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Inspiratory Pressure Rise Time, Ventilator Hardware, and Software Influence Regional Ventilation in a Simulated
Ibrahim A Sammour1, Robert L Chatburn2
1Cleveland Clinic, Cleveland, Ohio. sammoui@ccf.org.
Insights
Prolonging inspiratory pressure rise time (IRT) in mechanical ventilation improved lung volume balance in a simulated bronchopulmonary dysplasia (BPD) model, but reduced overall tidal volume. Ventilator type also impacted outcomes independently.
Area of Science:
- Neonatal Physiology
- Mechanical Ventilation
- Respiratory Mechanics
Background:
- Bronchopulmonary dysplasia (BPD) presents significant challenges in ventilating premature infants due to its heterogeneous nature.
- Optimizing ventilator settings is crucial for managing BPD and preventing further lung injury.
Purpose of the Study:
- To investigate the impact of inspiratory pressure rise time (IRT) and different mechanical ventilators on ventilation distribution in a simulated BPD lung model.
- To assess how ventilator hardware and software updates influence ventilation balance between heterogeneous lung units.
Main Methods:
- A dual-chamber lung model simulating moderate BPD with distinct time constants was used with the IngMar ASL5000.
- Three ventilators (Servo-i, Avea with/without volume guarantee) delivered pressure control intermittent mandatory ventilation, with adjustable IRT.
- Measurements included tidal volume, peak inspiratory flow, mean inspiratory pressure, and volume balance, analyzed using linear regression.
Main Results:
- Increasing IRT led to decreased peak inspiratory flow, mean inspiratory pressure, and chamber-specific tidal volumes.
- Volume balance between heterogeneous lung units improved with longer IRT, but at the cost of reduced total tidal volume.
- Ventilator hardware and software significantly influenced pressure control intermittent mandatory ventilation waveforms, independently affecting outcomes.
Conclusions:
- In a heterogeneous lung model of BPD, extending IRT improved volume distribution between lung units, though it reduced overall tidal volume.
- Different ventilators and their software configurations act as independent variables influencing ventilation dynamics beyond IRT.
- Findings suggest IRT is a modifiable parameter for optimizing ventilation in BPD, but ventilator-specific characteristics must also be considered.
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.
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