A mathematical model for carbon dioxide exchange during mechanical ventilation with Tracheal Gas Insufflation (TGI)

A mathematical model is presented to study the effect of Tracheal Gas Insufflation (TGI) on the alveolar ventilation during passive, mechanical ventilation. Equations are derive that relate the physiologic dead space and alveolar ventilation to the physiologic parameters of the patient (compliance, inspiratory and expiratory resistances, anatomical dead space, cardiac output, and shunting), the ventilator settings (frequency, inspiratory time fraction, and pressure waveform), and the catheter settings (flow rate and flow duration). It is shown that optimal alveolar ventilation exists for certain frequencies of ventilation and these frequencies are dependent on the catheter flow.