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Inspiratory work of breathing in ventilated preterm infants
H Lorino1, G Moriette, C Mariette
1INSERM U296, Hôpital Henri Mondor, Créteil, France.
Insights
In preterm infants on ventilators, inspiratory efforts before machine breaths significantly increase the work of breathing (WOB). This effort contributes substantially to overall WOB, especially during assist-control ventilation.
Area of Science:
- Neonatal Medicine
- Respiratory Physiology
- Mechanical Ventilation
Background:
- Ventilated newborns may experience work of breathing (WOB) from inspiratory efforts preceding ventilator support.
- Quantifying this pre-inspiratory effort is crucial for optimizing ventilation strategies in preterm infants.
Purpose of the Study:
- To quantify the contribution of inspiratory efforts preceding ventilator flow to the total work of breathing (WOB) in intubated preterm infants.
Main Methods:
- Six intubated preterm infants were studied using the Dräger Babylog 8000 ventilator.
- Ventilatory modes included intermittent mandatory ventilation (IMV), continuous positive airway pressure (CPAP), and assist-control ventilation (ACV).
- Mouth flow and esophageal pressure were measured to calculate WOB, comparing efforts starting at flow onset (WOBi) versus muscle effort onset (WOBm).
Main Results:
- Work of breathing calculated from muscle effort onset (WOBm) was significantly higher than from flow onset (WOBi) across all modes.
- The difference (delta W) represented approximately 30% of WOBm in IMV/CPAP and 60% in ACV.
- Delta W did not significantly depend on the ventilatory mode itself.
Conclusions:
- Inspiratory efforts preceding mechanical breaths constitute a significant portion of the work of breathing in ventilated preterm infants.
- Understanding and potentially reducing this pre-inspiratory effort may improve respiratory support and outcomes.
- Assist-control ventilation showed a higher relative contribution of pre-inspiratory effort compared to IMV and CPAP.
Abstract:
In ventilated newborns, part of the inspiratory work of breathing (WOB) may be due to the inspiratory efforts preceding inspiratory ventilator flow. This study was designed to quantify the contribution of these efforts to WOB. WOB was evaluated in six intubated preterm infants ventilated by the Dräger Babylog 8000. The ventilatory modes studied were intermittent mandatory ventilation (IMV), continuous positive airway pressure (CPAP), and assist-control ventilation at 10 (ACV10) and 15 (ACV15) cmH2O peak pressure. Mouth flow (V) and esophageal pressure (Pe) were recorded, and WOB was estimate from the area delineated by the esophageal pressure-volume curve, where volume is the time integral of V. Calculation of WOB started either at the onset of the infant's inspiratory flow (WOBi), or at the beginning of the infant's inspiratory muscle efforts, detected on Pe and confirmed on the V tracing (WOBm). WOBm was found to be significantly higher than WOBi under all ventilatory conditions studied. The difference in work of breathing (delta W) between WOBm and WOBi did not depend on the type of ventilatory mode. When delta W was related to WOBm, it amounted to about 30% of WOBm in IMV and CPAP, and 60% in ACV (P < 0.05, ACV15 vs. IMV). These results suggest that, in preterm infants connected to a ventilator, inspiratory efforts preceding flow inspiration might account for a large fraction of the inspiratory work of breathing.