A Lattice Boltzmann Method for immiscible multiphase flow simulations using the Level Set Method

We consider the lattice Boltzmann method for immiscible multiphase flow simulations. Classical lattice Boltzmann methods for this problem, e.g. the colour gradient method or the free energy approach, can only be applied when density and viscosity ratios are small. Moreover, they use additional fields defined on the whole domain to describe the different phases and model phase separation by special interactions at each node. In contrast, our approach simulates the flow using a single field and separates the fluid phases by a free moving interface. The scheme is based on the lattice Boltzmann method and uses the level set method to compute the evolution of the interface. To couple the fluid phases, we develop new boundary conditions which realise the macroscopic jump conditions at the interface and incorporate surface tension in the lattice Boltzmann framework. Various simulations are presented to validate the numerical scheme, e.g. two-phase channel flows, the Young-Laplace law for a bubble and viscous fingering in a Hele-Shaw cell. The results show that the method is feasible over a wide range of density and viscosity differences

Gap in funding for specialist hospitals treating patients with traumatic spinal cord injury under an activity-based funding model in New South Wales, Australia.

Objective The aim of this study was to estimate the difference between treatment costs in acute care settings and the level of funding public hospitals would receive under the activity-based funding model. Methods Patients aged ≥16 years who had sustained an incident traumatic spinal cord injury (TSCI) between June 2013 and June 2016 in New South Wales were included in the study. Patients were identified from record-linked health data. Costs were estimated using two approaches: (1) using District Network Return (DNR) data; and (2) based on national weighted activity units (NWAU) assigned to activity-based funding activity. The funding gap in acute care treatment costs for TSCI patients was determined as the difference in cost estimates between the two approaches. Results Over the study period, 534 patients sustained an acute incident TSCI, accounting for 811 acute care hospital separations within index episodes. The total acute care treatment cost was estimated at A$40.5 million and A$29.9 million using the DNR- and NWAU-based methods respectively. The funding gap in total costs was greatest for the specialist spinal cord injury unit (SCIU) colocated with a major trauma service (MTS), at A$4.4 million over the study period. Conclusions The findings of this study suggest a substantial gap in funding for resource-intensive patients with TSCI in specialist hospitals under current DRG-based funding methods. What is known about the topic? DRG-based funding methods underestimate the treatment costs at the hospital level for patients with complex resource-intensive needs. This underestimation of true direct costs can lead to under-resourcing of those hospitals providing specialist services. What does this paper add? This study provides evidence of a difference between true direct costs in acute care settings and the level of funding hospitals would receive if funded according to the National Efficient Price and NWAU for patients with TSCI. The findings provide evidence of a shortfall in the casemix funding to public hospitals under the activity-based funding for resource-intensive care, such as patients with TSCI. Specifically, depending on the classification system, the principal referral hospitals, the SCIU colocated with an MTS and stand-alone SCIU were underfunded, whereas other non-specialist hospitals were overfunded for the acute care treatment of patients with TSCI. What are the implications for practitioners? Although health care financing mechanisms may vary internationally, the results of this study are applicable to other hospital payment systems based on diagnosis-related groups that describe patients of similar clinical characteristics and resource use. Such evidence is believed to be useful in understanding the adequacy of hospital payments and informing payment reform efforts. These findings may have service redesign policy implications and provide evidence for additional loadings for specialist hospitals treating low-volume, resource-intensive patients

Identifying Predictors of Higher Acute Care Costs for Patients with Traumatic Spinal Cord Injury and Modeling Acute Care Pathway Redesign: A Record Linkage Study

Study Design.Record linkage study using healthcare utilization and costs data.Objective.To identify predictors of higher acute-care treatment costs and length of stay for patients with traumatic spinal cord injury (TSCI).Summary of Background Data.There are few current or population-based estimates of acute hospitalization costs, length of stay, and other outcomes for people with TSCI, on which to base future planning for specialist SCI health care services.Methods.Record linkage study using healthcare utilization and costs data; all patients aged more than or equal to 16 years with incident TSCI in the Australian state of New South Wales (June 2013-June 2016). Generalized Linear Model regression to identify predictors of higher acute care treatment costs for patients with TSCI. Scenario analysis quantified the proportionate cost impacts of patient pathway modification.Results.Five hundred thirty-four incident cases of TSCI (74% male). Total cost of all acute index episodes approximately AUD$40.5 (95$45,473 (Interquartile Range: $15,535-$94,612). Patient pathways varied; acute care was less costly for patients admitted directly to a specialist spinal cord injury unit (SCIU) compared with indirect transfer within 24 hours. Over half (53%) of all patients experienced at least one complication during acute admission; their care was less costly if they had been admitted directly to SCIU. Scenario analysis demonstrated that a reduction of indirect transfers to SCIU by 10% yielded overall cost savings of AUD$3.1 million; an average per patient saving of AUD$5,861.Conclusion.Direct transfer to SCIU for patients with acute TSCI resulted in lower treatment costs, shorter length of stay, and less costly complications. Modeling showed that optimizing patient-care pathways can result in significant acute-care cost savings. Reducing potentially preventable complications would further reduce costs and improve longer-term patient outcomes.Level of Evidence: 3

Assessing the impact of care pathways on potentially preventable complications and costs for spinal trauma patients: Protocol for a data linkage study using cohort study and administrative data

Introduction Traumatic spinal cord injuries have significant consequences both for the injured individual and the healthcare system, usually resulting in lifelong disability. Evidence has shown that timely medical and surgical interventions can lead to better patient outcomes with implicit cost savings. Potentially preventable secondary complications are therefore indicators of the effectiveness of acute care following traumatic injury. The extent to which policy and clinical variation within the healthcare service impact on outcomes and acute care costs for patients with traumatic spinal cord injury (TSCI) in Australia is not well described. Methods and analysis A comprehensive data set will be formed using record linkage to combine patient health and administrative records from seven minimum data collections (including costs), with an existing data set of patients with acute TSCI (Access to Care Study), for the time period June 2013 to June 2016. This person-level data set will be analysed to estimate the acute care treatment costs of TSCI in New South Wales, extrapolated nationally. Subgroup analyses will describe the associated costs of secondary complications and regression analysis will identify drivers of higher treatment costs. Mapping patient care and health service pathways of these patients will enable measurement of deviations from best practice care standards and cost-effectiveness analyses of the different pathways. Ethics and dissemination Ethics approval has been obtained from the New South Wales Population and Health Services Research Ethics Committee. Dissemination strategies include peer-reviewed publications in scientific journals and conference presentations to enable translation of study findings to clinical and policy audiences

Identifying Predictors of Higher Acute Care Costs For Patients With Traumatic Spinal Cord Injury and Modelling Acute Care Pathway Redesign: A Record Linkage Study

Study Design. Record linkage study using healthcare utilization and costs data. Objective. To identify predictors of higher acute-care treatment costs and length of stay for patients with traumatic spinal cord injury (TSCI). Summary of Background Data. There are few current or population-based estimates of acute hospitalization costs, length of stay, and other outcomes for people with TSCI, on which to base future planning for specialist SCI health care services. Methods. Record linkage study using healthcare utilization and costs data; all patients aged more than or equal to 16 years with incident TSCI in the Australian state of New South Wales (June 2013\u2013June 2016). Generalized Linear Model regression to identify predictors of higher acute care treatment costs for patients with TSCI. Scenario analysis quantified the proportionate cost impacts of patient pathway modification. Results. Five hundred thirty-four incident cases of TSCI (74% male). Total cost of all acute index episodes approximately AUD$40.5 (95$45,473 (Interquartile Range: $15,535\u2013$94,612). Patient pathways varied; acute care was less costly for patients admitted directly to a specialist spinal cord injury unit (SCIU) compared with indirect transfer within 24 hours. Over half (53%) of all patients experienced at least one complication during acute admission; their care was less costly if they had been admitted directly to SCIU. Scenario analysis demonstrated that a reduction of indirect transfers to SCIU by 10% yielded overall cost savings of AUD$3.1 million; an average per patient saving of AUD$5,861. Conclusion. Direct transfer to SCIU for patients with acute TSCI resulted in lower treatment costs, shorter length of stay, and less costly complications. Modeling showed that optimizing patient-care pathways can result in significant acute-care cost savings. Reducing potentially preventable complications would further reduce costs and improve longer-term patient outcomes. Key words: complications, costs, length of stay, record linkage, traumatic spinal cord injury

Identifying Predictors of Higher Acute Care Costs for Patients With Traumatic Spinal Cord Injury and Modeling Acute Care Pathway Redesign: A Record Linkage Study.

STUDY DESIGN: Record linkage study using healthcare utilization and costs data. OBJECTIVE: To identify predictors of higher acute-care treatment costs and length of stay for patients with traumatic spinal cord injury (TSCI). SUMMARY OF BACKGROUND DATA: There are few current or population-based estimates of acute hospitalization costs, length of stay, and other outcomes for people with TSCI, on which to base future planning for specialist SCI health care services. METHODS: Record linkage study using healthcare utilization and costs data; all patients aged more than or equal to 16 years with incident TSCI in the Australian state of New South Wales (June 2013-June 2016). Generalized Linear Model regression to identify predictors of higher acute care treatment costs for patients with TSCI. Scenario analysis quantified the proportionate cost impacts of patient pathway modification. RESULTS: Five hundred thirty-four incident cases of TSCI (74% male). Total cost of all acute index episodes approximately AUD$40.5 (95$45,473 (Interquartile Range: $15,535-$94,612). Patient pathways varied; acute care was less costly for patients admitted directly to a specialist spinal cord injury unit (SCIU) compared with indirect transfer within 24 hours. Over half (53%) of all patients experienced at least one complication during acute admission; their care was less costly if they had been admitted directly to SCIU. Scenario analysis demonstrated that a reduction of indirect transfers to SCIU by 10% yielded overall cost savings of AUD$3.1 million; an average per patient saving of AUD$5,861. CONCLUSION: Direct transfer to SCIU for patients with acute TSCI resulted in lower treatment costs, shorter length of stay, and less costly complications. Modeling showed that optimizing patient-care pathways can result in significant acute-care cost savings. Reducing potentially preventable complications would further reduce costs and improve longer-term patient outcomes. LEVEL OF EVIDENCE: 3

A Lattice Boltzmann Method for immiscible multiphase flow simulations using the Level Set Method

We consider the lattice Boltzmann method for immiscible multiphase flow simulations. Classical lattice Boltzmann methods for this problem, e.g. the colour gradient method or the free energy approach, can only be applied when density and viscosity ratios are small. Moreover, they use additional fields defined on the whole domain to describe the different phases and model phase separation by special interactions at each node. In contrast, our approach simulates the flow using a single field and separates the fluid phases by a free moving interface. The scheme is based on the lattice Boltzmann method and uses the level set method to compute the evolution of the interface. To couple the fluid phases, we develop new boundary conditions which realise the macroscopic jump conditions at the interface and incorporate surface tension in the lattice Boltzmann framework. Various simulations are presented to validate the numerical scheme, e.g. two-phase channel flows, the Young-Laplace law for a bubble and viscous fingering in a Hele-Shaw cell. The results show that the method is feasible over a wide range of density and viscosity differences

A geospatial examination of specialist care accessibility and impact on health outcomes for patients with acute traumatic spinal cord injury in New South Wales, Australia: a population record linkage study.

BackgroundTimely treatment is essential for achieving optimal outcomes after traumatic spinal cord injury (TSCI), and expeditious transfer to a specialist spinal cord injury unit (SCIU) is recommended within 24 hours from injury. Previous research in New South Wales (NSW) found only 57% of TSCI patients were admitted to SCIU for acute post-injury care; 73% transferred within 24 hours from injury. We evaluated pre-hospital and inter-hospital transfer practices to better understand the post-injury care pathways impact on patient outcomes and highlight areas in the health service pathway that may benefit from improvement.MethodsThis record linkage study included administrative pre-hospital (Ambulance), admissions (Admitted Patients) and costs data obtained from the Centre for Health Record Linkage, NSW. All patients aged ≥16 years with incident TSCI in NSW (2013-2016) were included. We investigated impacts of geographical disparities on pre-hospital and inter-hospital transport decisions from injury location using geospatial methods. Outcomes assessed included time to SCIU, surgery and the impact of these variables on the experience of inpatient complications. ResultsInclusion criteria identified 316 patients, geospatial analysis showed that over half (53%, n=168) of all patients were injured within 60 minutes road travel of a SCIU, yet only 28.6% (n=48) were directly transferred to a SCIU. Patients were more likely to experience direct transfer to a SCIU without comorbid trauma (p<0.01) but higher ICISS (p<0.001), cervical injury (p<0.01), and transferred by air-ambulance (p<0.01). Indirect transfer to SCIU was more likely with two or more additional traumatic injuries (p<0.01) or incomplete injury (p<0.01). Patients not admitted to SCIU at all were older (p=0.05) with lower levels of injury (p<0.01). Direct transfers received earlier operative intervention (median (IQR) 12.9(7.9) hours), compared with patients transferred indirectly to SCIU (median (IQR) 19.5(18.9) hours), and had lower risk of complications (OR 3.2 v 1.4, p<0.001). Complications included pressure injury, deep vein thrombosis, urinary infection, among others. ConclusionsGetting patients with acute TSCI patients to the right place at the right time is dependent on numerous factors; some are still being triaged directly to non-trauma services which delays specialist and surgical care and increases complication risks. The higher rates of complication following delayed transfer to a SCIU should motivate health service policy makers to investigate reasons for this practice and consent to improvement strategies. More stringent adherence to recommended guidelines would prioritise direct SCIU transfer for patients injured within 60 minutes radius, enabling the benefits of specialised care