Virtual Experiments: May VCV Impede Circulation More than PCV in (Virtual) Patients in the Lateral Position?

The position of artificially ventilated patients has to be changed into a lateral one to avoid a bed score. Such a position causes asymmetrical work of lungs, esp. in older patients when the closing capacity (CC) of the dependent lung is greater than its functional residual capacity (FRC). If CC>FRC, a lung is closed at the end of expirations, and in consequence certain time is necessary to open it during inspirations. Virtual organs may be useful for initial testing of wide range of problems, such as differences in volume control ventilation (VCV) and pressure control ventilation (PCV) influences on local intrapleural pressure affecting pulmonary blood flow, when CC>FRC for the dependent lung. Methods: Virtual respiratory system elaborated previously was used for simulation of VCV with constant inspiratory airflow and PCV with constant inspiratory pressure applied to a standard patient in the left lateral position when CC>FRC for the dependent (left) lung and CCintrapleural pressures (as well as the difference between the left and right alveolar pressures) was greater during VCV than during PCV. Since pulmonary blood flow depends inversely on these pressures, perfusion of better ventilated lung was worse. However, all the above facts depended on the mediastinum compliance (the higher the compliance, the smaller the differences). Additionally, the left lung was ventilated better during PCV, and thus both lungs considered together were ventilated better, too. Conclusion: PCV appears to be more unfailing than VCV despite that VCV is commonly assumed as the ventilation mode that always supplies the desired tidal volume.