Introduction
The Global Lung Function Initiative (GLI), an international
collaboration with the goal of developing universal reference equations
for children and adults11ReferencesCooper BG, Stocks J, Hall GL, Culver B, Steenbruggen I, Carter KW,
Thompson BR, Graham BL, Miller MR, Ruppel G, Henderson J, Vaz Fragoso
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J; ERS Global Lung Function Initiative. Multi-ethnic reference values
for spirometry for the 3-95-yr age range: the global lung function
2012 equations. Eur Respir J. 2012 Dec;40(6):1324-43.. These
reference equations, obtained from healthy children, may potentially add
to a better understanding of lung growth. A careful analysis of changes
in the forced expiratory volume in the first second of the maneuver
(FEV1) as a proportion of the forced vital capacity
(FVC), or the FEV1/FVC ratio, with age through childhood
and adolescence demonstrated a remarkable shape to the curve33Quanjer
PH, Stanojevic S, Stocks J, Hall GL, Prasad KV, Cole TJ, Rosenthal M,
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intercontinental study. Eur Respir J. 2010 Dec;36(6):1391-9.. Figure
1a demonstrates that the mean ratio of FEV1/FVC rapidly
decreases through childhood in healthy children, at least up to about
10-12 years of age, followed by a small increase during early
adolescence, before resuming an inexorable downhill decrease throughout
life44Quanjer PH, Stocks J, Polgar G, Wise M, Karlberg J,
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measurements in children. Eur Respir J Suppl. 1989 Mar; 4:184S-261S..
It is generally accepted that FEV1/FVC decreases from
childhood to old age55Quanjer PH, Stocks J, Polgar G, Wise M,
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function measurements in children. Eur Respir J Suppl. 1989
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Collaborative Initiative. Am J Respir Crit Care Med. 2009 Sep
15;180(6):547-52.. The reasons for this “Shepherd’s Hook”
appearance in early adolescence are not well understood. One suggestion
is that this age-dependent increase in the ratio may be due to
well-recognized changes in thoracic configuration, and as a result,
decreased chest-wall compliance in adolescents77Merkus PJ, ten
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particularly during the adolescent growth spurt and puberty88Schrader
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1984 Jul-Aug;20(4):381-8.. This might result in slower growth in
measured vital capacity relative to FEV199Degroodt
EG, Quanjer PH, Wise ME, et al. Changing relationships between stature
and lung volumes during puberty. Respir Physiol 1986; 65: 139-153.,1010Smeets
M, Brunekreef B, Dijkstra L, Houthuijs D. Lung growth of
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The primary objective of this study was to analyze the relationship
between FEV1/FVC and age in children and adolescents
with asthma. The cross-sectional area of the airways may not increase
relative to alveolar volume in adolescents with asthma, as much as in
healthy adolescents. If so, this might result in a reduced
FEV1/FVC ratio. If individuals with asthma do not have
this temporary adolescent growth spurt in FEV1/FVC ratio
noted in healthy adolescents, the trajectory of FEV1/FVC
throughout adulthood might remain permanently lower. Secondary
objectives were to assess the role of gender, obesity, and measurements
of lung volumes on the relationship between age and
FEV1/FVC.