Locating helicopter emergency medical service bases to optimise population coverage versus average response time

__Background:__ New South Wales (NSW), Australia has a network of multirole retrieval physician staffed helicopter emergency medical services (HEMS) with seven bases servicing a jurisdiction with population concentrated along the eastern seaboard. The aim of this study was to estimate optimal HEMS base locations within NSW using advanced mathematical modelling techniques. __Methods:__ We used high resolution census population data for NSW from 2011 which divides the state into areas containing 200-800 people. Optimal HEMS base locations were estimated using the maximal covering location problem facility location optimization model and the average response time model, exploring the number of bases needed to cover various fractions of the population for a 45 min response time threshold or minimizing the overall average response time to all persons, both in green field scenarios and conditioning on the current base structure. We also developed a hybrid mathematical model where average response time was optimised based on minimum population coverage thresholds. __Results:__ Seven bases could cover 98% of the population within 45mins when optimised for coverage or reach the entire population of the state within an average of 21mins if optimised for response time. Given the existing bases, adding two bases could either increase the 45 min coverage from 91% to 97% or decrease the average response time from 21mins to 19mins. Adding a single specialist prehospital rapid response HEMS to the area of greatest population concentration decreased the average state wide response time by 4mins. The optimum seven base hybrid model that was able to cover 97.75% of the population within 45mins, and all of the population in an average response time of 18 mins included the rapid response HEMS model. __Conclusions:__ HEMS base locations can be optimised based on either percentage of the population covered, or average response time to the entire population. We have also demonstrated a hybrid technique that optimizes response time for a given number of bases and minimum defined threshold of population coverage. Addition of specialized rapid response HEMS services to a system of multirole retrieval HEMS may reduce overall average response times by improving access in large urban areas

Een boost voor verduurzaming

In lijn met de klimaatdoelen heeft de Nederlandse overheid in 2016 de ambitie uitgesproken om uiterlijk in 2030 alle dieselbussen in Nederland te vervangen door duurzaam aangedreven bussen. Sindsdien werken het Rotterdamse vervoerbedrijf RET en de Rotterdam School of Management, Erasmus University samen om deze transitie van dieselbussen naar elektrische bussen soepel te laten verlopen. Het gaat hierbij voornamelijk om de operationele uitdaging van het plannen van de laadmomenten van de bussen. In 2019 zijn de eerste 50 elektrische bussen in gebruik genomen en in de komende jaren zullen er snel meer volgen

Scheduling non-urgent patient transportation while maximizing emergency coverage

Many ambulance providers operate both advanced life support (ALS) and basic life support (BLS) ambulances. Typically, only an ALS ambulance can respond to an emergency call, whereas non-urgent patient transportation requests can either be served by an ALS or a BLS ambulance. The total capacity of BLS ambulances is usually not enough to fulfill all non-urgent transportation requests. The remaining transportation requests then have to be performed by ALS ambulances, which reduces the coverage for emergency calls. We present a model that determines the routes for BLS ambulances while maximizing the remaining coverage by ALS ambulances. Different from the classical Dial-A-Ride Problem, only one patient can be transported at a time and not all request are known in advance. Throughout the day, new requests arrive and we present an online model to deal with these requests

Comparing population and incident data for optimal air ambulance base locations in Norway

Background: Helicopter emergency medical services are important in many health care systems. Norway has a nationwide physician manned air ambulance service servicing a country with large geographical variations in population density and incident frequencies. The aim of the study was to compare optimal air ambulance base locations using both population and incident data. Methods: We used municipality population and incident data for Norway from 2015. The 428 municipalities had a median (5-95 percentile) of 4675 (940-36,264) inhabitants and 10 (2-38) incidents. Optimal helicopter base locations were estimated using the Maximal Covering Location Problem (MCLP) optimization model, exploring the number and location of bases needed to cover various fractions of the population for time thresholds 30 and 45 min, in green field scenarios and conditioned on the existing base structure. Results: The existing bases covered 96.90% of the population and 91.86% of the incidents for time threshold 45 min. Correlation between municipality population and incident frequencies was -0.0027, and optimal base locations varied markedly between the two data types, particularly when lowering the target time. The optimal solution using population density data put focus on the greater Oslo area, where one third of Norwegians live, while using incident data put focus on low population high incident areas, such as northern Norway and winter sport resorts. Conclusion: Using population density data as a proxy for incident frequency is not recommended, as the two data types lead to different optimal base locations. Lowering the target time increases the sensitivity to choice of data

Correlations in Scale-Free Networks: Tomography and Percolation

We discuss three related models of scale-free networks with the same degree distribution but different correlation properties. Starting from the Barabasi-Albert construction based on growth and preferential attachment we discuss two other networks emerging when randomizing it with respect to links or nodes. We point out that the Barabasi-Albert model displays dissortative behavior with respect to the nodes' degrees, while the node-randomized network shows assortative mixing. These kinds of correlations are visualized by discussig the shell structure of the networks around their arbitrary node. In spite of different correlation behavior, all three constructions exhibit similar percolation properties.Comment: 6 pages, 2 figures; added reference

Tree Networks with Causal Structure

Geometry of networks endowed with a causal structure is discussed using the conventional framework of equilibrium statistical mechanics. The popular growing network models appear as particular causal models. We focus on a class of tree graphs, an analytically solvable case. General formulae are derived, describing the degree distribution, the ancestor-descendant correlation and the probability a randomly chosen node lives at a given geodesic distance from the root. It is shown that the Hausdorff dimension $d_H$ of the causal networks is generically infinite, in contrast to the maximally random trees, where it is generically finite.Comment: 9 pages, 2-column revtex format, 1 eps figure, misprints correcte

Intraoperative Music to Promote Patient Outcome (IMPROMPTU):A Double-Blind Randomized Controlled Trial

Introduction: Perioperative music can have beneficial effects on postoperative pain, anxiety, opioid requirement, and the physiological stress response to surgery. The aim was to assess the effects of intraoperative music during general anesthesia in patients undergoing surgery for esophagogastric cancer. Materials and methods: The IMPROMPTU study was a double-blind, placebo-controlled, randomized multicenter trial. Adult patients undergoing surgery for stage II-III esophagogastric cancer were eligible. Exclusion criteria were a hearing impairment, insufficient Dutch language knowledge, corticosteroids use, or objection to hearing unknown music. Patients wore active noise-cancelling headphones intraoperatively with preselected instrumental classical music (intervention) or no music (control). Computerized randomization with centralized allocation, stratified according to surgical procedure using variable block sizes, was employed. Primary endpoint was postoperative pain on the first postoperative day. Secondary endpoints were postoperative pain during the first postoperative week, postoperative opioid requirement, intraoperative medication requirement, the stress response to surgery, postoperative complication rate, length of stay, and mortality, with follow-up lasting 30 d. Results: From November 2018 to September 2020, 145 patients were assessed and 83 randomized. Seventy patients (music n = 31, control n = 39) were analyzed. Median age was 70 [IQR 63–70], and 48 patients (69%) were male. Music did not reduce postoperative pain (numeric rating scale 1.8 (SD0.94) versus 2.0 (1.0), mean difference −0.28 [95% CI -0.76–0.19], P = 0.236). No statistically significant differences were seen in medication requirement, stress response, complication rate, or length of stay. Conclusions: Intraoperative, preselected, classical music during esophagogastric cancer surgery did not significantly improve postoperative outcome and recovery when compared to no music using noise-cancelling headphones.</p