2025 Volume 74 Issue 3 Pages 480-487
The peripheral airways (inner diameter less than 2.0 mm), particularly the bronchioles, are important in the pathogenesis of chronic respiratory diseases, such as chronic obstructive pulmonary disease (COPD). Since the pathological lesions in the peripheral airways are associated with airflow obstruction in COPD, early detection of these lesions is important. However, current pulmonary function tests only assess the function of entire lungs, making it difficult to detect precise lesions in the peripheral airways and to identify their location. We have developed and improved a miniaturized thermal flow sensor, which enables the assessment of peripheral airways via bronchoscopy, by using microelectromechanical systems (MEMS) technology. In this study, we measured pulmonary functions in rats, which trachea has a similar diameter to human peripheral airways, using our developed miniaturized thermal flow sensor. Respiratory changes were measured and assessed under normal breathing conditions, following the administration of bronchoconstrictive agents, and in COPD model rats, based on respiration rate, tidal volume, and respiratory time using our sensor. The sensor detected respiration rate and tidal volume under normal breathing conditions. The extension of respiratory time and reduction in tidal volume were detected by the administration of a bronchoconstrictive agent. Furthermore, the extension of expiratory time and the reduction in expiratory volume in COPD model rats were also detected by the sensor. These results suggest that our developed sensor may be a valuable tool for diagnosing and assessing the disease severity, as well as evaluating the drug efficacy, in various diseases, where peripheral airway lesions play a significant role, including COPD.
