Forced expiratory flows and volumes in infants - Normative data and lung growth

Forced expiratory flows (FEF) can be measured in infants from lung volumes initiated near total lung capacity. In order to establish reference values and to evaluate lung growth, we obtained measurements in 155 healthy subjec ts between 3 and 149 wk of age. Forced vital capacity (FVC) was highly corr elated with body length; however, after accounting for length, age was also significant. When subjects were divided at the median age (40 wk) younger compared with older subjects had a significantly larger slope for length (3 .7 versus 2.8; p = 0.002). The flow parameters (FEF50, FEF75, FEF85, and FE F25-75) were highly correlated with length, and those infants whose mothers smoked had lower flows. For FEF75, male subjects had lower flows than fema le subjects. The relationship between FEF and volume was assessed using FEV 0.5/FVC, which decreased with increasing length. Smaller subjects emptied t heir lung volume proportionately faster. We conclude that our study provide s reference values for this age group and demonstrates that smoke-exposed i nfants and male subjects have decreased FEF. In addition, our findings indi cate that lung volume increases most rapidly during the first year of life and that airways are large relative to lung volume very early in life.