Evaluation of alveolar development beyond the postnatal period of rapid septation has generally involved alveolar counting. We used an alternate approach to assess postseptation parenchymal development: measurement of the lengths of various types of alveolar septal borders. This technique directly addresses changes in the elastin fiber network that determines parenchymal complexity. Lungs from weanling and adult ferrets, inflated to 15 cmH2O, were perfusion fixed and dehydrated, and 2-μm sections were stained with Miller’s elastin stain for light microscopy. We used standard morphometric methods to measure the lengths of the various types of alveolar septal borders. Three types comprised >90% of all septal borders: 1) free septal ends (“ends”) containing an elastin cable; 2) angled meetings of two alveolar septa (“bends”), also with a cable; and 3) the near-symmetrical intersections of three septa (“junctions”) devoid of elastin. When scaled for lung volume, ends and bends were 23 and 37% greater in adults ( P < 0.001), reflecting the increase in parenchymal complexity with growth. The 17% difference in scaled junction lengths was not significant ( P = 0.10). Bends increased out of proportion to the increase in ends, and both bends and ends increased to a greater degree than any possible increase in junctions ( P < 0.001 for all comparisons). Although the interpretation of changes in the distribution of alveolar border lengths is not straightforward, an increase in bends resulting in an increase in the complexity of individual alveoli may contribute to the increase in alveolar gas-exchanging surface area with growth. Septation, the process responsible for the rapid early postnatal increase in parenchymal complexity in many species, should tend to increase the lengths of ends and junctions and decrease the lengths of bends. Therefore, these data suggest that septation is not the predominant mechanism of later postnatal parenchymal development in the ferret.

BackgroundThe aim of this study was to determine whether the use of visual freeze indicators on vaccines would assist health care providers in identifying vaccines that may have been exposed to potentially damaging temperatures.MethodsTwenty-seven sites in Connecticut involved in the Vaccine for Children Program participated. In addition to standard procedures, visual freeze indicators (FREEZEmarker® L; Temptime Corporation, Morris Plains, NJ) were affixed to each box of vaccine that required refrigeration but must not be frozen. Temperatures were monitored twice daily.ResultsDuring the 24 weeks, all 27 sites experienced triggered visual freeze indicator events in 40 of the 45 refrigerators. A total of 66 triggered freeze indicator events occurred in all 4 types of refrigerators used. Only 1 of the freeze events was identified by a temperature-monitoring device. Temperatures recorded on vaccine data logs before freeze indicator events were within the 35°F to 46°F (2°C to 8°C) range in all but 1 instance. A total of 46,954 doses of freeze-sensitive vaccine were stored at the time of a visual freeze indicator event. Triggered visual freeze indicators were found on boxes containing 6566 doses (14.0% of total doses). Of all doses stored, 14,323 doses (30.5%) were of highly freeze-sensitive vaccine; 1789 of these doses (12.5%) had triggered indicators on the boxes.ConclusionsVisual freeze indicators are useful in the early identification of freeze events involving vaccines. Consideration should be given to including these devices as a component of the temperature-monitoring system for vaccines.

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Critical Care of Infants and Children joins a group of two or three other textbooks in offermg a comprehensive overview of the care of critically ill children It is edited by one of the fathers of pediatric intensive care, David Todres In its premier edition, its list of contnbutors is