Abstract
The aim of this study was to determine which lung function test employed in the perinatal period gave the results most significantly associated with respiratory problems in infancy. The ratio of the proportion of time to reach peak tidal expiratory flow to total expiratory time 
, thoracic gas volume (TGV) and airway resistance 
(from which specific conductance 
was calculated) measurements were examined from 85 infants born at or near term. The infants were followed until at least one year of age and described as symptomatic if they wheezed for at least 24 hours. Twenty-three infants were symptomatic in the first year. The symptomatic group, compared to the asymptomatic, had a higher median FRC (p < 0.01) and 
(p < 0.001); their median 
was lower (p < 0.001). It was possible to obtain 
results from only 61 infants; the median did not differ significantly between symptomatic and asymptomatic infants. Logistic regression analysis demonstrated a high and FRC, but not a low , independently related to positive symptom status. A high 
was the most sensitive (83%) predictor of subsequent respiratory problems, but all the tests examined had low positive predictive values.
Keywords: lung function tests, tidal breathing parameters