To examine the relationship between body weight in children and aerobic parameters of exercise, we determined the anaerobic threshold (AT), maximum O2 uptake (VO2max), work efficiency, and response time for O2 uptake (RT-VO2) in 109 healthy children (51 girls and 58 boys, range 6-17 yr old) using a cross-sectional study design. Gas exchange during exercise was measured breath by breath. The protocol consisted of cycle ergometry and a linearly increasing work rate (ramp) to the limit of the subject's tolerance. Both AT and VO2max increased systematically with body weight, whereas work efficiency and RT-VO2 were virtually independent of body size. The ratio of AT to VO2max decreased slightly with age, and its mean value was 60%. AT scaled to body weight to the power of 0.92, not significantly different from the power of 1.01 for VO2max. Thus both the AT and the VO2max increase in a highly ordered manner with increasing size, and as judged by AT/VO2max, the onset of anaerobic metabolism during exercise occurred at a relatively constant proportion of the overall limit of the gas transport system. We conclude that in children cardiorespiratory responses to exercise are regulated at optimized values despite overall change in body size during growth.

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ABSTRACT. The purpose of this study was t o determine how ventilation (VE) and C 0 2 production (VC03 in response to exercise change during the growth process in children and teenagers. Dynamic gas exchange responses were measured in two types of studies: 1) 128 healthy children ranging in age from 6 to 18 yr performed progressive exercise tests ("ramp" type protocol) for measurement of,the slope of the relationship between VE and VCOZ-AVE/AVCOZ; and 2) the response characteristics of VE and VC02 in the transition between rest and exercise were measured in 11 teenagers and 11 younger children. Gas exchange was measured breath by breath. We found a small but significant decrease in AVE/AVCOz with increasing body weight ( r = -0.46, p <0.05), height, or age (mean slope of 27 in the youngest in 21 in the .oldest subjects). The response characteristics of VE and VCOZ (measured as the time constant of the best-fit exponential response) were longer than for VOz in both younger children and teenagers; but the time constants for VE and VC02 were each approximately 30% faster in younger children compared to teenagers. In addition, end-tidal PCO, during exercise was significantly lower in the younger subjects (mean value of 39.6 torr) compared to the teenagers (mean value of 43.5 torr). The results suggest that the process of respiratory control in exercise matures to a small degree during childhood in that PCO, may be regulated at lower levels in younger children and there may be growth-related differences in the relative amounts of COz that can be stored in tissues. (Pediatr Res 21: 568-572, 1987) Abbreviations vE, ventilation VC02, COZ output V O~, O2 uptake AT, anaerobic threshold RCP, respiratory compensation point Babies have different respiratory control than do adults. For example, the arterial PC02 is regulated at lower levels, the pattern of breathing is erratic and marked by periodicity, and the ventilatory response to hypoxia and hyperoxia differs from the adult (1, 2). Thus, while it is apparent that the respiratory control apparatus undergoes maturation in the normal human being, there is a dearth of information on the ontogeny of these mechanisms during childhood. We hypothesized, therefore, that maturation of respiratory control could be detected and characterized during growth in children.In adults, it is known that the degree of V, is linked to the metabolic production of C 0 2 (3-8). This linkage is marked by homeostasis for C 0 2 concentration in the blood, such that PC02 is kept within a very narrow range despite large fluctuations in the VC02 as occur during exercise. But the child is faced with problems not encountered by the mature individual-while the ventilatory apparatus in both the adult and child must quickly respond to the increased C 0 2 load induced by physical activity, the child must, in addition, deal with greater C02 loads imposed by the increasing body size of the growth process itself. This research is focused on the precise linkage between VC02 and VE during exercise in growing ch...

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We measured the gas exchange response to exercise in 109 normal children (51 girls and 58 boys, ranging in age from 6 to 17 yr old) using noninvasive breath-by-breath techniques. The protocol consisted of cycle ergometry in which the work rate increased in a linear manner (ramp forcing function) until the limit of the subject's tolerance was reached. We measured the maximal oxygen uptake (VO2max) and the VO2 at the anaerobic threshold (AT). We found that both of these parameters were highly correlated with increasing height, and that for both the AT and VO2max, the values for boys were significantly higher than girls. We compared our results of VO2max to those obtained by Astrand over 30 years ago using different techniques. When boys and girls were considered together, there were no significant differences between our study and Astrand's; however, girls in our study had significantly lower values for VO2max than did girls in Astrand's study. These data provide normal values for both VO2max and AT and can be used to evaluate the exercise impairment resulting from disease in children.

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SummaryAlthough body size and muscle mass increase considerably during growth in children, certain aerobic responses to exercise appear to be regulated so that the delivery of oxygen to muscle is maintained at optimized levels. We proposed that the relationship between oxygen uptake, (Voz) and heart rate (HR) was one of the regulated responses. We further hypothesized that the increase in Vo2 per increase in HR during progressive exercise would differ in subjects of different size, but when normalized to body weight would be constant since changes in muscle mass are highly correlated to changes in body mass. To test this, we performed a cross-sectional study of 107 normal children, 50 girls and 57 boys ranging in age from 6 to 17 years. The protocol consisted of a continuously increasing work rate on a cycle ergometer, to the limit of the child's tolerance (ramp forcing function). Gas exchange was measured breath-by-breath for the determination of Voz, and heart rate was measured beat-by-beat. We used linear regression techniques to.determine M, the slope, and B, t h e y intercept of the equation: Vo2 = M X HR -B. In both boys and girls, M increased significantly with body weight, but when normalized for body weight (Mlkg), there was no systematic change with increasing weight or age, the mean value being 0.33 +I 0.10 ml/min/kg (SD). The mean value for the boys was 0.37 f 0.10 which was significantly greater than that of the girls (0.29 f 0.08, p < 0.01). Using allometric equations, we found M, B, and the O2-pulse (VoZ/HR) at a heart rate of 140 beatslmin and at the anaerobic threshold, all scaled in direct Received July 8. 1983: accepted February 7. 1984. Reprint requests may be addressed to Dan M. Cooper, M.D. A-15 Annex, Halbor-UCLA Medical Center. Torrance, CA 90509.Senior Investigator of the American Heart Association, Greater Los Angeles Affiliate.proportion to body weight (i.e., to 1.0 power of body weight). We conclude that during growth, the output of the heart is closely tied to the size of the muscles so that delivery of oxygen during exercise is maintained at optimized levels from early in childhood. Abbreviations vo2, oxygen uptake Vozmax, maximum oxygen uptake AT, anaerobic threshold HR, heart rate SV, stroke volume (a -V)Oz, arteriovenous oxygen content differenceWe have recently demonstrated that certain aerobic parameters of exercise appear to be highly regulated as body weight changes during gro?h in children. The work efficiency and the response time for V O~ following the onset of exercise are independent of body size, whereas the Vo2max and the A T increase in direct proportion to body weight (6). Moreover, the Vo2 increases linearly with work rate in both adults and children (6,19) indicating that as more muscle units are activated, the flow of oxygen is optimized so that a unique work efficiency is maintained at virtually all levels of energy demand. In addition, other investigators have shown that the relationship between Vo2 and HR is linear during progressive exercise in children, and t...

The association between asthma and sinonasal disease has been known for years. Effective treatment of sinonasal disease, which is one of the factors that exacerbate asthma, may also improve and stabilize the asthmatic condition. This study examines the outcome of functional endoscopic sinus surgery (FESS) on asthmatic patients with massive nasal polyposis. Thirty-four asthmatic patients were included in the study. All were operated on in our department and were analysed for pre-operative data regarding their asthma and sinonasal disease. A questionnaire regarding subjective evaluation of asthma and sinonasal status was presented to the patients, and objective evaluations, including nasal endoscopy and spirometry, were performed. Follow-up endoscopy revealed satisfactory results in 88 per cent, with positive correlation to the patients' subjective assessment of nasal status. No such correlation was found with regard to subjective and objective assessment of asthma: a small group of patients had completely clean sinonasal cavities with no perceived improvement in their asthmatic condition. The use of prednisolone and bronchodilators was significantly reduced post-operatively. However, in a subgroup of 13 patients followed at the asthma clinic, who had adequate pre-operative and post-operative data, there was no difference in their pre- and post-operative asthma condition. Seven had minimal improvement and in six there was a definite worsening of their asthma; nevertheless, nasal breathing and quality of life improved in most patients. The mean follow-up was 2.1 years. Thus, we conclude that in this study FESS does not improve asthma, but does improve the quality of the life of the patient.