Assessment of mechanical ventilation parameters on respiratory mechanics

Design of a new artificial breathing system for simulating the human respiratory activities

The purpose of this work is the conception and implementation of an artificial active respiratory system that allows the simulation of human respiratory activities. The system consists of two modules, mechanical and electronical. The first one represents a cylindrical lung adjustable in resistance and compliance. This lung is located inside a transparent thoracic box, connected to a piston that generates variable respiratory efforts. The parameters of the system, which are pressure, flow and volume, are measured by the second module. A computer application was developed to control the whole system, and enables the display of the parameters. A series of tests were made to evaluate the respiratory efforts, resistances and compliances. The results were compared to the bibliographical studies, allowing the validation of the proposed system.

Effect of mechanical ventilation waveforms on airway wall shear

Better understanding of airway wall shear stress/strain rate is very important in order to prevent inflammation in patients undergoing mechanical ventilation due to respiratory problems in intensive-care medicine. The objective of this study was to investigate the role of mechanical ventilation waveforms on airway wall shear/strain rate using computational fluid dynamics analysis. Six different waveforms were considered to investigate the airway wall shear stress (WSS) from fluid dynamics analysis for the airway geometry of two-to-three generations. The simulation results showed that Original with Sine Inhale Waveform (OSIW) produced the highest WSS value and the Near True Sine Waveform produced the lowest WSS value. Also, the Original with Sine Inhale Waveform and the Short Sine Inhale with Long Sine Exhale Waveform (SSILSEW) produced a higher shear strain rate in comparison to the Original Waveform (OW). These results, combined with optimization, suggest that it is possible to develop a set of mechanical ventilation waveform strategies to avoid inflammation in the lung.

Analysis for stress environment in the alveolar sac model

Better understanding of alveolar mechanics is very important in order to avoid lung injuries for patients undergoing mechanical ventilation for treatment of respiratory problems. The objective of this study was to investigate the alveolar mechanics for two different alveolar sac models, one based on actual geometry and the other an idealized spherical geometry using coupled fluid-solid computational analysis. Both the models were analyzed through coupled fluid-solid analysis to estimate the parameters such as pressures/velocities and displacements/stresses under mechanical ventilation conditions. The results obtained from the fluid analysis indicate that both the alveolar geometries give similar results for pressures and velocities. However, the results obtained from coupled fluid-solid analysis indicate that the actual alveolar geometry results in smaller displacements in comparison to a spherical alveolar model. This trend is also true for stress/strain between the two models. The results presented indicate that alveolar geometry greatly affects the pressure/velocities as well as displacements and stresses/strains.