Characteristics and Outcomes of ICU Patients Without COVID-19 Infection-Pandemic Versus Nonpandemic Times: A Population-Based Cohort Study.

Outcomes for critically ill COVID-19 are well described; however, the impact of the pandemic on critically ill patients without COVID-19 infection is less clear. OBJECTIVES: To demonstrate the characteristics and outcomes of non-COVID patients admitted to an ICU during the pandemic, compared with the previous year. DESIGN: A population-based study conducted using linked health administrative data comparing a cohort from March 1, 2020, to June 30, 2020 (pandemic) to a cohort from March 1, 2019, to June 30, 2019 (nonpandemic). SETTING AND PARTICIPANTS: Adult patients (18 yr old) admitted to an ICU in Ontario, Canada, without a diagnosis of COVID-19 during the pandemic and nonpandemic periods. MAIN OUTCOMES AND MEASURES: The primary outcome was all-cause in-hospital mortality. Secondary outcomes included hospital and ICU length of stay, discharge disposition, and receipt of resource intensive procedures (e.g., extracorporeal membrane oxygenation, mechanical ventilation, renal replacement therapy, bronchoscopy, feeding tube insertion, and cardiac device insertion). We identified 32,486 patients in the pandemic cohort and 41,128 in the nonpandemic cohort. Age, sex, and markers of disease severity were similar. Fewer patients in the pandemic cohort were from long-term care facilities and had fewer cardiovascular comorbidities. There was an increase in all-cause in-hospital mortality among the pandemic cohort (13.5% vs 12.5%; p < 0.001) representing a relative increase of 7.9% (adjusted odds ratio, 1.10; 95% CI, 1.05-1.56). Patients in the pandemic cohort admitted with chronic obstructive pulmonary disease exacerbation had an increase in all-cause mortality (17.0% vs 13.2%; p = 0.013), a relative increase of 29%. Mortality among recent immigrants was higher in the pandemic cohort compared with the nonpandemic cohort (13.0% vs 11.4%; p = 0.038), a relative increase of 14%. Length of stay and receipt of intensive procedures were similar. CONCLUSIONS AND RELEVANCE: We found a modest increase in mortality among non-COVID ICU patients during the pandemic compared with a nonpandemic cohort. Future pandemic responses should consider the impact of the pandemic on all patients to preserve quality of care.

On the Importance of Gravity in DNAPL Invasion of Saturated Horizontal Fractures.

Invasion percolation (IP) models of dense non-aqueous phase liquid (DNAPL) invasion into saturated horizontal fractures typically neglect viscous and gravity forces, as it is assumed that capillarity dominates in many situations. An IP model simulating DNAPL invasion into saturated horizontal fractures was modified to include gravity as a local effect. The model was optimized using a genetic algorithm, and demonstrated that the inclusion of gravity is important for replicating the architecture of the DNAPL invasion pattern. The optimized gravity-included simulation showed the DNAPL invasion pattern to be significantly more representative of the experimentally observed pattern (80% accuracy) than did the optimized gravity-neglected simulation (70% accuracy). Additional simulations of DNAPL invasion in 360 randomly generated fractures were compared with and without gravity forces. These simulations showed that with increasing fracture roughness, the minimum difference between simulations with and without gravity increases to 35% for a standard deviation of the mid-aperture elevation field (SDz ) of 10 mm. Even for low roughness (SDz = 0.1 mm), the difference was as high as 30%. Furthermore, a scaled Bond Number is defined which includes data regarding DNAPL type, media type and statistical characteristics of the fracture. The value of this scaled Bond Number can be used to determine the conditions under which gravity should be considered when simulating DNAPL invasion in a macroscopically horizontal fracture. Finally, a set of equations defining the minimum and maximum absolute percentage difference between gravity-included and gravity-neglected simulations is presented based on the fracture and DNAPL characteristics.

Mass flux from a non-aqueous phase liquid pool considering spontaneous expansion of a discontinuous gas phase.

The partitioning of non-aqueous phase liquid (NAPL) compounds to a discontinuous gas phase results in the repeated spontaneous expansion, snap-off, and vertical mobilization of the gas phase. This mechanism has the potential to significantly affect the mass transfer processes that control the dissolution of NAPL pools by increasing the vertical transport of NAPL mass and increasing the total mass transfer rate from the surface of the pool. The extent to which this mechanism affects mass transfer from a NAPL pool depends on the rate of expansion and the mass of NAPL compound in the gas phase. This study used well-controlled bench-scale experiments under no-flow conditions to quantify for the first time the expansion of a discontinuous gas phase in the presence of NAPL. Air bubbles placed in glass vials containing NAPL increased significantly in volume, from a radius of 1.0 mm to 2.0 mm over 215 days in the presence of tetrachloroethene (PCE), and from a radius of 1.2 mm to 2.3 mm over 22 days in the presence of trans-1,2-dichloroethene (tDCE). A one-dimensional mass transfer model, fit to the experimental data, showed that this expansion could result in a mass flux from the NAPL pool that was similar in magnitude to the mass flux expected for the dissolution of a NAPL pool in a two-fluid (NAPL and water) system. Conditions favouring the significant effect of a discontinuous gas phase on mass transfer were identified as groundwater velocities less than approximately 0.01 m/day, and a gas phase that covers greater than approximately 10% of the pool surface area and is located within approximately 0.01 m of the pool surface. Under these conditions the mass transfer via a discontinuous gas phase is expected to affect, for example, efforts to locate NAPL source zones using aqueous concentration data, and predict the lifetime and risk associated with NAPL source zones in a way that is not currently included in the common conceptual models used to assess NAPL-contaminated sites.

Dissolution of entrapped DNAPLs in variable aperture fractures: experimental data and empirical model.

An appreciation of the dissolution from entrapped nonaqueous phase liquids (NAPLs) in fractures is essential as we attempt to understand and predict the fate of NAPLs present in fractured rock systems. Eight long-term dissolution experiments using 1,1,1-trichloroethane and trichloroethylene were conducted in two laboratory-scale dolomitic limestone variable aperture fractures under various conditions. Between 560 and 2600 fracture volumes of water were passed through the fractures resulting in the removal of 10-60% of the initial mass trapped. The effluent concentration profiles revealed three distinct and characteristic stages of dissolution: an initial pseudosteady stage, a transient stage, and a tailing stage. On average, 8% of the initial volume of NAPL present was removed during the initial pseudosteady stage. Data from the dissolution experiments were used in conjunction with statistical techniques to develop a continuous empirical model describing the initial pseudosteady and transient stages of dissolution. The model was used to successfully replicate effluent concentration data from two separate and independent dissolution experiments. The experimental results provide an indication of the expected dissolution behavior of entrapped NAPLs, while the developed model is a useful tool for characterizing mass transfer rates in variable aperture fractures.

Hemochorial placentation in the primate: expression of vascular endothelial growth factor, angiopoietins, and their receptors throughout pregnancy.

Vascular development and its transformation are necessary for successful hemochorial placentation, and vascular endothelial growth factor (VEGF), angiopoietins, and their receptors may be involved in the molecular regulation of this process. To determine the potential role of these putative regulators in a widely studied primate, the common marmoset, we investigated their mRNA expression and protein location in the placenta throughout pregnancy using in situ hybridization, Northern blot analysis, and immunocytochemistry. VEGF was localized in decidual and cytotrophoblast cells, and its highest expression was found in the maternal decidua. The Flt receptor was exclusively detected in the syncytial trophoblast with increasing expression in placentae from 10 wk to term. Soluble Flt (sFlt) was also detectable by Northern blot analysis. KDR receptor expression was restricted to mesenchymal cells during early placentation and to the fetoplacental vasculature during later placentation. KDR expression increased throughout pregnancy. Angiopoietin-1 (Ang-1) was localized in the syncytial trophoblast, being highly expressed in the second half of gestation. Ang-2 mRNA localized exclusively to maternal endothelial cells, and was highly expressed in 10-wk placentae. The Tie-2 receptor was found in cytotrophoblast cells and in fetal and maternal vessels. High Tie-2 levels were detected in the wall of chorion vessels at 14-wk, 17-wk, and term placentae. These results suggest that the processes of trophoblast invasion, maternal vascular transformation, and fetoplacental vascular differentiation and development are regulated by the specific actions of angiogenic ligand-receptor pairs. Specifically, 1) VEGF/Flt and Ang-1/Tie-2 may promote trophoblast growth, 2) VEGF/KDR and Ang-1/Tie-2 may support fetoplacental vascular development and stabilization, 3) sFlt may balance VEGF actions, and 4) Ang-2/Tie-2 may remodel the maternal vasculature.