Accuracy of Reported Tidal Volume During Neonatal Ventilation With Airway Leak: A Lung Model Study

To determine the accuracy of tidal volume reported by neonatal ventilators, with and without leak compensation, in invasive and noninvasive ventilation modes in the presence of airway leak; and, to determine what factors have a significant effect on the accuracy of tidal volume reported by ventilators with leak compensation in the presence of airway leak. We hypothesized that ventilators with a leak compensation function that includes estimation of tidal volume could accurately report tidal volume in the presence of airway leak, but that the accuracy of reported tidal volume may be affected by variables such as the identity of the ventilator, lung mechanics, leak size, positive end-expiratory pressure level, and body size.

In vitro assessment of ventilator volume delivery was conducted for seven acute care ventilators using a passive lung simulator.

Laboratory-based measurements.

The error of reported tidal volume was calculated under three ventilation modes (noninvasive-pressure-control, invasive-pressure-control, and invasive-dual-control ventilation), three models of lung mechanics (normal and restrictive and obstructive lung disease), a range of airway leak values, two positive end-expiratory pressure values, and two body weights for each ventilator. Ventilators with and without leak compensation were studied.

In the absence of airway leak, all ventilators reported tidal volume accurately. In the presence of airway leak, the error of reported tidal volume increased for all ventilators without a leak compensation algorithm while ventilators with leak compensation that included estimation of tidal volume accurately reported tidal volume. In the presence of airway leak, clinically significant effects on the error of reported tidal volume by ventilators with leak compensation were associated with the choice of ventilator in all modes and with lung mechanics in invasive ventilation modes.

Reported tidal volume is affected by the presence of airway leak, but in many ventilators a leak compensation algorithm that includes estimation of tidal volume can correct for the discrepancy between actual and reported tidal volume. However, even in ventilators with leak compensation, choice of ventilator and lung mechanics in invasive ventilation modes have a significant effect on error of reported tidal volume.