Abstract
Prematurely born children frequently have respiratory problems at follow-up. A non-invasive and easily performed lung function test would greatly facilitate their evaluation and appropriate treatment. We have, therefore, assessed whether the shape of the tidal breathing expiratory flow curve would give useful information in such a population. One hundred and twenty traces were randomly selected from plethysmographic measurements of thoracic gas volume and airway resistance made during a follow-up study of a prematurely born population. The children had a median gestational age of 29 (range 23-35, interquartile range 27-31) weeks and postnatal age at the time of measurement of 11 (range 6-24, interquartile range 7-13) months. From the flow and volume signals, the mean time to reach peak tidal expiratory flow as a proportion of the total expiratory time 
was determined for each child. The median 
differed significantly between children who, in the neonatal period, had or had not required mechanical ventilation 
and had or had not had an increased inspired oxygen requirement (p < 0.01), and who were or were not symptomatic at follow-up (p < 0.001). Logistic regression analysis demonstrated that a low ratio was independently associated with symptom status. These results suggest that assessment of a tidal breathing parameter during follow-up of prematurely born children may be useful. As can be measured without sedation, relatively quickly and with simple equipment, potentially large study populations could be investigated, and this technique should now be evaluated in a non-sedated group of young prematurely born children.
Keywords: prematurity, lung function measurement, tidal breathing parameters