Trajectories of Hypoxemia & Pulmonary Mechanics of COVID-19 ARDS in the NorthCARDS Dataset

Background: Understanding heterogeneity seen in patients with COVIDARDS and comparing to non-COVIDARDS may inform tailored treatments. Methods: A multidisciplinary team of frontline clinicians and data scientists worked to create the Northwell COVIDARDS dataset (NorthCARDS) leveraging over 11,542 COVID-19 hospital admissions. The data was then summarized to examine descriptive differences based on clinically meaningful categories of lung compliance, and to examine trends in oxygenation. Findings: Of the 1595 COVIDARDS patients in the NorthCARDS dataset, there were 538 (34·6%) who had very low lung compliance (<20ml/cmH2O), 982 (63·2%) with low-normal compliance (20-50ml/cmH2O), and 34 (2·2%) with high lung compliance (>50ml/cmH2O). The very low compliance group had double the median time to intubation compared to the low-normal group (107 hours (IQR 26·3, 238·3) vs. 37·9 hours (IQR 4·8, 90·7)). Overall, 67·5% (n=1049) of the patients died during the hospitalization. In comparison to non-COVIDARDS reports, there were less patients in the high compliance category (2.2%vs.12%, compliance ≥50mL/cmH20), and more patients with P/F ≤ 150 (57·8% vs. 45.6%). No correlation was apparent between lung compliance and P/F ratio. The Oxygenation Index was similar, (11·12(SD 5·67) vs.12·8(SD 10·8)).1

A piezoelectric contact problem with slip dependent friction and damage

The aim of this paper is to study a quasistatic contact problem between an electro-elastic viscoplastic body with damage and an electrically conductive foundation. The contact is modelled with an electrical condition, normal compliance and the associated version of Coulomb’s law of dry friction in which slip dependent friction is included. We derive a variational formulation for the model and, under a smallness assumption, we prove the existence and uniqueness of a weak solution.

Numerical Analysis of a Sliding frictional contact problem with Normal Compliance and Unilateral Contact

This paper represents a continuation of [15] and [18]. Here, we consider the numerical analysis of a non trivial frictional contact problen in a form of a system of evolution nonlinear partial differential equations. The model describes the equilibrium of a viscoelastic body in sliding contact with a moving foundation. The contact is modeled with a multivalued normal compliance condition with memory term restricted by a unilateral constraint, and is associated to a sliding version of Coulomb's law of dry friction. After a description of the model and some assumptions, we derive a variational formulation of the problem, which consists of a system coupling a variational inequality for the displacement field and a nonlinear equation for the stress field. Then, we introduce a fully discrete scheme for the numerical approximation of the sliding contact problem. Under certain solution regularity assumptions, we derive an optimal order error estimate and we provide numerical validation of this result by considering some numerical simulations in the study of a two-dimensional problem.