How is the resistance in mechanical ventilation calculated?

In mechanical ventilation, resistance (Raw) is calculated using the difference between the peak inspiratory pressure (PIP) and the plateau pressure (Pplat) divided by the flow rate. This is articulated in the formula Raw = (PIP - Pplat) / flow.

PIP is the pressure recorded at the airway during inspiration, while Pplat is the pressure measured during an inspiratory pause, reflecting the pressure in the alveoli when there is no airflow. The difference between these two pressures indicates the amount of pressure that is being lost due to resistance in the airways. When you divide this difference by the flow rate, you can quantify the resistance the ventilatory system encounters during the breathing cycle.

Understanding this calculation is critical for clinicians managing patients on mechanical ventilation, as it helps assess the functional integrity of the airways and identify potential causes of increased resistance, such as bronchospasm or airway obstruction.