Abstract
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.
Highlights
Motion analysis systems are used to measure human movements
The aim of these experiments was two fold: (i) the dynamic response analysis allows controller parameters setting and optimization, with particular focus on PID gains; (ii) the measurement of time used by the system to complete the set displacement establishes the maximum number of breathings per minute that the chest wall simulator (CWS) can simulate, it can be considered the time employed by the CWS to perform its fastest inspiratory or expiratory phase
In this work we have described a custom made, bioinspired, mechatronic chest wall simulator (CWS) designed and controlled to assess the metrological performances of the Opto-electronic plethysmography (OEP) system: a human chest wall has been simulated during quite breathing by moving eight movable panels used as chest wall compartments
Summary
Motion analysis systems are used to measure human movements. The first study aiming at calculating three-dimensional chest wall volume changes dates back to 1994 [23], where authors developed the first motion analysis systems for assessing breathing mechanics, implementing an algorithm. The lung volume was evaluated through the ELITE system and verified by spirometry test: a good correlation with spirometric measurements has been observed with a maximum percentage error of 21.3 % in BTPS1 condition [23]. Cala et al [24] improved the accuracy of breathing volume measurements by means of 86 markers (i.e., percentage measurement error ranges between 2 % and 3.5 %) and developed a biomechanical model separating the chest wall into 3 compartments: the upper rib cage, the lower rib cage and the abdomen. In 1999, Gorini et al [25] proposed a 89 markers protocol for lung volume measurements
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