Battery applications in medical monitoring and the changing environment

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Battery applications in medical monitoring and the changing environment [Copy link]

As healthcare expands to include emerging technologies, as batteries shrink and connectivity increases, the medical field is poised for a paradigm shift in treatment options. In the next decade, doctors will routinely monitor hundreds of patients using online tools, without the need for in-person physical examinations, allowing healthcare systems to cope with an increasing number of patients. As this trend arrives, more and more medical and personal electronics companies are adopting wearable devices to improve patient outcomes and services during both inpatient and outpatient care. These companies are helping to improve patient care through a variety of innovations in medical devices, but one focus is changing the design so that all care devices can track patients throughout their hospital stay. Currently, significant resources are dedicated to moving patients and exchanging monitoring devices between different wards. All of this is time-consuming and laborious when nurses must prepare large equipment to receive patients from other wards and must coordinate logistics to return the equipment to its original location after the patient is transferred. More mobile devices can smoothly move patients from the intensive care unit to the general ward until the patient is eventually discharged. The transitional care process is also becoming more convenient by allowing devices to be connected to the patient, without the need for coordination between departments or even outside agencies. Portability is not a new concept, as most traditional medical devices already use batteries (albeit very large ones). However, the size of these batteries makes it difficult for most patients to be easily moved. To address this challenge, companies have taken a new approach, using basic sensors as the primary monitoring tool and providing designated secondary functions by connecting to the medical network. Eliminating all processing, storage and other non-monitoring processes reduces the cost and surface area of medical devices, making them more affordable, lightweight and versatile. By monitoring patient information as shown in Figure 1, from cutting-edge wearable devices to traditional hospital equipment such as bedside monitors, drug infusion pumps and sensor-equipped beds, medical devices can help patients stay connected to their medical teams.

Figure 1: Patient information that can be tracked and transmitted by a wearable display

Connectivity can improve a number of routine healthcare processes, including documentation, asset tracking, and patient care. Automated documentation prevents errors when recording vital signs. Constantly connected devices can maximize the use of devices, making them convenient and even complete routine healthcare procedures. For example, consider the process of preventing bedsores in bedridden patients. In the past, nurses had to remember to change and record the patient’s position every few hours to prevent pressure sores. However, connected hospital beds or sensors worn by patients can make this process much smoother, automatically tracking activity and alerting nurses when action is needed. These devices can also create an accurate log of the patient’s different body positions, providing doctors with useful information if the patient reports any pain or changes in status. With these small improvements, we are on the cusp of a healthcare revolution. Doctors can now do more with less, but only if these devices stay on. For this reason, 24/7 battery life is critical to the convenience and outcomes of patient care. The energy consumed by constant communications and other features such as touchscreens makes disposable batteries a viable solution in this new monitoring space. By powering these operations, these batteries quickly become depleted, significantly increasing the cost of each device operation. While rechargeable lithium-ion batteries are sufficient to solve the power problem, they require more stable temperature and protection, and proper charging is important. For medical applications that are small and susceptible to electrical noise, linear chargers can be used to perform the charging task. Linear chargers are easy to design into any power block and can provide up to 1.5A charge current, its solution size is smaller than a switching charger. TI's smallest linear charger, the bq25100, features termination current control with accuracy down to 1mA, leakage current of only 75nA (negligible compared to the self-discharge rate of the battery), and one of the lowest bill of materials (BOM) costs on the market. These features make the bq25100 ideal for simple applications that require charge currents below 250mA or precise termination currents, such as wearable applications and patient monitors. If you need a more sophisticated charger, the bq25120A is a good choice. This charger comes with integrated I2C, push-button control, low-dropout linear regulator (LDO), buck converter, fast charging and power path capabilities, while still being smaller than three grains of rice. It has the ability to power the system while charging the battery, enabling instant-on functionality. Push-button control helps to start or interrupt the connection to the microcontroller (MCU) from the rails, making it easy to use different operating modes. Fast charging allows for a large amount of charge in a short period of time, but doing so creates some additional wear on the battery. Built-in I2C communication control allows for full customization of the device. For example, the I2C interface lets you customize the charging profile through the MCU. You can configure the charge voltage, charge current, termination threshold, input current limit, safety timer limit, and more to meet a variety of specifications. This customization allows for the design of lightweight, wearable solutions with attached small batteries that can be charged without compromising performance or customization. Customization also allows for lower termination current, which means you can charge the battery to a higher capacity per cycle. See Figure 2. Figure 3 shows the use of a bq25100 or bq25120A linear charger in a wearable electrocardiogram (ECG) patch. This ECG patch would allow patients who are recently undergoing heart surgery to have their vital signs continuously tracked without obtrusive wires or devices connected to them. A miniaturized device like the bq25120A makes this design possible.

Figure 3: ECG Patch System Diagram

Batteries are becoming an integral part of medical technology as the need for small solutions continues to grow, enabling portability, long life, and continuous connectivity. Using devices that continuously monitor a patient's health not only enhances the patient care experience, but also improves the medical process within a hospital or healthcare facility. Size-conscious linear chargers like the bq25100 and bq25120A maximize battery life, allowing devices like ECG patches to meet the needs of patients' health checks without the need for constant battery replacement, which compromises monitoring. Of course, TI offers far more linear chargers than those mentioned in this article, and Texas Instruments is constantly developing new products to meet the latest needs of the medical industry. These include products that support the latest patient monitoring systems, helping to make modern healthcare from the ICU to the patient's home more optimal through more flexible and efficient performance. The future is full of uncertainty, but the prospects for this product are bright.