Ventilatory variables in normal children during rest and exercise

The aim of this study was to provide a complete description of normal ventilation at rest and exercise in children and to determine how best to correct for body size. One-hundred and six children aged 8-17 years (55 male) underwent incremental bicycle exercise testing from rest to exhaustion in 3 min, 15 W.m(-2) steps and thence through 9 min recovery. All variables were calculated using helium dilution mixed expired gas analysis together with measures of alveolar gas concentrations from continuous measurement at the mouth, all via an AMIS 2000 quadrupole mass spectrometer. Surface area was the best single measure to correct for body size but always explained <37% of the variance. Thus for example, surface area corrected oxygen consumption at rest in males was greater than females. Data is presented at rest, each work load and at "maximum" exercise. When presented per watt of work at each work load, this permits comparison of adaptability to exercise between sexes and age groups. Exercise appears to terminate when respiration reaches 45 and 40 breaths-min(-1) in males and females respectively and when alveolar oxygen concentrations rise. This simple protocol and near complete data set ought to permit accurate comparison with disease groups.