Characterization of multiscroll attractors using Lyapunov exponents and Lagrangian coherent structures.

The present work aims to apply a recently proposed method for estimating Lyapunov exponents to characterize-with the aid of the metric entropy and the fractal dimension-the degree of information and the topological structure associated with multiscroll attractors. In particular, the employed methodology offers the possibility of obtaining the whole Lyapunov spectrum directly from the state equations without employing any linearization procedure or time series-based analysis. As a main result, the predictability and the complexity associated with the phase trajectory were quantified as the number of scrolls are progressively increased for a particular piecewise linear model. In general, it is shown here that the trajectory tends to increase its complexity and unpredictability following an exponential behaviour with the addition of scrolls towards to an upper bound limit, except for some degenerated situations where a non-uniform grid of scrolls is attained. Moreover, the approach employed here also provides an easy way for estimating the finite time Lyapunov exponents of the dynamics and, consequently, the Lagrangian coherent structures for the vector field. These structures are particularly important to understand the stretching/folding behaviour underlying the chaotic multiscroll structure and can provide a better insight of phase space partition and exploration as new scrolls are progressively added to the attractor.

Does palliative care improve outcomes for patients with HIV/AIDS? A systematic review of the evidence.

BACKGROUND: The need for palliative care in HIV management is underlined by the high prevalence of pain and symptoms, the toxicity, side effects, and virological failure associated with antiretroviral therapy, emergence of co-morbidities, continued high incidence of malignancies, late presentation of people with HIV disease, and the comparatively higher death rates among the infected individuals. METHODS: A systematic review was undertaken to appraise the effect of models of palliative care on patient outcomes. A detailed search strategy was devised and biomedical databases searched using specific terms relevant to models of palliative care. Data from papers that met the inclusion criteria were extracted into common tables, and evidence independently graded using well described hierarchy of evidence. RESULTS: 34 services met the inclusion criteria. Of these, 22 had been evaluated, and the evidence was graded as follows: grade 1 (n = 1); grade 2 (n = 2); grade 3 (n = 7); grade 4 (n = 1); qualitative (n = 6). Services were grouped as: home based care (n = 15); home palliative care/hospice at home (n = 7); hospice inpatient (n = 4); hospital inpatient palliative care (n = 4); specialist AIDS inpatient unit (n = 2); and hospital inpatient and outpatient care (n = 2). The evidence largely demonstrated that home palliative care and inpatient hospice care significantly improved patient outcomes in the domains of pain and symptom control, anxiety, insight, and spiritual wellbeing. CONCLUSIONS: Although the appraisal of evidence found improvements across domains, the current body of evidence suffers from a lack of (quasi) experimental methods and standardised measures. The specialism of palliative care is responding to the clinical evidence that integration into earlier disease stages is necessary. Further studies are needed to both identify feasible methods and evaluate the apparent beneficial effect of palliative care on patient outcomes in the post-HAART era.

Factors associated with delays in accessing HIV primary care in rural Arkansas.

While debate continues at what stage of human immunodeficiency virus (HIV) disease to begin combination antiretroviral therapy, a number of clinical and public health benefits are linked to early entry into primary care soon after first testing HIV positive. However, HIV-infected patients continue to test late and delay entry into care. We used routinely collected demographic and clinical information to examine which factors are associated with delays in seeking care in a predominantly rural, economically poor area of Arkansas. The study population is 75% African American and male and 70% lack health insurance; nearly one fourth were referred from prison. At diagnosis, two thirds of the population had CD4 counts below 500 cells per microliter. Days from initial HIV diagnosis to entry into care declined from a median of 178 in 1994 to 24 in 1998. In 1998, 75% of the population entered into primary care within 2 months of diagnosis. However, CD4 counts at HIV diagnosis also declined in this period, from a median of 427 in 1995 to 208 cells per microliter in 1998. More recent year of diagnosis was associated with a shorter delay in seeking care; males, and individuals lacking health insurance took significantly longer to enter into care than females and those with insurance, respectively. Our univariate finding of extensive delays in seeking care in the prison population did not hold in the multivariate analysis. We found significant delays in time to initial HIV diagnosis, and further considerable delays in males and those lacking health insurance in the time taken to enter into primary care.

Satisfaction with services in innovative managed care programs for groups of traditionally underserved individuals with HIV/AIDS: empirical models.

As the number of people with HIV/AIDS receiving services in managed care models increases, concerns over quality of care and satisfaction with services have grown. This article examined data from three national demonstration projects that were funded to enroll traditionally underserved individuals and provide innovative medical services in programs developing models appropriate for managed care funding. Assessments of patient satisfaction were related to indicators of traditionally underserved status including demographic characteristics, behaviors, and other risk factors using the data modeling method of Exhaustive CHAID (Chi-squared Automatic Interaction Detector). Overall patient satisfaction levels with these programs were very high. Through the modeling methods, the groups most likely to experience the greatest program satisfaction are identified. In general, all groups were highly satisfied with the programs.

Perceived barriers to receiving HIV services in groups of traditionally underserved individuals: empirical models.

Persons living with HIV/AIDS face many issues that make them highly vulnerable to a number of health and social problems. As the demographics of the epidemic have shifted in recent years, many members of traditionally underserved groups have encountered barriers to entering the services system. This article uses data from seven national demonstration projects funded to enroll persons with HIV/AIDS who tend to "fall through the cracks" and help them access needed services. Data on the initial perceptions of the participants about barriers to accessing services were related to 17 indicators of traditionally underserved status including demographic characteristics and behavioral variables using the data modeling method of Exhaustive CHAID (Chi-squared Automatic Interaction Detector). Through the modeling methods, the groups most likely to experience a large number of barriers to service participation are identified. Having children needing care is particularly predictive of the level of barriers to care.

Finding the underserved: directions for HIV care in the future.

The demographic, behavior, and background characteristics of 4,804 participants in 17 national demonstration projects for HIV medical and/or psychosocial support services were coded for an index of "service need" or possible under-representation in the traditional healthcare system. Fifteen items were coded including status as a person of color, lack of private insurance, unemployment/disability, problem drinking, crack cocaine use, heroin use, other illicit drug use, less than 12 years of education, criminal justice system involvement, children requiring care while the patient receives services, sex work, being the sex partner of an injection drug user, unstable housing, primary language not English, and age less than 21 or over 55 years. Most (87.7%) of the program participants had four or more of these factors present. Through CHAID modeling, those groups with the highest levels of service need and vulnerability were identified. These data suggest that these projects, designed to attract and serve individuals potentially underrepresented in the health services system, had in fact achieved that goal. Implications of the changing demographics of the HIV epidemic for the health service delivery system are discussed.

Satisfaction with innovative community and university health clinic programs for groups of traditionally underserved individuals with HIV/AIDS: empirical models.

As the demographics of the populations of affected individuals have changed, systems of care have needed to adapt to be responsive to client needs. This article examines client satisfaction data from seven national demonstration projects funded to enroll individuals from traditionally underserved groups and help them access services using different strategies. Data on client satisfaction ratings were related to indicators of traditionally underserved status, including demographic characteristics, behaviors, and other risk factors using the data modeling method of Exhaustive CHAID (Chi-squared Automatic Interaction Detector). Client groups that were most likely to experience relatively higher and lower levels of satisfaction with services are identified. Overall, all client groups were highly satisfied with the innovative HIV/AIDS services received. The findings illustrate the success of these innovative HIV care models in being responsive and sensitive to the needs of their target populations.

Who receives Ryan White CARE Act services? A demographic comparison of CARE act clients and the general AIDS population.

This study examines the extent to which health and social service providers funded by the Ryan White Comprehensive AIDS Resources Emergency (CARE) Act serve women, minorities, and other vulnerable populations emphasized by the legislation. Demographic characteristics of AIDS-diagnosed clients served by CARE Act-funded providers in four metropolitan areas and two states are compared with Centers for Disease Control and Prevention estimates of AIDS prevalence. Clients of CARE Act-funded providers tend to reflect the demographics of local HIV/AIDS epidemics. Where differences exist, CARE Act clients are more likely to be women and minorities and less likely to be injecting drug users. CARE Act-funded providers are effectively reaching most medically underserved populations.

Service use patterns of youth with, and at high risk for, HIV: a care typology.

This paper uses confirmatory structural equation models to develop and test a theoretical model for understanding the service utilization history of 4679 youth who received services from 10 national HIV/AIDS demonstration models of youth-appropriate and youth-attractive services funded by the Special Projects of National Significance (SPNS) Program, HIV/AIDS Bureau, Health Resources and Services Administration. Although the projects differ from one another in the areas of emphasis in their service models, each is targeted to youth at high risk for HIV, or those youth who have already contracted HIV. Collectively, the projects represent a comprehensive adolescent HIV service model. This paper examines the characteristics of the services provided to young people ranging from outreach to intensive participation in medical treatment. Major typologies of service utilization are derived empirically through exploratory factor and cluster analysis methods. Confirmatory structural equation modeling methods are used to refine the exploratory results using a derivation and replication strategy and methods of statistical estimation appropriate for non-normally distributed service utilization indicators. The model hypothesizes that youth enter the service system through a general construct of connectedness to a comprehensive service model and through service-specific methods, primarily of outreach or emergency services. Estimates are made of the degree to which a comprehensive service model drives the services as opposed to specific service entry points.

Predicting substance abuse among youth with, or at high risk for, HIV.

This article describes data from 4,111 males and 4,085 females participating in 10 HIV/AIDS service demonstration projects. The sample was diverse in age, gender, ethnicity, HIV status, and risk for HIV transmission. Logistic regression was used to determine the attributes that best predict substance abuse. Males who were younger; HIV positive; homeless; involved in the criminal justice system; had a sexually transmitted disease (STD); engaged in survival sex; and participated in risky sex with men, women, and drug injectors were most likely to have a substance abuse history. For females, the same predictors were significant, with the exception of having an STD. Odds ratios as high as 6 to 1 were associated with the predictors. Information about sexual and other risk factors also was highly predictive of substance abuse issues among youth.

Improving HIV/AIDS services through palliative care: an HRSA perspective. Health Resources and Services Administration.

There has been a dramatic shift of the human immunodeficiency virus/ acquired immunodeficiency syndrome (HIV/AIDS) epidemic into poor, marginalized, and minority communities in the US. At the same time, the availability of new highly active antiretroviral treatments has made it possible for a large number of individuals to live for a much longer time with their disease. A net result is that the US is faced with an increasing number of people who are living with HIV/AIDS and are dependent on publicly supported health care services. In this paper, we review the palliative care efforts of the federal agency, the Health Resources and Services Administration (HRSA), responsible for providing Ryan White CARE Act HIV/AIDS care to medically underserved populations. In addition to supporting traditional hospice care, HRSA's HIV/AIDS Bureau has begun a series of initiatives that apply a broader concept of palliative care to its HIV programs in hospital- and community-based settings. Our interest is not to substitute palliation for access to new HIV therapies, such as highly active antiretroviral treatments, but to ensure that our health delivery systems attend to the alleviation of symptoms and suffering along with the provision of antiretroviral and other necessary treatments. HRSA's HIV/AIDS Bureau is organizing a broader provision of palliative care for its clients and actively contributing to improving care for the disenfranchised internationally.

Typology of quality of life experiences among persons living with HIV.

This article develops a typology of 2,038 participants in 13 innovative HIV/AIDS treatment model service demonstration projects targeted to traditionally underserved populations. The typology is based on self-reported health-related quality of life levels. Eight clusters were identified that classify HIV/AIDS patients based on their reported health-related quality of life. Participants were clustered based on their overall levels of quality of life, as well as by deficits in specific areas of functioning such as energy level, physical impairment, and role impairment. However, factor analysis suggests that health-related quality of life as perceived by the HIV-positive participants is best represented as a single underlying dimension and an ordering of the types shows that they are consistently related, in the same order, to several criterion measures of impairment. The results suggest that a general categorization of patients with HIV in terms of quality of life is more meaningful than an assessment of the relative areas of impairment. Since the impairment ratings were also self-reported, analyses relating quality of life clusters to actual symptom levels and healthcare utilization are needed. Implications for the assessment of health-related quality of life and the evaluation of service delivery programs for persons living with HIV are discussed.

Service needs and factors related to quality of life at time of service enrollment among persons living with HIV.

This article explores the relationships of HIV risk factors, service needs, and vulnerabilities to health-related quality of life in a sample of 1,371 participants newly enrolled into 13 innovative HIV/AIDS treatment model service demonstration projects. These projects targeted services to traditionally underserved populations. Eight distinct quality of life clusters of HIV patients were used in this analysis along with patient self-identified risk factors. The quality of life clusters were based on patient self-reported quality of life dimensions. The eight clusters were differentiated based on relative strengths and weaknesses in physical functioning, energy levels, and social functioning. Data on patient need-vulnerability factors and demographic characteristics were related to these eight clusters using the data modeling method of Exhaustive CHAID (Chi-squared Automatic Interaction Detector). Through this method, the characteristics most likely to be associated with higher and lower levels of quality of life at the time of enrollment into services were identified. The results provide further support that quality of life assessment is a useful clinical tool for monitoring patient progress.

Consistency in maintaining contact with HIV-related service providers: an analysis of the AIDS Cost and Services Utilization Study (ACSUS).

Patients (n = 1949) infected with HIV were recruited for the AIDS Cost & Service Utilization Survey (ACSUS) from ten U.S. cities and administered face to face interviews at three month intervals over an 18 month period from March 1, 1991 to August 31, 1992. The interview was designed to obtain information at each wave of data collection on the use of the following services: ambulatory care, hospitalization, emergency room use, support groups/counseling, drug and alcohol treatment, and dental care. Patients were found to be highly consistent in their patterns of utilization across time, regardless of the service in question. Of the patients who reported using an emergency room (ER) at Time 1, 52% also reported using an ER during the next three months later at Time 2. Of those who reported having been hospitalized during the Time 1 reporting period, almost 58% reported a hospitalization again at Time 2. Next, use of a service at Time 6 (n = 1404, 72.2%) was regressed onto whether the person received the service at Time 2 and the personal, financial, and medical variables. Except for dental services, utilization of a service one year in the past (Time 2) was the strongest predictor of Time 6 use. The findings indicated that the one factor consistently related to service use within this sample is a factor (as opposed to education, race, or even insurance) that is amenable to intervention: previous use of that service. The individuals studied established patterns of service utilization that are of reasonably long duration once they began use of a service. This continuity of care becomes more critical as the initiation of treatments begins with the diagnosis of HIV rather than AIDS. Findings suggest that HIV outreach efforts be targeted to increasing early use of medical and behavioral services in ambulatory care settings.

Factors influencing waiting time and successful receipt of cadaveric liver transplant in the United States. 1990 to 1992.

OBJECTIVES: Despite concern about access to liver transplantation, there has been no nationally based analysis of patients waiting for cadaveric liver transplant. Using data from the United Network for Organ Sharing Organ Procurement and Transplantation Network database waiting and recipient lists, we examined the influence of medical and non-medical factors on the length of time patients waited before transplant and whether they survived the wait. METHODS: The authors analyzed 7,422 entries to the waiting list from October 1, 1990 to December 31, 1992. Using Cox Proportional Hazard models, time to transplant was modelled by gender, nationality and ethnicity, age, blood type, medical status (critically ill versus non-critical), transplant number (first versus retransplant), United Network for Organ Sharing region of the country, and three measures of local demand and supply of organs. The risk of dying before being allocated an organ was compared with receiving an organ using multiple logistic regression models. RESULTS: In addition to differences by medical status, blood type, geographic region, and organ supply and demand, it was found that women, Hispanic-Americans, Asian-Americans, and children waited longer for transplant, whereas foreign nationals and repeat transplant patients waited fewer days. The risk of dying before transplant was greater for critically ill and repeat transplant patients, as well as for women, older patients, Asian-Americans, and African-Americans. Children were less likely to die, as were patients from certain blood groups and geographic regions. CONCLUSIONS: Results confirm known patterns of waiting list experience for liver transplant patients, but also identify factors previously unrecognized as influencing waiting time and outcome. Potential explanatory factors and areas for further inquiry are discussed.

A national program of innovative AIDS care projects and their evaluation.

As the number of people seeking HIV care in the U.S. has grown, the demand has increased not only for medical care, but also for a wide range of supportive services. This in turn has increased the need for demonstrated and tested HIV care service models that can address a comprehensive set of needs. The Special Projects of National Significance (SPNS) Program's HIV Innovative Models of Care Initiative funded by the Health Resources and Services Administration (HRSA) began on October 1, 1994. This initiative is an effort by 27 HRSA-funded projects to jointly establish goals and objectives, develop common evaluation methods, and produce comparable and measurable outcomes for innovative models of HIV care. The five projects of the SPNS Program Capitated Care Work Group share, as a central theme, the study of the health care provided to individuals with HIV disease under models where the health care is capitated, or paid on a "flat fee" basis per patient per month. These projects differ in the ways that they provide health care, ranging from community- and university-based clinics to a home-based hospice to a statewide health care system. Each of the projects shares the goals of determining costs for providing health care services to AIDS patients under a capitated care system and of ensuring that high quality care is provided under such a system.

A typological approach to the study of rural HIV service delivery networks.

Despite the rapid growth of AIDS cases in nonmetropolitan areas, little is known about the characteristics and needs of HIV-positive rural residents or how rural areas are responding to the epidemic. This paper proposes a typology for distinguishing among rural environments and examining variations in HIV service networks. The typology identifies three dimensions that have a major effect on the development of rural HIV service networks: degree of rurality, the prevalence of AIDS, and the epidemiological and demographic characteristics of the infected populations. Data from four case studies are used to illustrate how variations in rural environments can affect the organization and delivery of HIV/AIDS care. The typology contributes to public policy discussions by identifying key attributes of rural environments that influence program planning and implementation and the transferability of service delivery models.