Biomedical subjects

L McKenzie

Publications and source records attributed to L McKenzie.

At least 19 recordsLinked to original sources

PubMed2001

Development of perfluorocarbon (PFC) primary standards for monitoring of emissions from aluminum production.

An EPA Voluntary Aluminum Industrial Partnership (VAIP) program has been formed to help US primary producers focus on reducing the emissions of two perfluorocarbons (PFCs), tetrafluoromethane (CF4) and hexafluoroethane (C2F6), during the production of aluminum. To ensure comparability of measurements over space and time, traceability to national sources was desirable. Hence, the EPA approached the NIST to develop a suite of primary standards to cover a mole fraction (concentration) range of 0.1 to 1400 micromol mol(-1) for CF4 and 0.01 to 150 micromol mol(-1) of C2F6. A total of eight gravimetric PFC gas standards were prepared with relative expanded uncertainties of < or = 0.52% (approximately 95% confidence level). These primary standards were ultimately used to assign values to a series of secondary gas standards at three mole-fraction levels with relative expanded uncertainties ranging from +/- 0.7% to 5.3% (approximately 95% confidence level). This series of secondary standards was used within the aluminum industry to calibrate instruments used to make emission measurements. Assignment of values to the secondary standards was performed by use of gas chromatography with flame-ionization detection (GC-FID) and Fourier transform infrared spectrometry (FTIR). Real time pot-line and stack samples from a local aluminum plant were also obtained and sub-samples sent to each participating facility for analysis. The data generated from each facility were sent to NIST for analysis. The maximum difference between the NIST and individual facilities' values for the same sub-sample was +/- 26%.

Journal Article↗

PubMed2001

Symptom-based outcome measures for asthma: the use of discrete choice methods to assess patient preferences.

This paper reports on an application of discrete choice modelling to the measurement of patient preferences over asthma symptoms. A sample of patients with moderate to severe asthma was asked to choose between a series of pairs of scenarios characterised by different combinations of asthma symptoms. Their responses were analysed using a random effects ordered probit model. The results implied that patients weighted some symptoms more highly than others. Discrete choice modelling proved to be a useful approach for developing preference based outcome measures, although the results show how, in contexts where preferences over health care outcomes based on symptoms or some measure of health status are involved, a conventional linear additive model may not always be suitable.

Adolescent↗

PubMed2001

Patient weighting of importance of asthma symptoms.

BACKGROUND: Quality of life measures are increasingly important in evaluating outcomes in asthma. If some asthma symptoms are more troublesome to patients than others, this may affect their contribution to outcome measures. This study was designed to assess the relative importance of common symptoms in adults with asthma. METHODS: A postal survey using conjoint analysis was performed in 272 adults attending hospital outpatient clinics with moderately severe asthma. Patients were asked to chose between "symptom scenarios" offering different combinations of levels of five common asthma symptoms over one week. Two versions of the questionnaire were used with identical scenarios presenting symptoms in different orders. Different patients answered the two versions. Regression analysis was used to calculate symptom weights for daytime cough, breathlessness, wheeze and chest tightness, and sleep disturbance. RESULTS: Symptom order, percentage predicted peak expiratory flow (PEF), and symptoms in the week before the survey did not influence the choice of scenario. In both questionnaires patients were more likely to choose scenarios with low levels of cough and breathlessness than low sleep disturbance, wheeze or chest tightness. Regression weights for cough (-0.52) and breathlessness (-0.49) were twice those of wheeze (-0.25), chest tightness (-0.27), and sleep disturbance (-0.25). For 12% of patients cough dominated patient preferences, regardless of all other symptoms. Age was inversely related to weight given by patients to breathlessness. CONCLUSIONS: The prominence of cough among other asthma symptoms was unexpected. Daytime cough and breathlessness had greater impact for patients than wheeze or sleep disturbance. Age influenced symptom burden, with younger patients giving greater weight to breathlessness than older patients. Conjoint analysis appears to be a useful method for establishing the relative importance of common symptoms.

Adult↗

PubMed2000

Do medically unexplained symptoms matter? A prospective cohort study of 300 new referrals to neurology outpatient clinics.

OBJECTIVES: To determine (a) the proportion of patients referred to general neurology outpatient clinics whose symptoms are medically unexplained; (b) why they were referred; (c) health status and emotional disorder in this group compared with patients whose symptoms are explained by "organic" neurological disease. METHODS: The prospective cohort study with case note follow up at 6 months was carried out in the regional neurology service in Lothian, Scotland with 300 newly referred outpatients. Neurologists rated the degree to which patients' symptoms were explained by organic disease (organicity), GPs' reasons for referral, health status (SF-36), anxiety, and depressive disorders (PRIME-MD), RESULTS: Of 300 new patients 11% (95% confidence interval (95% CI) 7%-14%) had symptoms that were rated as "not at all explained" by organic disease, 19% (15% to 23%) "somewhat explained", 27% (22% to 32%) "largely explained", and 43% (37% to 49%) "completely explained" by organic disease. Reason for referral was not associated with "organicity". Comparison of these groups showed that although physical function was similar, the median number of physical symptoms and pain were greater in patients with lower organicity ratings (p<0.0005, p<0. 0005). Depressive and anxiety disorders were more common in patients with symptoms of lower organicity (70% of patients in the not at all group had an anxiety or depressive disorder compared with 32% in the completely explained group (p<0.0005). CONCLUSION: One third of new referrals to general neurology clinics have symptoms that are poorly explained by identifiable organic disease. These patients were disabled and distressed. They deserve more attention.

Adolescent↗

PubMed1999

Protein conformational stability in the hydrofluoroalkane propellants tetrafluoroethane and heptafluoropropane analysed by Fourier transform Raman spectroscopy.

Due to the inherent structural instability of proteins, development of chlorofluorocarbon (CFC) free metered dose inhalers (MDIs) containing these biomolecules is beset with numerous challenges. In assessing the conformation of proteins in any medium, both secondary and tertiary structures need to be elucidated. This study uses Fourier transform (FT-) Raman spectroscopy to probe protein conformational stability in hydrofluoroalkane (HFA) propellants. Assignments of molecular modes for lysozyme as a solid and in aqueous solution, and for the first time, HFAs tetrafluoroethane (HFA 134a) and heptafluoropropane (HFA 227) are given. The Raman spectra provided molecular structural information on the peptide backbone, disulfide bonds and C-C stretching vibrations of hen egg lysozyme, enabling the secondary conformation of protein in HFA propellants to be determined; structural integrity of this robust model protein was maintained in both propellants. These results demonstrate that FT-Raman may be a useful tool for the optimisation of protein MDI formulations.

Drug Stability↗

PubMed1999

Prescribing benzodiazepines--a critical incident study of a physician dilemma.

Use of benzodiazepines has been discussed extensively both among the public and within the medical society. The aim of this study was to explore the quality of dilemmas experienced by physicians when prescribing benzodiazepines. A questionnaire was sent to 213 Swedish General Practitioners. The critical incident technique was chosen as an appropriate method for surveying professional experiences. Concern for the patient and threats to the integrity of the physician were common dilemmas. The physicians did not believe that the patients were telling the truth or did not trust the patients' ability to handle the medicine. The most frequent consequences of the dilemmas were worry about a disturbed relationship with patients indicating an uncertainty as to how to create a good relationship with them. The participants in the study were aware of the national guidelines for prescribing benzodiazepines, but due to insufficient time a prescription was often chosen as a way to handle the dilemmas. Improvement in the rational use of benzodiazepines is not achieved by the medical board making new rules but rather by offering physicians education in communication and negotiating skills as well as more time with the individual patient who is requesting benzodiazepines.

Benzodiazepines↗

PubMed1996

Long chain polyunsaturated fatty acids and visual function in preterm infants.

Electroretinograms (ERG) were recorded at 40 weeks post-conceptual age (PCA) in 18 infants born prematurely (25-32 weeks gestation). Fatty acid composition of plasma and red cell phospholipids was measured within 4 days of birth and at time of ERG testing, and detailed record was kept of dietary intake. Correlations were seen between percentage intake of breast milk and docosahexaenoic acid (DHA) in both plasma (r = 0.818, P < 0.0001) and red cells (r = 0.534, P = 0.035) and significant differences in fatty acid profiles were seen between infants receiving > 50% and < 50% breast milk. No difference was seen in retinal sensitivity between infants receiving > 50% or < 50% breast milk. A positive correlation was seen between scotopic (rod) b-wave implicit time on ERG and DHA in both plasma (r = 0.733, P = 0.001) and red cells (r = 0.502, P = 0.04). A positive correlation was seen between arachidonic acid and rod ERG amplitude (r = 0.565, P = 0.022) which may reflect the higher AA/DHA ratio in the developing retina. These data did not support our hypothesis that increased dietary DHA results in enhanced retinal maturation. Visual acuity measured at 40 weeks PCA and again 3 months later was similar between groups. While subtle relationships were demonstrated between long chain polyunsaturated fatty acids and visual function, all infants were felt to be within age-appropriate normal range at expected date of delivery and at 3 months corrected age.

Breast Feeding↗

PubMed1995

Systemic lupus erythematosus in a child with sickle cell disease.

Although sickle cell disease (SCD) and systemic lupus erythematosus (SLE) are two distinct chronic diseases, many clinical features are common to both conditions. We describe a young patient who had a mild clinical course of SCD until SLE developed when he was 15 years old. His initial manifestations of SLE including fever, chest pain, and lung infiltration with pleural effusion were thought to be complications of SCD. However, a deteriorating clinical course, presence of facial and truncal rash, and persistent pleural effusion led to the diagnosis of SLE. We compare our case and the 10 previously reported cases and discuss the possible association of complement defects and the pathogenesis of SLE in patients with SCD. Our report illustrates the importance of considering other disease processes when clinical features are atypical of SCD.

Adolescent↗

PubMed1994

Cross-functional teams in health care organizations.

Cross-functional teams in health care organizations provide a comprehensive view of problems and are highly useful in designing and implementing improvements in work processes. Several potential obstacles may impede team progress, but these can be overcome. Cross-functional teams must develop norms that guide the interactions of team members. Individual team members must display behaviors that serve task accomplishment and team spirit. The promise of cross-functional teams for health care organizations is great. These promises, however, will not be fulfilled without the positive support of health care supervisors.

Behavior↗

PubMed1993

Process management: two control charts.

It is not at all surprising that many persons avoid involvement in statistical process control. The statistical procedures developed in industry to monitor production processes are somewhat different from those employed in biostatistics and social science applications. Many find it difficult to adjust to these procedures and to apply statistical process control techniques to situations in health care settings. Not everyone involved in a QI process, however, needs to become versed in statistical process control techniques. At the Indiana University Medical Center several persons from different hospital departments have volunteered to form a cadre of internal statistical process control consultants. The group has come to be known by some as the statistical process control "think tank." No doubt a small group of individuals who are interested in statistics, quality control, and computers can be found in most hospitals. While it is necessary that the large majority of managers and supervisors in any health care organization are knowledgeable about process management and control charts at the concept level of understanding, it takes a relatively few to understand and use such control charts. As internal consultants, these few persons can provide technical assistance when such aid is needed.

Computer Graphics↗

PubMed1993

Variation in cesarean section rates among hospitals in Washington State.

OBJECTIVES: This study examined hospital characteristics and hospital population risk factors and their associations with hospital-specific cesarean section rates in Washington State. METHODS: Data were obtained from 1987 birth certificates. The study population included all hospitals that had 12 or more singleton live births. RESULTS: Hospital-specific cesarean section rates varied from 0% to 43% and were positively associated with proprietary ownership, size of delivery service, and the proportions of women who had complications or high-birthweight infants. The proportion of women who had late prenatal care was inversely associated with cesarean section rates. Although proprietary hospitals had higher cesarean section rates, their patient populations were lower risk than patients of public or teaching hospitals. CONCLUSIONS: Variation in cesarean section rates among hospitals cannot be fully explained by either hospital or patient population characteristics. A combined strategy may be necessary to lower unjustifiably high cesarean section rates.

Adolescent↗

PubMed1993

Management ethics for the health care supervisor.

Someone once described the difference between ethical and unethical behavior in these terms: After doing something ethical you feel good; after doing something unethical you feel bad. Not quite. Feelings have something to do with ethics but not everything. Feelings may legitimately play into the moral reasoning associated with senses of guilt and guiltlessness, but moral reasoning demands critical thinking if it is to be honest. The ability to think critically on moral issues, it is argued here, is a competence that must be exercised by all professionals.

Confidentiality↗

PubMed1992

Using decision analysis to calculate the optimum treatment for microinvasive cervical cancer.

Decision theory was used to calculate the optimum treatment of microscopic squamous cervical cancer using probabilities obtained from an exhaustive literature review and a range of plausible value estimates. This showed that if there is no vascular involvement, survival is maximised by conservative treatment if tumour invasion is less than 3 mm while treatment by radical surgery results in maximal survival rates if the tumour invasion is over 3 mm. Radical surgery also maximises survival for smaller lesions where lymph channel involvement is present, especially if a surgical mortality at the lower end of the reported range is assumed. Refinement of our analysis to include an assessment of patient values showed that these conclusions are still valid regardless of the patient's relative preference for death from surgery or death from cancer. However, the wish to preserve fertility sharply reduces the overall net benefit of surgery. Conservative treatment becomes the preferred option for all microinvasive lesions even for patients who are prepared to trade-off a small (e.g. 2%) risk of death in order to retain their fertility.

Adult↗

PubMed1992

Familial Scheuermann disease: a genetic and linkage study.

Scheuermann juvenile kyphosis or Scheuermann disease is the most frequent cause of kyphosis in adolescence. However, the natural history and genetic basis is still unknown. Reports of identical radiological changes in monozygotic twins, sib recurrence, and transmission over three generations suggest underlying heritability. In this study, 12 probands were referred to us. Upon radiological examination of the proband's parents and sibs, seven were shown to have familial Scheuermann disease with an autosomal dominant pattern of inheritance. Of the remaining five probands, four had chromosomal anomalies. The three largest pedigrees were subjected to linkage analysis with three candidate genes: Duffy, COL1A1, and COL1A2. Linkage of Scheuermann disease was excluded with Duffy (lod score = -2.195 at theta = 0.10) and COL1A2 (lod score = -2.750 at theta = 0.05) in these families.

Adolescent↗

PubMed1992

Critical thinking in health care supervision.

Henry Ford is reputed to have said that thinking is the hardest work there is, which is probably why so few people engage in it. Perhaps many people have felt this way sometimes, especially when they viewed the foibles of the human race displayed prominently on the evening television news. Some people do stupid things; some people seem to be mindless in what they do. This applies also to some in managerial and supervisory positions in health care organizations. The percentage of these thoughtless managers and supervisors is probably comparable to the percentage of the thoughtless people in the general population. Fortunately every normal functioning human being is capable of becoming a more critical thinker. Of course, no amount of effort is adequate to the development of critical thinking when a person lacks fundamental good sense. On the other hand, no amount of genius suffices when someone does not put forth adequate effort to become a more critical thinker.

Decision Making, Organizational↗

PubMed1991

Estrogen therapy and variable-resistance weight training increase bone mineral in surgically menopausal women.

This study was undertaken to examine the effect of estrogen replacement therapy alone and estrogen replacement therapy plus variable-resistance weight training on the bone mineral content of surgically menopausal women. A total of 20 surgically menopausal women were randomized and treated with either 0.625 mg conjugated estrogen daily or the same dose of estrogen plus a closely monitored exercise program involving the use of Nautilus muscle strengthening/endurance equipment. After 1 year's observation, the bone mineral density (BMD) of the spine determined by dual-photon absorptiometry increased in the exercising subjects by 8.3 +/- 5.3% (p = 0.004), 95% confidence limits (CL) 3.9-12.8%; the group with estrogen replacement therapy alone maintained their BMD: 1.5 +/- 12.4% (p = 0.36; 95% CL = -6.9-9.8%). The total body BMD of the exercising group increased by 2.1 +/- 1.5% (p = 0.003; 95% CL = 0.8-3.3%); the nonexercising women had a nonsignificant 0.6 +/- 2.9% change (p = 0.30; 95% CL = -1.4-2.5%). A significant increase of 4.1 +/- 4.3% (p = 0.01; 95% CL = 0.8-7.4%) in the radial midshaft BMD of the exercising group was found; the estrogen alone group recorded a nonsignificant change of -0.3 +/- 3.1% (p = 0.33; 95% CL = -1.7-2.4%). The results of this study suggest that variable-resistance training in estrogen-replete women adds bone to both the axial and appendicular skeleton.

Absorptiometry, Photon↗

PubMed1991

The effect of low-dose oral contraceptives on lipids and lipoproteins in two at-risk populations: young female smokers and older premenopausal women.

Young women who smoke and women over age 35 are considered to be at high risk for cardiovascular complications associated with oral contraceptive use. This study evaluated the effects of low-dose oral contraceptives on lipid and lipoprotein concentrations in 45 high-risk patients before, during, and after 6 months of treatment. Neither group showed a significant change from baseline in cholesterol, HDL cholesterol, LDL cholesterol or cholesterol ratios. Triglycerides increased and HDL2a levels decreased significantly in both groups but returned to baseline after treatment was discontinued, with the largest changes in both triglycerides and HDL2a levels occurring at 1 month. The change in triglyceride and HDL2a blood levels were within the laboratories' reference range. The lipid profile of these patients, therefore, was not worsened significantly through 6 months of oral contraceptive use. The young women who smoked did have consistently lowered levels of HDL cholesterol and its HDL2a subfraction when compared to their elder non-smoking cohort.

Adult↗

PubMed1990

Ablation of endometriotic implants in rabbits by hematoporphyrin derivative photoradiation therapy using the gold vapor laser.

In a rabbit model, endometriotic lesions were utilized to study hematoporphyrin derivative (HPD) uptake and the effect of photoradiation using the gold vapor laser. Morphological studies confirmed successful induction of ectopic endometrial growth and the lesions displayed preferential HPD uptake compared to normal intraperitoneal structures. Gold vapor laser irradiation of the lesions in HPD pretreated animals produced necrosis of the endometriotic lesions leaving surrounding tissues healthy. Results from this study suggest that HPD-mediated photodynamic therapy may be a suitable means of treating endometriosis in the human.

Animals↗