BACKGROUND: Assessment of tidal breathing parameters may be a useful method of predicting respiratory problems in early childhood. Low values of TPTEF/TE (the ratio of the proportion of time to reach peak tidal expiratory flow to total expiratory time) outside the neonatal period have been significantly related to respiratory tract illness with wheezing in boys in the first year of life. METHODS: TPTEF/TE measurements in the perinatal period were evaluated in nonsedated infants and the predictive value of this early measurement for subsequent respiratory morbidity during infancy was assessed. Flow during tidal breathing was measured while the infant slept quietly in a plethysmograph using a Fleisch pneumotachograph inserted into an infant face mask. Recruitment continued until traces from 60 infants with 10 consecutive flow curves without artefacts were obtained. In addition, plethysmographic measurements of airway resistance (Raw) and thoracic gas volume (TGV) were measured and specific conductance (sGaw) calculated. Parents recorded their infant's cough and wheeze during the first 12 months of life. RESULTS: Sixty five measurements were made in 60 infants with a mean age of two days and gestational age of 40 weeks. Two observers separately calculated TPTEF/TE ratios on 25 traces randomly selected from the pool of 60. The mean difference between the two observers was -0.004 (limits of agreement 0.048 to -0.056). Thirteen infants became symptomatic (wheeze, with or without cough); their median TPTEF/TE ratio (0.349) was significantly lower than the rest of the cohort (median 0.412) and they also had significantly higher Raw and lower sGaw. The positive predictive value of a low TPTEF/TE ratio, however, was only 41%. CONCLUSIONS: These results suggest that the use of this test in the prediction of future respiratory disease in an individual is limited.
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