Influence of ventilation mode on blood oxygenation - investigation with Polish Virtual Lungs and Italian Model of Circulation

Positive alveolar (PA) and thoracic (Pr) pressures during artificial ventilation disturb pulmonary circulation, and might influence arterial blood oxygenation (PaO2). Initial analysis of such influence of different artificial ventilation modes is the goal of this paper. Previously elaborated virtual respiratory system (IBIB PAS, Warsaw, Poland) and cardiovascular system model (ICP CNR, Rome, Italy) were connected with two files-buffers to work as one virtual cardio-pulmonary system. Dependence of PaO2 on two methods (continuous inspiratory airflow (VCV) or pressure (PCV)), two ventilatory frequencies (fV = 15 or 7.5/min), and two values of the minute ventilation (Vmin = 6 or 8L/min) was investigated. Perfusion dependence on gravity was neglected as the virtual patient was in the supine position. Simulations showed that when fV = 15/min, neither the used method nor Vmin influence pulmonary blood flow significantly, whereas they influence the flow during expiration when fV = 7.5 (blood flow falls more for PCV and Vmin = 8 L/min). Vmin more significantly influences alveolar partial pressure of oxygen (P02) when fV = l5/min. P02 was greater for PCV. As effects on the flow and PO2 were contradictory, Pa02 was almost independent of the used method and fV. It depended on Vmin more significantly if fV = 15/min.