Neural feedback is insufficient in preterm infants during neurally adjusted ventilatory assist

Objectives To investigate the effects of changing assistance levels on respiratory patterns, including peak inspiratory pressure (PIP), overassistance, work of breathing, and discomfort in preterm infants during neurally adjusted ventilatory assist (NAVA). Working hypothesis Once the lungs reach optimal inflation, negative feedback suppresses neural respiratory drive and therefore, the electrical activity of the diaphragm (Edi) such that the lungs are protected from overinflation and breathing work is reduced. Study design A prospective study was conducted in 14 preterm infants (median postconceptional age of 32.1 weeks) who received at least 24 hours of ventilatory support for respiratory distress. Methodology Increasing and decreasing NAVA levels (from 0.5 to 4.0 cmH(2)O/mu V with an interval of 0.5 cmH(2)O/mu V) were applied for 10 minutes each. Data recorded for the last 5 minutes of each NAVA level were analyzed. Heart rate and oxygen saturation were recorded and premature infant pain profiles were calculated. Results An inflection point for PIP was not evident during increasing and decreasing assistance. Increasing NAVA levels caused greater variability in PIP and a higher proportion of the excessive tidal volume of more than 10 mL/kg. Peak Edi and discomfort scale decreased shortly after a small change in NAVA levels during increasing assistance. However, during decreasing assistance, peak Edi and discomfort scale remained low until a large reduction in NAVA levels. Conclusion Although NAVA can effectively alleviate the respiratory muscle work and discomfort, the neural feedback for protection from lung overinflation seems to be insufficient in preterm infants.