A new biomedical sensor for measuring PCO2

Measuring PCO2 (partial pressure of carbon dioxide) in an organ can enable early detection of ischemia. However, there are few clinical applicable solutions for measuring PCO2. Based upon the requirement for clinical applications, a conductivity based PCO2 sensor is proposed. A conductivity based PCO2 sensor measures conductance in an aqueous solution separated from the measured object by a gas-permeable membrane. A bridge design with two cavities is favored for such a sensor. A planar and a cylindrical macro prototype based upon the bridge design were studied. The design criteria were based on the contribution from the electrode polarization, stray capacitances, contact area with the sample and design ability to miniaturize the sensor. The cylindrical sensor is favored because of its large contact area and advantages for miniaturization. Further investigation has to be done to confirm the functionality of such a design in a miniaturized form and its clinical performance.     

Volume estimation of small phantoms and rat kidneys using three-dimensional ultrasonography and a position sensor

To evaluate the accuracy of small volume estimation, both in vivo and in vitro, measurements with a three-dimensional (3D) ultrasound (US) system were carried out. A position sensor was used and the transmitting frequency was 10 MHz. Balloons with known volumes were scanned while rat kidneys were scanned in vivo and in vitro. The Archimedes' principle was used to estimate the true volume. For balloons, the 3D US system gave very good agreement with true volumes in the volume range 0.1 to 10.0 mL (r = 0.999, n = 45, mean difference +/- 2SD = 0.245 +/- 0.370 mL). For rat kidneys in vivo (volume range 0.6 to 2.7 mL) the method was less accurate (r = 0.800, n = 10, mean difference +/- 2SD = -0.288 +/- 0.676 mL). For rat kidneys in vitro (volume range 0.3 to 2.7 mL) the results showed good agreement (r = 0.981, n = 23, mean difference +/- 2SD = 0.039 +/- 0.254 mL). For balloons, kidneys in vivo and in vitro, the mean percentage error was 9.3 +/- 4.8%, -17.1 +/- 17.4%, and 4.6 +/- 11.5%, respectively. This method can estimate the volume of small phantoms and rat kidneys and opens new possibilities for volume measurements of small objects and the study of organ function in small animals. (E-mail ).     

Reducing the duration of untreated first-episode psychosis: effects on clinical presentation

CONTEXT: Most studies on first-episode psychosis show an association between a long duration of untreated psychosis (DUP) and poorer short-term outcome, but the mechanisms of this relationship are poorly understood. OBJECTIVE: To determine whether it is possible to reduce the DUP for first-episode patients in a defined health care area through the introduction of an early detection (ED) program, compared with parallel health care areas without an ED program (No-ED). SETTING AND PATIENTS: We included consecutive patients with a DSM-IV diagnosis of nonorganic, nonaffective psychosis coming to their first treatment in the study health care areas between January 1, 1997, and December 31, 2000. A total of 281 patients (76% of the total) gave informed consent. INTERVENTIONS: The ED and No-ED health care areas offered an equivalent assessment and treatment program for first-episode psychosis. The ED area also carried out an intensive ED program. RESULTS: The DUP was significantly shorter for the group of patients coming from the ED area, compared with patients from the No-ED areas (median, 5 weeks [range, 0-1196 weeks] vs 16 weeks [range, 0-966 weeks]). Clinical status measured by the Positive and Negative Syndrome Scale and the Global Assessment of Functioning Scale was significantly better for patients from the ED area at start of treatment and, with the exception of Positive and Negative Syndrome Scale positive subscale, at 3 months. Multiple linear regression analyses gave no indication that confounders were responsible for these differences. CONCLUSIONS: It is possible to reduce the DUP through an ED program. The reduction in DUP is associated with better clinical status at baseline that is maintained after 3 months.     

Electromagnetic breast imaging: average tissue property values in women with negative clinical findings

Representative data are provided for three electromagnetic breast imaging techniques-near-infrared spectroscopy, electrical impedance spectroscopy, and microwave imaging spectroscopy-to serve as potential benchmarks for future investigation. The breasts of 23 women without clinical or mammographic findings of disease were imaged in the coronal plane with nonionizing radiation of varying frequencies. Average electromagnetic property values were reconstructed at each frequency on the basis of computational models of light diffusion, current flow, and microwave propagation. Electromagnetic properties were correlated with subject characteristics and between techniques. Each technique yielded information on breast tissue features (eg, conductivity, permittivity, light scattering, and absorption) that had not previously all been measured in the same individuals.     

Pre- and inter-hospital transport of severely head-injured patients in rural Northern Norway

The purpose of this study was to survey the time consumed during the pre- and inter-hospital transport of severely head injured patients in Northern Norway. All patients (n = 85) operated for an intracranial mass lesions within 48 h after injury during the 10-year period 1986-1995 were included in this retrospective analysis. Ambulance records, transfer notes, and hospital records were reviewed. The transport of patients was classified as either direct from the trauma scene to the University Hospital (direct admission group) or as an inter-hospital transfer (transfer group). Forty-seven (55%) patients were in the direct admission group, and 38 (45%) were transferred through another hospital. The majority of patients (81%) were transported by air ambulance. Median time from injury to arrival in the emergency room was 5 (1-44) h. Time necessary for transport was significantly (p < 0.001) shorter in the direct admission group (median 3 h) compared to the transfer group (median 8 h). The inter-hospital transfer time was < or = 3 h in 17%. Clearly, the advanced air ambulance service in Northern Norway makes rapid inter-hospital transfer possible despite extremely long geographical distances. Our findings indicate that this possibility is not always utilized.     

Power and sample size calculations for generalized regression models with covariate measurement error

Covariate measurement error is often a feature of scientific data used for regression modelling. The consequences of such errors include a loss of power of tests of significance for the regression parameters corresponding to the true covariates. Power and sample size calculations that ignore covariate measurement error tend to overestimate power and underestimate the actual sample size required to achieve a desired power. In this paper we derive a novel measurement error corrected power function for generalized linear models using a generalized score test based on quasi-likelihood methods. Our power function is flexible in that it is adaptable to designs with a discrete or continuous scalar covariate (exposure) that can be measured with or without error, allows for additional confounding variables and applies to a broad class of generalized regression and measurement error models. A program is described that provides sample size or power for a continuous exposure with a normal measurement error model and a single normal confounder variable in logistic regression. We demonstrate the improved properties of our power calculations with simulations and numerical studies. An example is given from an ongoing study of cancer and exposure to arsenic as measured by toenail concentrations and tap water samples.     

How to promote prevention--economic incentives or legal regulations or both?

Legal regulations of the work environment are probably regarded as the main tools for promoting prevention at the workplace. Legal regulations are expressed as occupational exposure limits, bans, and taxes. Taxes can be regarded as economic incentives as well, and other economic incentives are insurance systems for employers' and consumers' actions. The latter have been found to have profound effects regarding environmental issues and may also, in the future, be a powerful tool for workplace-related prevention. The research in this area is rather limited, but there are some research results that can be obtained from the area of environmental economics. This paper discusses some examples in which legal regulations, economic incentives, or both have been used. Legal regulations and market-based economic incentives may produce similar results, but the economic cost and political feasibility typically differ. This situation makes the selection and design of instruments an important field for future research.