Bronchodilator responsiveness in wheezy infants predicts continued early childhood respiratory morbidity

<i>Objective</i>: Spirometry including bronchodilator responsiveness is considered routine in the workup of asthma in older children. However, in wheezy infants the existence of bronchodilator responsiveness and its prognostic significance remain unclear. <i>Methods</i>: Infants (&lt; 2 years) with chronic or recurrent wheezing or coughing were evaluated by infant pulmonary function testing (PFT). Maximal expiratory flow at the point of functional residual capacity (V̇_maxFRC) was measured before and 20 minutes after salbutamol administration. Only infants with an obstructive profile (V̇_maxFRC &lt; 80% predicted) were included. The infants were divided into two groups with regard to whether or not a response to salbutamol was observed on PFT. A response was defined as a mean V̇maxFRC after salbutamol administration exceeding the upper confidence interval limit of individual pre-bronchodilator V̇_maxFRC measurements. Follow-up data was gathered after a mean of 2 years. <i>Measurements and Main Results</i>: Sixty infants were included in the study of which 32 (53%) demonstrated responsiveness to bronchodilators. The infants in the responsive group had a significantly higher frequency of physician visits for wheezing than the non-responders (3.0 mean visits/yr vs. 1.5 respectively, <i>P</i> = 0.03), and had a higher likelihood of having received asthma medication in the last year of the follow-up period (84% vs. 50% respectively, RR: 1.68[1.10–2.56]). At the end of the follow-up period, more parents in the responsive group reported continued respiratory disease (71% vs. 22%, RR:3.21[1.30–7.95]). <i>Conclusions</i>: Bronchodilator responsiveness can be demonstrated by infant PFT in infants with recurrent wheezing and can predict increased respiratory morbidity until 3 years of age.