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At least 775 records · Page 43Linked to original sources
PubMed1991

Presence of fecal material in diapers as a potential source of error in estimations of postmortem interval using arthropod development rates.

Second instar larvae of the fly Chrysomya megacephala (Diptera, Calliphoridae) were recovered from the diapers of a 16-month-old child abandoned by her mother on Oahu, Hawaii. The development of these larvae indicated a minimum period of 23.5 h of exposure prior to discovery of the child. Larvae of this species of fly are not normally associated with living tissues in Hawaii, but rather with feces and remains during the early stages of decomposition. Had the child in this case died and data not been provided detailing the site of infestation, the postmortem interval estimated would have been significantly longer than was actually the case, because of the development of the larvae inside the diapers of the living child. The need for caution in cases involving deaths of infants, the elderly, and individuals not capable of caring for themselves is stressed.

Animals↗
PubMed1990

[Assessment, reproducibility and sources of error in sonographic examination of the hip].

To the sonographic examination of the hip middle-category devices with real-time working and 5 MHz linear probing heads are necessary. Special laying and documentation is suggested to the rapid and easy execution and assessment of the examinations. If the examination is carried out in a standard plane the points of orientation characterising the acetabulum are represented unequivocally and clearly, the results gained can be reproduced and compared.

Diagnostic Errors↗
PubMed1991

[Sources of error in the diagnosis and therapy of hypertension].

Possible errors in the diagnosis and treatment of hypertension are discussed. The problems of blood pressure determinations are reviewed by comparing the results of sphygmomanometry in the doctor's office, of automated ambulatory blood pressure recording and of blood pressure self-measurement. In screening for renovascular hypertension one should be aware that no test is yet available which shows adequate sensitivity and specificity. Therefore, the only investigation that should be used to demonstrate a true stenosis is arteriography. When treating hypertensives it must be kept in mind that the benefits of antihypertensive medication, i.e. reducing morbidity and mortality from cardiovascular disease, should exceed the costs and side effects of the treatment. Finally, the effects of reduction in dose and discontinuation of antihypertensive medication are discussed.

Antihypertensive Agents↗
PubMed1990

[Phantom measurements of blood flow using color-coded Doppler sonography (Quantum Angiodynograph): accuracy and sources of error].

Flow measurements were carried out on a phantom simulating tissue, using systematic variations of various parameters and of relevant geometric factors. The effect of imaging and flow parameters on the accuracy of the measurements is described and the conditions are defined which are necessary for obtaining a high degree of accuracy. Large errors are introduced by measurements carried out with large Doppler angles or if the delimiters used for automatic vessel measurements have not been set up accurately.

Blood Flow Velocity↗
PubMed1990

Maternal obesity: a potential source of error in sonographic prenatal diagnosis.

Sonograms from 1622 consecutively scanned singleton pregnancies at a mean gestational age of 28.5 weeks were analyzed to determine whether maternal obesity affected visualization of fetal anatomy. Fetal head (cerebral ventricles), heart (four-chamber view), stomach, kidneys, bladder, diaphragm, intestines, spinal column, extremities, and umbilical cord were classified as visualized or suboptimally visualized. Maternal body mass index was used as a measure of relative leanness. No significant impairment of ultrasound visualization was noted until a body mass index above the 90th percentile, when visualization fell by an average of 14.5%. Reduction in visualization was most marked for the fetal heart, umbilical cord, and spine. Among non-obese women, advancing gestation and decreasing body mass index were the most important determinants of visualization. However, among obese women, body mass index was the best predictor of visualization, with no improvement seen with advancing gestation or duration of examination.

Body Constitution↗
PubMed1990

[In electric nerve stimulation can the distance from the nerves be inferred from the intensity of muscle contraction? Possible parameters and sources of error].

Electrical nerve stimulation is a useful tool in regional anesthesia; it assists in locating the nerves. This investigation deals with electrical resistances at adhesive electrodes attached to the skin. The influence of external electrical resistance on the stimulating impulse is demonstrated. A new type of nerve stimulator is described; which integrates a measuring device that indicates the electrical impulse actually flowing in the patient. With this device, relationships between stimulating impulse, intensity of muscle contraction, and distance of the puncture cannula from the nerve can be assessed. MATERIALS AND METHODS. The electrical curve I = f (R) was determined using 3 different nerve stimulators (R = 1 - 15k omega). On each of five test persons, five adhesive electrodes were attached to the skin 10 cm apart. The resistance was assessed between these electrodes and a subcutaneously inserted puncture needle. The right and left brachial plexuses of the 5 subjects were punctured, using the axillary approach. A synchronized video camera simultaneously recorded the following values: (1) electrical impulse; (2) corresponding muscle contraction; and (3) the position of the puncture cannula. A scale ranging from 0-5 was applied to define the strength of the muscle contractions. RESULTS. The external resistance as measured under clinical conditions may limit the output impulse of nerve stimulators. In this case, the exerting impulse is lower than that indicated by the appliance. This error can only be identified using an impulse-measuring device. Nerve stimulators not equipped with a measuring device increase the risk of malpuncture, potentially resulting in nerve lesions. Skin resistance at adhesive electrodes varied from patient to patient within a range of 1.1 to 8.2 K omega. Preparing the skin appropriately (wiping with sandpaper) decreased the resistance by only 6% during the first 30 min. Within a distance of 50 cm to the puncture needle, the position of the adhesive electrode did not play a significant role. Axillary puncture of the brachial plexus resulted in the following values: (1) A stimulating impulse (cross-wave) of 1 mA and 1 ms exerted at a distance of 4 mm to the nerve induced a contraction of strength 3. (2) Reducing the impulse at this site by one-half (0.55 mA) resulted in just-visible contractions (strength 1). (3) Advancing the cannula at a stimulating impulse of 0.55 mA inside the neurovascular sheath again produced contractions of strength 3. (4) Performing the puncture with a blunt needle and tracing a distinct resistance, the impulse of 0.6 mA elicited contractions of strength 2. The needle tip was still outside the vascular nerve sheath. If this resistance was overcome and the needle tip lay inside the neurovascular sheath, the impulse could be reduced by one-half (0.32 mA) to produce contractions of strength 2.

Anesthesia, Conduction↗
PubMed1990

[Determining gunshot distance without bullet entry--a new source of error in determining gunshot distance from point of entry].

A court case lead to a quantitative determination of lead and antimony by atomic-absorption at distances 10 to 20 cm from the bullet hole. As a surprising result at first the area-concentrations of lead and antimony increased with rising distance from the muzzle and reached a maximum, after that maximum like expected a decrease was found. The phenomena is of general interest because otherwise misinterpretations in chemical determination of gunshot firing distances would be possible.

Antimony↗
PubMed1990

[Sources of errors and pitfalls in tuberculosis diagnosis].

Three cases of tuberculosis infection are presented (spondylitis, meningitis, pericarditis). Pitfalls and blunders delaying tuberculosis diagnosis are reported. The authors emphasize that: Children at risk have to be vaccinated with BCG (1.1). Health professionals must repeatedly be taught in the interpretation of tuberculin test results and chest X-rays. Tuberculous meningitis may be hidden by the presentation of only encephalitis symptoms and liquor analysis reveals an atypical result (3). Spontaneous resolution of the symptoms or an improvement under non-tuberculostatic therapy does not exclude tuberculosis. In fact encephalitic signs may improve or disappear spontaneously despite subsequent positive liquor culture (4).

Adolescent↗
PubMed1989

Interaction between pyridine nucleotide coenzymes and heme proteins as a possible source of error in assay of activities of coenzyme-linked enzyme.

The ultraviolet absorbance spectra of pyridine nucleotide coenzymes change in the presence of heme-containing proteins. The positions of each of the two main absorbance peaks of NADH are shifted progressively towards shorter wavelengths in the presence of increasing concentrations of hemoglobin, and the third peak, at 220 nm, disappears altogether. Similar changes are seen in the spectra of NAD+ and NADPH, and similar effects on these spectra are produced by myoglobin and cytochrome c, but not by comparable concentrations of albumin. The spectral shifts are generally accompanied by a decreased peak height. This finding may help explain problems reported by previous workers in the measurement of the activity of enzymes such as transketolase or lactate dehydrogenase in erythrocyte hemolysates. Errors may be considerable if allowance is not made for this effect, especially if the concentration of heme protein in the spectrophotometer cuvette much exceeds 1 g/L. The interaction appears to indicate some form of bonding, occurring generally between pyridine nucleotide coenzymes and the heme group in proteins. We relate the findings to measurement of activities of pyridine nucleotide-linked enzymes in erythrocyte lysates and in plasma containing myoglobin after muscle breakdown.

Coenzymes↗
PubMed1989

Pulmonary function testing: sources of error in measurement and interpretation.

Valid pulmonary function data require that attention be paid to issues that can lead to errors in measurement or in interpretation. Routine procedures designed to reduce errors should be established. Among the most important of these are (1) assuring the accurate measurement and calculation of lung function parameters, which requires attention to accuracy when an instrument is brought into service in a laboratory and again when it is updated; (2) selecting reference equations and lower limits of normal appropriate for the patients being studied and for the equipment being used; (3) avoiding the errors introduced by using an excessive number of measurements in generating an interpretation; and (4) avoiding interpretation of results without considering the clinical setting and the pertinent elements of a complete data base.

Equipment Failure↗