3D Printed Spirometer for Pulmonary Health Assessment Based on Fiber Bragg Gratings

The evaluation of lungs functionality enables the diagnose and monitoring of several pulmonary disorders. Spirometry is an established technique for pulmonary function tests, which provides information about several respiratory parameters, such as the forced vital capacity (FVC), corresponding to the maximum volume of expired air; the forced expiratory volume in 1 second (FEV1), which is the volume of exhaled air after the first second of the forced respiratory maneuver; the peak expiratory flow (PEF), representing the maximum flow of exhaled air during the maneuver; and the ratio of FEV1/FVC. In this work, a spirometer based on fiber Bragg gratings (FBGs), integrated in a 3D printed structure is proposed. The dynamics and magnitude of the air flow are determined through the resultant strain variations applied on the FBG sensor, along with the differentiation between the inhalation and exhalation phases. The air flow temperature effect was evaluated and its compensation was also performed for the accuracy of the results. The performance of the reported system was theoretically analyzed and experimentally tested. The implementation results were compared to the ones obtained with a commercial handheld spirometer, to assess the accuracy of the developed device. The accordance in the values obtained proved the suitability of the developed system to act as a reliable spirometer.