Abstract
FEV 1/FVC normally decreases through childhood,
increases briefly during early adolescence, and then declines throughout
life. The physiology behind this temporary increase during early
adolescence is not well understood. The objective of this study was to
determine if this pattern also occurs in children with asthma.
Design: Single-center, cross-sectional, retrospective analysis
of pulmonary function tests (PFTs) obtained over a 5-year period in
children 5 to 18 years of age with persistent asthma. Results:
1,793 patients satisfied all inclusion and exclusion criteria. Mean age
(± SD) was 10.4 ± 3.8 years. 48% were female. Mean FEV
1 /FVC was 0.83 ± .09. FEV 1 /FVC in
children with persistent asthma declined from age 5 to age 11 by 5.7 %
compared to 7.3% in healthy girls, and 5.8% compared to 9.4% in
healthy boys. FEV 1/FVC increased by 1.2% until age 16
in children with asthma, compared to 2.2% in healthy girls, and 2.5%
compared to 2.3% in healthy boys. The ratio was lower in obese children
with asthma at all ages but demonstrated the same curvilinear shape as
in healthy children. In absolute terms, FEV 1 grew
proportionately more than FVC during early adolescence, so the ratio of
FEV 1/FVC increased during that period. The curvilinear
shape of the curve remained in postbronchodilator testing, though
significantly blunted. Conclusions: The “Shepherd’s Hook”
pattern in the FEV 1/FVC curve is preserved in children
with persistent asthma. This was also true in obese patients with
asthma, although their FEV 1/FVC ratios were lower
throughout all stages of childhood and adolescence.