The use of the tidal breathing flow-volume loop (TBFVL) in full-term newborns as a predictive tool for the risk of lower respiratory tract pathologies: an observational study

<bold>Introduction:</bold> The tidal breathing flow-volume loop (TBFVL) is a safe, quick, and noninvasive pulmonary function test; in the newborn it provides useful information on the patient's pulmonary characteristics. Bronchiolitis is a potentially serious lower respiratory tract disease even in children without comorbidities, however there are no tools capable of predicting which patients will develop a more severe form of the disease. <bold>Objectives.</bold> Evaluate the early use of TBFVL as a predictive tool to identify subjects at risk of developing bronchiolitis in the first six months of life. <bold>Methods.</bold> Term newborns who did not require respiratory assistance at birth were consecutively enrolled at the Policlinico Umberto I Hospital in Rome, Italy. TBFVL test was performed on the 5th day of life, in the sleeping state. The patients were followed for one year with quarterly telephone follow-up of the families, and the possible onset of bronchiolitis was monitored. <bold>Results.</bold> We recruited 41 infants (20 M, 21 F) between November 2021 and November 2022; 3 subjects (7.3%) developed bronchiolitis, of which 2 (4.8%) required hospitalization. The mean value of the ratio tPTEF/Te recorded at birth in subjects who developed bronchiolitis is significantly lower than the mean value observed in the population who did not experience bronchiolitis (28.4% vs 40.6% p=0.04). <bold>Conclusions.</bold> Our results suggest that a lower tPTEF/Te ratio, indicative of smaller airways, may be used to early identify subjects at risk of having more serious clinical manifestations of bronchiolitis, and who could benefit from more targeted prevention measures.