'Oxygen Level in a Tissue' - What Do Available Measurements Really Report?

The aim of the paper is to discuss what currently is feasible clinically to measure the level of oxygen and how that measurement can be clinically useful. Because oxygen in tissues is quite heterogeneous and all methods of measurement can only provide an average across heterogeneities at some spatial and temporal resolution, the values that are obtained may have limitations on their clinical utility. However, even if such limitations are significant, if one utilizes repeated measurements and focuses on changes in the measured levels, rather than 'absolute levels', it may be possible to obtain very useful clinical information. While these considerations are especially pertinent in cancer, they also pertain to most other types of pathology.

Clinical and Statistical Considerations when Assessing Oxygen Levels in Tumors: Illustrative Results from Clinical EPR Oximetry Studies.

The success of treatment for malignancies, especially those undergoing radiation therapy or chemotherapy, has long been recognized to depend on the degree of hypoxia in the tumor. In addition to the prognostic value of knowing the tumor's initial level of hypoxia, assessing the tumor oxygenation during standard therapy or oxygen-related treatments (such as breathing oxygen-enriched gas mixtures or taking drugs that can increase oxygen supply to tissues) can provide valuable data to improve the efficacy of treatments. A series of early clinical studies of tumors in humans are ongoing at Dartmouth and Emory using electron paramagnetic resonance (EPR) oximetry to assess tumor oxygenation, initially and over time during either natural disease progression or treatment. This approach has the potential for reaching the long-sought goal of enhancing the effectiveness of cancer therapy. In order to effectively reach this goal, we consider the validity of the practical and statistical assumptions when interpreting the measurements made in vivo for patients undergoing treatment for cancer.

Skeletal Muscle Oxygenation Measured by EPR Oximetry Using a Highly Sensitive Polymer-Encapsulated Paramagnetic Sensor.

We have incorporated LiNc-BuO, an oxygen-sensing paramagnetic material, in polydimethylsiloxane (PDMS), which is an oxygen-permeable, biocompatible, and stable polymer. We fabricated implantable and retrievable oxygen-sensing chips (40 % LiNc-BuO in PDMS) using a 20-G Teflon tubing to mold the chips into variable shapes and sizes for in vivo studies in rats. In vitro EPR measurements were used to test the chip's oxygen response. Oxygen induced linear and reproducible line broadening with increasing partial pressure (pO2). The oxygen response was similar to that of bare (unencapsulated) crystals and did not change significantly on sterilization by autoclaving. The chips were implanted in rat femoris muscle and EPR oximetry was performed repeatedly (weekly) for 12 weeks post-implantation. The measurements showed good reliability and reproducibility over the period of testing. These results demonstrated that the new formulation of OxyChip with 40 % LiNc-BuO will enable the applicability of EPR oximetry for long-term measurement of oxygen concentration in tissues and has the potential for clinical applications.

Calculation of dose conversion factors for doses in the fingernails to organ doses at external gamma irradiation in air.

Absorbed doses to fingernails and organs were calculated for a set of homogenous external gamma-ray irradiation geometries in air. The doses were obtained by stochastic modeling of the ionizing particle transport (Monte Carlo method) for a mathematical human phantom with arms and hands placed loosely along the sides of the body. The resulting dose conversion factors for absorbed doses in fingernails can be used to assess the dose distribution and magnitude in practical dose reconstruction problems. For purposes of estimating dose in a large population exposed to radiation in order to triage people for treatment of acute radiation syndrome, the calculated data for a range of energies having a width of from 0.05 to 3.5 MeV were used to convert absorbed doses in fingernails to corresponding doses in organs and the whole body as well as the effective dose. Doses were assessed based on assumed rates of radioactive fallout at different time periods following a nuclear explosion.

Assessing symptom improvement after elective prostatectomy for benign prostatic hypertrophy.

BACKGROUND: Elective surgery for benign prostatic hypertrophy requires estimates of likely improvement. METHODS: Data are from a prospective study of all patients without cancer who underwent transurethral prostatectomy. After eliminating patients for whom surgery was not elective, we examined symptom improvement. RESULTS: Surgery was effective in reducing symptoms for all but those with very mild preoperative symptoms. For the remainder, the average level of postoperative outcomes achieved was independent of the initial symptom severity. CONCLUSIONS: Elective prostatectomy is effectiveness for improving symptoms. The improvement is typically sustained, and for some symptoms improvement continues during the first year after surgery. Patients with severe symptoms were as likely to achieve the same level of postoperative improvement as were patients with less severe problems initially. However, patients with very mild symptoms benefited little or none from surgery.

Key challenges in studying organizational issues in the delivery of healthcare to older Americans.

OBJECTIVE: Drawing from the articles presented in this special issue, to provide an overview of three key challenges facing researchers in the area of organizational issues in primary care delivery to older adults. CONCLUSIONS: To improve the quality of research done in this area we would recommend that researchers attend to the complexity of (1) defining an appropriate unit of analysis; (2) reframing our traditional models of service delivery to reflect ongoing changes in healthcare system actors and boundaries; and (3) reconceptualizing the outcomes of care to reflect adequately the reality of care for the aging patient.

Effectiveness in professional organizations: the impact of surgeons and surgical staff organizations on the quality of care in hospitals.

In this research, we examine the relative importance of different structural units in a professional organization, the hospital, as they affect organizational effectiveness. The difficulties of measuring effectiveness in a complex professional organization are discussed, and an adjusted measure of surgical outcome is developed. Data are drawn from a prospective study of over 8,000 surgical patients treated by more than 500 surgeons in 15 hospitals throughout the nation. Two different types of analyses are presented, both indicating that hospital features have more impact on surgical outcomes than do surgeon characteristics. The second analysis assesses the relative importance of specific attributes of the hospital, surgical staff organization, and surgeon characteristics on surgical outcomes.

How do HMOs achieve savings? The effectiveness of one organization's strategies.

OBJECTIVE: To examine how a group practice used organizational strategies rather than provider-level incentives to achieve savings for health maintenance organization (HMO) compared to fee-for-service (FFS) patients. DATA SOURCES/STUDY SETTING: A large group practice with a group model HMO also treating FFS patients. Data sources were all patient encounter records, demographic files, and clinic records covering 3.5 years (1986-1989). The clinic's procedures to record services and charges were identical for FFS and HMO patients. All FFS and HMO patients under age 65 who received any outpatient services during approximately 100,000 episodes of the seven study illnesses were eligible. STUDY DESIGN: Using an explanatory case design, we first compared HMO and FFS rates of resource utilization, in standardized dollars, which measured the impact of organizational strategies to influence patient and provider behavior. We then examined the effect of HMO insurance and organizational measures to explain total outpatient use. Key variables were standardized charges for all outpatient services and the HMO's strategies. PRINCIPAL FINDINGS: Patient and provider behavior responded to organizational strategies designed to achieve savings for HMO patients; for instance, HMO patients used midlevel providers and generalists more often and ER and specialists less often. Overall HMO savings, adjusted for case mix, were explained by the specialty of the physicians the patients first visited and appeared to affect patients with average health more than others. CONCLUSION: Organizational strategies, without resort to differential financial incentives to each provider, resulted in lower rates of outpatient services for HMO patients. Savings from outpatient use, especially for common diseases that rarely require hospitalization, can be substantial.

Criterion validation of the Nottingham Health Profile: patient views of surgery for benign prostatic hypertrophy.

As part of a prospective cohort study of 388 men undergoing TURP for benign prostatic hypertrophy, the Nottingham Health Profile (NHP) was self-administered before and at 3, 6 and 12 months after surgery. By comparison of pre- and post-operative NHP scores with other patient-reported health measures the criterion validity of the Profile was examined. Before surgery, statistically significant linear trends were observed for increasing NHP score (i.e. having more health problems) with both worsening self-rated general health and increasing severity of prostatic symptoms. One year after surgery, the extent of reduction in NHP score was significantly linearly associated with a perceived favourable outcome of surgery and to a lesser extent with a reduction in prostatic symptoms. In addition, changes in NHP scores during follow-up were associated with perceived changes in operative outcome during the same period, patients with the greatest reduction in NHP score tending to report more successful surgery at 12 months than at the 3 month assessment.

Through the lenses of organizational sociology: the role of organizational theory and research in conceptualizing and examining our health care system.

This paper reviews various theoretical perspectives on organizational change which have been and could be applied to medical organizations. These perspectives are discussed as both filters influencing our observations (research) and mirrors of the shifting dynamics of delivery system reform (policy). We conclude with an examination of how such theories can provide useful insights into our rapidly changing health care system.

The promise and pitfalls of explicitly rewarding physicians based on patient insurance.

In a large multi-specialty group practice treating approximately equal numbers of health maintenance organization (HMO) and fee-for-service (FFS) patients, we analyzed a natural experiment by the administration to introduce a dual incentive system for physicians. We examine the impact on care when they announced that each physician would be remunerated for HMO care based on a per capita budget, but for FFS care based on billable services. Data were 86,230 episodes for treating patients under age 65 with seven common illnesses. There was no evidence that the intended impact (reducing HMO care) occurred; instead, there were undesired and unintended effects (reduced care for FFS and upset physicians and threats to their corporate culture).

No insurance, public insurance, and private insurance: do these options contribute to differences in general health?

This paper examines the validity of two of the basic assumptions made about health care insurance and health, namely that having any insurance is associated with better health and, in particular, that having public, welfare-based insurance has better health consequences for the poor than does having no insurance. These questions were addressed using data from the National Medical Expenditure Survey, a national household-based survey in 1987 of more than 36,000 people who were asked to report in detail about their medical care use and expenditures, health insurance coverage, and health and functional status. The results of the analysis indicate that being without insurance is associated with having poorer general health compared to persons with private insurance, and that the health of persons who qualify for public insurance is the poorest of any group--poorer even than those without insurance.

Peaks and pits of using large data bases to measure quality of care.

This review of the advantages (peaks) and problems (pits) of large data bases to study quality contrasts their suitability with randomized control trials. Researchers need to advise policymakers and others about when statistically significant differences in quality are also politically and socially significant and deserve responsible reactions.

Organizational determinants of services, quality and cost of care in hospitals.

Characteristics of hospitals may be useful predictors of the economy, efficiency, and effectiveness of services delivered. But it is difficult to explain the variables of cost and quality among hospitals until differences among patients and outcomes are accounted for. A promising new research approach is explored as a source of information on that most elusive of all measures in service organizations--the outcome experienced by clients.

Does practice make perfect? Part I: The relation between hospital volume and outcomes for selected diagnostic categories.

The effect of a greater volume of patients with similar conditions being treated at a hospital on the outcomes achieved is studied using a variety of categories of patients, 15 surgical and 2 medical, and involving 550,000 patients treated in over 1,200 nonfederal United States acute care hospitals. After demonstrating that there are significant differences in the outcomes of patients, taking into account patient health status, the authors examine the impact of being treated in a hospital with a high or low volume of similar patients. Strong and consistent evidence is found that high volume is associated with better outcomes for surgical patients, which supports regionalizing patient care by procedure. Two additional variables, relative difficulty of the procedure and risk level of the patients, are analyzed to determine whether they change the relationship between volume and outcome. Some evidence is found that low-volume hospitals are associated with the poorest outcome for low-risk surgical patients. The evidence for medical patients is weak and mixed. Possible alternative explanations for the observed findings for surgical and medical patients are discussed.

Does practice make perfect? Part II: The relation between volume and outcomes and other hospital characteristics.

The effect of a greater volume of patients with similar conditions being treated at a hospital on the outcomes achieved is investigated for almost 500,000 selected surgical and medical patients treated in over 1,200 nonfederal United States hospitals. In Part I the authors found strong and consistent evidence for surgical patients that high volume is associated with better outcome; evidence for medical patients was mixed. In this paper the authors include other hospital variables related both to volume and outcome--hospital size, teaching status, and expenditures--to determine whether they mask the true relationship; still, strong and consistent evidence that greater volume produces better outcome was found for both surgical and medical patients. This relation was significant for low-, medium-, and high-risk patients. Among the hospital variations added, only size was consistently and strongly related to outcome; greater size was associated with poorer outcome after accounting for volume. The potential importance of the findings for reducing deaths and days in hospital on a national level is discussed. The evidence is strongly supportive of the need for policies that would promote greater regionalization of a given service, and not greater size, to obtain better quality outcome for patients treated.

Measuring the complexity and uncertainty of surgery and postsurgical care.

This article reports the results of a survey of a nationwide sample of more than 900 surgeons and post-surgical nurses, who were asked to rate the relative complexity and uncertainty of 71 surgical procedures frequently performed in hospitals. Average scores assigned to each surgical procedure by both types of raters are reported and the extent of agreement is assessed across indicator questions and types of raters. A surprisingly high level of agreement was observed. Explanations for the extent of agreement are discussed and uses for these scores are described.