A few years ago, I heard on the news that many people were being hospitalized with a condition of excess fluid in the lungs, called pulmonary edema. It’s common in elderly patients. Pulmonary edema is dangerous and can lead to breathing difficulties and lung failure. Because it has the potential to develop suddenly, it can be a serious medical emergency.

As a NIST researcher interested in the application of technology in healthcare, I wondered: Is there a way to monitor this condition at home with a simple wearable device?

Specifically, I was curious if the excess fluid in the lungs affects the electrical properties of the lung’s tissues in a way that can be sensed through radio frequency waves with a wearable device. The idea was to put a pair of wearable sensors on the patient’s chest and back. The devices would connect wirelessly through the lungs to monitor the change in the amount of liquid.

If the device detected the onset of pulmonary edema, it could alert the patient or their caregiver to contact a medical professional. The tool could also potentially send that information directly to the healthcare provider via a smartphone or other device.

I consulted with an expert from the National Institutes of Health on whether such a device would be helpful in practice. He confirmed it would be helpful in two ways: The device could provide regular screening of people susceptible to pulmonary edema. It would also be a useful tool to monitor patients who have been discharged from the hospital as they recover from this condition at home.

This simple idea led to an interesting research project.

Creating a wearable monitor

The first task was to create computational models of the lungs with different levels of excess fluid. The models needed to effectively capture the effect of excess fluid on the lungs’ electrical properties.

Another challenge we faced in this process was extending our computational models to incorporate an additional variable—breathing. This is needed because the amount of air in the lungs, in addition to the excess fluid, affects radio frequency waves. The air in the lungs ebbs and flows during breathing, so the amount varies. We needed to account for this in our model.

Our collaborator at the Duke University School of Medicine provided anatomical models based on CT scan data of patients’ breathing. That information allowed us to create another sequence of 3D computational models. These models helped us to capture the effect of the air on the electrical properties of the lungs during inhalation and exhalation.

Using that research, we showed the feasibility of the underlying idea. In other words, a simple, wireless wearable technology could monitor the variation of the fluid in the lung and alert the patient or the doctor when it exceeds a certain level.

While we’re excited about our progress so far, there’s still much work to be done before this technology is available to doctors and patients. Once we finish our comprehensive study and performance evaluation of the concept, we’ll have to work with a company interested in building a device prototype.

Once the prototype is ready, the manufacturer will have to run a clinical trial to test the product’s safety and performance. Often, this process leads to adjustment or modification of the prototype. The final stage would be the manufacturing and sale of the device.

Sayrafian uses a computer model in a NIST visualization lab. Credit: NIST

After I started this project, I learned more about pulmonary edema from the perspective of a family member. My mother had two episodes of this condition, one of which required emergency services.

Some known symptoms of pulmonary edema include coughs, wheezing, and shortness of breath. However, for elderly patients who might also suffer from other underlying conditions, it is sometimes unclear whether those symptoms are due to pulmonary edema or an unrelated issue.

I found it quite stressful to wonder whether my mom’s symptoms were pulmonary edema or something less serious. I imagine the same would be true for other caregivers, and hope a wearable product to monitor this condition helps patients, their families, and their doctors.

The IoT comes to your doctor’s office

You may be familiar with the term internet of things (IoT), which refers to connected “smart” devices like home thermostats, baby monitors, and vacuum cleaners. But IoT has other uses, including wearable, ingestible, or implantable medical devices.

For example, a doctor can check a patient’s stomach and esophagus using a procedure called endoscopy. It involves using a long, flexible tube equipped with a camera that passes through the patient’s throat to reach the esophagus and stomach. This procedure can now be done with a small, wireless camera embedded in a capsule that the person swallows. The capsule then moves through the digestive tract. The embedded camera takes periodic photos and transmits them to several receivers placed in a belt around the patient’s abdomen.

Other examples of the application of IoT in healthcare are wearable technologies such as glucose monitoring devices. These products typically have one or more sensors that measure biological or physiological data from the user’s body and then transfer those data to a doctor or the patient.

As these products become more common, I believe they’ll empower people to take a more active role in monitoring their health. However, more technological advances are needed before achieving full-scale seamless connectivity for IoT health devices.

NIST’s role in IoT for healthcare

One of the initial challenges in this field is that experts need to better measure how wireless signals generated by an implant or a wearable device travel through the body. The signals that carry the patient’s physiological information must be strong enough to establish a reliable communication path with the receiving device. At the same time, the signal strength should stay within the required limits to maintain safety and avoid harming tissues. The receiver may be located inside the body, on the surface of the body, or outside it.

Another consideration is the limited battery life for these devices’ operation, especially as they get smaller and more advanced. Each application typically requires a customized, detailed computational model to better measure and understand the wireless signal propagation inside the body.

For example, in the capsule endoscopy project I worked on, we developed a detailed computational model of the body’s gastrointestinal tract that allowed for simulation of a wireless endoscopy pill. The model helped us learn more about how the wireless signal emanating from the pill at various positions inside the gastrointestinal tract reaches the surface of the abdomen.

The mathematical models we developed from extensive measurements help NIST facilitate standardization. So, it’s exciting to conduct research that could contribute to future standards for these devices. If adopted by the healthcare industry, standards could help make these devices widely available. Ideally, standards-based communication protocols will allow these devices to work together and enable consumers to select the best products based on their individual healthcare needs.

Improving quality of life through connected healthcare

My own technical background is in networking and information theory. I remember coming across the general topic of IoT in healthcare in the early 2000s when I was attending a standards meeting for wireless specialty networks. At the time, I noticed a small study group discussing the standardization of communication and networking protocols for wearables and implants, also called “body area networks.” Not many people in the U.S. were working in this area at the time, but I saw so much potential for these devices to improve people’s health and quality of life. I wanted to get involved, and I’ve worked in this research area ever since.

If you are a scientist and want to help people, there is no shortage of problems to research in this area. I love working on topics and projects that could improve people’s lives and health, and I look forward to exciting advances in this research in the years to come.

Published Aug. 13, 2025, in NIST’s Taking Measure blog.