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PubMedDate not supplied

A method for estimation of bias and variability of continuous gas monitor data: application to carbon monoxide monitor accuracy.

A method is presented for the evaluation of the bias, variability, and accuracy of gas monitors. This method is based on using the parameters for the fitted response curves of the monitors. Thereby, variability between calibrations, between dates within each calibration period, and between different units can be evaluated at several different standard concentrations. By combining variability information with bias information, accuracy can be assessed. An example using carbon monoxide monitor data is provided. Although the most general statistical software required for these tasks is not available on a spreadsheet, when the same number of dates in a calibration period are evaluated for each monitor unit, the calculations can be done on a spreadsheet. An example of such calculations, together with the formulas needed for their implementation, is provided. In addition, the methods can be extended by use of appropriate statistical models and software to evaluate monitor trends within calibration periods, as well as consider the effects of other variables, such as humidity and temperature, on monitor variability and bias.

Bias↗
PubMed1999

ICP monitoring in the rat: comparison of monitoring in the ventricle, brain parenchyma, and cisterna magna.

Various methods of continuous intracranial pressure (ICP) monitoring during experimental procedures in the rat have been described. However, no systematic comparison of ICP monitoring in the ventricle, brain parenchyma, and cisterna magna has been reported. Since accurate and reliable ICP measurements are important in experimental models of traumatic brain injury, the present study was conducted to compare simultaneous ICP measurements from ventricular, cisterna magna, and intraparenchymal monitors during ICP changes. Subdural hematoma was produced by infusion of 0.3 ml of autologous blood into the subdural space over 6 min. The ventricular and the intraparenchymal fiberoptic catheter produced reliable and comparable pressure recordings, that did not statistically differ (p = 0.4), throughout the one hour monitoring time. In contrast, the cisterna magna catheter was less reliable and produced significantly lower readings throughout the monitoring time (p<0.001). The intraparenchymal device produced greater cortical damage than the ventricular catheter. In conclusion, ventricular ICP monitoring is the preferred method under these circumstances, since it is accurate and induces least brain damage.

Animals↗
PubMed2003

Harmonisation (legal, dosimetric, quality aspects) of individual monitoring, and integration of monitoring for external and internal exposures (EURADOS Working Group).

The EURADOS Working Group II on 'Harmonisation of individual monitoring' consists of experts from almost all EU Member States and Newly Associated States (NAS), involved in tasks related to the assessment of doses for internal and external radiation. The final objective is to achieve harmonisation in individual monitoring for occupational exposures. Sub-group 2 activities are focused on investigating how the results from personal dosemeters for external radiation and workplace monitoring and from monitoring for internal exposure can be combined into a complete and consistent system of individual monitoring. Three questionnaires were prepared, covering 'Individual monitoring of external radiation' (Questionnaire 1), 'Internal exposure' (Questionnaire 2) and 'Natural sources of radiation at the workplace' (Questionnaire 3). With the agreement of a 'contact-person', selected in each country, the distribution of the three EURADOS 2002 questionnaires was carried out by e-mail among the dosimetry facilities of 28 European countries. The preliminary results of these actions are presented here.

Advisory Committees↗
PubMed2004

Workplace monitoring for exposures to radon and to other natural sources in Europe: integration of monitoring for internal and external exposures.

Part of the action of the EURADOS working group (European Radiation Dosimetry Group) on "Harmonisation of Individual Monitoring in Europe" was to investigate how the results from personal dosemeters for external radiation, from monitoring for internal exposure and from workplace monitoring, can be combined into a complete and consistent system of individual monitoring. To facilitate this work, the "EURADOS questionnaire Q3" relating to radon and other natural sources of radiation in the workplace was distributed to relevant institutes across Europe. A total of 24 countries replied to the questionnaire. This study offers an important overview on actual regulations, national standards and reference levels for protection of employees from radon and other natural sources in different workplace scenarios. Information was also collected on individual monitoring and area monitoring to determine individual doses in workplaces with elevated levels of natural radiation. The article discusses in detail the results obtained showing by country the reference level in workplaces for radon gas and other natural sources. In both instances, exposures in mines, other underground workplaces, industry workplaces/waterworks, offices, schools and day-care homes were considered. The resultant data clearly indicate that there is a need for harmonisation among countries, not least in the areas of regulation and use of reference levels in the workplace.

Background Radiation↗
PubMed2006

Is C2 monitoring or another limited sampling strategy superior to C0 monitoring in improving clinical outcomes in adult liver transplant recipients?

Cyclosporine (CsA) has had a major impact on the process and success of solid organ transplantation. Early in the use of CsA, therapeutic monitoring using the predose (trough, or C0) concentration became the standard of care. However, there are complications with the use of C0 monitoring that have only partly been mitigated with the advent of the micro-emulsion formulation (CsA-ME). More recently, limited sampling strategies (LSSs) for measuring the area under the CsA concentration-time curve (AUC) have been investigated to improve the monitoring of CsA post-transplantation. Many centres now routinely monitor CsA therapy using the concentration at 2 hours postdose (C2). In this paper the strength of the evidence for C2 (or other LSSs) relative to C0 monitoring of CsA-ME for improving clinically important outcomes in liver transplant patients is critically examined. Additionally, gaps in the literature are identified and recommendations are made for clinical research that could be done to provide more definitive evidence for the use of C2 or other LSSs in monitoring liver transplant patients.

Area Under Curve↗
PubMed2004

Brachial blood pressure monitoring versus ankle monitoring during colonoscopy.

OBJECTIVES: To compare ankle and brachial blood pressure monitoring before and during colonoscopy using automated noninvasive blood pressure (NIBP) monitors. METHODS: Forty-five consecutive patients who presented for outpatient colonoscopy had both ankle and brachial blood pressure monitoring with automated NIBP using an appropriately sized cuff for arm or leg size. Three baseline measurements were obtained, and then measurements were taken at 5-minute intervals during conscious sedation, with brachial blood pressure being the standard. RESULTS: The average of all of the ankle blood pressures was significantly higher for all systolic and mean arterial blood pressure readings. Diastolic blood pressure readings were higher at baseline, but not significantly different during the procedure. CONCLUSIONS: Ankle systolic and mean arterial blood pressures using automated NIBP monitoring for conscious sedation are significantly higher than brachial blood pressures. Ankle NIBP monitoring should only be used if brachial NIBP monitoring is not feasible, taking into consideration that ankle NIBP pressures are generally higher than brachial.

Adult↗
PubMed2005

The BpTRU automatic blood pressure monitor compared to 24 hour ambulatory blood pressure monitoring in the assessment of blood pressure in patients with hypertension.

BACKGROUND: Increasing evidence suggests that ABPM more closely predicts target organ damage than does clinic measurement. Future guidelines may suggest ABPM as routine in the diagnosis and monitoring of hypertension. This would create difficulties as this test is expensive and often difficult to obtain. The purpose of this study is to determine the degree to which the BpTRU automatic blood pressure monitor predicts results on 24 hour ambulatory blood pressure monitoring (ABPM). METHODS: A quantitative analysis comparing blood pressure measured by the BpTRU device with the mean daytime blood pressure on 24 hour ABPM. The study was conducted by the Centre for Studies in Primary Care, Queen's University, Kingston, Ontario, Canada on adult primary care patients who are enrolled in two randomized controlled trials on hypertension. The main outcomes were the mean of the blood pressures measured at the three most recent office visits, the initial measurement on the BpTRU-100, the mean of the five measurements on the BpTRU monitor, and the daytime average on 24 hour ABPM. RESULTS: The group mean of the three charted clinic measured blood pressures (150.8 (SD10.26) / 82.9 (SD 8.44)) was not statistically different from the group mean of the initial reading on BpTRU (150.0 (SD21.33) / 83.3 (SD12.00)). The group mean of the average of five BpTRU readings (140.0 (SD17.71) / 79.8 (SD 10.46)) was not statistically different from the 24 hour daytime mean on ABPM (141.5 (SD 13.25) / 79.7 (SD 7.79)). Within patients, BpTRU average correlated significantly better with daytime ambulatory pressure than did clinic averages (BpTRU r = 0.571, clinic r = 0.145). Based on assessment of sensitivity and specificity at different cut-points, it is suggested that the initial treatment target using the BpTRU be set at <135/85 mmHG, but achievement of target should be confirmed using 24 hour ABPM. CONCLUSION: The BpTRU average better predicts ABPM than does the average of the blood pressures recorded on the patient chart from the three most recent visits. The BpTRU automatic clinic blood pressure monitor should be used as an adjunct to ABPM to effectively diagnose and monitor hypertension.

Adult↗
PubMed1997

Assessment of dialysis adequacy using the dialysate urea monitor: preliminary experience of the dialysate urea monitor.

Numerous studies have identified a strong linkage between the delivered dialysis dose (Kt/V) and the survival of hemodialysis (HD) patients. However, the current method used to calculate Kt/V requires multiple blood samples and the process is complex and time consuming. We evaluate the performance of a recently developed on-line monitor (Biostat 1000 dialysate urea monitor, Baxter) that measures the urea concentration in the effluent dialysate and displays Kt/V and nPCR immediately after hemodialysis. To verify the performance of the urea monitor, we selected 21 hemodialysis patients, calculated their Kt/V and nPCR values from blood samples obtained during each hemodialysis, and compared the results with data obtained using the urea monitor. The Kt/V and nPCR values calculated by the urea monitor were both significantly correlated with those obtained using blood samples (R = 0.804, p < 0.001 in Kt/V and R = 0.749, p < 0.001 in nPCR). Our results suggest that the urea monitor may be used for on-line assessment of dialysis adequacy and obviates the need for blood sampling.

Blood Urea Nitrogen↗
PubMed2000

[Long-term monitoring of patients with a syncope of obscure etiology with an implantable monitoring device].

INTRODUCTION: Generally available methods for the diagnosis of syncopal conditions such as Holter monitoring, the tilt test and invasive electrophysiological examinations, lead to the assessment of the cause of sporadic syncopes only in some patients. The implantable monitoring device REVEAL protracts significantly the monitoring period. METHODS, RESULTS: The authors implanted the implantable monitoring device REVEAL in the course of 14 months to 19 patients with syncopes of obscure origin. During this period it was possible to prove the cause of the syncope in a total of 10 patients (53%), in 8 patients the cause was arrhythmia, in another two an arrhythmic cause was ruled out. During monitoring the authors did not record any serious undesirable events. CONCLUSION: Implantable monitoring devices are an asset in the diagnosis of sporadic syncopes where currently available invasive and non-invasive methods fail. Its use in patients without obvious structural cardiovascular disorders is safe.

Adult↗
PubMed1990

What should be monitored? The past, present, and future of physiological monitoring.

The status of conventional monitoring by vital signs and present concepts of invasive monitoring with the balloon-tipped pulmonary artery (Swan-Ganz) catheter are reviewed. Survivors of high-risk general surgery were observed to have cardiac index (CI) values averaging 4.5 L/min.m2, oxygen delivery (DO2) greater than 600 mL/min.m2, and oxygen consumption (VO2) greater than 170 mL/min.m2. By contrast, those who subsequently died during their hospitalization maintained relatively normal CI, DO2, and VO2 values. However, in the immediate postoperative period, values for other hemodynamic variables were not greatly different for survivors and nonsurvivors or different from the normal range. A predictive index based on these observations predicted outcome correctly in 94% of the subjects in a subsequent prospective study. The use of survivor values as appropriate therapeutic goals was tested in prospective randomized clinical trials and was found to reduce mortality and morbidity significantly. Simultaneous invasive and noninvasive hemodynamic and oxygen-transport monitoring systems were evaluated in high-risk postoperative patients to describe unanticipated adverse circulatory events. Before the monitored event, about three-fourths of the patients exhibited normal function. At the nadir, cardiac functions decreased in about two-thirds, perfusion decreased in more than one-half, and paO2 fell in only one-fourth. Two-thirds recovered with increased cardiac function, more than one-half had improved perfusion, and paO2 increased in fewer than one-fifth of monitored events. These data provide an information base for criteria needed to develop therapeutic decision rules for noninvasive monitoring systems. When noninvasive data are continuously displayed early in the course of critical illness and high-risk conditions, therapy may be instituted early, while physiological deficits are still minimal and easily reversible.

Critical Care↗
PubMed1998

College of American Pathologists Conference XXXI on laboratory monitoring of anticoagulant therapy: laboratory monitoring of oral anticoagulant therapy.

OBJECTIVE: To review the state of the art of laboratory monitoring of oral anticoagulant therapy, as reflected by the medical literature and the consensus opinion of recognized experts in the field, and to make recommendations for improvement in laboratory monitoring of oral anticoagulant therapy. DATA SOURCES: Review of the medical literature, primarily from the last 10 years, and current laboratory practices by a panel of 8 international experts in the field of oral anticoagulant monitoring. DATA EXTRACTION AND SYNTHESIS: After an initial assessment of the literature, key points were identified. Experts were assigned to do an in-depth review of the literature and current practices relevant to each of the key points and to prepare a summary of their findings and recommendations. A draft manuscript was prepared and circulated to every participant in the College of American Pathologists Conference XXXI on Laboratory Monitoring of Anticoagulant Therapy prior to the conference. Each of the key points and associated recommendations was then presented for discussion at the Conference. Recommendations were accepted if a consensus of the 26 experts attending the Conference was reached. The results of the discussion were used to revise the manuscript into its final form. CONCLUSIONS: Consensus was reached on 12 recommendations concerning the laboratory monitoring of oral anticoagulant therapy. Detailed discussion of the rationale for each of these recommendations is found in the text of this article. Discussion of points on which consensus was not reached is also included in the text. It is hoped that widespread adoption of these recommendations will further improve the laboratory monitoring of oral anticoagulant therapy.

Administration, Oral↗
PubMed1994

A comparison of two quality assessment instruments: Monitor and Senior Monitor.

Similarities and differences between the two U.K. generic quality assessment instruments, Monitor and Senior Monitor, are outlined. The relative merits of each are explored to determine the most valid instrument for assessing the quality of care of elderly patients. Both instruments were simultaneously administered to 46 patients aged 70 years or over in three medical, three surgical and three elderly care wards. Senior Monitor scores were significantly lower than Monitor scores for the nine wards overall. This remained the case when the sections in Senior Monitor that do not feature in Monitor were removed from the analysis. Factors to be taken into account when selecting which instrument to use with elderly patients are outlined.

Aged↗
PubMed1991

Data monitoring committees for multicenter clinical trials sponsored by the National Institutes of Health. I. Roles and membership of data monitoring committees for trials sponsored by the National Eye Institute.

The operational aspects of data monitoring committees for multicenter clinical trials have received little attention in the published literature, in contrast to a wealth of publications concerning the statistical aspects of data monitoring. Occasional anecdotal reports suggest that the role of these committees is complex and that responsibilities and decisions extend beyond choice of a stopping rule. In an effort to gain a better appreciation of the domain of responsibilities shared by all or most of the data monitoring committees (DMCs) for the 20 multicenter studies (30 clinical trials) sponsored by the National Eye Institute, one of the National Institutes of Health, published information was studied and key members of the DMCs for these studies were surveyed. Information about the membership of these important groups also was sought in order to guide those with responsibility for appointing future DMCs. Three tasks--all directly associated with monitoring accumulating data for evidence of benefit or harm to trial patients--were reported unanimously to be the responsibility of the DMCs. In addition, many responsibilities concerned with study oversight rather than data monitoring were assigned to the DMC in 75% or more of the trials. The domain of responsibilities common to a majority of the DMCs suggests that these groups function in most NEI-sponsored multicenter trials as combined data monitoring and policy boards, even when not so designated. The median size of the 20 DMCs was 10 members, with six appointed and four ex officio members. Ophthalmologists accounted for 38% of all DMC positions and statisticians for 33%.

Clinical Trials as Topic↗
PubMed1999

Data monitoring committees and interim monitoring guidelines.

Most large randomized clinical trials have a data monitoring committee that periodically examines efficacy and safety results. A typical data monitoring committee meets every 6 months, but the interim monitoring guidelines for many trials specify formal analyses that are years apart. In this article we argue that study protocols should include monitoring guidelines with formal looks at each data monitoring committee meeting. Such guidelines are shown to reduce the average duration of a trial with negligible effect on power and estimation bias. Some of the common statistical monitoring guidelines require extreme evidence to stop a trial early and do not distinguish between stopping a trial during active accrual and follow-up stages. We propose practical solutions for these issues.

Bayes Theorem↗