Background & Objective Multiple Breath Washout (MBW) systems are designed to minimize equipment dead space volume (Vd). Animal and infant studies have demonstrated the impact of increased Vd on MBW measurements. In this study we investigate the effect of Vd of a N2MBW system affects MBW measurements in preschool children. Methods N2MBW measurements were performed in healthy adults under standard conditions; Vd was added to match the relationship between Vd and lung volumes observed in preschool children. Subsequently, subjects were measured on a SF6MBW system under standard conditions, and with Vd added to match that of the N2MBW system. Healthy preschool children and children with cystic fibrosis were tested on both the N2MBW and SF6MBW in random order on the same day. A correction equation was derived based on the adult experiments and tested on the preschool data. Results Increasing the Vd of the N2MBW system resulted in a higher Lung Clearance Index (LCI). A strong non-linear relationship between N2LCI and the Vd/Vt was observed. When the Vd was equivalent between systems, LCI measured by the SF6MBW system was similar to that measured by the N2MBW. LCI was higher on the N2MBW than the SF6MBW in preschool children. Correcting for the equipment Vd of the N2MBW resulted in better agreement. Conclusions Equipment Vd affects LCI measurements, especially in young children where Vd is large relative to lung volumes.

The objective of this study was to assess the evolution of diffusion-weighted imaging (DWI) and diffusion-tensor imaging (DTI) over the first month of life in asphyxiated newborns treated with hypothermia and to compare it with that of healthy newborns. Asphyxiated newborns treated with hypothermia were enrolled prospectively; and the presence and extent of brain injury were scored on each MRI. Apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values were measured in the basal ganglia, in the white matter and in the cortical grey matter. Sixty-one asphyxiated newborns treated with hypothermia had a total of 126 ADC and FA maps. Asphyxiated newborns developing brain injury eventually had significantly decreased ADC values on days 2-3 of life and decreased FA values around day 10 and 1 month of life compared with those not developing brain injury. Despite hypothermia treatment, asphyxiated newborns may develop brain injury that still can be detected with advanced neuroimaging techniques such as DWI and DTI as early as days 2-3 of life. A study of ADC and FA values over time may aid in the understanding of how brain injury develops in these newborns despite hypothermia treatment.