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Biomedical subjects

P W Bradley

Publications and source records attributed to P W Bradley.

8 recordsLinked to original sources
PubMed1989

Development of valid pulmonary function equations for trained athletes.

The validity of commonly recommended pulmonary function prediction equations (Bulletin Européen de Physiopathologie Respiratoire, Clinical Respiratory Physiology) was tested with two samples (n1 = 156; n2 = 218) of well-trained athletes. Pulmonary function measures (FVC, TLC, RV, FEF25%-75%, FEV1.0, PEF, RV/TCL ratio, FEV1.0/FVC ratio) were typically very reliable but inaccurately predicted with recommended equations based upon anthropometric characteristics. Newly developed "unisex" regression equations were developed with "dummy" coding of gender (i.e., 0 = female; 1 = male), age, height, weight, and various interactions. The new equations were validated with a subsample of group one, cross-validated with the remaining portion of group one, and then cross-validated again with the 218 subjects from sample two. The newly created pulmonary function prediction equations are more valid for well-trained athletes than the equations in use for the general population.

Adult↗
PubMed1986

Impaired exercise performance and pulmonary function in elite cyclists during low-level ozone exposure in a hot environment.

We evaluated the effects of low concentrations of ozone on the exercise performance and pulmonary function of 17 top-caliber endurance cyclists under conditions simulating competition and realistic temperature (31 degrees C). Each subject was randomly exposed to filtered air (FA), 0.12 and 0.20 ppm O3 on separate days in an environmental chamber. Each subject attempted to maintain submaximal exercise on a cycle ergometer equivalent to approximately 70% of maximal oxygen consumption (VO2max) for 60 min, followed by incremented (maximal) exercise until exhaustion. During submaximal exercise, average minute ventilation (VE) (89 L/min), VO2 (51 ml/min/kg or 72% VO2max), work load (260 W), and work time (57 min) were similar across all exposures. During maximal exercise, average peak VE (150 L/min), VO2 (68 ml/min/kg), work load (382 W), and ride time (263 s) were similar between 0.12 ppm O3 and FA. However, significant reductions in peak VE (18%), VO2 (16%), tidal volume (22%), work load (8%), and ride time (30%) occurred in 0.20 ppm O3 compared with those in FA. Postexercise decrements in forced expired volume in one second (FEV1) averaged 5.6% and 21.6% in 0.12 and 0.20 ppm O3, respectively. Ozone-related symptoms were mild in 0.12 ppm O3 but intensified and probably limited maximal performance in 13 subjects in 0.20 ppm O3. Changes in carbon monoxide diffusing capacity (adjusted for alveolar volume) were not significant across exposures. Nine subjects showed histamine hyperresponsiveness (i.e., greater than 20% decrease from the control postdiluent FEV1) after exposure to 0.20 ppm O3 as compared with 1 subject in 0.12 ppm O3.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Accuracy of measured and predicted residual lung volume on body density measurement.

The effects of measured and predicted residual lung volume on the accuracy of body density and percent fat (%Fat) were investigated. Adult fitness subjects (N = 46) had residual lung volume measured with the oxygen dilution method while those from an athlete sample (N = 134) utilized the nitrogen washout technique. Residual lung volume was also predicted with gender-specific regression equations using height and age and from 24% of vital capacity (%FVC). Residual lung volume alpha reliability for the average of four residual lung volume trials exceeded 0.90 (SEM less than = 161 ml) for the oxygen dilution method and 0.99 (SEM = 30 ml) for the average of two nitrogen washout measures. The standard errors for predicted residual lung volume were 579 and 355 ml, respectively, for the men and women in the adult sample and 288 ml for the trained athlete sample. Estimating residual lung volume from %FVC yielded a SEE of 318 ml for the trained athlete sample. Measured residual lung volume errors resulted in errors of 1.04%Fat, 0.87%Fat, and 0.21%Fat for the men, women, and trained athlete samples, respectively. In contrast, predicted residual lung volume measurement errors resulted in errors of 3.70%Fat, 2.85%Fat, and 1.98%Fat for the respective samples and 2.18%Fat when using %FVC with the trained athletes. Measured residual lung volume introduces little %Fat error while predicted residual lung volume introduces a substantial source of measurement error.

Adipose Tissue↗
PubMed1980

Immunogenetics of response to a purified antigen from group A streptococci. I. Complex segregation analysis.

A purified, extracellular protein, M. W. 17500, from group A streptococci was used in an in vitro model to study genetic aspects of immune responsiveness. Peripheral blood lymphocytes from members of eight nuclear families and one kindred of three generations were isolated and purified by F-icoll-Isopaque flotation and cultured together with varying concentrations of antigen. A summary measure of the antigen response data (measured as CPM) was constructed through a weighted regression analysis of response on dose. Commingling analysis of the standardized regression coefficients provided evidence for the existence of two underlaying distributions. Segregation analysis confirmed that response to this antigen is controlled by a major gene and is inherited in an autosomal dominant manner.

Adolescent↗
PubMed1980

Immunogenetics of response to a purified antigen from group A streptococci. II. Linkage of response to HLA.

Employing an in vitro blastogenesis model, evidence has been set forth for a major gene locus which controls response to a purified, extracellular antigen from group A streptococci. Response to this antigen is inherited in an autosomal dominant manner. Analysis of the data for linkage to HLA was done with the computer program LINKAS which can resolve pleiotropy from linkage and can detect and estimate recombination in the presence of etiological heterogeneity. Maximum likelihood estimation and likelihood ratio tests were used to assess the relative support for competing hypotheses. The results of this analysis indicate that at least two loci are involved in one of two ways: one locus that is closely linked to HLA and one locus that is unlinked; or a two-locus system of complementary alleles which are both tightly linked to HLA.

Adolescent↗
PubMed1980

Relation between respiratory valve dead space and tidal volume.

We measured the "effective" dead space of five commonly used respiratory valves: Hans Rudolph valve, two-way J valve, triple-J valve, and modified Otis-McKerrow valves without and with vane. The dead space was measured using a technique that mimicked the operation of valves during ordinary laboratory procedures. The valves were ventilated with tidal volumes ranging from 0.35-3.00 liters and at different frequencies. With all valves, there was a marked tendency for "effective" dead space to be tidal volume dependent. The measured dead space approached the water-displacement volume of the common chamber of the valve only at tidal volumes in excess of 2.0 liters. The relation between valve dead space and tidal volume was independent of frequency.

Mathematics↗
PubMedDate not supplied

Substantiation of reported child abuse or neglect: predictors and implications.

Underreporting and overreporting of suspected child abuse and neglect cases reduce the efficiency of child protection services. We used all the reports in South Australia for 1988-1989 (N = 3,228) to study the determinants of the decision by child protection workers to register a reported incident as being one of child abuse and neglect. Logistic regression showed that registration (substantiation) was predictable from two variables: the age of the alleged victim and the caseworker's estimate of severity. This latter variable needs investigation, as despite its crucial role we have no information on how caseworkers form a judgment about severity.

Child↗