Exhalatory dynamic interactions between patients connected to a shared ventilation device

Abstract

In this work a shared pressure-controlled ventilation device for two patients is considered. By the use of different valves incorporated to the circuit, the device enables the restriction of possible cross contamination and the individualization of tidal volumes, driving pressures, and positive end expiratory pressure PEEP. Possible interactions in the expiratory dynamics of different pairs of patients are evaluated in terms of the characteristic exhalatory times. These characteristic times can not be easily established using simple linear lumped element models. For this purpose, a 1D model using the Hydraulic and Mechanical libraries in Matlab Simulink was developed. In this sense, experiments accompany this study to validate the model and characterize the different valves of the circuit. Our results show that connecting two patients in parallel to a ventilator always resulted in delays of time during the exhalation. The size of this effect depends on different parameters associated with the patients, the circuit and the ventilator. The dynamics of the exhalation of both patients is determined by the ratios between patients exhalatory resistances, compliances, driving pressures and PEEPs. Adverse effects on exhalations became less noticeable when respiratory parameters of both patients were similar, flow resistances of valves added to the circuit were negligible, and when the ventilator exhalatory valve resistance was also negligible. The asymmetries of driving pressures, compliances or resistances exacerbated the possibility of auto-PEEP and the increase in relaxation times became greater in one patient than in the other. In contrast, exhalatory dynamics were less sensitive to the ratio of PEEP imposed to the patients.

Ventilator output splitting interface ‘ACRA’: Description and evaluation in lung simulators and in an experimental ARDS animal model

“…In the ACRA interface, a 6 mm diameter, 15 cm length tube was used as bypass circuit. This was selected considering previously obtained results from our research group [ 22 ] and two important factors: 1) the flow resistance of the bypass circuit is proportional to the tube length and to the diameter elevated to the fourth power and, 2) the total air volume of the bypass circuit is proportional to the length and to the squared diameter. In our study, the selected tube permitted to operate with adequate pressure signals and at the same time guaranteed a negligible back flow.…”

“…The testing of the ACRA on two paired animals with different respiratory mechanics contributed to the experiment with real-time biological and hemodynamic responses from dual ventilation. Although the presence of asymmetrical ΔP and compliance between paired units could lead to adverse events such as auto-PEEP [ 22 ], the results obtained in this study could serve as a promising background in the face of shortage or for further investigations. It must be considered that although our animal model did not show significant differences on the compliance between paired units, the lung lavages were effective to simulate an ARDS scenario and the model considered useful to demonstrate that a different ΔP could be obtained with the use of the ACRA interface.…”

Sharing Mechanical Ventilator: In Vitro Evaluation of Circuit Cross-Flows and Patient Interactions

“…Recently, many efforts have been made to characterize ventilation sharing. In addition, ventilator circuit modifications and monitoring have been proposed to provide personalized ventilation and improve the safety profile [ 13 , 14 , 15 , 16 , 17 ]. The ethical aspects related to ventilator sharing are still under discussion [ 18 , 19 , 20 , 21 ].…”

Multiple Mechanical Ventilation: historical review and cost analysis

“…[21][22] [15][23][24] [25][26][27][18][28][29][30][31][32] Control: 2L volume, breathing rate of 10 breaths/min and PEEP of 5 cm H2O. Performed combinations of resistance and compliance of the lung simulatorsThe authors conclude that multiple pulmonary ventilation is an attractive concept; however, it is not possible to control the current volume for each subject, and the disparity of it is proportional to the variability in compliance.…”