Biomedical subjects

H Krueger

Publications and source records attributed to H Krueger.

At least 19 recordsLinked to original sources

PubMed2001

Contraception. Myths, facts and methods.

OBJECTIVES: After reading this article, the reader should be able to: 1. Recognize the mechanism of action, side effects, contraindications, precautions and instructions for use of a variety of contraceptive methods. 2. Understand the advantages and disadvantages of the various contraceptive methods. 3. List the common myths and misconceptions about conception and contraception, and recognize how they can influence contraceptive decisions. Unintended pregnancy is a serious problem in the United States. Counseling a patient about conception and contraception involves more than simply imparting information and answering questions. Clinicians should actively detect and correct any myths and misapprehensions on the patient's part. These myths are quite common and can interfere with treatment if not attended to. This article summarizes common myths about pregnancy and contraception and reviews the key facts about both.

Contraception↗

PubMed2000

Hospital downsizing and trends in health care use among elderly people in British Columbia.

BACKGROUND: There has been considerable downsizing of acute care services in British Columbia over the past 2 decades. In this population-based study we examined changes in the proportion of elderly people who used acute care, long-term care and home care services between 1986-1988 and 1993-1995 to explore whether the downsizing has influenced use. Changes in death rates were also examined. METHODS: The British Columbia Linked Health Database was used to select all British Columbia residents aged 65 years, 75-76 years, 85-87 years or 90-93 years as of Jan. 1, 1986 (cohort 1), and Jan. 1, 1993 (cohort 2). Each person was assigned to 1 of 6 mutually exclusive categories of health care use reflecting different intensities of use (i.e., hospital, long-term or home care). The proportions of people within each category were compared between the 2 periods, as were the age-standardized death rates. RESULTS: There were 79,175 people in cohort 1 and 92,320 in cohort 2. Overall, the relative proportion of people in each use category was similar between the 2 study periods. The most substantial changes were an increase of 2 percentage points in the proportion of people who received no facility or home care services and a decrease of 2 to 3 percentage points in the proportion who received some acute care but no facility-based continuing care. The age-adjusted all-cause death rates for the earlier and later cohorts were virtually identical (15.7% and 15.8% respectively), although the rate increased from 63.6% to 70.1% among those in the "full-time facility with acute care" group. INTERPRETATION: Overall changes in health care use were small, which suggests that the repercussions of the decline in acute care services for elderly people have been minimal. The higher age-adjusted death rates in the later cohort in full-time care suggests that long-term stays are becoming reserved for a sicker group of elderly people than in the past.

Aged↗

PubMed2000

Lipopolysaccharide-induced nasal cytokine response: a dose-response evaluation.

Information on the dose-response relationship is a prerequisite to defining the non-response threshold of exposure. We investigated whether nasal lipopolysaccharide (LPS) challenges induce an inflammatory response in a dose-dependent way. In three settings nasal lavage was performed before, and 20 min, 1, 6, 23, and 29 h after instillation of 0 microg, 10 microg, and 40 microg LPS for 10 s, in seven healthy subjects. Lavage fluids were analysed for concentrations of interleukin-6 (IL-6), IL-8, tumour necrosis factor-alpha (TNF-alpha), histamine, and albumin. Symptoms were recorded by questionnaire and spirometric lung function was assessed after each lavage. The instillation of 40 microg LPS caused a small increase in nasal symptoms. TNF-alpha was below the detection limit (0.5 pg/ml) in most subjects and, like IL-8 and albumin, showed no relation to the LPS challenge. IL-6 increased over twofold with 10 microg LPS and over 13-fold with 40 microg LPS, with a peak at 6 h after LPS provocation, and the repeated design ANOVA was significant for dose and for time. Six hours after the 40 microg LPS challenge the histamine level significantly increased compared to the saline treatment. We conclude that short-lasting instillation of LPS causes a dose-dependent IL-6 release in the upper airways and minor nasal symptoms.

Administration, Inhalation↗

PubMed2000

Experimental exposure to methylformate and its neurobehavioral effects.

OBJECTIVES: The aim of the study was to investigate the acute effects of experimental methylformate exposure on the nervous system. METHODS: In an exposure chamber, 20 subjects were exposed to methylformate at 100 ppm [Swiss maximum allowable concentration (MAC)] for 8 h. The same number of subjects with the same ages (between 20 and 30 years), gender and education level (university) were examined by the same procedure as a control group. The subjects did not know if they were exposed or not. Three times (morning, noon, evening) during these 8 h, mood [Profile of Mood States (POMS)], neurobehavioral performance (reaction, Stroop, nonverbal learning, determination, tracking; Wiener Test System), vision (visual acuity, contrast sensitivity, color sensitivity) and postural sway were tested. During an undemanding test (POMS) and a demanding performance task (determination test), pulse, electromyography (EMG) of the forehead and of the neck were recorded. In the morning and evening spirometry [forced vital capacity (FVC), forced one-second expiration volume (FEV), medium expiration flow (MEF) and peak expiration flow (PEF)] and the odor perception threshold were measured. RESULTS: In the evening, in the exposed group, fatigue was significantly increased and the EMG of the forehead during a demanding task showed a different development during exposure. The other tests showed no significant solvent effect, but 16 of 43 test parameters showed a significant effect of time. CONCLUSIONS: The results of this study indicate a possible effect of methylformate exposure on the subjective feeling of fatigue after 8 h exposure at 100 ppm in young and healthy subjects, without measurable impairment of neurobehavioral performance. We assume that a similar effect in normal work, combined with a heavy workload and shift work, can lead to an impairment of productivity, and increase the risk of accidents.

Adult↗

PubMed2000

Isopropanol and methylformate exposure in a foundry: exposure data and neurobehavioural measurements.

OBJECTIVES: The aim of this study was to determine the dose-effect relationship between solvent exposure and acute neurobehavioural effects at the worksite. METHODS: In a balanced design, ten workers in a Swiss foundry were monitored for 15 days at ten different times during work. Urine samples were taken in the morning and at the time of examination, and personal exposure to isopropanol and methylformate was measured with active samplers. Neurobehavioural tests such as postural balance (bipedal, bipedal blind, monopedal), simple reaction time and digit span of the Neurobehavioural Evaluation System (NES2) and a combined memory and reaction-time test, the combi-test, were performed. A rating of well-being, and the last consumption of alcohol, caffeine, nicotine and medication were reported. RESULTS: Average environmental concentrations of isopropanol were at 44 ppm ( +/- 16 ppm), and at 36 ppm (+/-21 ppm) for methylformate. Maximum values of personal exposure to isopropanol reached barely the maximal allowable concentration (MAC) value (400 ppm); the methylformate personal exposure of three workers exceeded the MAC value (100 ppm). Urine concentrations of methanol were high (3.1 +/- 2.3 mg/l in the morning, 7.8 +/- 4.9 mg/l after exposure) compared with the results of other studies; concentrations of isopropanol were rather low (0.88 +/- 0.73 mg/l after exposure). CONCLUSIONS: Nevertheless, between personal exposure and biomonitoring, linear correlation was found. Methylformate exposure correlated with methanol and formic acid concentration in the urine, and isopropanol exposure with its concentration in the urine. With the neurobehavioural tests used, no solvent effect in relation to the dose could be determined.

2-Propanol↗

PubMed2000

Neurobehavioural effects of experimental isopropanol exposure.

OBJECTIVES: The study investigated the acute effects of isopropanol exposure at the maximum allowable concentration (MAC) level on the performance of neurobehavioural functions. METHODS: In an exposure chamber 20 healthy subjects aged between 21 and 30 years were exposed to isopropanol at a concentration of 400 ppm (Swiss MAC value) for 8 h. A control group of another 20 subjects of the same age range, gender and education as used in a previous study with methylformate were subjected to the same test procedures without exposure. Mood was measured with the profile of mood states (POMS) in the morning, at noon and in the evening. Neurobehavioural performance tests were administered using the Wiener Test System (Wiener reaction test, Stroop, nonverbal learning, Wiener determination test, "Konturtracking" test), and the digit span test of the Neurobehavioural evaluation system (NES2). A test for postural sway was also conducted. During the POMS and the Wiener determination test the electromyography of the forehead and the left neck muscle as well as the pulse were registered. In the morning and evening spirometry (FVC, FEV, MEF and PEF) and odour threshold were measured. RESULTS: Only postural sway in bipedal standing at noon showed stronger deterioration in the exposed than in the control group when compared with the morning values. The evening values of monopedal standing were also more impaired in the exposed than the control group. In the other tests, no solvent effect could be established. CONCLUSIONS: It can be assumed, that, similar to other alcohols, isopropanol affects postural balance. Our results point to such a disturbance, but because it is the only study so far using the MAC value, any conclusions about safety risks would be premature.

2-Propanol↗

PubMed2000

Motor-unit activity in the trapezius muscle during rest, while inputting data, and during fast finger tapping.

The Cinderella hypothesis postulates the continuous activity of specific motor units during low-level muscle contraction and contradicts the concept of motor-unit substitution. Constant trapezius muscle activity has been reported in typical visual-display-unit-related tasks. If it can be shown that constant muscle activity can be caused by the continuous firing of single motor units, this could explain the frequent complaints of muscular neck pain reported by computer users. The present study was undertaken to investigate motor-unit activity in the trapezius muscle during resting with closed eyes, while inputting three-digit numbers with auditory presentation at a rate of 0.5 Hz, and while tapping on a key with the right index finger at a rate of 5 Hz. Electrodes with four fine wires were inserted into the right upper trapezius muscle of six healthy subjects, and three-channel intramuscular electromyography was recorded. The decomposition programme MAPQuest, developed to analyse short-term one-channel signals, was complemented with MAPView, a programme that merges the short-term results of 10 s to a 3-min analysis. The results showed that activity in the trapezius muscle was induced in one subject while resting, in two subjects while inputting data, and in five subjects while finger tapping. Long-lasting single motor-unit firing was observed in two subjects while inputting data and in one subject while finger tapping. Whilst our findings may support the Cinderella hypothesis, the measurement periods are too short to confirm it fully, and for further discussion it is necessary to record and analyse for longer periods.

Adult↗

PubMed2000

Co-activity of the trapezius and upper arm muscles with finger tapping at different rates and trunk postures.

In the context of finding a model that describes the pathophysiological mechanisms leading to muscle pain at low-intensity repetitive work, in this study we investigated whether a simplified finger motor task that requires little mental demand can cause increased muscle activity in the upper arms and neck, and examined the impact of the variation of two parameters, finger tapping rate and body posture. Using the 5th and 95th percentiles from the surface electromyogram of six muscles of the fingers, upper arm and neck, we determined the static and dynamic components of the muscle activity. Correlation methods were used to find a component in the muscle activity that originated from the rhythm of the finger tapping. Further investigations included tapping steadiness and finger force. It was found that in many, but not all subjects, low or even high activity was constantly present in the upper arm and trapezius muscles, sometimes even during relaxation. Fast tapping and a forward-leaning body posture caused considerable increases, while a slightly reclined posture helped to reduce co-activity. However, motor control patterns varied strongly between individuals. Since certain subjects showed no co-activity at all we can assume that trapezius and upper-arm activation is not necessarily required for the completion of a task similar to ours. This may explain why some VDU users develop work-related musculoskeletal disorders while others remain healthy.

Adult↗

PubMed1999

A tutorial on creating logfiles for event-driven applications.

This paper describes the practical steps necessary to write logfiles for recording user actions in event-driven applications. Data logging has long been used as a reliable method to record all user actions, whether assessing new software or running a behavioral experiment. With the widespread introduction of event-driven software, the logfile must enable accurate recording of all the user's actions, whether with the keyboard or another input device. Logging is only an effective tool when it can accurately and consistently record all actions in a format that aids the extraction of useful information from the mass of data collected. Logfiles are often presented as one of many methods that could be used, and here a technique is proposed for the construction of logfiles for the quantitative assessment of software from the user's point of view.

Computers↗

PubMed1998

[Effects of presbyopia on clinical phoria].

BACKGROUND: Due to accommodation-vergence cross-link we can expect that presbyopia will affect vergence as well. From investigations of cross-link as function of age one may assess strain of visual system due to presbyopia. Furthermore, this observation will give hints on innervation of ciliary muscle. MATERIAL AND METHOD: Vergence is assessed as function of stimulus of accommodation in 27 subjects (24-65 years). RESULTS: Presbyops tend to be exophoric for near vision. Vergence is linked to accommodation by means of a quadratic polynome rather than by a linear function. CONCLUSIONS: We may expect, that missing vergence strains visual system of presbyops. Results support Hess-Gullstrand theory of presbyopia and indicate a loss of innervation of ciliary muscle with increasing age.

Accommodation, Ocular↗

PubMed1998

What makes an automated teller machine usable by blind users?

Fifteen blind and sighted subjects, who featured as a control group for acceptance, were asked for their requirements for automated teller machines (ATMs). Both groups also tested the usability of a partially operational ATM mock-up. This machine was based on an existing cash dispenser, providing natural speech output, different function menus and different key arrangements. Performance and subjective evaluation data of blind and sighted subjects were collected. All blind subjects were able to operate the ATM successfully. The implemented speech output was the main usability factor for them. The different interface designs did not significantly affect performance and subjective evaluation. Nevertheless, design recommendations can be derived from the requirement assessment. The sighted subjects were rather open for design modifications, especially the implementation of speech output. However, there was also a mismatch of the requirements of the two subject groups, mainly concerning the key arrangement.

Adult↗

PubMed1997

[Microfluctuations in accommodation].

BACKGROUND: So called microfluctuations of the power of crystalline lens are uncontested in scientific community. However, there are still open questions about possible artefacts which deserve discussion. PURPOSE: This contribution is intended to reopen discussion of matters concerning fundamentals about microfluctuations of the crystalline lens. METHOD AND RESULTS: Thoughts are outlined which render characteristics or even existence of microfluctuations questionable. CONCLUSION: There is still a need for a conclusive experiment to determine existence and role of microfluctuations.

Accommodation, Ocular↗

PubMed1996

A study of the quality of life and cost-utility of renal transplantation.

The objective of this study was to assess the cost-utility of renal transplantation compared with dialysis. To accomplish this, a prospective cohort of pre-transplant patients were followed for up to two years after renal transplantation at three University-based Canadian hospitals. A total of 168 patients were followed for an average of 19.5 months after transplantation. Health-related quality of life was assessed using a hemodialysis questionnaire, a transplant questionnaire, the Sickness Impact Profile, and the Time Trade-Off Technique. Fully allocated costs were determined by prospectively recording resource use in all patients. A societal perspective was taken. By six months after transplantation, the mean health-related quality of life scores of almost all measures had improved compared to pre-transplantation, and they stayed improved throughout the two years of follow up. The mean time trade-off score was 0.57 pre-transplant and 0.70 two years after transplantation. The proportion of individuals employed increased from 30% before transplantation to 45% two years after transplantation. Employment prior to transplantation [relative risk (RR) = 23], graft function (RR 10) and age (RR 1.6 for every decrease in age by one decade), independently predicted employment status after transplantation. The cost of pre-transplant care ($66,782 Can 1994) and the cost of the first year after transplantation ($66,290) were similar. Transplantation was considerably less expensive during the second year after transplantation ($27,875). Over the two years, transplantation was both more effective and less costly than dialysis. This was true for all subgroups of patients examined, including patients older than 60 and diabetics. We conclude that renal transplantation was more effective and less costly than dialysis in all subgroups of patients examined.

Adult↗

PubMed1996

[The suitability of various cephalometric planes for the determination of vertical alignment of the head].

Different cephalometric lines or planes may be used to determine vertical head tilt. 94 subjects were used to assess the difference in inclination between the Frankfurt horizontal and Reid's line by means of a photographic method. We found that the inclination of Reid's line differs about 13 degrees from the inclination of the Frankfurt horizontal and depends on the subject's sex but not on their age. Hand held inclinometer are used in most studies for determining the inclination of the head. In our study different experimenters assessed the above mentioned inclinations at our 94 subject's using a hand held inclinometer. It turned out that the results depend statistically significant on the experimenter. Data were compared to the ones assessed using the photographic method. By means of an analysis of variance in which the experimenter is considered, a significant correlation (p < 0.001) between data assessed with the two different methods was found. However, only 51% of the variance can be explained by our model. Variance might be due to inaccuracy in determining some of the points defining the Frankfurt horizontal and Reid's line, i.e. the lower orbit and the centre of the outer ear channel. The inclination of another reference line running from the tragion to the outer canthus was measured using the same subjects and the same experimental procedure as mentioned above. This line is easier to determine than the Frankfurt horizontal or Reid's line as its defining points can be assessed with greater accuracy. The inclination of this differs 10.5 degrees from the one of the Frankfurt horizontal.

Analysis of Variance↗

PubMed1994

Direction of gaze and comfort: discovering the relation for the ergonomic optimization of visual tasks.

Perceived exertion caused by the extraocular muscles was assessed as a function of the direction of gaze and recorded in 114 subjects using a psychometric method. The results confirm statements in the literature that maximum comfort is achieved when gaze is aimed downwards. We found no correlations between perceived exertion and age or viewing distance. The relationship is relevant to ergonomics, for example in lens fitting and workplace layout.

Adult↗

PubMed1993

The cost impact of cytomegalovirus disease in renal transplant recipients.

A retrospective case controlled study was performed to determine the cost impact of cytomegalovirus disease in the first year following renal transplantation as a basis for the analysis of cost effectiveness of prophylactic and therapeutic regimens directed at CMV infection. Eleven sequential cases of organ-specific CMV disease were matched with 22 controls for age, diabetic status, and donor/recipient CMV serologic status from 119 consecutive first cadaveric renal transplant recipients performed at a single university-affiliated, solid organ transplant unit between January 1, 1988 and March 31, 1990. The groups were comparable for sex, HLA match and mismatch, incidence of initial graft dysfunction, and immunosuppression. Hospitalization data, resource utilization, and costs for all 33 subjects were obtained for a one-year period after transplantation. The mean initial hospitalization time was comparable for both CMV cases and controls (14.5 vs. 15.0 days, P = NS), but patients developing CMV disease averaged 59 hospital days during the first year posttransplant versus 22 days in the control group (P = 0.001). A mean of 31 days hospitalization was directly related to CMV disease. Mean total institutional costs, calculated in 1988 Canadian dollars, were 2.5 times higher for patients with CMV disease than for controls ($42,611 vs. $17,309, P = 0.001), reflecting predominantly a difference in general ward ($19,988 vs. $7484, P = 0.001), hotel ($2508 vs. $927, P = 0.001), clinical laboratory ($5420 vs. $2558, P = 0.0001), radiology ($1581 vs. $640, P = 0.05), and pharmacy ($4916 vs. $1782, P = 0.01) costs and utilization. Operating room, special ward, ancillary, and mean per diem costs ($719 vs. $790, P = NS) were not significantly different between the two groups. Functional graft survival at 1 year was 72% in patients with CMV disease compared with 86% in controls, reducing the mean calculated cost-effectiveness of transplantation by 2.9-fold. These data show that CMV disease has significant economic impact on renal transplantation as a result of extended hospitalization. In order to develop a cost effective management approach to CMV infection, this impact must be considered when assessing therapeutic and prophylactic regimens and protocols of organ allocation.

Case-Control Studies↗

PubMed1993

Effects of a bronchoprovocation challenge test with cigarette sidestream smoke on sensitive and healthy adults.

In order to study the acute effects of environmental tobacco smoke on lung function, a cigarette sidestream smoke provocation test (analogous to a nonspecific bronchial provocation test) was performed. Ten persons with airways hyperreactive to methacholine and ten normoreactive persons were tested. A dose-response relationship was found for symptoms. The lung function of the normoreactive persons was not altered by short-time inhalation of sidestream smoke. The hyperreactive subjects, however, experienced significant decreases in FEV1, FVC, and MEF50. The decrease was most pronounced after the lowest dose of 2 ppm smoke-induced CO, leading to a mean fall of 6.3 percent in FEV1. Five of ten subjects with hyperreactive airways showed a decrease in FEV1 of more than 10 percent during the sidestream smoke provocation, one of them a decrease of over 20 percent after inhalation of 16 ppm CO sidestream smoke. We conclude that even short exposure to low concentrations of cigarette sidestream smoke causes significant impairment of lung function in sensitive persons.

Adult↗

PubMed1992

Coronary artery bypass grafting: how much does it cost?

OBJECTIVE: To calculate the cost of coronary artery bypass grafting (CABG) and to compare it with the costs determined in two previous Canadian studies. DESIGN: Retrospective cost-analysis study. SETTING: A tertiary care referral hospital. PATIENTS: Fifty patients who had undergone successful triple and quadruple CABG between Jan. 3 and 30, 1989. MAIN RESULTS: The cost of CABG per patient varied from $10,982 to $33,676 (mean $14,328) (in 1988 Canadian dollars). The cost tended to increase with age and number of vessels grafted. Compared with the patients in the two previous Canadian studies our patients were older, had more vessels grafted and cost more to treat, even after the total hospital costs were adjusted for inflation. CONCLUSIONS: The population undergoing CABG is changing: it is older and has more diseased vessels. These changes have had a significant impact on the cost of CABG. Further study is required to determine the outcome and benefit of CABG in this group of patients.

Age Factors↗