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Optimal prediction of spirometric indices

Changing body proportions from infancy to adulthoodFrom birth to adolescence leg length grows faster than trunk height. This process comes to an end at about the age of sexual maturity. It will therefore not come as a surprise that lung volume, a component of the contents of the trunk, cannot be predicted solely on the basis of standing height; somehow age should enter into the equation.

As delineated earlier the Global Lung Function Initiative used smoothing splines to adjust for the shortcomings of linear regression equations, and included a term for ethnic group.

The FEV1/FVC ratio, hitherto thought to decline monotonously with age from childhood to old age, displayed a a nonlinear pattern in childhood and adolescence.

FEV1/FVC ratio in childrenThere is a rapid fall of the FEV1/FVC ratio from pre-school age to the start of the adolescent growth spurt. The same is observed in boys. The RV/TLC ratio shows a similar curvilinear pattern to that of FEV1/FVC. In this period the FVC growth faster than the total lung capacity and the FEV1. This is because during the first years of life, both the number and size of the alveoli increase, which are likely to lead to a faster increase in lung volume than in airway calibre. Functional and morphological changes (elongation of the thorax and different position of the diaphragm), which near completion at the start of puberty, contribute to development of a proportionately larger vital capacity from childhood to the adolescent growth spurt. This is followed by stiffening of the thorax, which limits full expirations. PedPulm.

 

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