A mathematical model for carbon dioxide elimination: an insight for tuning mechanical ventilation

Purpose

The aim is to provide better understanding of carbon dioxide ( $mathrm{CO}_2$ ) elimination during ventilation for both the healthy and atelectatic condition, derived in a pressure-controlled mode. Therefore, we present a theoretical analysis of $mathrm{CO}_2$ elimination of healthy and diseased lungs.

Methods

Based on a single-compartment model, $mathrm{CO}_2$ elimination is mathematically modeled and its contours were plotted as a function of temporal settings and driving pressure. The model was validated within some level of tolerance on an average of 4.9 % using porcine dynamics.

Results

$mathrm{CO}_2$ elimination is affected by various factors, including driving pressure, temporal variables from mechanical ventilator settings, lung mechanics and metabolic rate.

Conclusion

During respiratory care, $mathrm{CO}_2$ elimination is a key parameter for bedside monitoring, especially for patients with pulmonary disease. This parameter provides valuable insight into the status of an atelectatic lung and of cardiopulmonary pathophysiology. Therefore, control of $mathrm{CO}_2$ elimination should be based on the fine tuning of the driving pressure and temporal ventilator settings. However, for critical condition of hypercapnia, airway resistance during inspiration and expiration should be additionally measured to determine the optimal percent inspiratory time (%TI) to maximize $mathrm{CO}_2$ elimination for treating patients with hypercapnia.