Development of a Bio-Inspired Mechatronic Chest Wall Simulator for Evaluating the Performances of Opto-Electronic Plethysmography

Instrumented gait analysis based on optoelectronic systems is an expensive technique used to objectively measure the human movement features and it is generally considered as the gold standard. Opto-electronic plethysmography (OEP) is a particular motion analysis system able to: (i) determine chest wall kinematic via the evaluation of marker displacements placed on the thorax and (ii) compute respiratory volumes during breathing. The aim of this work is to describe the performances of a custom made, bio-inspired, mechatronic chest wall simulator (CWS), specifically designed to assess the metrological performances of the OEP system. The design of the simulator is based on the chest wall kinematic analysis of three healthy subjects previously determined. Two sets of experiments were carried out: (i) to investigate the CWS dynamic response using different target displacements (1 - 12 mm), and (ii) to assess the CWS accuracy and precision in simulating quite breathing, covering the physiological range of respiratory frequency and tidal volume. Results show that the CWS allows simulating respiratory frequency up to ~ 60 bpm. The difference between the actual displacement and the set one is always < 9 μm. The precision error, expressed as the ratio between measurement uncertainty and the actual displacement, is lower than 0.32%. The observed good performances permit to consider the CWS prototype feasible to be employed for assessing the performances of OEP system in periodical validation routines