A Quantitative Analysis Of The Relationship Between Medicare Payment And Service Volume For Cataract, Glaucoma, And Retina Procedures From 2005 To 2009

The purpose of this study was to evaluate the extent to which changes in the Medicare Physician Fee Schedule influence the volume and intensity of ophthalmic services for cataract, glaucoma, and retina procedures. We conducted a retrospective, longitudinal analysis using a fixed-effects regression model of Medicare Part B carriers representing all fifty states and the District of Columbia from 2005 to 2009 to calculate Medicare payment-volume elasticities, defined as the percent change in Medicare service volume per 1% change in Medicare payment, for twelve procedures: non-complex and complex cataract surgery (CPT 66984 and CPT 66982), laser trabeculoplasty (CPT 65855), trabeculectomy without and with previous surgery (CPT 66170 and CPT 66172), aqueous shunt to reservoir (CPT 66180), laser iridotomy (CPT 66761), scleral reinforcement with graft (CPT 67255), intravitreal injection (CPT 67028), laser treatment for retinal edema (CPT 67210), laser treatment for proliferative retinopathy (CPT 67228), and optical coherence tomography (OCT) imaging (CPT 92135). For cataract surgery, we found a significant negative Medicare payment-service volume elasticity. For every 1% decrease in non-complex cataract surgery payment, non-complex cataract service volume increased 0.27% (95% CI [-0.47, -0.06], p=0.01). For every 1% decrease in complex cataract surgery payment, complex cataract service volume increased 1.34% (95% CI [-1.54, -1.14], p\u3c0.001). For glaucoma procedures, the payment-volume elasticity was non-significant for four of six procedures studied: laser trabeculoplasty (elasticity=-0.27, 95% CI [-1.31, 0.77], p=0.61), trabeculectomy without previous surgery (elasticity=-0.42, 95% CI [-0.85, 0.01], p=0.053), trabeculectomy with previous surgery (elasticity=-0.28, 95% CI [-0.83, 0.28], p=0.32), and aqueous shunt to reservoir (elasticity=-0.47, 95% CI [-3.32, 2.37], p=0.74). For laser iridotomy, the payment-volume elasticity was -1.06 (95% CI [-1.39, -0.72], p\u3c0.001). For scleral reinforcement with graft, the payment-volume elasticity was -2.92 (95% CI [-5.72, -0.12], p=0.041). For all three retinal procedures, the regression coefficients representing the payment-volume elasticity were non-significant: intravitreal injection elasticity was -0.75 (95% CI [-1.62, 0.13], p=0.09); laser treatment for retinal edema elasticity was 0.14 (95% CI [-0.38, 0.65], p=0.59); and laser treatment for proliferative retinopathy elasticity was 0.05 (95% CI [-0.26, 0.35], p=0.77). For every 1% decrease in Medicare payment for OCT imaging, OCT imaging service volume increased 0.84% (95% CI [-1.36, -0.32], p=0.002). Our analysis of twelve ophthalmic procedures from 2005 to 2009 suggest that there may not be a significant association between Medicare payment and service volume for many glaucoma and retina procedures. Among those procedures, including cataract surgery, that have a significant relationship, different elasticities are observed, suggesting that the volume response to changes in Medicare payments is not uniform across all Medicare procedures. Further research should explore the contributions of patient demand and physician supply to this response

Improving the Power Outage Resilience of Buildings with Solar PV through the Use of Battery Systems and EV Energy Storage

Buildings with solar photovoltaic (PV) generation and a stationary battery energy storage system (BESS) may self-sustain an uninterrupted full-level electricity supply during power outages. The duration of off-grid operation is dependent on the time of the power fault and the capabilities of the home energy management system (HEMS). In this paper, building resilience is quantified by analyzing the self-sustainment duration for all possible power outages throughout an entire year. An evaluation method is proposed and exercised on a reference house in California climate zone 9 for which the detailed electricity usage is simulated using the EnergyPlus software. The influence of factors such as energy use behavioral patterns, energy storage capacity from the BESS, and an electric vehicle (EV) battery on the building resilience is evaluated. Varying combinations of energy storage and controllable loads are studied for optimally improved resilience based on user preferences. It is shown that for the target home and region with a solar PV system of 7.2 kW, a BESS with a capacity of 11 kWh, and an EV with a battery of 80 kWh permanently connected to the home, off-grid self-sustained full operation is guaranteed for at least 72 h

Combined Use of EV Batteries and PV Systems for Improving Building Resilience to Blackouts

Californian residencies face increased risk of blackout. The state depends more on imported electricity that may not always be available to fill the gap between renewable generation and demand. For buildings with PV panels, storing the surplus solar power to support the load during a blackout can be achieved with a large energy storage system (ESS). The electric vehicle (EV) provides potential solutions as it can expand the energy capacity of the residential ESS with its battery. In this paper, a reference house in California was modeled in EnergyPlus. The building resilience for a house with different load percentages were studied, for both with, and without EV scenarios

Optimization of Aggregated EV Power in Residential Communities with Smart Homes

Electric vehicles (EVs) tend to increase peak power for residences in the evening when house owners return home and begin charging. The aggregated EV charging demand can cause a sudden rise in the peak power at the distribution system level, resulting in a “dragon curve” Such phenomenon, combined with the “duck curve” that is caused by high photovoltaic (PV) penetration in residential communities, requires fast ramping rates and expanded capabilities for local distribution transformers and main feeder cables provided by the utility. As a solution, a residential energy storage system (RESS) can store surplus PV generation during midday and use the stored energy to support the peak power demand in the evening. House owners benefit from this strategy by avoiding electricity sales to the grid at low rates and by reducing energy usage during high Time-of-Use (ToU) periods. In this paper, a community with smart homes that include PV systems, RESSs and EVs was modeled. The EV models were developed based on data from the National Travel Household Survey (NHTS). The EV charging and RESS operation were scheduled to reduce the daily utility charge. The entire power system worked as virtual power plant as it kept the aggregated power constant for a long period of time

Load Variation Reduction by Aggregation in a Community of Rooftop PV Residences

This paper performs computational studies and develops control schemes for a virtual power plant (VPP) network formed by a community of homes with rooftop solar PV generation, and battery energy storage. Appropriate control and scheduling of the battery operations, and peer-peer power flow between the homes provide a possible solutions for reducing the higher costs and uncertainties brought to grid by high solar PV penetration. The residential community studied here includes twelve homes categorized into four types depending on whether they have energy storage or rooftop solar PV panels. The homes exchange power among themselves, and the real-time electricity rate and the energy assignment for each are decided based on their individual bidding schemes. The homes benefit due to the lower electricity rate enabled by this aggregation, as compared with that available from the utility grid. In this work, the PV generation and load consumption for the different types of homes are calculated from building models. Simulation studies demonstrate that the advantages of the proposed transactive power flow include lower maximum power demand as well as reduced peak-peak power on the duck curve

Stochastic Battery SOC Model of EV Community for V2G Operations Using CTA-2045 Standards

An electric vehicle (EV) battery has large energy storage capacity in the context of residential total usage, and the potential to provide large energy reserves for Home energy Management (HEM) systems. In an electric distribution system, groups of EVs could provide vehicle-to-grid (V2G) service in response to control signals and enable virtual power plant (VPP) operation of the car batteries. The CTA-2045 standards were considered for integration of the EV controls into the HEM system for maximal interoperability with other appliances, such as residential battery, electric water heater, and heating, ventilation, and air conditioning (HVAC) system. The power distribution system under study was modeled based on a modified IEEE 123-bus feeder test case in OpenDSS software. The availability and state of charge (SOC) of EVs were calculated based on the national household travel survey (NHTS) data following a new procedure to create synthetic communities following experimental probability density functions (PDFs). Example case studies for long and short term V2G services were completed in this paper from the perspective of the distribution system. The power flow for the distribution system, the voltages on the buses, as well as the SOCs and available energies of the EVs were calculated following the control signals on an example day

Home Energy Management System for Coordinated PV and HVAC Controls Based on AI Forecasting

Introduction This HEMS serves to transform HVAC system demand into a schedulable load bank or “dispatchable load” through controls based on day ahead forecasts Within this poster, a complete structure from data acquisition to day-ahead load scheduling is proposed For the purpose of study, measured data is used in place of forecasts to showcase best case results