Study status consistency and duplicate-read protection in a distributed architecture.

UNLABELLED: This presentation will discuss the benefits and pitfalls of implementing a study status and duplicate-read protection mechanism within a distributed picture archiving and communication system (PACS) architecture. There are many advantages to a distributed PACS network in which image studies are proactively pushed to reading stations before they are required by a radiologist. The absence of a central server, which serves on demand, makes managing study status and protecting against duplicate reads challenging. The system to manage study status and read access must be efficient, robust, and easy to administer. A system is presented that accomplishes these goals while maintaining the advantages of a distributed architecture. METHODS: The basic workflow of the system is that image studies acquired at a modality device are automatically sent to an archive server. Using a set of advanced routing rules, the archive automatically routes studies to diagnostic workstations where studies are candidates for diagnostic read. The workstations display a list of all local studies available for reading. A monitor application running on the workstations coordinates access to studies for diagnostic read. Once the status of a study has been changed, the workstations on the networks and the archive are notified, which causes the study to be automatically removed from any list on a workstation where it might be a read candidate. RESULTS: Implementation of this system provides a balanced workflow throughout the system while minimizing the need for costly high-speed network hardware. Additionally studies are read as soon as they are available by the next available radiologist. This workflow is enabled without the need for specific interaction by any of the radiologists on the network. By having the images available at the workstation in an organized worklist, this methodology increases the efficiency of the radiologist. CONCLUSION: The implementation of this system enables a radiology department, or even a specialty group within a department, to gain the benefit of a distributed system as well as the benefits provided by a central-server architecture. This can be done very cost effectively with minimal configuration overhead and hardware requirements.

Designing fault-tolerant distributed archives for picture archiving and communication systems.

PURPOSE: Distributed archives in a picture archiving and communication system (PACS) environment can provide added fault tolerance and fail-over capability, as well as increased load capacity at a more economical price than traditional 'high-availability" systems. Systems can be configured with varying levels of fault tolerance, depending on the amount of redundancy desired. There is, however, a direct correlation between the level of hardware redundancy and cost to implement. This presentation details the system design for fault-tolerant distributed archives as well as several options for redundancy, referencing implementation of a fault-tolerant archive system at the University of Utah. METHODS: The distributed archive system described here is based on Image Devices' image archive software, which can be implemented on multiple individual archive servers in order to distribute archive functionality and operational load. The configuration and implementation of the individual servers together make up the distributed archive system and does not impact the ability of the system to be scaled to meet future requirements. Several implementation and configuration options exist, including the ability for servers to maintain replicated databases containing patient and image information. Thus, each archive can be aware of all information and the location of this information within the distributed archive system. RESULTS: The goal is to produce systems that will still be operational in the event of any single point of failure, ie, a network connection failure between facilities or the failure of a single archive server within the distributed system. During normal operation, workload for image acquisition, image routing and image query requests will be distributed between the archive servers. If the system is deployed in a multifacility environment, each archive server can be configured to be responsible for the acquisition and image distribution management within that server's local facility. If the system is deployed in a single facility environment, load can be distributed evenly between the archive servers based on an understanding of the workload requirements generated be each acquisition and display device in the system. In the event that an archive server fails, other archive servers within the system will have the ability to provide some or all of the failed server's functionality. The degree of fail-over capability is dependent on the archive server's configuration as well as hardware redundancy employed. Three levels of fault-tolerant design can be achieved with this system architecture: (1) duplicate work capability only; (2) duplicate work capability and short-term image cache; (3) duplicate work capability, short-term image cache, and longterm image archival. Using the basic fault-tolerant design above, we have implemented a multifacility distributed archive system at the University of Utah. This system was implemented at a fraction of the cost of true "high-availability" archive architectures yet provides constant up time for the PACS system. If the network connection between the two locations goes down, each site is still fully functional for soft-copy read, as well as image acquisition and distribution. If either of the archive servers goes down, the image sources are redirected to the other archive server. The operational server then handles image distribution for both locations. Access to images in the short-term image cache is available to both archive servers and is not affected by loss of the network connection or remote server. Because there is ony one long-term archive device, the ability to retrieve images from long-term storage is the only function compromised by a network or server failure. CONCLUSION: By implementing distributed archives in a PACS environment, it is possible to achieve a highly fault-tolerant system without the expense of high-availability hardware and software. The design concepts outlined here can be applied to any PACS system that supports distributed archive functionality.

Cardiopulmonary monitoring at home: the CHIME monitor.

A new physiologic monitor for use in the home has been developed and used for the Collaborative Home Infant Monitor Evaluation (CHIME). This monitor measures infant breathing by respiratory inductance plethysmography and transthoracic impedance; infant electrocardiogram, heart rate and R-R interval; haemoglobin O2 saturation of arterial blood at the periphery and sleep position. Monitor signals from a representative sample of 24 subjects from the CHIME database were of sufficient quality to be clinically interpreted 91.7% of the time for the respiratory inductance plethysmograph, 100% for the ECG, 99.7% for the heart rate and 87% for the 16 subjects of the 24 who used the pulse oximeter. The monitor detected breaths with a sensitivity of 96% and a specificity of 65% compared to human scorers. It detected all clinically significant bradycardias but identified an additional 737 events where a human scorer did not detect bradycardia. The monitor was considered to be superior to conventional monitors and, therefore, suitable for the successful conduct of the CHIME study.

An electronic simulator for testing infant apnoea monitors that uses actual physiologic data.

An electronic simulator of physiologic signals used in infant monitoring has been designed, constructed and applied in the Collaborative Home Infant Monitor Evaluation (CHIME). A unique feature of the simulator is that it contains actual physiologic waveforms recorded from infants rather than artificial, idealized signals. The simulator stores breathing waveforms that can be used to test transthoracic-impedance- and inductance-plethysmography-based monitors, and heart rate channels are tested by playing a neonatal QRS complex at preset fixed rates or a variable rate as determined from infant recordings. The transfer characteristics of the simulator are constant over frequencies ranging from 0.5 to 8 Hz for the respiration channels. Data stored in memory are divided into 60 second epochs that can be presented to the monitor being tested in a programmable sequence. A group of 66 CHIME monitors was tested using a simulator programmed with 17 apnoea and bradycardia waveforms. The agreement between monitors as to the duration of detected apnoea decreases as the amount of artefact in the signal increases. Discrepancies between monitors in detecting apnoea duration were found to be similar to inconsistencies between CHIME investigators manually scoring similar waveforms.

Do physicians spend less time with older patients?

In view of the additional time that older persons require for giving and receiving information, as well as for the examination process, it is important for manpower and reimbursement planning to better understand the nature of the physician-patient encounter with the elderly. We examined a series of national surveys of physicians' professional activities and found that physicians tend to spend less time with their older patients and also that encounter time by physicians in different specialties varies widely. Internists and cardiologists spend substantially more time with patients compared with general and family practitioners. For 65-74-year-old ambulatory patients, the average visit lengths are 18.3 minutes for internists, 18.0 for cardiologists, 11.2 for general practitioners, and 12.1 for family practitioners. Compared with ambulatory visit lengths for patients aged 45 to 64 years, average encounter times for 75-year-olds with family physicians were 0.8 minutes shorter, with general practitioners 1.2 minutes shorter, with internists 2.3 minutes shorter, and with cardiologists 3.0 minutes shorter. However, when all characteristics of the visit were considered, the effect of patient age remained significant only for general practitioners. A multivariate analysis of factors related to physician time for ambulatory care showed that more time is associated with multiple problems, problem severity, and the use of diagnostic testing. For general and family practice, the greater the number of previous visits for a problem, the shorter the encounter time is. Additional characteristics associated with shorter physician-patient encounter times include the volume of patients per week and the use of physician assistants within the practice. These findings have implications for medical education and manpower projections.

Are physicians sensitive to the special problems of older patients?

The sensitivity of primary care physicians to the health care needs of older patients was explored by means of an analysis of the use of diagnostic tests and therapeutic procedures during ambulatory visits. Survey data on a total of 28,265 visits to internists, family and general practitioners were examined to determine possible age-related differences in care. The study found that diagnostic testing falls off significantly for patients 75 years of age or older and that internists use substantially more tests for each age group than do family and general practitioners. The pattern of use of diagnostic tests in this secondary analysis does not address the issue of "appropriateness" but does suggest a pattern that makes little sense based on the known distribution of disease and functional disability in aging populations.

Case-mix and treatment in end-stage renal disease: hemodialysis v peritoneal dialysis.

The University of Southern California School of Medicine conducted a nationwide survey of 336 nephrologists to obtain demographic and clinical data on 6,411 patients with end-stage renal disease (ESRD). Patient demographic data, along with ESRD etiology and comorbid conditions noted by the physician, were compared across various modalities of dialysis. Characteristics of the treatment provided were differentiated by the mode of dialysis and the location of the patient encounter. Results of the analysis show that patients on peritoneal dialysis are more likely to be female and have higher rates of diabetes compared with hemodialysis (HD) patients. Statistically, patients on intermittent peritoneal dialysis are older, more likely to be black, and have a higher incidence of cardiovascular conditions. Continuous ambulatory peritoneal dialysis patients have greatest problem severity and require more physician time and more complex services, whereas home HD patients require the greatest number of diagnostic tests and therapeutic procedures. Hospital inpatient care shows greater case-mix severity and more intensive treatment, but this does not differ by the mode of dialysis. Finally, patients of freestanding dialysis facilities are more likely to have hypertensive renal disease, whereas patients at hospital-based facilities are older, more likely to be seen in the hospital, have more urgent and severe problems during dialysis rounds, and require more physician time, more complex services, and more diagnostic tests and therapeutic procedures.

Patient counselling by primary care physicians: results of a nationwide survey.

The rate of patient counseling in primary care medicine is a pivotal element of inter-specialty differences in styles of care. Using national data on patient care provided in both ambulatory care settings and in the hospital, this study examines the use of counseling by general and family practitioners, pediatricians, internists, and obstetrician/gynecologists. The findings show substantial differences based on physician specialty, with highest rates of counseling for family practitioners and internists, and rates of patient education for these two specialties almost three times that for general practitioners. The data also show generally higher counseling rates for hospital care and for first encounters with patients, and a tendency for office-based pediatricians and solo general practitioners to use less patient counseling compared to their institution-based counterparts. Projections of annual visit rates for the United States show that general practice and internal medicine account for a disproportionate amount of patient counseling compared to other primary care specialties, based on patient volume.

Styles of care provided to children in the United States: a comparison by physician specialty.

This study was based on findings from a national survey of physicians that was conducted from 1975 to 1977. The data concern face-to-face encounters with children in the ambulatory care setting. Over one half of the practices of pediatricians consisted of infants and preschoolers, whereas well over 50 percent of the child patients of other types of physicians were 10 to 19 years old. The proportion of visits dealing with a problem already under care was consistently greater for specialists other than primary care physicians; the proportion of visits for preventive care was much lower in the practices of these specialists than in primary care practice. These findings suggest that other specialists are functioning in ways different from primary care physicians. As compared with family physicians, pediatricians performed more diagnostic tests for all diagnoses and more immunizations and counseling about growth and development, were more likely to have seen children previously for problems other than the one dealt with in the visit under consideration, and were more likely to report that no specific therapy was required (except for well-child care). However, family physicians did more counseling about family and sex matters than pediatricians, were much more likely to have seen musculoskeletal and skin problems among 10- to 19-year-old patients, and were much more likely to have administered cauterization, cryotherapy, or suturing for skin problems. Family physicians provided more counseling of all types and did more minor surgical procedures than general practitioners. These and other findings show the existence of systematic differences across specialties in the care of children, even for apparently similar problems.

Who provides health care to children and adolescents in the United States?

Face-to-face visits by children and adolescents in office-based practice in the mid-1970s were studied. Pediatricians, family physicians, and general practitioners accounted for 35%, 6%, and 30%, respectively, of all child visits. Although 40% to 45% of preventive and medical encounters were with pediatricians, only 12% of visits for minor surgery, 20% of visits for psychosocial problems, and 9% of visits for combined medical-surgical reasons were to pediatricians. Only in very young children did pediatricians provide a substantial proportion of care for each of the types of visits. For some common diagnoses (acne, refractive error) most care was provided by specialists other than primary care specialists, but less than 16% of all preventive care visits (including routine eye examinations) was provided by specialists other than primary care physicians. A substantial proportion of the prenatal care and management of minor trauma was provided by family physicians and general practitioners. Although the limitations of the study (including an average response rate of 55%, exclusion of certain specialties and institutional physicians, sampling at different times of the year, lack of control for area of location of practice, and lack of information about response rates of different types of physicians within each specialty) preclude definitive conclusions, the findings raise important questions for future study.

The relative complexity of primary care provided by medical specialists.

Utilizing national data on patient care provided by family practitioners, general internists, and subspecialists in internal medicine, this study examines the complexity of care provided by generalist physicians versus subspecialty physicians on a disease-specific basis. Limiting the analysis to "principal care" provided by office-based physicians, the study finds the complexity of care provided by cardiologists for heart disease and by endocrinologists for diabetes mellitus to be somewhat greater than that provided by family practitioners and general internists, though the magnitude of the differences is not large. For chronic obstructive pulmonary disease, however, pulmonary disease specialists are shown to provide care that is substantially more complex than that provided by their generalist colleagues. For all disease and specialties, hospital care is substantially more complex than ambulatory care.

A profile of pediatric practice in the United States.

We profiled pediatric practice in the United States through a second-order analysis of data gathered in 1977 from 429 practicing pediatricians. Age, sex, board certification status, practice arrangement, and practice location of pediatricians in the United States were evaluated, as well as their patterns of practice. The number of and reasons for visits made to pediatricians by patient age and sex were tabulated. Child health supervision and diseases of the upper and lower parts of the respiratory tract accounted for 84.5% of the principal diagnoses made in 21,784 visits to the sample of pediatricians studied. These data may be useful in planning pediatric primary care residency training program curricula and in making planning decisions regarding the number and distribution of pediatricians nationally.

Effect of patient age on duration of medical encounters with physicians.

The authors analyzed the USC/DRME Practice Study data to determine if the characteristics of physician patient encounters change with patient age. The only significant change observed was a decline in encounter time for patients 65 years of age and older compared with those 45 through 64 years of age. This decrease was significant for raw data and for data weighted for the number of physicians of various types and standardized for complexity of case mix in various age groups, also for both nonhospital and hospital encounters and for almost all classes of encounters. Three types of generalists and four types of medical subspecialists were studied; encounter times for all types were, for patients 65 and older, either the same as or less than those for patients 45 through 64. The observed phenomenon may reflect a conscious decision on the part of some physicians to allot less time to elderly patients.

Manpower for obstetrics-gynecology. III. Contributions to total female medical care.

This final report from the cooperative manpower study of the University of Southern California and The American College of Obstetricians and Gynecologists describes the development of a female data file that outlines the care of women patients by all specialties. Obstetrician-gynecologists are compared to other specialists; they see 300,000 women per day in the United States and provide a wide range of care. Preventive care plays a larger role than in other major specialties, patient counseling and education are emphasized, and obstetric care is a major commitment. Nonetheless, acute and serious surgical and medical diagnoses are an important component of the practices of obstetrician-gynecologists.

PIP: This paper, a report from the comparative manpower study of the University of Southern California and the American College of Obstetrics and Gynecologists compares the contribution of obstetricians-gynecologists (ob-gyns) to that of other specialists in providing medical care to the total female population. 24 allopathic medical and surgical specialities were studied, accounting for 2/3 of the nation's physicians. Patient-physician encounters in the female data file total 211,780. Obstetrics-gynecology and general internal medicine each account for 1 of 7 visits by female patients. The chief types of problems addressed by ob-gyns are preventive, medical and surgical. Ob-gyns have about 1/5 of their encounters in the latter 3 groups in the younger and postmenopausal age groups, contrasting with care provided by other specialists where the percentage drops from 13.9% at 20-24 years of age to 2.8% for those 65 and older. For patients of all ages ob-gyns obtain samples for cervical cytologic examinations at 32.9% of all visits. Twice as much preventive care is provided by ob-gyns as by the other leading generalist specialities. Almost 40% of the ob-gyns' primary patient problems are classed as obstetric, whereas 2/3 of the generalists' are medical and less than 20% of the ob-gyns' are exclusively medical. Care of special conditions and examinations without sickness accounts for over 60% of the ob-gyns work compared to 12% for the other generalists. Most of the neoplasms seen by ob-gyns are benign whereas the opposite is true for other generalists. It is clear from this data that women do make choices in regard to which physician in which specialty they see and under what conditions.

The professional role of physician's assistants in adult ambulatory care practices.

This article describes the methodology and findings of a national survey of Physician's Assistants (PAs) in adult, ambulatory care practices. Data on patient care roles and other professional activities were collected for a three-day period via a comprehensive self-reporting, log-diary instrument. Completing the instrument were 356 (50.4%) PAs. Survey results address the following questions: What is the typical work week for PAs? How do PAs allocate their time in a professional day? What direct patient care services do PAs provide? How productive are PAs with respect to number of patients seen and dollar income generated? In general, the data are consistent with the PA role model of a primary health care professional who provides basic health care services with an emphasis on patient counseling and disease prevention.

Neurosurgical manpower: the physician's viewpoint.

This paper reports a national study of physicians in 24 medical and surgical specialties, and reveals the opinions of neurosurgeons and their professional colleagues with regard to the adequacy of the supply of neurosurgical manpower. Among neurosurgeons, 30.4% believe the supply to be excessive, 60.1% think it is about right, 7.5% believe that there is a shortage, and 2.0% have no opinion. Neurologists' opinions do not differ significantly from those of neurosurgeons, but physicians and surgeons in 22 other specialties are significantly less likely to regard the supply as excessive and are more likely to perceive a shortage. Primary care physicians, as a group, are most likely to perceive a shortage, and least likely to indicate an excess. Among the 24 specialties studied, 9.3% of physicians believe the supply of neurosurgeons to be excessive, 55.1% think it is about right, 22.9% believe that there is a shortage, and 12.8% have no opinion.

Neurosurgery in the United States: a log-diary study.

The Division of Research in Medical Education and of the University of Southern California, with the cooperation and assistance of the American Association of Neurological Surgeons and the Congress of Neurological Surgeons, has conducted a national study of the professional activities of neurological surgeons in the United States. One of a series of 24 surveys of medical and surgical specialties, the survey obtained information on patient workloads, the allocation of physician time, the characteristics of patients and the circumstances under which they were seen, patient diagnoses, and the care that was provided--including whether an operation was performed. This paper provides a selection of the findings deemed most relevant to manpower issues in neurosurgery. A later paper will examine regional differences in patient care, including the frequency with which selected surgical procedures are used for different clinical conditions.

Assessing the utilization and productivity of nurse practitioners and physician's assistants: methodology and findings on productivity.

This article describes the research design, survey instrument and methodology employed in a national study to assess the utilization and productivity of nurse practitioners and physician assistants (NP/PAs) in primary care settings. All practices (N = 455) used in the study employed formally trained NP/PAs who treated, or were eligible to treate, Medicare patients on an outpatient basis, and included a general practitioner, family practitioner or a general internist as the supervising physician. A matched group of comparison practices were subject to the same eligibility criteria except that they did not employ NP/PAs. A comprehensive diary-type instrument focusing on patient care was used to collect detailed data on each practitioner's daly professional activities. Data are presented on the productivity of NPs, PAs and physicians as measured by seven basic variables related to patient volume, time in patient care and revenue generated. Numerous inter- and intraspecialty comparisons were made across various practice arrangements and across location variables such as rural vs. urban, remote vs. nonremote, and health care resource areas. Interpretations of the data indicate clearly that PAs are considerably more productive than NPs. However, although NPs spend more time with individual patients, the cause of this differential productivity was not revealed.