Modified face mask detects chronic kidney disease through breath

Surgical face masks help prevent the spread of airborne pathogens and therefore were ubiquitous during the COVID-19 pandemic. Now, a modified mask could also protect a wearer by detecting health conditions, including chronic kidney disease. Researchers reporting in ACS Sensors incorporated a specialized breath sensor within the fabric of a face mask to detect metabolites associated with the disease. In initial tests, the sensor correctly identified people with the condition most of the time.

Kidneys remove waste products made by the body's metabolic processes. But in the case of chronic kidney disease (CKD), these organs have become damaged and lose function over time, which can have wide-ranging implications on a person's health. The U.S. Centers for Disease Control and Prevention estimates that 35 million Americans have CKD, and many more could have the disease without knowing it, possibly at an early stage. Currently, medical professionals diagnose the condition by measuring metabolites in blood or urine, but low-cost, low-tech systems, like the ones made from specialized candies, could make the process easier.

Chemical breath sensors are another diagnostic tool currently being explored because people with CKD exhale elevated levels of ammonia - a chemical associated with the condition. However, ammonia is also associated with other health conditions. Corrado Di Natale and colleagues wanted to create a specific sensor that simultaneously detects ammonia and other CKD-related metabolites.

For ease of use, they incorporated the sensor into a familiar form: a surgical face mask. To create the breath sensor, the team first coated silver electrodes with a conductive polymer that is commonly used in chemical sensors. The polymer was modified with porphyrins - molecules sensitive to volatile compounds - to boost the sensitivity. The coated electrodes were placed between the layers of a disposable medical face mask, and wires connected the device to an electronic readout. When select gases interacted with this specialized polymer, it caused a measurable change of electrical resistance. These initial experiments in air confirmed the high sensitivity of the sensor for CKD-related metabolites, including ammonia, ethanol, propanol and acetone.

Then the specialized face masks were tested on 100 individuals. About half of the participants had a CKD diagnosis, and the other half (the control group) did not. The sensors detected several compounds in the participants' breath, and statistical analysis of the data revealed a clear pattern distinguishing the participants with CKD from the control group. The team's sensor correctly identified when a patient had CKD 84% of the time (true positive) and that a patient did not have CKD 88% of the time (true negative). In addition, the results suggest that the sensor data can be used to estimate the stage of CKD, which could be highly valuable in the diagnostic process.

The researchers say that these findings present the potential for straightforward, non-invasive and cost-effective monitoring of CKD patients.

"The implementation of this technology is expected to enhance the management of CKD patients by facilitating the timely identification of changes in disease progression," say Sergio Bernardini and Annalisa Noce, coauthors of the study.