Objectives: During volume targeted ventilation, the ventilator’s algorithm adjusts the peak inspiratory pressure (PIP) to maintain the expired tidal volume close to the target. In hyperventilating infants PIP is frequently very low, just above the level of positive end-expiratory pressure (PEEP). The impact of this on ventilator parameters and blood gases was investigated. Methods: Data were collected and analysed computationally from 195 infants over 968 days of mechanical ventilation. The median ventilator inflating pressure (Pinfl, which is PIP minus PEEP) was determined before each blood gas (n=3,371) for periods of different duration between 15 minutes and 24 hours. Ventilator parameters and blood gases were compared between periods when the inflating pressure was <5 mbar and periods when it was higher. Results: 1-hour periods when median Pinfl was <5 mbar occurred in 30% of the babies. These were associated with similar tidal volumes and minutes ventilation as periods with higher Pinfl, despite the lower target tidal volume. Babies triggered more ventilator inflations, had more spontaneous breaths and had lower their oxygen requirement when Pinfl was low. Low inflating pressures were associated with lower blood carbon dioxide levels and did not lead to acidosis. Lactate levels were higher but the group included more babies with perinatal hypoxia. Analyzing data over shorter (15 or 30 minutes) or longer (up to 24 hours) periods before the blood gases gave similar results. Conclusions: Episodes of low inflating pressure occur frequently in babies receiving volume targeted ventilation. This does not lead to exhaustion, hypercapnia or acidosis.

Objectives: To examine the success rate of less invasive surfactant administration (LISA), to identify early predictive factors for the outcome of LISA and to compare neonatal outcomes between the LISA failure group and the group of infants who were succesfully treated with LISA. Design: A retrospective cohort study. Patients: Infants born at less than 33 weeks of gestation (n=158) and treated with LISA for respiratory distress syndrome. Results: LISA was successful in 86 cases (54.4%), 72 preterm infants (45.6%) needed additional surfactant therapy and/or mechanical ventilation in the first 72 hours. In a multivariate logistic regression analysis, six independent predictors were identified: core temperature at the time of admission (adjusted OR 3.56), suboptimal dose of surfactant (adjusted OR 0.254), elevated CRP (>10 mg/L) at 24 hours of life (adjusted OR 0.28), highest respiratory severity score during the first hour of life or at the time of LISA (adjusted OR 0.463), maternal age (adjusted OR 0.923) and birth weight (adjusted OR 1.003). The ROC curve created by using the identified factors indicates good predictive power with an area under the curve of 0.85. LISA failure was associated with a substantially higher risk of pneumothorax, bronchopulmonary dysplasia, intraventricular hemorrhage, severe retinopathy of prematurity, longer duration of mechanical ventilation and prolonged length of hospital stay. Conclusion: Failure of LISA is relatively frequent event in very preterm infants and is associated with adverse outcomes. Prevention of hypothermia during early stabilization and appropriate dosing of surfactant increase may LISA success rates and improve patient outcome.