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Biomedical subjects

K Lindström

Publications and source records attributed to K Lindström.

At least 163 records · Page 9Linked to original sources
PubMed1978

Aspects of present and future possibilities for intraluminal pressure recordings in the urogenital tract.

In this brief survey some aspects of present and future possibilities for intraluminal pressure recordings in the urogenital tract are considered. It is emphasized that present water-filled catheter-manometer systems are afflicted with several biotechnical disadvantages. Although the micro-transducers and centre-hole catheters seem to be superior to conventional pressure recording systems, they ought to be further improved. Feed-back pressure transducers, electronic compensation, and micro-manometers could be realistic alternatives for pressure recordings in the urogential tract in the future. Some results from pressure recordings obtained with different measuring systems are presented and discussed.

Catheterization↗
PubMed1978

Some methodiological aspects on the measurement of intraluminal pressures in the female urogenital tract in vivo.

This short survey presents some methodological aspects on intraluminal pressure recordings in vivo from the female urogenital tract. The importance of adequate calibration is stressed and a calibration unit for different types of recording equipments is described. Calculations of measuring errors are outlined. The selection of recording catheters is disucssed from both the theoretical and the practical point of view. Finally some practical aspects are considered on pressure recordings in vivo from the ureter, the bladder, the urethra and the uterus. This discussion is illustrated by pressure diagrams obtained with different recording techniques from the actual organs.

Female↗
PubMed1978

Exposure-response relationship between styrene exposure and central nervous functions.

For the study of the relationship between styrene exposure and symptoms and signs of central nervous dysfunctions, 98 male workers occupationally exposed to styrene were given clinical, neurophysiological and psychological examinations; also a symptom survey was made. Urinary mandelic acid concentrations, measured once a week during five consecutive weeks, were used to express the exposure intensity. Different unexposed groups were used for reference. No exposure-response relationship was observed between symptoms of ill health and the urinary mandelic acid concentration, although the exposed group as a whole expressed significantly more symptoms than the reference group. The occurrence of abnormal electroencephalograms was about 10% in the group of workers with mandelic acid concentrations below 700 mg/l, but it was 30% among those whose mandelic acid concentration exceeded 700 mg/l, a level corresponding to the 8-h time-weighted average (TWA) of styrene exposure of about 30 ppm. With regard to psychological functions, the first change in visuomotor accuracy became discernible when the urinary mandelic acid concentration exceeded 800 mg/l. A more pronounced decrement appeared in both visuomotor accuracy and psychomotor performance when the mandelic acid concentration exceeded 1,200 mg/l, which corresponds to an 8-h TWA of styrene exposure of about 55 ppm.

Adolescent↗
PubMed1978

Alcohol consumption and tolerance of workers exposed to styrene in relation to level of exposure and psychological symptoms and signs.

A group of 98 male workers occupationally exposed to styrene was interviewed for information on the amount and frequency of alcohol consumption and changes in consumption frequency and tolerance. Alcohol consumption and changes in consumption were not compared to any reference data, but the changes in tolerance were. The styrene-exposed workers revealed a lowered tolerance somewhat more often than the unexposed group. Neither the duration nor the intensity of styrene exposure was related to any of the alcohol "behavior" variables. The amount of over-time work in exposure had a slight relationship to high alcohol consumption, but the interpretation of this relationship remains undecided. Subjective symptoms, like hand tremor and difficulties in staying asleep, were associated with the alcohol "behavior" variables, but these two symptoms were unrelated to intensity of styrene exposure. Of the psychological functions studied, lowered visuomotor speed showed a slight relationship to high alcohol consumption. Visuomotor inaccuracy, which had proved to be related to a high intensity of styrene exposure, revealed no connection with the alcohol "behavior" variables. It was concluded that alcohol consumption among styrene-exposed workers is not related to the same psychological symptoms and signs as styrene exposure.

Adolescent↗
PubMed1977

Evaluation of catheter-manometer systems for adequate intravascular blood pressure measurements in small animals.

Various catheter-manometer systems possible for intravascular blood pressure measurments on rats have been elaborated and tested in vitro and in vivo. Using a pressure-step calibrator, it was observed from in vitro studies that microtransducers had superior frequency response compared to conventional transducers. Of the catheters tested, Pe-90 tapered to a 40 mm tip with an inner diameter of 0.3 mm had the best frequency response as judged from fall and settling times. Because of the damping effect, tapering increased fall time to 1.8 ms, which was still quite acceptable. By the same token settling time was minimized to 22.4 ms. With a special calculation method the theoretical percentile fault of the recordings was estimated to be 9.66%. When the measurement error was calculated from the actual in vivo recordings, it was found to be no more than 2.7%. These results show that the technique described is adequate for continuous intravascular blood pressure recordings on small animals. Finally it is emphasized that careful handling of the catheters and avoidance of stopcocks and air bubbles are essential for obtaining accurate and reproducible values.

Amplifiers, Electronic↗
PubMed1977

A new technique for simultaneous urethrocystometry including measurements of the urethral pressure profile.

A new standardized technique for continuous recording of the urethral pressure profile simultaneously with intravesical pressure has been developed. The pressure are recorded using two microtransducers enclosed in a thin Dacron catheter. The catheter is moved at a constant speed through the urethra with the aid of a specially designed withdrawal instrument. Using electronic subtraction the closure pressure can easily be measured simultaneously with the intravesical and intraurethral pressure. About 900 investigations have been performed with this technique. It has been testified that very detailed information about normal micturition as well as stress and urgency incontinence can be obtained. The functional as well as the absolute length of the urethra can be estimated within half a millimeter.

Female↗
PubMed1976

Disturbances in psychological functions of workers occupationally exposed to styrene.

The relationship between long-term occupational styrene exposure and disturbances in psychological functions was studied. The exposed group consisted of 98 male workers exposed to styrene in the manufacture of polyester plastic products, and the comparison group comprised 43 concrete reinforcement workers. The duration of exposure in years and the mean mandelic acid concentration in urine (five determinations during 5 weeks before the clinical examination) and the cumulative dose of exposure were used as the indicators of exposure. The psychological functions studied were intelligence, visuomotor speed, visuomotor accuracy, memory, vigilance, and psychomotor performance. Some personality test variables were also included. In a group comparison two variables (visuomotor inaccuracy and poor psychomotor performance) out of 20 showed statistically significant differences and characterized the styrene exposed group. These findings were confirmed when workers with low and high styrene exposure were compared. One variable measuring visuomotor speed and another measuring visual memory were related to the duration of exposure (R = 0.28, p less than 0.05). In a multiple regression analysis disturbances in visuomotor accuracy, poor psychomotor performance, and lowered vigilance proved to have some connection with a high mandelic acid concentration (R = 0.49, p less than 0.01). In addition workers with disturbances in visuomotor accuracy and slight disturbances in virumotor speed had higher mandelic acid concentrations when compared with those workers without any deterioration. The results indicate that disturbances in visuomotor accuracy and, to a lesser degree, in psychomotor performance are the main findings measured by test methods used in this study and related to one indicator of styrene exposure, mandelic acid concentration. The psychological methods used revealed subclinical symptoms related to exposure, and they should aid in making group diagnoses, e.g., when additional information is needed for the determination of the threshold limit value. The deterioration found in visuomotor accuracy could be related to lowered safety in work and traffic.

Adolescent↗
PubMed1976

New ultrasonic device for monitoring foetal breathing movements.

Ultrasonography is the accepted method of choice for registering foetal breathing movements in man. The conventional apparatus hitherto used for this purpose is disadvantageous and could yield misleading artefacts. A new differential echoscope has been designed and developed especially for recording intrauterine foetal movements. It allows a simultaneous registration of movements of two foetal structures: the proximal and distal thoracic wall, or the foetal heart and the thoracic wall. It is equipped with two alternately emitting transducers, each with a repetition frequency of 150 HZ, and an intensity-modulated display of the triggering echoes within the gates. Time-to-volgate converters transform the movements of two gated echoes into electrical signals. An internal differential circuit produces on-line recordings of the true difference between movements of the two selected echoes. This device will appreciably facilitate the selection of proper echoes and reduce signal artefacts during foetal monitoring. Various errors and pitfalls in measuring foetal breathing movements are discussed.

Amplifiers, Electronic↗
PubMed1975

A catheter-manometer calibrator--a new clinical instrument.

Although catheter-manometer systems are widely used in clinical medicine, little effert has been make to evaluate the accuracy of these systems. There is consequently a need for an acceptable method of evaluating the complete pressure recording system under clinical conditions, i.e. a catheter-transducer system that be put together and kept sterilised during the preparation of the patient and applied promptly after static and dynamic calibration of pressure under sterile conditions is described. All kinds of catheters, connectors, transducers, as well as the effect of different fluids or air bubbles on the measuring system, can be investigated. The value of the instrument, especially in clinical practice, is demonstrated and discussed.

Catheterization↗