Simulation of the enhancement factor from an individual 3D hemisphere-on-post field emitter by using finite elements method.

This paper presents a 3D computational framework for evaluating electrostatic properties of a single field emitter characterized by the hemisphere-on-post geometry. Numerical simulations employed the finite elements method by using Ansys-Maxwell software. Extensive parametric simulations were focused on the threshold distance from which the emitter field enhancement factor (γ) becomes independent from the anode-substrate gap (G). This investigation allowed demonstrating that the ratio between G and the emitter height (h) is a reliable reference for a broad range of emitter dimensions; furthermore, results permitted establishing G/h ≥ 2.2 as the threshold condition for setting the anode without affecting γ.

Automated analysis of respiratory behavior in extremely preterm infants and extubation readiness.

BACKGROUND: Rates of extubation failure of extremely preterm infants remain high. Analysis of breathing patterns variability during spontaneous breathing under endotracheal tube continuous positive airway pressure (ETT-CPAP) is a potential tool to predict extubation readiness. OBJECTIVE: To investigate if automated analysis of respiratory signals would reveal differences in respiratory behavior between infants that were successfully extubated or not. METHODS: Respiratory Inductive Plethysmography (RIP) signals were recorded during ETT-CPAP just prior to extubation. Signals were digitized, and analyzed using an Automated Unsupervised Respiratory Event Analysis (AUREA). Extubation failure was defined as reintubation within 72 hr. Statistical differences between infants who were successfully extubated or failed were calculated. RESULTS: A total of 56 infants were enrolled and one was excluded due to instability during the ETT-CPAP; 11 out of 55 infants studied failed extubation (20%). No differences in demographics were observed between the success and failure groups. Significant differences on the variability of some respiratory parameters or 'metrics' estimated by AUREA were observed between the 2 groups. Indeed, a simple classification using the variability of two metrics of respiratory behavior predicted extubation failure with high accuracy. CONCLUSION: Automated analysis of respiratory behavior during a short ETT-CPAP period may help in the prediction of extubation readiness in extremely preterm infants.

Developing a neonatal unit ventilation protocol for the preterm baby.

Mechanical ventilation is a resource-intensive complex medical intervention associated with high morbidity. Considerable practice style variation exists in most hospitals and is not only confusing for parents, but the lack of consistently high standard of optimal ventilation deprives some infants of the benefits of state-of-the-art care. Developing a unit protocol for mechanical ventilation requires exhaustive research, inclusion of all stake-holders, thoughtful protocol development and careful implementation after a thorough educational process, followed by monitoring. A protocol for respiratory support should be comprehensive, addressing respiratory support in the delivery room, the use of non-invasive support, intubation criteria, surfactant administration, specific ventilation modes and settings, criteria for escalating therapy, weaning protocols, extubation criteria, and post-extubation management. Evidence favors the use of non-invasive support as first line treatment, progressing to assist/control or pressure support ventilation combined with volume guarantee, if needed, and high-frequency ventilation only for specific indications. The open lung strategy is crucial to lung-protective ventilation.

Weaning infants from mechanical ventilation.

Protracted mechanical ventilation is associated with increased morbidity and mortality in preterm infants and thus the earliest possible weaning from mechanical ventilation is desirable. Weaning protocols may be helpful in achieving more rapid reduction in support. There is no clear consensus regarding the level of support at which an infant is ready for extubation. An improved ability to predict when a preterm infant has a high likelihood of successful extubation is highly desirable. In this article, available evidence is reviewed and reasonable evidence-based recommendations for expeditious weaning and extubation are provided.

Severe airway obstruction during surfactant administration using a standardized protocol: a prospective, observational study.

OBJECTIVE: The objective of this study was to evaluate the occurrence of adverse effects during surfactant delivery, using a standardized protocol for administration and management of complications. STUDY DESIGN: The protocol was developed, implemented and used for 6 months. Vital signs and ventilatory parameters were prospectively recorded during the procedure. Infants were classified into three groups, based on the occurrence and severity of complications: no, minor or major. RESULT: A total of 39 infants received surfactant and 19 presented some complication: 11 minor and 8 major. Six of the major complications were episodes of severe airway obstruction (SAO) and five occurred in extreme low birth weight (ELBW) infants that had more severe lung disease before surfactant delivery. Two cases of persistent pulmonary hypertension occurred in infants with birth weight>1000 g. CONCLUSION: This study identified a high rate of SAO and provides data to support changes in the protocol, which should include faster and more robust increases in positive inspiratory pressures in ELBW infants presenting with SAO.

Prediction of extubation readiness in extreme preterm infants based on measures of cardiorespiratory variability.

The majority of extreme preterm infants require endotracheal intubation and mechanical ventilation (ETT-MV) during the first days of life to survive. Unfortunately this therapy is associated with adverse clinical outcomes and consequently, it is desirable to remove ETT-MV as quickly as possible. However, about 25% of extubated infants will fail and require re-intubation which is also associated with a 5-fold increase in mortality and a longer stay in the intensive care unit. Therefore, the ultimate goal is to determine the optimal time for extubation that will minimize the duration of MV and maximize the chances of success. This paper presents a new objective predictor to assist clinicians in making this decision. The predictor uses a modern machine learning method (Support Vector Machines) to determine the combination of measures of cardiorespiratory variability, computed automatically, that best predicts extubation readiness. Our results demonstrate that this predictor accurately classified infants who would fail extubation.

Syringomyelia and chronic respiratory failure in a term infant delivered by Caesarean section.

The case of a term, male neonate (birthweight 3785g) with cephalic presentation, Caesarean-section (C-section) delivery, and failure to thrive is reported. The infant presented with generalized hypotonia and respiratory failure immediately following birth. An initial diagnosis of hypoxic-ischemic encephalopathy was made. However, ventilator dependency and slow recovery of generalized tonus over the following weeks could not be explained. Late cervical magnetic resonance imaging showed extensive syringomyelia from C2 to C7. To the authors' knowledge, this is the first report of syringomyelia after a C-section delivery following cephalic presentation without any associated abnormalities. Follow-up at 2 years of age revealed no improvement on neurological examination: poor head control, difficulty swallowing, flaccid paralysis of upper limbs, and spasticity of lower limbs with exacerbated deep reflexes and spontaneous clonus. Difficulties in establishing the diagnosis and managing the case are discussed.

Congenital pulmonary lymphangiectasia presenting as nonimmune fetal hydrops and severe respiratory distress at birth: not uniformly fatal.

Pulmonary lymphangiectasia is a rare cause of respiratory distress in the newborn associated with a very poor outcome. We describe three premature newborns presenting at birth with nonimmune hydrops, bilateral chylothorax, and severe respiratory distress in the immediate newborn period secondary to pulmonary lymphangiectasia. We review the similarities of these cases and discuss their antenatal and neonatal course. One patient survived and is thriving at 9 months of age. With continuing advances in antenatal and neonatal care, an improved outcome may be possible in what was previously described as a uniformly fatal condition.