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Biomedical subjects

P C Schrader

Publications and source records attributed to P C Schrader.

5 recordsLinked to original sources
PubMed1993

Growth of airways and air spaces in teenagers is related to sex but not to symptoms.

To determine growth patterns of the lung and airways in adolescents, we analyzed maximal expiratory flow-volume curves, closing capacity, and residual volume. They were obtained every 6 mo for up to 7 yr in 430 boys and 125 girls (11-19 yr), of whom 143 boys and 36 girls were classified as symptomatic; symptoms were most often minor and limited to childhood. Development of flows vs. volumes was used to investigate growth of the airways relative to lung size. A model of isotropic growth of the airways and air spaces (J. Appl. Physiol. 65: 822-828, 1988) was modified for increasing elastic recoil pressure with growth. Growth of airways relative to volume occurred faster in teenage boys than in teenage girls and was compatible with isotropic growth in 92% of asymptomatic boys and in 44% of asymptomatic girls: dysanaptic growth in teenage girls seems to be a normal phenomenon and not a unique characteristic of symptomatic subjects. Subjects with respiratory symptoms in childhood and/or adolescence have lower flows for a given lung size and airway closure at a greater lung volume when they enter adulthood. However, no difference in patterns of lung growth was observed in association with the presence of respiratory symptoms.

Adolescent↗
PubMed1988

Respiratory muscle force and ventilatory function in adolescents.

In 94 girls and 90 boys, aged 12.5-20.3 yr, the relationship of respiratory pressures or forces with lung volumes and ventilatory flows was studied. There was great variability in respiratory muscle performance, which helps to explain differences in lung volumes between individuals. Respiratory muscle force increases almost proportionally with thoracic dimensions, so that inspiratory and expiratory pressures generated at the level of residual volume (RV), functional residual capacity (FRC) and total lung capacity (TLC) are approximately constant with age. In the oldest boys there is evidence that the continued increase in lung volumes when they stop growing is due to a 'muscularity effect'. Boys generate larger pressures than girls at all lung volumes. Thus boys attain a larger TLC, and in spite of narrower airways, the same peak expiratory flow and a larger FIV1/FVC ratio than girls. Effort independent flows (FEV1 and MMEF), however, are larger in girls.

Adolescent↗
PubMedDate not supplied

Changes in the FEV1-height relationship during pubertal growth.

In two cohorts of boys (n = 167) and two cohorts of girls (n = 131), FEV1, stature, body weight and two thoracic dimensions were measured eight times at intervals of about six months; the mean ages of each cohort at the start of the study were 12.5 and 13.5 years respectively. In each of the repeated cross-sections, FEV1 could be described as a power function of stature (FEV1 = aHk). In boys, the power (derived from regression of In FEV1 on ln H) increased from 2.60 to 3.04 and declined to 2.40; in girls, it decreased steadily from 2.87 to 1.94, attaining adult values at about age 15. A similar but less pronounced trend was observed for ln FEV1 against ln body mass. The adolescent growth spurt could be best studied in the boys. The individual (longitudinal) log-log plots of FEV1 versus stature or thoracic height were obviously non-linear in 52% and 33% of the boys respectively, with the greatest increase in FEV1 towards the end of the curve. In 78 boys with an apparently straight ln FEV1-ln H plot, the slopes of individual curves varied between 1.86 and 7.53; the mean value (3.99) was larger than in any of the repeated cross-sections. Applying allometric principles of similarity, FEV1 was about isometrically related to body mass but varied as about the 3.5th power of stature, with age-related trends in boys and girls. These findings reflect changes in bodily proportions and shape during the adolescent growth spurt, with growth in lung volume lagging behind growth in standing height.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMedDate not supplied

Selection of variables from maximum expiratory flow-volume curves.

Various methods are in use for estimating physiological variables from maximum expiratory flow-volume curves, and some of these are recommended by international bodies for use on adults. We have compared eight such methods in 433 adolescents aged 12-16 years. The mean values of expiratory flows, FVC and FEV1 by each method differed less than 6% from those obtained by the method recommended by the ATS, except for MEF25, where differences between methods were substantially larger. The mean within-individual coefficients of variation of FVC and FEV1 did not differ between methods and improved from about 3.1 to 2.6% and 2.7 to 2.3% respectively when using 5 instead of 3 acceptable curves. For expiratory flows, the coefficients of variation ranged between 4.2 and 9.4% and improved slightly but not consistently when using more than 3 acceptable curves. Reproducibilities were systematically poorer when flows were derived from one "best" FVC manoeuvre. It is concluded that taking more than 3 acceptable blows is not cost-effective, even in inexperienced adolescents. An envelope method and maximum composite curve from FVC reproducible within 5% from the largest one are recommended for use with teenagers.

Adolescent↗