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Biomedical subjects

R W Helms

Publications and source records attributed to R W Helms.

30 records · Page 2Linked to original sources
PubMed1989

Home air nicotine levels and urinary cotinine excretion in preschool children.

We examined the extent of correlation between home air nicotine levels and urine cotinine/creatinine ratios (CCR) in 27 children who attended a research day care program where they were not exposed to environmental tobacco smoke (ETS) during the daytime hours. Average concentrations of nicotine in home air were determined by active air sampling during the evening and night hours on 2 consecutive days. Urine samples for cotinine and creatinine determinations were collected before, during, and after the two sampling periods. In addition, four sequential weekly urine samples for CCR were obtained from study children to determine the extent to which single determinations of CCR were representative for individual children. Fifteen children resided in homes with smokers, and 12 did not. Urine CCR consistently distinguished most exposed and unexposed children. However, three exposed children had urine CCRs that clustered routinely around the criterion CCR (30 ng/mg cotinine-creatinine) that best distinguished exposed and unexposed children. In children exposed to ETS in the home, there was a significant correlation between average home air nicotine levels and the average logarithm of urine CCR the two mornings after the home air monitoring periods (r = 0.68; p = 0.006). In study children, urine CCRs were remarkably stable over the 1-month observation period. Rank correlation coefficients for sequential weekly determinations of CCR were consistently greater than r = 0.88; p less than 0.0001.

Child, Preschool↗
PubMed1989

Maximum likelihood estimation for incomplete repeated-measures experiments under an ARMA covariance structure.

A stochastic model is presented for the analysis of incomplete repeated-measures experiments. The general linear model is used to relate the response measures to other variables which are thought to account for inherent variation; an autoregressive moving average (ARMA) time series representation is used to model disturbance terms. Maximum likelihood estimation procedures are considered, and the properties of these estimators are derived. It is concluded that while the assumptions underpinning the ARMA covariance models may be somewhat restrictive, they provide a useful inferential vehicle, particularly in the presence of missing values.

Analysis of Variance↗
PubMed1988

Perceptions of appearance and speech by adolescent patients with cleft lip and palate and by their parents.

This study surveyed 102 patients with cleft lip, cleft palate, or cleft lip and cleft palate (ages 13 to 19) and their parents to assess satisfaction with appearance, speech ability, and intelligibility. The data were based upon standardized interviews conducted at a cleft palate treatment center, using simple questions with high face validity. Surgical experience was high among this sample, as reflected by the finding that the majority of patients (55.7%) had had three or more operations on the face or mouth. Patient ratings of facial appearance showed that most patients were very pleased (59.3%) or moderately pleased (13.2%); others were somewhat (18.7%) or very (8.8%) disappointed. Many parents indicated that their children expressed occasional (22.0%) or frequent (27.5%) concerns about appearance. Nearly all patients (91.9%) felt that their operations had accomplished what they expected, though some of the cleft lip patients (35.7%) and their parents (43.9%) were less than very pleased with the appearance of the lip. When asked how pleased they were with the way they presently talked, most patients (69.1%) were very pleased, though some disappointment was expressed. Although often pleased with their current speech status, many patients rated themselves as only moderately understandable (19.1%) or as not understandable (8.5%). No significant gender effects were found in satisfaction, appearance, or speech ratings. There were no significant differences found between parent and child ratings. The findings indicate that at a center delivering team-based cleft palate care, both adolescent patients and their parents have considerable concerns about appearance and speech results.

Adolescent↗
PubMed1985

Serum cotinine as a measure of tobacco smoke exposure in children.

To document passive smoke exposure, we measured concentrations of serum cotinine, a major metabolite of nicotine, in 38 young children and compared the results with the smoking histories of home residents. Cotinine was detected in 26 children (68%), of which ten had no household exposure according to a questionnaire. The serum cotinine concentration was significantly elevated in blacks compared with whites after controlling for the number of smokers in the home. After stratifying by race, there was a significant direct correlation between the serum cotinine concentration and the number of smokers in the home, the amount smoked by the mother, and the amount smoked by others in the home. We conclude that the serum cotinine concentration is a useful indicator of the actual exposure of young children to tobacco smoke and that unexplained racial differences in cotinine levels exist.

Black or African American↗
PubMed1984

A longitudinal study of spirometry in young black and young white children.

Spirometry was performed longitudinally over a period of 8 yr on 72 children (29 black females, 26 black males, 9 white females, and 8 white males) starting as early as 3 yr of age. Weighted straight-line regressions of 6 maximal expiratory flow-volume parameters--forced vital capacity (FVC), forced expiratory volume in one second (FEV1), peak expiratory flow (PEF), forced expiratory flow during the middle half of the FVC (FEF25-75), and maximal expiratory flows after 50 and 75% of the FVC had been exhaled (Vmax50 and Vmax75, respectively) - on height were computed and were found to describe adequately the data over a height range of 100 to 150 cm. Statistical comparisons of regression lines revealed significant differences for FVC and FEV1 when white females were compared with white males, white females with black females, and white males with black males, but not for black females with black males. Regressions of FEF25-75 and Vmax50 for black females were significantly lower than for white females, and those for white males were lower than those for white females, but no differences were detected when black females and white males were compared with black males. Only white females compared with black females revealed significant differences for Vmax75. There were no significant differences for any of the comparisons for PEF. The data presented expand the age range for evaluating lung function in children, indicate the feasibility of testing pre-school-age subjects, and provide new approaches to analysis of longitudinally collected information.

Anthropometry↗
PubMed1981

Food substitution with worker feeding programs: energy supplementation in guatemalan sugarcane workers.

An energy supplementation program provided free of charge a low energy (15 kcal) and a high energy (350 kcal) soft drink to two group of sugarcane workers in Guatemala. The high energy supplement supplied 550 kcal/day on a weekly basis. The workers tended to be moderately energy deficient before supplementation. Significant increases in total daily energy intake were obtained with the high energy supplement, but by less than the energy content of the supplement. Workers maintained energy balance with supplementation. The degree of substitution with energy supplementation was not related to the energy intake status of the workers' households. These households did generally not improve their energy intake status with worker supplementation.

Adolescent↗
PubMed1981

Seasonal variations of serum IgE levels in normal children.

The importance of season as a variable in total IgE production in normal children is demonstrated. Recent history of allergen exposure as well as respiratory infection, both of which are seasonally determined, should be considered in evaluating serum IgE values.

Adenoviruses, Human↗
PubMedDate not supplied

Chronic lung disease in children referred to a teaching hospital.

Etiology, symptomatology, and host factors were studied in 184 children referred to a teaching hospital for evaluation in an attempt to classify chronic or potentially chronic lung disease. A standardized historical questionnaire, physical findings, chest radiographs, and a laboratory panel identified a diagnosis that could be related directly or indirectly to chronic lung disease in 22% of the subjects. Among the remaining 78%, bronchiectasis was found in 9%, chronic pneumonia in 9%, chronic diseases with wheezing in 56%, and no significant lower respiratory disease in 4%. Analysis of cases with no apparent etiology revealed that the majority of patients had historical evidence of wheezing; often this previously had not been appreciated. Laboratory tests, such as eosinophil count and immunoglobulin E (IgE) testing, did not differentiate between wheezing and nonwheezing patients. Spirometric evaluation was limited because most subjects were younger than 5 years old. For the same reason, testing for bronchial hyperreactivity was not done. This study reemphasizes that wheezing is a major symptom of chronic lung disease in childhood and provides an outline for its evaluation. Although clinical airways reactivity, as exemplified by wheezing, proved to be the most prominent host defect found in this study, its nature, genetic or otherwise, remains to be defined.

Child, Hospitalized↗
PubMedDate not supplied

A study of spirometry in children from Mexico City.

A study was conducted in two elementary schools in Mexico City to determine values for pulmonary function tests in school-aged residents of Mexico City. The schools were located in Xalostoc, a highly industrialized area of Mexico City, and San Lorenzo, a suburban area of the city. Although data regarding atmospheric pollution were not available, there is an acknowledged higher level of macroenvironmental air pollution in Xalostoc. Pulmonary function tests were performed on 468 children in San Lorenzo and 405 children in Xalostoc. No differences between residents of the two communities for acute or chronic respiratory conditions were detected by questionnaire. The pulmonary function data demonstrate that boys have larger forced vital capacities (FVC) and forced expiratory flows over the middle half of the FVC (FEF25-75) than girls. Slopes of regression lines for FVC but not for FEF25-75 are greater in boys and girls from Xalostoc than in boys and girls from San Lorenzo. This suggests that young children from Xalostoc may experience ill effects of air pollution but develop catch-up growth later. There were no important community or gender effects on slopes of regression lines for height and weight on age. In general, the regression lines for FVC and FEF25-75 were below regression lines reported for children of Mexican ancestry living at sea level.

Adolescent↗
PubMedDate not supplied

Intentionally incomplete longitudinal designs: I. Methodology and comparison of some full span designs.

Longitudinal designs are important in medical research and in many other disciplines. Complete longitudinal studies, in which each subject is evaluated at each measurement occasion, are often very expensive and motivate a search for more efficient designs. Recently developed statistical methods foster the use of intentionally incomplete longitudinal designs that have the potential to be more efficient than complete designs. Mixed models provide appropriate data analysis tools. Fixed effect hypotheses can be tested via a recently developed test statistic, FH. An accurate approximation of the statistic's small sample non-central distribution makes power computations feasible. After reviewing some longitudinal design terminology and mixed model notation, this paper summarizes the computation of FH and approximate power from its non-central distribution. These methods are applied to obtain a large number of intentionally incomplete full-span designs that are more powerful and/or less costly alternatives to a complete design. The source of the greater efficiency of incomplete designs and potential fragility of incomplete designs to randomly missing data are discussed.

Longitudinal Studies↗
PubMedDate not supplied

Nitrogen dioxide exposure and urinary excretion of hydroxyproline and desmosine.

The relationship between average and peak personal exposure to nitrogen dioxide and urinary excretion of hydroxyproline and desmosine was investigated in a population of preschool children and their mothers. Weekly average personal nitrogen dioxide exposures for subjects who resided in homes with one or more potential nitrogen dioxide source (e.g., a kerosene space heater, gas stove, or tobacco smoke) ranged between 16.3 and 50.6 ppb (30.6 and 95.1 micrograms/m3) for children and between 16.9 and 44.1 ppb (12.8 and 82.9 micrograms/m3) for mothers. In these individuals, the hydroxyproline-to-creatinine and desmosine-to-creatinine ratios were unrelated to personal nitrogen dioxide exposure--even though continuous monitoring documented home nitrogen dioxide concentration peaks of 100-475 ppb lasting up to 100 h in duration. Significantly higher hydroxyproline-to-creatinine and desmosine-to-creatinine ratios were observed in children, compared with mothers (p < .001 and .003, respectively).

Adult↗