No abstract

We identified 3 types of LVAD-related blood flow obstruction, and developed an algorithm for optimal diagnosis and treatment.

Background In face of the Coronavirus Disease (COVID)-19 pandemic, best practice for mechanical ventilation in COVID-19 associated Acute Respiratory Distress Syndrome (ARDS) is intensely debated. Specifically, the rationale for high positive end-expiratory pressure (PEEP) and prone positioning in early COVID-19 ARDS has been questioned. Methods The first 23 consecutive patients with COVID-19 associated respiratory failure transferred to a single ICU were assessed. Eight were excluded: five were not invasively ventilated and three received veno-venous ECMO support. The remaining 15 were assessed over the first 15 days of mechanical ventilation. Best PEEP was defined by maximal oxygenation and was determined by structured decremental PEEP trials comprising the monitoring of oxygenation, airway pressures and trans-pulmonary pressures. In nine patients the impact of prone positioning on oxygenation was investigated. Additionally, the effects of high PEEP and prone positioning on pulmonary opacities in serial chest x-rays were determined by applying a semiquantitative scoring-system. This investigation is part of the prospective observational PA-COVID-19 study. Findings Patients responded to initiation of invasive high PEEP ventilation with markedly improved oxygenation, which was accompanied by reduced pulmonary opacities within 6 h of mechanical ventilation. Decremental PEEP trials confirmed the need for high PEEP (17.9 (SD ± 3.9) mbar) for optimal oxygenation, while driving pressures remained low. Prone positioning substantially increased oxygenation ( p <0.01). Interpretation In early COVID-19 ARDS, substantial PEEP values were required for optimizing oxygenation. Pulmonary opacities resolved during mechanical ventilation with high PEEP suggesting recruitment of lung volume. Funding German Research Foundation, German Federal Ministry of Education and Research.

Impact of the research: Although bilateral phrenic nerve stimulation did not increase the proportion of successful weaning from mechanical ventilation compared to the standard of care, it resulted in substantial improvements in inspiratory pressure generation capacity without major safety issues. In the absence of previous clinical data, these findings suggest that diaphragm pacing could be effective in mitigating diaphragm dysfunction in patients difficult to wean from mechanical ventilation. Author contributions:The academic authors (MD, MGDA, TS) wrote the first draft of the manuscript and verified the underlying data. All authors critically reviewed and approved the manuscript and are accountable its accuracy and integrity. Dr Martin Dres had full access to all the data in the study and takes full responsibility for the integrity of the data and the accuracy of the data analysis. Teresa Nelson conducted and is responsible for the data analysis. Support:The study was funded by Lungpacer Medical Inc, PA, USA.

The current article presents a novel physiological feedback controller for turbodynamic ventricular assist devices (tVADs). This controller is based on the recording of the left ventricular (LV) pressure measured at the inlet cannula of a tVAD thus requiring only one pressure sensor. The LV systolic pressure (SP) is proposed as an indicator to determine the varying perfusion requirements. The algorithm to extract the SP from the pump inlet pressure signal used for the controller to adjust the speed of the tVAD shows robust behavior. Its performance was evaluated on a hybrid mock circulation. The experiments with changing perfusion requirements were compared with a physiological circulation and a pathological one assisted with a tVAD operated at constant speed. A sensitivity analysis of the controller parameters was conducted to identify their limits and their influence on a circulation. The performance of the proposed SP controller was evaluated for various values of LV contractility, as well as for a simulated pressure sensor drift. The response of a pathological circulation assisted by a tVAD controlled by the introduced SP controller matched the physiological circulation well, while over- and underpumping events were eliminated. The controller presented a robust performance during experiments with simulated pressure sensor drift.