Determinants of point-of-care ultrasound lung sliding amplitude in mechanically ventilated patients.

BACKGROUND: Although lung sliding seen by point-of-care ultrasound (POCUS) is known to be affected to varying degrees by different physiologic and pathologic processes, it is typically only reported qualitatively in the critical care setting. Lung sliding amplitude quantitatively expresses the amount of pleural movement seen by POCUS but its determinants in mechanically ventilated patients are largely unknown. METHODS: This was a single-center, prospective, observational pilot study examining 40 hemithoraces in 20 adult patients receiving mechanical ventilation. Each subject had lung sliding amplitude measured in both B-mode and by pulsed wave Doppler at their bilateral lung apices and bases. Differences in lung sliding amplitude were correlated with anatomical location (apex vs base) as well as physiologic parameters including positive end expiratory pressure (PEEP), driving pressure, tidal volume and the ratio of arterial partial pressure of oxygen (PaO2) to fraction of inspired oxygen (FiO2). RESULTS: POCUS lung sliding amplitude was significantly lower at the lung apex compared to the lung base in both B-mode (3.6 ± 2.0 mm vs 8.6 ± 4.3 mm; p < 0.001) and the pulsed wave Doppler mode (10.3 ± 4.6 cm/s vs 13.9 ± 5.5 cm/s; p < 0.001) corresponding to expected distribution of ventilation to the lung bases. Inter-rater reliability of B-mode measurements was excellent (ICC = 0.91) and distance traversed in B-mode had a significant positive correlation with pleural line velocity (r2 = 0.32; p < 0.001). There was a non-statistically significant trend towards lower lung sliding amplitude for PEEP ≥ 10 cmH2O, as well as for driving pressure ≥ 15 cmH2O in both ultrasound modes. CONCLUSION: POCUS lung sliding amplitude was significantly lower at the lung apex than the lung base in mechanically ventilated patients. This was true when using both B-mode and pulsed wave Doppler. Lung sliding amplitude did not correlate with PEEP, driving pressure, tidal volume or PaO2:FiO2 ratio. Our findings suggest that lung sliding amplitude can be quantified in mechanically ventilated patients in a physiologically predictable way and with high inter-rater reliability. A better understanding of POCUS derived lung sliding amplitude and its determinants may aid in the more accurate diagnosis of lung pathologies, including pneumothorax, and could serve as a means of further reducing radiation exposure and improving outcomes in critically ill patients.

Genetic diversity and evolution of Pneumocystis fungi infecting wild Southeast Asian murid rodents.

Pneumocystis organisms are airborne-transmitted fungal parasites that infect the lungs of numerous mammalian species with strong host specificity. In this study, we investigated the genetic diversity and host specificity of Pneumocystis organisms infecting Southeast Asian murid rodents through PCR amplification of two mitochondrial genes and tested the co-phylogeny hypothesis among these fungi and their rodent hosts. Pneumocystis DNA was detected in 215 of 445 wild rodents belonging to 18 Southeast Asian murid species. Three of the Pneumocystis lineages retrieved in our phylogenetic trees correspond to known Pneumocystis species, but some of the remaining lineages may correspond to new undescribed species. Most of these Pneumocystis species infect several rodent species or genera and some sequence types are shared among several host species and genera. These results indicated a weaker host specificity of Pneumocystis species infecting rodents than previously thought. Our co-phylogenetic analyses revealed a complex evolutionary history among Pneumocystis and their rodent hosts. Even if a significant global signal of co-speciation has been detected, co-speciation alone is not sufficient to explain the observed co-phylogenetic pattern and several host switches are inferred. These findings conflict with the traditional view of a prolonged process of co-evolution and co-speciation of Pneumocystis and their hosts.

Racial/ethnic and socioeconomic disparities in the use of helmets in children involved in bicycle accidents.

PURPOSE: While bicycle helmet use reduces bicycle-related head injury, few children wear them regularly. We aimed to describe racial/ethnic and socioeconomic differences in pediatric helmet use in Los Angeles County (LAC) to help target groups for injury prevention programs. METHODS: A retrospective review of all pediatric patients involved in bicycle-related accidents in LAC between 2006 and 2011 was performed. Our primary analysis examined the association between helmet use and age, gender, insurance status, and race/ethnicity. We also evaluated the association between helmet use and the need for emergency surgery, mortality, and length of hospital stay (LOH), after adjusting for injury severity score (ISS), age, insurance status, and race/ethnicity. RESULTS: Of 1248 patients, 11.3% wore helmets, with decreased use among children 12years and older, minorities, and those without private insurance. Overall, 5.9% required an emergency operation, 34.1% returned to their pre-injury capacity, and mortality was 0.7%. On multivariable analysis, higher ISS increased LOH, the risk for emergency surgery, and mortality. CONCLUSION: Nearly 90% of children involved in bicycle-related accidents were not wearing helmets. Helmet use was lower among older children, minorities, and those from a low socioeconomic status. Injury prevention programs targeting low-income middle and high schools and minority communities may help increase helmet use in children in LAC.

Electrochemical hydrogen insertion in substoichiometric titanium carbide TiC0.6: influence of carbon vacancy ordering.

Substoichiometric titanium carbide of formula TiC0.6 with different degrees of carbon vacancy ordering has been synthesized first by reactive sintering at high temperature (2100 °C) and then by annealing at low temperature (730 °C) for different durations. The effect of annealing on the structure of the carbide and its capacity to electrochemically insert hydrogen has been investigated. The XRD study reveals two phase transitions in the carbide during annealing. First, annealing of disordered TiC0.6 (space group Fm3¯m) for 40 h leads to a trigonal superstructure of space group R3¯m thanks to ordering of carbon vacancies. After the longest annealing time of 120 h, the structure of the carbide becomes cubic anew, but with a space group of Fd3¯m. The electrochemical hydrogen insertion in these different types of TiC0.6, as studied by cyclic voltammetry, strongly depends on the crystalline structure of the carbide. The maximum storage capacity is obtained for 40 h, corresponding to the R3¯m ordered phase. Because the R3¯m structure consists of alternately empty and full (111) carbon atomic planes, we show that the hydrogen insertion and diffusion in the material is rendered possible by the presence of vacant (111) planes. This behavior is very similar to that of a cation-ordered manganese-nickel spinel vis-à-vis lithium ion insertion.