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Biomedical subjects

D Carlson

Publications and source records attributed to D Carlson.

At least 37 records · Page 2Linked to original sources
PubMed1997

Development of fatigue symptoms during simulated driving.

Why do people sometimes allow themselves to be overcome by fatigue? Ancient human survival may have depended on ignoring fatigue. Its modern occurrence in the absence of strain may further render us insensitive to its warning value. To test whether deliberate monitoring of certain symptoms may help drivers and other workers realize when they need to rest to avoid hazard, the development of fatigue while driving a simulator was objectively measured in terms of how many persons quit driving as a function of time. Some subjects asked to stop after 90 minutes; others lasted 240 minutes. Grouping data from an adapted Pearson [(1957) Journal of Applied Psychology, 44, 186-191] fatigue checklist revealed a curious phenomenon. No matter how long subjects drove before wanting to quit, they still developed much the same subjective level of fatigue at the end. This suggests that people do not differ greatly in how much fatigue they can tolerate but rather how quickly they reach a certain critical level of fatigue. Averaging fatigue scores backwards from the time subjects quit produced a function similar to the quitting function. Similar treatment of the other data revealed certain clusters of symptoms whose development also paralleled the development of fatigue.

Adolescent↗
PubMed1997

Sleep in the laboratory and sleep at home: comparisons of older insomniacs and normal sleepers.

Many laboratory polysomnographic (LPSG) studies have shown only modest sleep differences between insomniacs and matched, noncomplaining normal controls. However, the extent to which LPSG methodology affects the outcome of such comparisons has yet to be tested. In the current investigation, 32 (16 females, 16 males) older (age > or = 60 years) insomniacs and an age-matched and gender-matched sample of 32 noncomplaining normal sleepers underwent three consecutive nights of LPSG monitoring and another three consecutive nights of PSG monitoring in their homes (HPSG). By random assignment, one-half of the subjects in each group underwent LPSG first, whereas the remaining subjects underwent HPSG first. Each PSG recording was blindly scored using conventional scoring criteria, and resulting measures of total sleep period, total sleep time, sleep efficiency percent, stage 1 time, slow-wave sleep time, and rapid eye movement latency were used to compare the two subject groups within each PSG recording site (i.e. lab and home). Statistical analyses showed the normals sleepers and insomniacs evidenced similar pronounced first night effects (FNEs) when undergoing LPSG. However, neither mean values of the selected sleep parameters nor measures reflecting their night-to-night variability differentiated the insomniacs from the normal sleepers when such measures were derived from LPSG. In contrast, FNEs were generally absent for both subject groups when they underwent HPSG. Moreover, the insomniacs displayed significantly greater variability in several of their sleep measures during HPSG than did the normal sleepers. Overall, results suggest FNEs are a concern mainly when using LPSG, and HPSG may be more sensitive than LPSG for documenting sleep differences between normal sleepers and insomniacs. Additional studies are needed to determine if the findings reported herein are similar for young and middle-aged adults.

Aged↗
PubMed1997

Do our methods lead to insomniacs' madness?: Daytime testing after laboratory and home-based polysomnographic studies.

Complaints of daytime dysfunction are common among chronic insomniacs, but laboratory comparisons of insomniacs and age-matched and gender-matched normal controls have generally failed to document these complaints. However, a few studies, which allowed subjects to sleep in their homes on the nights before daytime testing, have shown some relative diurnal deficits among insomniacs. The current study compared the effects of nocturnal laboratory and home polysomnogram (PSG) studies on subsequent daytime test results among older insomniacs and normal sleepers. Insomniacs (n = 32) and normal sleepers (n = 32) were randomly assigned to first undergo three nights of nocturnal PSG monitoring either in the sleep laboratory (16 insomniacs, 16 normal sleepers) or in their homes (16 insomniacs, 16 normal sleepers). Following the third night of PSG monitoring, subjects spent 1 day in the sleep laboratory, where they completed a four-trial multiple sleep latency test along with four trials of a computer-administered performance test battery. Results showed that insomniacs, as a group, were slightly, albeit consistently, sleepier than were normal sleepers following nights of home sleep monitoring, but a reverse of this trend was found among subjects who underwent nocturnal laboratory PSG before daytime testing. Furthermore, normal sleepers showed faster reaction times on a signal detection task than did insomniacs within the subgroup who underwent home PSGs prior to such testing. However, within the subgroup that underwent nocturnal laboratory PSGs, insomniacs' signal detection reaction times were significantly faster than those shown by normal sleepers. Results provide some support for the speculation that the nocturnal PSG monitoring site, used as a precursor to daytime testing, may systematically affect daytime comparisons between insomniacs and matched controls. Moreover, these results suggest that the use of home-based nocturnal PSG monitoring prior to daytime testing may provide an enhanced understanding of insomniacs' diurnal complaints.

Aged↗
PubMed1996

IS outlook '96: predictions & predilections. Roundtable discussion.

Musings from some of the leading national and international HIT organizations make it clear that the need for a computer-based patient record is approaching the critical point. Half of our respondents identified the CPR as the single most important technology in 1996. One of our participants goes so far as to say that the era prior to the electronic medical record will one day be remembered as the "paper age." Progress in the development of standards--crucial to the CPR--could be dramatic this year, say experts from two of the major standards organizations. For a look at these issues and others, including key government policies to watch this year, read on.

Computer Communication Networks↗
PubMed1996

Standardization of clinical decision making for the conduct of credible clinical research in complicated medical environments.

The likelihood that past experience will produce correct guides to current practice depends on the signal-to-noise ratio for the clinical problem of interest. If the signal-to-noise ratio is high, the decision will be sound and patient benefit likely to occur. If the signal-to-noise ratio is low, as is commonly the case with difficult clinical decisions, then personal experience and the best intentions will not assure sound clinical decisions. When the probability of benefit cannot be quantified, clinicians in complex settings are in danger of being misled by data and experience. Quantifiable probabilities established by group experiment or observation will be necessary for clinical decisions that can be expected to confer benefit on the patient. Explicit methods are necessary for interventions that can be replicated in experiments or in practice. Computerized protocols force the articulation of explicit clinical care methods and standardize clinical decision making. We have developed explicit, rule-based protocols, implemented them in our hospital, exported them to other hospitals, and successfully achieved a rigorous experimental environment in the clinical ICU. Exportation of such explicit methods may narrow the gap between efficacy (university hospital) and effectiveness (community hospital) research results.

Clinical Trials as Topic↗
PubMed1995

Verification & validation algorithms for data used in critical care decision support systems.

A decision support system is only as good as the data generating that decision support system. If the data is incorrect, doesn't relate to the other pieces of data, is missing or is not consistent, the decision support system conclusions may be incorrect and inconsistent. While collecting data from several sites during a multicenter randomized clinical trial, we found that some critical data elements were missing, out of correct ranges, totally illogical, and/or inconsistently recorded. In order to get consistent, correct, and dependable information from a our decision support system, the data elements used in that system had to be checked for completeness, valid values, consistent units of measurement, and relationships to other items. Development of data quality assurance rules and the application of those rules is imperative to using the data to generate daily scores for multiple organ failure, sepsis, and barotrauma.

Algorithms↗
PubMed1995

Medical informatics academia and industry: a symbiotic relationship that may assure survival of both through health care reform.

There are often clear lines drawn identifying the demilitarized zone between medical informatics academics and industry. Academics were "pure" intellectuals sequestered in ivory towers that effectively shielded them from the realities of the world. Industry has historically focused on creating effective products that produce financial return to the corporation. Both the paradigms of academia and industry are quickly becoming dinosaurs in the era of health care reform where both medical informatics academia and industry are under increasing pressure to develop and prove that medical informatics has a positive impact on health care both in terms of the quality of care as well as cost. Unfortunately, neither academia or industry alone are going to be able to successfully complete this task. The purpose of this paper is to describe such a collaborative effort that has produced a computerized decision support system for the management of mechanical ventilation in patients with the Adult Respiratory Distress Syndrome (ARDS) that is now installed and supported on three different commercial CIS platforms. This collaborative effort has allowed us to successfully mount a large multi-center clinical trial designed to determine efficacy.

Clinical Protocols↗
PubMed1994

A randomized community trial of prepackaged and homemade oral rehydration therapies.

OBJECTIVE: To compare the effectiveness of prepackaged oral rehydration solutions with homemade cereal-based oral rehydration therapy in the treatment of acute childhood diarrhea in children younger than 5 years. BACKGROUND: In Ethiopia, approximately 40% of all mortality in children younger than 5 years, or over 200,000 annual deaths, is attributable to acute childhood diarrhea. Less than 15% of the episodes of acute childhood diarrhea are treated with oral rehydration solutions. SUBJECTS: Two hundred ninety-one children younger than 5 years with acute childhood diarrhea. METHODS: A randomized field trial comparing the effectiveness of an entirely homemade cereal-based oral rehydration therapy (HC-ORT, n = 103) with two alternative prepackaged salt solutions, a glucose-based oral rehydration solution (G-ORS, n = 98) and a cereal-based oral rehydration solution (C-ORS, n = 90), in the treatment of mild to moderate acute childhood diarrhea in children younger than 5 years. RESULTS: Subjects in the HC-ORT group demonstrated equivalent or better weight gain than those in the C-ORS or G-ORS groups at 24, 48, 72, and 96 hours following the onset of treatment. The beneficial weight-gain effect of HC-ORT was most pronounced in infants younger than 12 months, following adjustment for demographic and baseline clinical characteristics. Compliance with ORT use through 96 hours was significantly better among caretakers of children receiving HC-ORT. Minor errors in the preparation of these oral rehydration regimens occurred more frequently among caretakers preparing either of the cereal-based ones. CONCLUSIONS: That HC-ORT is an effective, culturally more acceptable alternative to G-ORS or C-ORS. The implementation of well-monitored, community-based HC-ORT programs in less developed countries is recommended.

Acute Disease↗
PubMed1994

Prenatal diagnosis and dysmorphic findings in mosaic trisomy 16.

We report two cases of mosaic trisomy 16 diagnosed by amniocentesis, with dysmorphic findings in both cases evident upon delivery. Following elective termination, case 1 demonstrated a trisomy 16 cell line in fetal skin (4 per cent) and placental tissue (64 per cent). Molecular studies on the disomic cell line indicated that both chromosome 16s were maternal in origin, suggesting loss of the paternal chromosome 16 from a trisomic zygote (uniparental heterodisomy). At birth, case 2 demonstrated only disomic cells in skin and blood, with trisomy 16 present in 4 per cent of cells from the amnion. Molecular studies confirmed both maternal and paternal contributions of the chromosome 16s. We analysed DNA from one previously reported case of mosaic trisomy 16 (Williams et al., 1992) and failed to find signs of uniparental disomy in this child with congenital heart defects. These cases had distinctive but different dysmorphic features. We suggest that trisomy 16 embryos may revert to disomy during the course of pregnancy, allowing for longer survival with various abnormalities in growth and morphogenesis. The clinical significance of prenatally detected mosaic trisomy 16 may not be completely defined by additional cytogenetic, molecular, and ultrasound studies.

Adult↗
PubMed1993

Lower electrical membrane potential and altered pHi homeostasis in multidrug-resistant (MDR) cells: further characterization of a series of MDR cell lines expressing different levels of P-glycoprotein.

Recently [Roepe, P.D. (1992) Biochemistry 31, 12555-12564], increased steady-state levels of chemotherapeutic drug efflux from multidrug-resistant (MDR) myeloma cells were correlated with intracellular alkalinization. To better understand elevated pHi in MDR cells, Na(+)- and Cl-dependent recovery of pHi upon intracellular acid or alkaline shock has been examined for this same series of MDR cell lines. In agreement with another recent report [Boscoboinik, D., Gupta, R.S., & Epand, R.M. (1990) Br. J. Cancer 61, 568-572], we find that the rate of Na(+)-induced alkalinization after an intracellular acid shock is increased in the MDR cells, relative to the drug-sensitive parent. Interestingly, we also now find that mRNA encoding the human Na+/H+ exchanger (NHE) is overexpressed in these MDR cells, but the level of overexpression does not correlate with the relative drug resistance or steady-state pHi. It is also found that the efficiency of Cl(-)dependent reacidification of pHi, after an intracellular alkaline shock is reduced in the MDR cells. This effect appears to correlate with the relative expression of MDR protein, but not the relative expression of Cl-/HCO3- exchanger (AE), which we now find is also altered in the series of cells. Since elevated pHi will increase delta pH across the plasma membrane, we have also measured the electrical potential for these cells using three different methods. Most interestingly, the magnitude of the plasma membrane electrical potential (delta psi) decreases concomitant with increased expression of the MDR protein. Energy provided by increased delta pH compensates for the lowered delta psi, such that the total electrochemical membrane potential (delta mu H+) remains similar among the cells in this series (delta mu H+ = delta psi - Z delta pH). These data, along with other recent experiments that associated an increased Cl- conductance with the expression of MDR protein [Valverde, M., Diaz, M., Sepúlveda, F.V., Gill, D.R., Hyde, S.C., & Higgins, C.F. (1992) Nature 355, 830-833], are consistent with a model for MDR protein-mediated multidrug resistance that does not entail direct active transport of lipophilic drugs by the MDR protein.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1993

Fetal akinesia/hypokinesia sequence: prenatal diagnosis and intra-familial variability.

Intrauterine fetal movement plays a key role in normal embryonic and fetal development (Moessinger, 1983). When movement is absent or decreased, abnormal development takes place which can be appreciated in newborns and/or fetuses with the fetal akinesia/hypokinesia sequence. This sequence is caused by a number of heterogeneous entities which result in decreased fetal movements by the action of intrinsic or extrinsic factors. Prenatal diagnosis of the akinesia/hypokinesia sequence may be possible during the second trimester through the use of real-time ultrasonographic evaluation of fetal movement. We report a family with three consecutive affected pregnancies in which the prenatal presentation of this sequence varied. Based on the phenotypic findings of the three affected fetuses, we believe that although they superficially resemble those features found in the New-Laxova syndrome, they are probably affected with a distinctly different lethal form of akinesia/hypokinesia transmitted in an autosomal recessive fashion.

Abnormalities, Multiple↗
PubMed1993

Cook obstetrics and gynecology catheter multicenter chorionic villus sampling trial: comparison of birth defects with expected rates.

OBJECTIVE: The null hypothesis was that offspring of women undergoing first-trimester chorionic villus sampling do not experience a rate of birth defects exceeding background rates. STUDY DESIGN: Follow-up information regarding major malformations was prospectively sought on offspring of 4105 women undergoing first-trimester chorionic villus sampling from nine centers participating in a collaborative study with the Cook obstetrics and gynecology catheter. These data were compared with data from the Collaborative Perinatal Project and other registries. RESULTS: A total of 84 offspring with major malformations was identified (2.36%). Compared with background rates, there was no increase in the incidence of total malformations or specific malformations (including limb reduction defects) in the subjects. One institution experienced all three limb reduction defects in this series; the probability of this occurring by chance alone is < 1%. CONCLUSION: Chorionic villus sampling was not found to result in an increase in major birth defects or in specific categories of birth defects in this series.

Catheterization↗
PubMed1993

A community-based randomized trial of home-made oral rehydration therapies.

A field trial of the relative efficacy of three oral rehydration therapies (ORT) in the treatment of acute childhood diarrhoea in children < 5 years old was carried out in a rural Ethiopian district. The three ORT were 1) pre-packaged glucose and salt solution (GORS; n = 153), 2) home-made cereal added to pre-packaged salt solution (CBORS; n = 154), and 3) entirely home-made cereal-based and salt therapy (CBORT; n = 156). Out of 127 eligible peasant associations, 18 were randomly selected, and groups of six were then randomly assigned to receive one of the three treatment options. In infants aged 0-12 months, after adjusting for baseline weight and diarrhoea frequency, CBORT was found to be superior (P < 0.01) to GORS and CBORS in terms of weight gain at 24, 48, and 96 hours. There were no significant between-group differences in weight gain in children > 12 months old. Over the 96-hour duration of follow-up, mothers' compliance was significantly better among those giving CBORT when compared to CBORS (P < 0.001) or GORS (P < 0.013). The results of this field trial indicate that CBORT is an efficacious alternative to GORS or CBORS in the treatment of acute childhood diarrhoea in rural community settings. Larger scale, effectiveness studies are recommended.

Child, Preschool↗
PubMed1990

The Caltrac accelerometer as a physical activity monitor for school-age children.

The performance of the Caltrac accelerometer was studied in elementary school-age children under field and laboratory conditions. In Study 1, 35 children (20 boys, 15 girls, mean age = 10.8 yr) wore the accelerometer and a heart rate (HR) monitor for 2 d. Caltrac activity counts per hour were compared to the mean "activity HR", which was calculated by subtracting the mean of the five lowest HRs of the day from each recorded HR. Pearson r's between accelerometer and activity HR were 0.54 (P less than 0.001) on day 1 and 0.42 (P less than 0.02) on day 2. Inter-instrument reliability in the field was r = 0.96. Both accelerometer and HR data were significantly correlated with physical activity recalls of the same day. In Study 2, 15 children walked/ran for 10 min at 3, 4, and 5 mph on a horizontal treadmill while wearing two accelerometers. Oxygen uptake was directly measured each minute. Reliability of the Caltracs in the laboratory was 0.89. Activity count correlated r = 0.82 (SEE = 23%) with net calorie cost per kg of body weight. Net caloric expenditure per kg of weight was 0.101 kcal.kg-1.d-1 per Caltrac activity count. These data support the use of the Caltrac accelerometer as a physical activity measure for school-age children, and the objective data tended to corroborate the children's short-term activity recalls.

Adolescent↗
PubMed1990

Guidelines for implementing HL7.

There is no magic HL7 software that connects and transfers data between hospital systems. Successful implementation of an HL7 interface depends not only on the software, but, more importantly, it demands close communication between the System Integrator and the vendors, and careful management of the interface process.

Database Management Systems↗
PubMed1989

Data acquisition and processing system for drug release characterization by thin layer chromatography.

Samples of an antibiotic released from an ocular insert in an in vitro test are characterized by thin layer chromatography (TLC). Conventional characterization methods include cutting and weighing strip chart paper peak profiles obtained with a scanning densitometer for spotted TLC plates, and relating peaks for unknowns to peaks for standards on the basis of relative weights. A data collection and processing system is described in which the data collection and processing is highly automated utilizing a specially developed software program. A Kontes densitometer (Model 800) and a personal computer (IBM PC-AT or Zenith-248) are interfaced using a Keithley 570 data acquisition system. Two BASIC software programs were developed to provide quantitative evaluation of chromatograms of an antibiotic (tylosin tartrate); the first program generates chromatograms on the computer screen through initiating controlled operation of a scanning densitometer for TLC plate analysis, and the second program processes the data providing quantitative analysis of the spectral output through a peak detection and peak integration routine. The approach represents a new general, versatile, quick and effective method to characterize TLC samples for various numbers of peaks for unknowns and standards for different concentration levels.

Chromatography, Thin Layer↗