The Difference Between Set and Delivered Tidal Volume: A Lung Simulation Study

Precise control of tidal volume is one of the keys in limiting ventilator-induced lung injury and ensuring adequate ventilation in mechanically ventilated neonates. The aim of the study was to compare the tidal volume (mVT) measured from the expiratory limb of the ventilator with the actual tidal volume (aVT) that would be delivered to the patient using a lung model to simulate a neonate.

This study was conducted using the ASL5000 lung simulator. Three combinations of parameters were set: resistance (cmH₂O/L/sec) and compliance (mL/cmH₂O) of 50 and 2 (Group 1), 100 and 1 (Group 2), and 150 and 0.5 (Group 3), respectively. The ASL5000 was connected to each of the ventilators including one anesthesia machine ventilator (Drager Fabius GS) and two ICU ventilators (Servo-i Universal and Evita Infinity V500). Each ventilator was evaluated with a set tidal volume of 30 mL (sVT) and a respiratory rate of 25 breathes/minute in both the volume-controlled ventilation (VCV) and dual-controlled ventilation (DCV) modes.

The discrepancies between sVT, mVT and aVT were highest with the Fabius anesthesia machine ventilator and increased in the simulated lung injury groups. When comparing the ICU ventilators, the difference was greater the Servo-i and increased when using the DCV mode and with simulated lung injury.

Accurate tidal volumes were achieved only with the Infinity ICU ventilator. This was true regardless of mode of ventilation and even during simulated lung injury.