-term use.
The 3M-2477P specifications do not recommend that the acrylic-based adhesive be used against the skin.
Not all biometric sensor securement applications are the same, so there exists a wide selection of medical securement tapes. The use conditions of medical tape, including the ergonomics of the situation, determines the materials used for the backing and adhesive. Standardizing on one supplier for medical tape simplifies purchasing and inventory, reduces errors, and provides consistency in documentation.
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