Hollow Microcatheter Actuator and MEMS Thermal Flow Sensor Hybridization Toward Respiration Measurement Inside 1 MM Diameter Bronchioles in Lung Airway

Respiratory diseases, particularly chronic obstructive pulmonary disease (COPD), are a major global health concern, yet existing clinical tools fall short in accurately assessing airflow within small, lesion-affected regions of the lungs. To overcome this limitation, here we developed a novel hollow microcatheter-based actuator-sensor system capable of measuring respiration directly within the bronchioles. The system integrated a tubular airflow rate sensor, fabricated through a standard micro-electro mechanical systems (MEMS) process, into the base of a microcatheter, while the tip consisted of a hollow actuator with an outer diameter of as small as 0.8 mm. This compact design enabled accurate airflow measurement in airways as small as 0.825 mm in diameter, which corresponds to the 13<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> branch of airway in healthy adults. Additionally, we systematically analyzed the relationship between airway diameter, catheter insertion depth, and airflow through the catheter to optimize measurement performance in bronchioles approximately 1 mm wide.