466 - Patient-Ventilator Interactions in Obstructive Type 2 Severe Bronchopulmonary Dysplasia (BPD); A Bench-top Simulated Examination

Poster Number: 466
Publication Number: 466.229

Ibrahim Sammour, Cleveland Clinic Children's, Beachwood, OH, United States; Allison Peluso, Cleveland Clinic Children's, Cleveland, OH, United States; Robert Chatburn, Cleveland Clinic, Cleveland Heights, OH, United States

Background: 16% of premature newborns develop severe BPD; a minority exhibit an obstructive phenotype making them difficult to support. It has been suggested that a low-rate high-tidal volume strategy would be more a more beneficial ventilation strategy.

Objective: To examine Total-PEEP (PEEPt) build up in a simulated model of severe obstructive BPD using different ventilation strategies and assess the impact of these changes on patient-ventilator synchrony.

Design/Methods: A severe obstructive BPD model was constructed using an IngMar ASL5000 simulator (Fig 1a) to approximate a 4 kg infant with BPD. A passive effort model was used to evaluate PEEPt. An active model with a simulator effort of 7 breaths above the ventilator set rate was used to evaluate synchrony (Fig 1b). A Servo-I (Maquet) ventilator with an Evaqua2 Infant Circuit (Fisher & Paykel) were used. The ventilator was cycled through various rate and target tidal volume combinations in PC-CMVa (PRVC) to maintain minute ventilation of 0.2 L/kg/min (Fig 1c). For the passive model, peak pressure (PIP), airway PEEP (PEEPaw), Total PEEP (PEEPt), and measured tidal volume (VT) were extracted. Perceived compliance (Comp) was calculated using VT / (PIP – PEEPaw). For the actively breathing model, actual breath rate, trigger response time, maximum pressure drop during trigger event, and "spontaneous" breaths (defined if any effort was detected at any time during a delivered mechanical breath) were extracted. To assess synchrony, we defined the % ineffective breaths (%I) as the percentage of missed extra simulator breaths over the rate set on the ventilator, and evaluated the fraction of ventilator breaths coinciding with simulator effort. Linear regression was used to evaluate passive continuous variables, and one-way ANOVA (Tukey post-hoc) was used to evaluate synchrony variables (Minitab 20).

Results: Increasing the ventilator rate while maintaining minute ventilation led to increased PEEPt development compared to PEEPa with a decline in Comp in the passive obstructive BPD model (Fig 2 a&b). The ventilator was able to detect all spontaneous efforts at rates of ≤ 20 bpm but became progressively asynchronous with higher set rates. For settings that allowed for complete capture of effort, decreasing the rate, and increasing VT allowed for an improvement in trigger response time with a less negative pressure drop during the trigger events (Fig 3 a-d).Conclusion(s): Low-rate and high-tidal volume strategies allow for a reduction in PEEPt and improve ventilator triggering in a simulated obstructive severe BPD model.
Fig 1: ASL5000 Lung Model & Ventilator Settings Used.a) ASL5000 Single compartment model of obstructive severe BPD
b) ASL5000 Active breathing model
c) Servo-I Ventilator settings used
Fig 2: Passive Lung Model: Increasing Total PEEP and Decreasing Dynamic Compliance.a) Total PEEP increases significantly more than airway PEEP with increasing ventilator rate
b) Perceived compliance decreases with increasing ventilator rate.