Synchronised inflations generate greater gravity dependent lung ventilation in neonates

ABSTRACT Objective Synchronising positive pressure inflations with an infant’s own breathing is considered lung protective, but the ventilation patterns within the infant lung during synchronous and asynchronous inflations are unknown. The aim of this study was to describe the regional distribution patterns of tidal ventilation within the lung during mechanical ventilation that is synchronous or asynchronous with an infant’s own breathing effort. Methods Intubated infants receiving synchronised mechanical ventilation at The Royal Children’s Hospital NICU were studied. During four 10-minute periods of routine care, regional distribution of tidal volume (V T ; Electrical Impedance Tomography), delivered pressure and airway flow (Florian Respiratory Monitor) were measured for every inflation. Post hoc, each inflation was then classified as synchronous or asynchronous from video data of the ventilator screen, and the distribution of absolute V T and delivered ventilation characteristics determined. Results 2749 inflations (2462 synchronous) were analysed in 19 infants; mean (SD) age 28 (30) day, GA 35 (5) weeks. Synchronous inflations were associated with a shorter respiratory cycle (p=0.004) and more homogenous V T (centre of ventilation) along the right (0%) to left (100%) lung plane; 45.3 (8.6)% vs 48.8 (9.4)% (uniform ventilation 46%). The gravity dependent centre of ventilation was a mean (95% CI) 2.1 (−0.5, 4.6)% more towards the dependent lung during synchronous inflations. Tidal ventilation relative to anatomical lung size was more homogenous during synchronised inflations in the dependent lung. Conclusion Synchronous mechanical ventilator lung inflations generate more gravity dependent lung ventilation and more uniform right to left ventilation than asynchronous inflations.