Multilevel Ventilation: Theory and Simplified Mathematical Model

Abstract

Considering the issues of artificial ventilation (AV) in non-homogenous pathological lung processes (acute lung injury, acute respiratory distress syndrome, pneumonia, etc.), the authors created a mathematical model of multicompartment non-homogenous injured lungs that were ventilated by a new mode of AV, the so-called three-level ventilation. Multilevel ventilation was defined a type (modification) of ALV whose basic ventilation level was produced by the modes CMV, PCV or PS (ASB) and add-on level, and the so-called background ventilation was generated by the levels of PEEP and high PEEP (PEEPh) with varying frequency and duration. Multi-level ventilation on 3 pressure levels was realized by the mathematical model as a combination of pressure-controlled ventilation (PCV) and two levels of PEEP and PEEPh. The objective was to prove that in cases of considerably non-homogenous gas distribution in acute pathological disorders of lungs, gas entry into the so-called slow bronchoalveolar compartments could be improved by multilevel AV, without substabtially changing the volume of so-called fast compartments. Material and Method. Multi-level ventilation at 3 pressure levels was realized by the mathematical model as a combination of PCV and two levels of PEEP and PEEPh. Results. By comparing the single-level AV in the PCV mode with the so-called three-level ventilation defined as a combination of PCV+PEEPh/PEEP, the authors have discovered that the loading of slow compartments in the model was considerably improved by 50—60% as compared with the baseline values. In absolute terms, this difference was as many as 2—10 times of the volume. Conclusion. The mathematical model may demonstrate that the application of the so-called three-level AV causes considerable changes in gas distribution in the lung parenchyma disordered by a non-homogenous pathological process. The authors state that the proposed mathematical model requires clinical verification in order to evaluate the efficiency of this modification of AV. Key words: artificial ventilation, multilevel artificial ventilation, acute lung injury, acute respiratory distress syndrome.