Wearable Transcutaneous CO₂ Monitor Based on Miniaturized Nondispersive Infrared Sensor

Transcutaneous oxygen and carbon dioxide provide the status of pulmonary gas exchange and are of importance in diagnosis and management of respiratory diseases. Though significant progress has been made in oximetry, not much has been explored in developing wearable technologies for continuous monitoring of transcutaneous carbon dioxide. This research reports the development of a truly wearable sensor for continuous monitoring of transcutaneous carbon dioxide using miniaturized nondispersive infrared sensor augmented by hydrophobic membrane to address the humidity interference. The wearable transcutaneous CO
₂
monitor shows well-behaved response curve to humid CO
₂
with linear response to CO
₂
concentration. The profile of transcutaneous CO
₂
monitored by the wearable device correlates well with the end-tidal CO
₂
trend in human test. The feasibility of the wearable device for passive and unobstructed tracking of transcutaneous CO
₂
in free-living conditions has also been demonstrated in field test. The wearable transcutaneous CO
₂
monitoring technology developed in this research can be widely used in remote assessment of pulmonary gas exchange efficiency for patients with respiratory diseases, such as COVID-19, sleep apnea, and chronic obstructive pulmonary disease (COPD).