BackgroundMorphological changes in preterm infants with bronchopulmonary dysplasia (BPD) have functional consequences on lung volume, ventilation inhomogeneity and respiratory mechanics. Although some studies have shown lower lung volumes and increased ventilation inhomogeneity in BPD infants, conflicting results exist possibly due to differences in sedation and measurement techniques.Methodology/Principal FindingsWe studied 127 infants with BPD, 58 preterm infants without BPD and 239 healthy term-born infants, at a matched post-conceptional age of 44 weeks during quiet natural sleep according to ATS/ERS standards. Lung function parameters measured were functional residual capacity (FRC) and ventilation inhomogeneity by multiple breath washout as well as tidal breathing parameters. Preterm infants with BPD had only marginally lower FRC (21.4 mL/kg) than preterm infants without BPD (23.4 mL/kg) and term-born infants (22.6 mL/kg), though there was no trend with disease severity. They also showed higher respiratory rates and lower ratios of time to peak expiratory flow and expiratory time (t PTEF/t E) than healthy preterm and term controls. These changes were related to disease severity. No differences were found for ventilation inhomogeneity.ConclusionsOur results suggest that preterm infants with BPD have a high capacity to maintain functional lung volume during natural sleep. The alterations in breathing pattern with disease severity may reflect presence of adaptive mechanisms to cope with the disease process.

It was hypothesized that the mucous layer lining the tracheas of rats and guinea pigs contains surfactant material capable of lowering the air/mucus surface tension, gamma, and that exposure to an irritant aerosol would raise the gamma. The gamma of the surface film was measured directly by a spreading droplet technique and indirectly by displacement of polymethyl methacrylate particles into the aqueous layer. The morphology of the mucous film was examined by electron microscopy after nonaqueous fixation. gamma was 33.3 +/- 0.70 (SE) mN/m and 32.3 +/- 0.68 (SE) mN/m for the normal rat and guinea pig trachea, respectively. Exposure for 4 h to aerosols of sulfuric acid (94.1 +/- 18.68 (SD) and 43.3 +/- 4.57 (SD) mg/m3) caused a several-fold increase in thickness of the mucous layer with exudation of protein-like material. The osmiophilic surfactant film at the air/mucus interface became irregularly thickened and multilayered. Despite these morphological changes gamma remained low, 33.2 +/- 0.43 (SE) mN/m and 32.6 +/- 0.60 (SE) mN/m for rats and guinea pigs, respectively, and displacement of particles into the subphase was not compromised. The results indicate that rodent tracheas are able to maintain a low surface tension in the presence of injury.

The regulation of air quality is important for ensuring the health of a population. Current air quality decision support systems are very useful if the user possesses sufficient data to operate them and the necessary expertise to interpret their results. In general, these systems suffer as a result of their excessive complexity. The present study describes the development of a scalable air quality decision support system using the CALPUFF air dispersion model and a Geospatial Information System (GIS). This system uses receptor level exposure modeling and outputs from CALPUFF to estimate the relative impacts on human populations from multiple air pollution sources by calculating intake, defined as the amount of pollution that is inhaled by a population and intake fraction, defined as the fraction of pollutant emitted by a pollution source that is inhaled by a population. Unlike ground level pollution concentration, intake and intake fraction consider receptors and offer a more valuable estimate of pollution exposure, especially when faced with limited input data. The system also leverages the inherent strength of GIS to improve accessibility of geospatial data by generating maps of ground level pollutant concentration, intake, and intake fraction using graduated color schemes. This enables any user to identify potentially hazardous pollution sources and prioritize decisions such as development, maintenance, and decommission.

This study reports experiments designed to evaluate the dose and temporal effects of an atmospheric pollutant, sulfuric acid (H2SO4) aerosol, on the dynamic components of the respiratory cycle. Ventilation was measured in a whole-body barometric plethysmograph in unanesthetized, unrestrained animals following a 4-h exposure to H2SO4 aerosol at 14.1, 20.1, or 43.3 mg/m3. Lung injury was assessed by histopathology and bronchoalveolar lavage (BAL). Aerosol exposure with H2SO4 caused marked alterations in both the magnitude and composition of the ventilatory response, which were both dose and time dependent. At the highest concentration tested, there was a significant increase in tidal volume (deltaVt) and a decrease in breathing frequency (f) immediately after exposure. Analysis of BAL fluid at this time showed increased inflammatory cells and protein in the acid exposed animals, and histology showed hyaline membranes and acute inflammatory cells in the proximal acinar region. By 24 h postexposure, f significantly increased whereas deltaVt decreased. This pattern of breathing was interspersed with short periods of apnea. The onset of rapid, shallow breathing was associated with histological evidence of diffuse pulmonary edema. By contrast, the immediate postexposure period at the lowest concentration of H2SO4 aerosol was characterized by a significant increase in f and little or no effect on deltaVt. These effects diminished with time, and at 24 h postexposure ventilatory parameters were indistinguishable from baseline values. An apparent crossover between the effects associated with the high and low exposure concentrations was seen at the intermediate exposure concentration; however, closer inspection of these findings on an animal-by-animal basis revealed two populations of animals with respiratory characteristics of either the high-exposure or low-exposure groups. The data suggest that the guinea pig exhibits complex interactions between dose and time to response that are consistent with the activation of neural reflexes. The indirect plethysmographic method provides a simple means to assess these responses in a model system that avoids the use of anesthetics, surgery, and restraint.