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 Insuf flation (TGI) on the alveolar ventilation during passive, mechanical ventil ation. Equations are derive that relate the physiologic dead space and alve olar ventilation to the physiologic parameters of the patient (compliance, inspiratory and expiratory resistances, anatomical dead space, cardiac outp ut, and shunting), the ventilator settings (frequency, inspiratory time fra ction, and pressure waveform), and the catheter settings (flow rate and flo w duration). It is shown that optimal alveolar ventilation exists for certa in frequencies of ventilation and these frequencies are dependent on the ca theter flow. (C) 1999 Elsevier Science Ltd. All rights reserved.