Signal-correction errors in the EasyOne Pro LAB multiple-breath washout device significantly impact outcomes in children and adults.

Multiple-breath washout (MBW) is an established technique to assess functional residual capacity (FRC) and ventilation inhomogeneity in the lung. Indirect calculation of nitrogen concentration requires accurate measurement of gas concentrations. To investigate the accuracy of the CO2 concentration and molar mass (MM) values used for the indirect calculation of nitrogen concentration in a commercial MBW device [EasyOne Pro LAB (EOPL), ndd Medizintechnik AG, Switzerland] and its impact on outcomes. We used high-precision gas mixtures to evaluate CO2 and MM sensor output in vivo and in vitro. We developed updated algorithms to correct observed errors and assessed the impact on MBW outcomes and FRC measurement accuracy compared with body plethysmography. The respiratory exchange ratio (RER)-based adjustment of the measured CO2 signal used in the EOPL led to an overestimated CO2 signal (range -0.1% to 1.0%). In addition, an uncorrected dependence on humidity was identified. These combined effects resulted in an overestimation of expired nitrogen concentrations (range -0.7% to 2.6%), and consequently MBW outcomes. Corrected algorithms reduced the mean (SD) cumulative expired volume by 15.8% (9.7%), FRC by 6.6% (3.0%), and lung clearance index by 9.9% (7.6%). Differences in FRC between the EOPL and body plethysmography further increased. Inadequate signal correction causes RER- and humidity-dependent expired nitrogen concentration errors and overestimation of test outcomes. Updated algorithms reduce average signal error, however, RER values far from the population average still cause measurement errors. Despite improved signal accuracy, the updated algorithm increased the difference in FRC between the EOPL and body plethysmography.NEW & NOTEWORTHY We investigated the accuracy of the molar mass (MM) and CO2 sensors of a commercial multiple-breath washout device (ndd Medizintechnik AG, Switzerland). We identified humidity and respiratory exchange ratio-dependent errors that in most measurements resulted in an overestimation of expired nitrogen concentrations, and consequently, MBW results. Functional residual capacity and lung clearance index decreased by 6.6% and 9.9%, respectively. Despite improved signal accuracy, the difference in FRC between the EOPL and body plethysmography increased.

Digital Guinea Pig: Merits and Methods of Human-in-the-Loop Simulation for Upper-Limb Exoskeletons.

Exoskeletons operate in continuous haptic interaction with a human limb. Thus, this interaction is a key factor to consider during the development of hardware and control policies for these devices. Physics simulations can complement real-world experiments for prototype validation, leading to higher efficiency in hardware and software development iterations as well as increased safety for participants and robot hardware. Here, we present a simulation framework of the full rigid-body dynamics of a coupled human and exoskeleton arm built to validate the full software stack. We present a method to model the human-robot interaction dynamics as decoupled spring-damper systems based on anthropometric data. Further, we demonstrate the application of the simulation framework to predict the closed-loop haptic-rendering performance of a 9-DOF exoskeleton in interaction with a human. The simulation was capable of simulating the closed-loop system's reaction to an impact on a haptic wall. The intrusion into the compliant walls was predicted with a relative accuracy of 6% to 13%. Admissible control gains could be predicted with an accuracy of around 14%, and higher prediction accuracy is indicated when modeling the torque tracking bandwidth of the actuators. Hence, the simulation is valuable for validating prototype software, developing intuition, and a better understanding of the complex characteristics of the coupled system dynamics, even though the quantitative prediction is limited.