RESUMO
In preterm infants, lung function monitoring is important for lung-protective mechanical ventilation. In this study, we used a neonatal lung model to investigate the effect of endotracheal tube (ETT) leakage on the monitoring of tidal volume (VT) and lung mechanics using different ventilators. A neonatal lung model was ventilated via a 3 mm ETT using three ventilators, Babylog 8000, Leoni, and Stephanie. ETT leakage was simulated by open silicone tubes with different lengths. The volume delivered to the lung model was measured and compared with the displayed expiratory VT of the three ventilators. The effect of ETT leakage on lung mechanical parameters displayed by the ventilators was investigated for respiratory rates from 20 min-1 to 70 min-1 and a constant inspiratory time: expiratory time ratio of 1:1. The displayed ETT leakage depended on the size of the leak, ventilator settings, and the ventilator used. In the presence of ETT leakages, for all three ventilators, the displayed VT underestimated the true volume delivered to the lung. With increasing ETT leakage, displayed compliance was overestimated by Babylog 8000 and Stephanie, whereas Leoni underestimated compliance. The displayed resistance increased with increasing ETT leakage for the three ventilators, but quite different. The effect of ETT leakage on displayed VT and lung mechanical parameters is ventilator-dependent. ETT leakage can lead to incorrect measurements that indicate reduced VT, improvement of lung compliance, or ETT obstruction.
