Abstract
BACKGROUND:
Bronchopulmonary dysplasia (BPD) is a heterogeneous disease that poses a challenge when ventilating premature infants. The purpose of this study was to determine how inspiratory pressure rise time (IRT), different ventilators, and their software updates affect the balance of ventilation among 2 heterogeneous lung units.
METHODS:
A passive dual-chamber lung model was constructed using the IngMar ASL5000 to approximate moderate BPD. One chamber had a short time constant, and the other had a long time constant. Three ventilators were used to provide pressure control intermittent mandatory ventilation: the Servo-i, an Avea ventilator with the volume guarantee software update, and an Avea ventilator without the volume guarantee software update. Using the same settings for pressure control intermittent mandatory ventilation, the IRT was adjusted between minimum and maximum settings. Data from 100 consecutive breaths/IRT were obtained. Inspiration time to 90% of plateau pressure was used as a surrogate for IRT; this was defined as the time needed to achieve a pressure of 18 cm H2O at the simulated trachea and was measured in 5 random breaths using ImageJ for each ventilator at each IRT. Outcome variables were tidal volume, peak inspiratory flow, mean inspiratory pressure, and volume balance (%) defined as the difference in chamber tidal volumes divided by total tidal volume. Linear regression was used to assess the impact of the IRT and ventilators on the different variables.
RESULTS:
In this model, increasing IRT decreased peak inspiratory flow, mean inspiratory pressure, chamber-specific tidal volume, and volume balance. Furthermore, different ventilator hardware and software influenced the waveforms in pressure control intermittent mandatory ventilation, which independently affected the measured variables.
CONCLUSIONS:
In a lung model of BPD with 2 very heterogeneous lung units, prolonging IRT without any volume balancing measures improved volume balance between the chambers at the expense of total tidal volume. Furthermore, the different ventilators acted as independent factors from the measured inspiration time to 90% of plateau pressure.
Keywords
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