Volume-targeted ventilation with a Fabian ventilator: maintenance of tidal volumes and blood CO2.

OBJECTIVE: To analyse the performance of the Fabian +NCPAP evolution ventilator during volume guarantee (VG) ventilation in neonates at maintaining the target tidal volume and what tidal and minute volumes are required to maintain normocapnia. METHODS: Clinical and ventilator data were collected and analysed from 83 infants receiving VG ventilation during interhospital transfer. Sedation was used in 26 cases. Ventilator data were downloaded with a sampling rate of 0.5 Hz. Data were analysed using the Python computer language and its data analysis packages. RESULTS: ~107 hours of ventilator data were analysed, consisting of ~194 000 data points. The median absolute difference between the actual expiratory tidal volume (VTe) of the ventilator inflations and the target tidal volume (VTset) was 0.29 mL/kg (IQR: 0.11-0.79 mL/kg). Overall, VTe was within 1 mL/kg of VTset in 80% of inflations. VTe decreased progressively below the target when the endotracheal tube leak exceeded 50%. When leak was below 50%, VTe was below VTset by >1 mL/kg in less than 12% of inflations even in babies weighing less than 1000 g. Both VTe (r=-0.34, p=0.0022) and minute volume (r=-0.22, p=0.0567) showed a weak inverse correlation with capillary partial pressure of carbon dioxide (Pco2) values. Only 50% of normocapnic blood gases were associated with tidal volumes between 4 and 6 mL/kg. CONCLUSIONS: The Fabian ventilator delivers volume-targeted ventilation with high accuracy if endotracheal tube leakage is not excessive and the maximum allowed inflating pressure does not limit inflations. There is only weak inverse correlation between tidal or minute volumes and Pco2.

Volume Guaranteed Ventilation During Neonatal Transport.

OBJECTIVES: To compare tidal volumes, inflating pressures and other ventilator variables of infants receiving synchronized intermitted mandatory ventilation with volume guarantee during emergency neonatal transport with those of infants receiving synchronized intermitted mandatory ventilation without volume guarantee. DESIGN: Retrospective observational study. SETTING: A regional neonatal emergency transport service. PATIENTS: We enrolled 77 infants undergoing emergency neonatal transfer. Forty-five infants were ventilated with synchronized intermittent mandatory ventilation with volume guarantee and 32 with synchronized intermitted mandatory ventilation without volume guarantee. INTERVENTIONS: Infants received synchronized intermitted mandatory ventilation with or without volume guarantee during interhospital emergency neonatal transport using a Fabian + nCPAP evolution neonatal ventilator (Software Version: 4.0.1; Acutronic Medical Instruments, Hirzel, Switzerland). MEASUREMENTS AND MAIN RESULTS: We downloaded detailed ventilator data with 0.5 Hz sampling rate. We analyzed data with the Python computer language and its data science packages. The mean expiratory tidal volume of inflations was lower and less variable in infants ventilated with volume guarantee than in babies ventilated without volume guarantee (group median 4.8 vs 6.0 mL/kg; p = 0.001). Babies ventilated with synchronized intermittent mandatory ventilation with volume guarantee had on average lower and more variable peak inflating pressures than babies ventilated without volume guarantee (group median 15.5 vs 19.5 cm H2O;p = 0.0004). With volume guarantee, a lower proportion of the total minute ventilation was attributed to ventilator inflations rather than to spontaneous breaths between inflations (group median 66% vs 83%; p = 0.02). With volume guarantee, babies had fewer inflations with tidal volumes greater than 6 mL/kg and greater than 8 mL/kg (group medians 3% vs 44% and 0% vs 7%, respectively; p = 0.0001). The larger tidal volumes in the non-volume guarantee group were not associated with significant hypocapnia except in one case. CONCLUSIONS: During neonatal transport, synchronized intermittent mandatory ventilation with volume guarantee ventilation reduced the occurrence of excessive tidal volumes, but it was associated with larger contribution of spontaneous breaths to minute ventilation compared with synchronized intermitted mandatory ventilation without volume guarantee.

Differential Expression of Markers in Extensive and Restricted Langerhans Cell Histiocytosis (LCH).

Langerhans cell histiocytosis (LCH) represents a poorly defined pathologic entity characterized by diverse clinical appearence and falling into two major categories namely a restricted and an extensive disease. Since the outcome and the course of the disease is variable, we postulated that this might be reflected by the phenotype of the Langerhans cells. We have selected 11 adult restricted cases and 10 extensive childhood cases and compared the phenotype of LCH cells by immunohistochemistry on paraffin sections. Morphometric analysis indicated a significantly higher expression of histiocytic (CD68, S-100, lysozyme) markers in the adult restricted cases compared to the extensive form of the disease. Both groups were equally positive for LCH marker CD1a and negative for T cell marker CD4. On the other hand, HLA-DR expression was significantly higher in LCH cells of the extensive childhood cases suggesting higher activation. These data suggest that LCH cells have a different phenotype in the extensive childhood and restricted adult LCH where the latter is characterized by a more differentiated histiocytic phenotype.