Presented at the Neonatal Society 2008 Autumn Meeting.
Wheeler K, Kamlin O, Morley C, Davis P (introduced by Prof Colin Morley)
Newborn Research, Royal Women’s Hospital, Melbourne, Parkville Victoria 3052, Australia
Aim: To observe changes in ventilator parameters during assist control volume guarantee ventilation (AC/VG) of preterm infants receiving surfactant.
Methodology: 22 preterm infants. Data recorded from Dräger Babylog 8000plus ventilators at 125Hz for 10 minutes before, and at least 1 hour following surfactant administration. FiO2, flow, pressure and volume were compared pre/post surfactant.
Ethical Approval: Data approved for use by the Women’s Hospital (Melbourne) Research and Ethics Committee
Results: Median (IQR) gestation age, birthweight and pre-surfactant peak inflation pressure (PIP) were 28 (26-29) weeks, 0.9 (0.7-0.14) kg and 19 (16-23) cm H2O respectively. Six (27%) were female patients, and 16 (72%) received antenatal steroids. 14 infants were studied during their first dose of surfactant administration at 1 (¾-4½) hours. The remaining eight were studied during their second dose at 13 (11-14½) hours.
Complete endotracheal obstruction occurred in 21 of 22 babies. PIP increased by median (range) 8 (1.5-14) cm H2O, and took 30-60 minutes to return to baseline. Inspired oxygen concentration was reduced from median (IQR) 39 (26-44) % to 26 (21 30) %.
In most infants, the maximum pressure setting (Pmax) limited PIP such that delivered tidal volumes were initially less than target (VTtarget) following surfactant delivery. In a subgroup of 11 infants where Pmax was set less than 10 cm H2O above baseline PIP, four were still receiving <90% VTtarget 20 minutes post surfactant.
Conclusions: When giving surfactant during AC/VG ventilation, complete obstruction is common. PIP increases and remains elevated for 30-60 minutes after surfactant. The Pmax setting may restrict tidal volume delivery.
Conflict of interest: None.
References
Grover A. et al. Volume-targeted ventilation in the neonate: time to change? Arch Dis Child Fetal Neonatal Ed 2008; 93(1):F7-13.
Hentschel R et al. Sequential changes in compliance and resistance after bolus administration or slow infusion of surfactant in preterm infants. Intensive Care Med 2002; 28(5):622-628.