The Effect of Endotracheal Tube Resistance and Respiratory Frequency on PCO2 Management During Pressure-Controlled Ventilation: A Modelling Study

Pressure Controlled Ventilation (PCV) is a commonly used mode of mechanical ventilation that allows for better control of airway pressure. The Endotracheal Tubes (ETTs) used in this mode of artificial ventilation can, under certain conditions, affect Partial Pressure of Carbon Dioxide (PCO2) values in addition to other well-known factors such as Respiratory Frequency (RF) and Tidal Volume (VT). We developed a mathematical model of the respiratory system during PCV, incorporating, in addition to the resistance and compliance of the respiratory system, the linear and non-linear mode resistance of a variety of ETTs with Internal Diameters (ID) ranging from 6.5 to 9 mm. The impact of these ETT resistances on PCO2 was studied under different RF. Our results demonstrated the validity of the models, and in addition to the known effect of RF, the non-linear resistance of the ETT has a significant impact on PCO2 during PCV particularly for leads with an ID of less than 7 mm. For this reason, the use of small-diameter Endotracheal tubes should be taken into consideration when setting mechanical ventilation parameters to ensure adequate ventilation without complication.