ABSTRACT
We report a patient with severe coronavirus disease 2019 (COVID-19) acute respiratory distress syndrome (ARDS) treated with veno-venous extracorporeal membrane oxygenation (VV ECMO) and programmed multi-level ventilation (PMLV). VV ECMO as a treatment modality for severe ARDS has been described multiple times as a rescue therapy for refractory hypoxemia. It is well known that conventional ventilation can cause ventilator-induced lung injury. Protective ventilation during VV ECMO seems to be beneficial, translating to using low tidal volumes, prone positioning with general concept of open lung approach. However, mechanical ventilation is still required as ECMO per se is usually not sufficient to maintain adequate gas exchange due to hyperdynamic state of the patient and limitation of blood flow via VV ECMO. This report describes ventilation strategy using PMLV during "resting" period of the lung. In short, PMLV is a strategy for ventilating non-homogenous lungs that incorporates expiratory time constants and multiple levels of positive end-expiratory pressure. Using this approach, most affected acute lung injury/ARDS areas can be recruited, while preventing overdistension in healthy areas. To our knowledge, case report using such ventilation strategy for lung resting period has not been previously published.
ABSTRACT
An algorithm allowing simulating vibrational spectra from classical time-dependent trajectories was applied for infrared absorption, vibrational circular dichroism, Raman, and Raman optical activity of model harmonic systems. The implementation of the theory within the TINKER molecular dynamics (MD) program package was tested with ab initio harmonic force fields in order to determine the feasibility for more extended MD simulations. The results suggest that sufficiently accurate frequencies can be simulated with integration time steps shorter than about 0.5 fs. For a given integration time step, lower vibrational frequencies ( approximately 0-2000 cm(-1)) could be reproduced with a higher accuracy than higher-frequency vibrational modes (e.g., O-H and C-H stretching). In principle, the algorithm also provides correct intensities for ideal systems. In applied simulations, however, the intensity profiles are affected by an unrealistic energy distribution between normal modes and a slow energy relaxation. Additionally, the energy fluctuations may cause weakening of the intensities on average. For ab initio force fields, these obstacles could be overcome by an arbitrary normal mode energy correction. For general MD simulations, averaging of many shorter MD trajectories started with randomly distributed atomic velocities provided the best spectral shapes. alpha-pinene, D-gluconic acid, formaldehyde dimer, and the acetylprolineamide molecule were used in the tests.
