Background Flow-cycled ventilation may allow more consistent tidal volume delivery with a decreased mean airway pressure and shorter inspiratory times, mimicking physiological breathing. However, questions still exist regarding its tolerance by preterm infants across different pressure settings.
Aim To establish whether flow-cycled pressure-support ventilation (PSV), as a sole ventilatory modality, is well-tolerated by preterm infants across different pressures, and leads to more consistent tidal volumes with a lower mean airway pressure compared with time-cycled pressure-limited synchronised intermittent mandatory ventilation (SIMV).
Methods Stable preterm infants (below 32 weeks’ gestation) with respiratory distress syndrome, from one tertiary neonatal unit over a 3 month period, with parents’ consent, underwent a randomised short-term cross-over trial on day 1 of life, of 1 hour epochs, exposed to two different levels of PSV, followed by two further 1 hour epochs on PSV and SIMV, with equal peak pressure settings. Physiological observations were recorded every 15 min, along with breath-by-breath mean airway pressure, tidal volume and calculated inspiratory time data, and blood gas analysis after each epoch. Mann Whitney U test was used to assess differences across the ventilatory settings.
Results Six preterm infants met the inclusion criteria, with gestation age ranging from 24 to 28 weeks’ gestation, birth weight 532–1156 grams. The different pressure settings on PSV were well-tolerated with no significant physiological disturbance. There was no significant difference in minute ventilation or pCO2 (p=0.70) across the two levels of pressure-support. A trend for a higher respiratory rate was seen with the lower pressure setting. The tidal volumes achieved were significantly more consistent (p<0.001), with shorter inspiratory times (0.07–0.20 (PSV) vs 0.37–0.4 (SIMV); p<0.001) and lower mean airway pressure (5–7 (PSV) vs 7–12 (SIMV); p<0.001) on flow-cycled compared with time-cycled ventilation.
Conclusion Flow-cycled ventilation as a sole ventilatory modality is well-tolerated by preterm infants with a stable respiratory drive and may be advantageous in meeting ventilatory requirements with a lower mean airway pressure, reducing potential ventilator-associated lung injury.
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