The Barriers to Rapid Reperfusion in Acute ST-Elevation Myocardial Infarction.

INTRODUCTION: This study aimed to quantify the contribution of various obstacles to timely reperfusion therapy in acute ST-elevation myocardial infarction (STEMI) and to improve performance in a mixed remote rural/urban region. METHODS: From November 1, 2020 to April 23, 2021, patients with acute STEMI were prospectively monitored with the critical time intervals, treatment modalities, and outcomes registered. Selected clinical decision-makers in 11 hospitals were appointed as improvement agents and systematically provided with weekly updated information about absolute and relative performance. Suggestions for improvements were invited and shared. RESULTS: Only 29% of the 146 patients received reperfusion therapy within recommended time limits [prehospital thrombolysis, 2/48; in-hospital thrombolysis, 0/20; primary percutaneous coronary intervention (pPCI), 37/68, with median intervals from the first medical contact of 44, 49, and 133 min, respectively]. Efficiency varied considerably between health trusts: median time from the first medical contact to prehospital thrombolysis ranged from 29 to 54 min (hazard ratio 4.89). The predominant, remediable causes for delays were erroneous tactical choices and protracted electrocardiographic diagnostication, decision-making, and administration of fibrinolytic medication. During the trial, the time to pPCI was non-significantly reduced. CONCLUSION: We found several targets for system improvements in order to mitigate reperfusion delays along the entire chain of care, regardless of reperfusion modality chosen. More patients should receive prehospital thrombolysis. The most important measures will be training to ensure a more efficient on-site workflow, improved protocols and infrastructure facilitating the communication between first responders and in-hospital clinicians, and education emphasizing prehospital transport times. CLINICAL TRIALS IDENTIFIER: NCT04614805.

Gas-phase diffusivity and tortuosity of structured soils.

Modeling gas-phase diffusion of volatile contaminants in the unsaturated zone relies on soil-gas diffusivity models often developed for repacked and structureless soil columns. These suffer from the flaw of not reflecting preferential diffusion through voids and fractures in the soil, thus possibly causing an underestimation of vapor migration towards building foundations and vapor intrusion to indoor environments. We measured the ratio of the gas diffusion coefficient in soil and in free air (D(p)/D(0)) for 42 variously structured, intact, and unsaturated soil cores taken from 6 Danish sites. Whilst the results from structureless fine sand were adequately described using previously proposed models, results that were obtained from glacial clay till and limestone exhibited a dual-porosity behavior. Instead, these data were successfully described using a dual-porosity model for gas-phase diffusivity, considering a presence of drained fractures surrounded by a lower diffusivity matrix. Based on individual model fits, the tortuosity of fractures in till and limestone was found to be highest in samples with a total porosity <40%, suggesting soil compaction to affect the geometry of the fractures. In summary, this study highlights a potential order of magnitude underestimation associated in the use of classical models for prediction of subsurface gas-phase diffusion coefficients in heterogeneous and fractured soils.

Variability of soil potential for biodegradation of petroleum hydrocarbons in a heterogeneous subsurface.

Quantifying the spatial variability of factors affecting natural attenuation of hydrocarbons in the unsaturated zone is important to (i) performing a reliable risk assessment and (ii) evaluating the possibility for bioremediation of petroleum-polluted sites. Most studies to date have focused on the shallow unsaturated zone. Based on a data set comprising analysis of about 100 soil samples taken in a 16 m-deep unsaturated zone polluted with volatile petroleum compounds, we statistically and geostatistically analysed values of essential soil properties. The subsurface of the site was highly layered, resulting in an accumulation of pollution within coarse sandy lenses. Air-filled porosity, readily available phosphorous, and the first-order rate constant (k(1)) of benzene obtained from slurry biodegradation experiments were found to depend on geologic sample characterization (P<0.05), while inorganic nitrogen was homogenously distributed across the soil stratigraphy. Semivariogram analysis showed a spatial continuity of 4-8.6 m in the vertical direction, while it was 2-5 times greater in the horizontal direction. Values of k(1) displayed strong spatial autocorrelation. Even so, the soil potential for biodegradation was highly variable, which from autoregressive state-space modeling was partly explained by changes in soil air-filled porosity and gravimetric water content. The results suggest considering biological heterogeneity when evaluating the fate of contaminants in the subsurface.

Soil Physical Constraints on Intrinsic Biodegradation of Petroleum Vapors in a Layered Subsurface.

Naturally occurring biodegradation of petroleum hydrocarbons in the vadose zone depends on the physical soil environment influencing field-scale gas exchange and pore-scale microbial metabolism. In this study, we evaluated the effect of soil physical heterogeneity on biodegradation of petroleum vapors in a 16-m-deep, layered vadose zone. Soil slurry experiments (soil/water ratio 10:30 w/w, 25°C) on benzene biodegradation under aerobic and well-mixed conditions indicated that the biodegradation potential in different textured soil samples was related to soil type rather than depth, in the order: sandy loam > fine sand > limestone. Similarly, O(2) consumption rates during in situ respiration tests performed at the site were higher in the sandy loam than in the fine sand, although the difference was less significant than in the slurries. Laboratory and field data generally agreed well and suggested a significant potential for aerobic biodegradation, even with nutrient-poor and deep subsurface conditions. In slurries of the sandy loam, the biodegradation potential declined with increasing in situ water saturation (i.e., decreasing air-filled porosity in the field). This showed a relation between antecedent undisturbed field conditions and the slurry biodegradation potential, and suggested airfilled porosity to be a key factor for the intrinsic biodegradation potential in the field.